General Description Features - SENSOR+TESTSymbol Parameter Min. Typ. Max. Unit tON Power-up rise...
Transcript of General Description Features - SENSOR+TESTSymbol Parameter Min. Typ. Max. Unit tON Power-up rise...
DATASHEET – epc600
Time-of-flight range-finder chip
General DescriptionThe epc600 chip is a general purpose, monolithic, fully integrated photoelectric CMOS device for optical distance measurement and object detection. Its working principle is based on the three-dimen-sional (3D) time-of-flight (TOF) measurement.
The system-on-chip (SOC) contains:■ A full data acquisition path with the driver for the LED, the photo-
receiver, the signal conditioning, the A/D converter and the signal processing.
■ An on-chip controller managing the data acquisition and the data communication.
■ A 2-wire interface for the command and data communication.
■ A supply-voltage power management unit.
Together with a tiny microprocessor (e.g. PIC 10F206) and few ex-ternal components, a fully functional TOF range-finder can be built.
The working principle is based on the elapsed time-of-flight (TOF) of a photon (modulated light) emitted by the transmitter (LED), re-flected back by the object to the photosensitive receiver.
The very high photosensitivity allows operating ranges up to sev-eral meters and an accuracy down to a centimeter depending on the lens and the illumination power.
Features■ Complete data acquisition system for distance measurement or
object detection on chip. Allows for minimum part count designs.■ On-chip high power LED driver.
■ Easy to use operation in combination with a tiny microprocessor.
■ Absolute distance measurement with digital data output.
■ Integrated signal-processing.
■ High sensitivity and resolution for measured distances up to 15m.
■ Response time of less than 1ms possible.
■ Digital data output with 12 bit distance data and 4 bit quality data.
■ Excellent ambient light suppression up to >100kLux.
■ Integrated ambient light meter (“Luxmeter”)e.g. for brightness control or dimmer functions.
■ Voltage supply with low power consumption.
■ Easy to use 2-wire interface with simple command set.
■ Fully SMD-compatible flip-chip CSP24 package with very small footprint.
Possible Applications■ Light barrier with powerful ambient light suppression
■ People and object counting sensor
■ Door opening and safety sensor
■ Limit and proximity switch
■ Machine control and safety sensor
■ Water tap and toilet flushing sensor
■ Single spot parking sensor
■ Distance measurement gauge
Functional Block Diagram
Controller
Correlator
PhasedetectorPhase shifter
Signal-processing
LED driverModulator
Voltageregulator
2-wireserial
interface
RAMEEPROM
CX1
CX2
XTAL
VDD 8.5V
SCLK
SDATA
LED
LEDF
AD
VDDBS -3.0V
Figure 1: epc600 on-chip data acquisition system for range-finders
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
1 / 25 Datasheet epc600 - V0.3www.espros.ch
Table of ContentsGeneral Description.............................................................................................................................................................................................1Features.............................................................................................................................................................................................................. 1Possible Applications...........................................................................................................................................................................................1Functional Block Diagram................................................................................................................................................................................... 1Absolute Maximum Ratings (Note 1, 2) ............................................................................................................................................................. 3Operating Ratings............................................................................................................................................................................................... 3Electrical Characteristics.....................................................................................................................................................................................3Timing and optical Characteristics...................................................................................................................................................................... 4Other Parameters................................................................................................................................................................................................5Pin Configuration.................................................................................................................................................................................................6Layout information (all measures in mm, )..........................................................................................................................................................7
CSP-24 Package.......................................................................................................................................................................................... 7Design precautions: EMC shielding..............................................................................................................................................................7Ambient Light (Backlight)..............................................................................................................................................................................7
Reflow Solder Profile...........................................................................................................................................................................................7Ordering information............................................................................................................................................................................................8Functional Description.........................................................................................................................................................................................9
1. Operation.................................................................................................................................................................................................. 91.1. Introduction............................................................................................................................................................................................ 91.2. General overview...................................................................................................................................................................................91.3. Operational mode................................................................................................................................................................................ 101.3.1. Distance measurement.....................................................................................................................................................................101.3.2. Sensitivity, integration time and operating range ..............................................................................................................................111.3.3. Ambient-light suppression................................................................................................................................................................ 121.3.4. Quality of the measurement result ....................................................................................................................................................121.3.5. Ambient-light measurement (“Luxmeter”).........................................................................................................................................131.3.6. Temperature metering.......................................................................................................................................................................131.3.7. Calibration and compensations........................................................................................................................................................ 131.3.8. Extended operating range................................................................................................................................................................ 131.3.9. Measurement sequence................................................................................................................................................................... 131.3.10. Multi range-finder application......................................................................................................................................................... 142. Hardware Design.................................................................................................................................................................................... 152.1. General Hardware Configuration.........................................................................................................................................................152.2. Power Supply, Clock and Mode setting............................................................................................................................................... 152.3. On-chip LED driver.............................................................................................................................................................................. 16Short range application design................................................................................................................................................................... 16Mid range application design......................................................................................................................................................................162.4. External LED driver..............................................................................................................................................................................16What performance can be achieved?.........................................................................................................................................................172.5. 2-wire interface.................................................................................................................................................................................... 18SCLK line.................................................................................................................................................................................................... 18SDATA line.................................................................................................................................................................................................. 183. Instruction Set.........................................................................................................................................................................................193.1. 2-wire serial interface...........................................................................................................................................................................193.2. Commands & responses..................................................................................................................................................................... 193.2.1. Command: Commands & Integration times..................................................................................................................................... 203.2.2. Response: Distance & Quality..........................................................................................................................................................203.2.3. Response: Ambient-light level .......................................................................................................................................................... 213.2.4. Response: Temperature................................................................................................................................................................... 213.3. Communication tasks.......................................................................................................................................................................... 213.3.1. Measurement sequence (Distance or ambient-light) ....................................................................................................................... 213.3.2. Read sequence (Temperature) .........................................................................................................................................................213.3.3. Error detection by the microprocessor ............................................................................................................................................. 213.3.4. Reset sequence................................................................................................................................................................................213.3.5. Error detection by the epc600 chip ...................................................................................................................................................223.3.6. Cycle times & reaction time.............................................................................................................................................................. 22Integration time tINT................................................................................................................................................................................... 22Duty cycle of the modulation signal............................................................................................................................................................ 22Measurement time tMEAS..........................................................................................................................................................................22Communication time tCOM.........................................................................................................................................................................23Measurement cycle time tCYCLE...............................................................................................................................................................23Data processing time tPROCESS.............................................................................................................................................................. 23Reaction time tREACTION......................................................................................................................................................................... 23LED on-time tLED-ON and LED duty cycle................................................................................................................................................234. Optical Design.........................................................................................................................................................................................24Photosensitive area.................................................................................................................................................................................... 24Signal sensitivity......................................................................................................................................................................................... 24Ambient-light suppression.......................................................................................................................................................................... 24Operating range.......................................................................................................................................................................................... 24
IMPORTANT NOTICE.......................................................................................................................................................................................25
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
2 / 25 Datasheet epc600 - V0.3www.espros.ch
Absolute Maximum Ratings (Note 1, 2) Operating RatingsSupply Voltage VDD -0.5V to +9.5V Operating temperature (TA) -20°C to +65°C
Voltage to any pin except VDD according voltage class VSC (Note 3)
-0.3V to VSC+0.3V Humidity, non-condensing 5% to 95%
Storage temperature (TA) -65°C to +150°C
Soldering Lead Temperature (TL), 4 sec +260°C
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating conditions indicate condi -tions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see Electrical Characteristics.
Note 2: This is a highly sensitive CMOS mixed signal device with an ESD rating of JEDEC HBM class 2 (<2kV). Handling and assembly of this device should only be done at ESD protected workstat ions.
Note 3: For voltage classes VSC refer to 5 and 4.
Electrical CharacteristicsOperational Ratings, unless otherwise specified. typ.: V DD = 8.5V, TA = +25°C
Symbol Parameter VSC Min. Typ. Max. Unit
VDD Supply voltage 8.5V +8.0 +8.5 +9.0 V
VPP Ripple on supply voltage VDD, peak-to-peak 8.5V 100 mV
IDD Average Supply current, average DC, excl. LED driver current 8.5V 20 mA
IDD Peak Supply current, peak, excl. LED driver current 8.5V 30 mA
VDDBS Bias voltage -3.0V -2.7 -3.0 -4.0 V
IDDBS Bias current -3.0V 1.0 mA
VLED Max. voltage at pin LED 5.0V 5.0 V
ILED1ON Sink current at LED 5.0V 180 mA
VLED-ON Forward voltage at LED, @ ILED-ON = 180mA 5.0V 200 mV
VLEDF-AC Input signal amplitude at LEDF, peak-to-peak 5.0V 0.5 5.0 V
VLEDF Input signal range at LEDF 5.0V 0.0 5.0 V
ILEDF Input leakage current at LEDF 5.0V 1.0 μA
VDigital-OH Output voltage high at SDATA 5.0V 4.5 5.2 V
VDigital-OL Output voltage low at SDATA 5.0V 0 0.5 V
IDigital-OH Source current DC at SDATA, average 5.0V 0.1 mA
IDigital-OL Sink current DC at SDATA 5.0V 8.0 mA
CDigital-Out Output load capacitance 5.0V 30 pF
VDigital-IH Input voltage high at SDATA and SCLK 5.0V 4.0 5.0 V
VDigital-IL Input voltage low at SDATA and SCLK 5.0V 0 1.0 V
IDigital-In Input leakage current DC without pull-up/-down resistor 5.0V 1.0 μA
CDigital-In Input capacitance 5.0V 3 pF
RUP or RDOWN Pull up or pull down resistor 5.0V 30 66 kΩ
Table 1: Electrical characteristics
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
3 / 25 Datasheet epc600 - V0.3www.espros.ch
Timing and optical CharacteristicsOperational Ratings. typ.: VDD = 8.5V, TA = +25°CIllumination: λ = 850±50nm, AOI = 0°, Modulation contrast = 100%, LED modulation frequency = 10MHz, Inte gration time = 103 μsec,Object: constant object signal 25% SAC max < SAC < 75% SAC max, constant distance in 10 to 90% of operation range, - or unless otherwise specified.
Symbol Parameter Min. Typ. Max. Unit
tON Power-up rise time for VDD 1 10 ms
tINIT Start-up time 100 ms
tOFF Power drop-down time for VDD 1 10 ms
fXTAL Center frequency of oscillator (crystal) 4 MHz
ΔfXTAL Deviation to center frequency of oscillator(any deviation is added as a linear distance error)
±100 ppm
ΔφXTAL Phase jitter of oscillator peak-to-peak (Cycle to cycle) 50 ps
fSCLK 2-wire interface clock frequency of SCLK 10 MHz
tSCLK 2-wire interface cycle time of SCLK = 1/fSCLK 100 ns
tH / tL 2-wire interface HIGH and LOW period of SCLK (refer to 7) 50ns 1.0ms ns
fMOD LED modulation frequency (Pin LED), see 15 0.625 20 MHz
tLED-rise/fall Required rise/fall time of the illumination LED at pin LED, @ 50ohm loadRemark: Use high speed LEDs with short switching times(e.g. Stanley DNK5306, Osram SFHSFH4059 Vishay VMB2000, etc.)
12 ns
ASENSOR Photosensitive area of the sensor 320x320 μm
SAC-PP Dynamic AC range of the receiver electronics:Input AC illumination power, peak-to-peak, refer to 3 and 15
16016.4
nW/mm2
nW
SDC Ambient-light suppression 303
W/m2
μW
SNF Photon shot noise floor (dark current) 160 μW/m2
λmax Peak wavelength for maximum sensitivity, see 2 850 nm
λ Operating wavelength range 550 1'000 nm
η Quantum efficiency @ λ = 850nm, AOI = 0° 90 %
φ50% Half angle, see 3 ±60 deg
tINT Integration time; programmable in 16 binary steps (see 15) 1.60 52'500 μs
tMEAS Measurement time 0.261 0.665 210 ms
DR Dynamic range @ a fixed integration time@ using an integration time range: 25.6μs – 26.3ms@ using a full range of integration times
3280
110
dBdBdB
DUA Operating range; unambiguity @10MHz LED modulation frequency 15.0 m
ΔDRES Distance resolution @10MHz LED modulation frequency 0.5 cm
ΔD Distance noise; 1σ; calibrated; depending on light power, integration time, lens, etc.
±1 cm
DOFFSET Distance offset compensation by external microprocessor ±DUA
ΔDDRIFT Distance drift, temperature range from -20°C to +65°C 0.1 %/°K
Table 2: Timing and optical characteristics
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
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Other ParametersOperational Ratings. typ.: VDD = 8.5V, TA = +25°CIllumination: λ = 850±50nm, AOI = 0°, Modulation contrast = 100%, LED modulation frequency = 10MHz, Inte gration time = 103 μsec,Object: constant object signal 25% SAC max < SAC < 75% SAC max, constant distance in 10 to 90% of operation range, - or unless otherwise specified.
Sensitivity epc600 with bandpass filter without filter
integration time:103μs
640nm± 27.5nm
860nm± 32.5nm
940nm± 30nm
sunlightequivalent
max. AC sensitivity SAC 210 nW/mm2 160 nW/mm2 210 nW/mm2
min. ambient-light suppression SDC
40 W/m2 53 klx
30 W/m2 52 klx
40 W/m2 145 klx
Table 3: Sensitivity and ambient-light suppression vs. wavelength
500 600 700 800 900 1000
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength [nm]
Re
lativ
e S
en
sitiv
ity
0 10 20 30 40 50 60 70 80 901.00
10.00
100.00
500nm 630nm 850nm 950nm
Angle of incidence (deg)
Ref
lect
ance
(%
)
Figure 2: Relative spectral sensitivity (Sλ)Sensitivity SAC vs. wavelength
Figure 3: Reflectance vs. illumination angle (AOI)
500 600 700 800 900 1000
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
wavelength [nm]
quan
tum
effi
cien
cy
Figure 4: Quantum efficiency for photons
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
5 / 25 Datasheet epc600 - V0.3www.espros.ch
Pin Configuration
Top View
17
1 2 3
VDDCPLEDLEDF
VREFGNDMVDDT
5
10
6
20
19
18
7
8
9
VDDCORE
XTAL1XTAL2
24 23
2221
16 15 11
VDDPLL VDD
GNDLED
GNDAGND
GNDPLL
VDDIO
VDDPX
VDDHPX
4
NC3
VDDBS
1.8V
5V
8.5V
10V
12V
-3V
Voltage classes
13 1214
SDATA
SCLK
NC1
NC2
LED
NC3
LEDF
VREF
VDDIO
VDDHPX
VDDPX
VDDCP
VDDBS
XTAL1
XTAL2
GNDM
VDDT
SDATA
SCLK
NC2
NC1
VDDPLL
VDDCORE
GNDLEDGNDPLLGNDAGND
VDD
epc600
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21 22 2324
Figure 5: Pin configuration Figure 6: Schematic symbol
Pin Name Pin No. Type VSC Description
SDATA 19 DOUTDIN
+5V Serial data, bidirectional data transmission of the 2-wire interface
SCLK 20 DIN +5V Serial clock input SCLK of the 2-wire interface
LED 12 AOUT +5V LED driver output, high current, open drain
LEDF 14 AIN +5V LED modulation feedback input (delay compensation for external components)
XTAL1 15 AIN +1.8V Oscillator input
XTAL2 15 AOUT +1.8V Oscillator output
VDD 10 SUPPLY +8.5V Power supply +8.5V
VDDCORE 2 SUPPLY +1.8V Decoupling of internal digital core supply +1.8V
VDDPLL 17 SUPPLY +1.8V Decoupling of internal PLL supply +1.8V
VREF 5 SUPPLY +5V Attention: Do not connect this pin
VDDIO 7 SUPPLY +5V Decoupling of the internal internal I/O supply +5V
VDDPX 8 SUPPLY +5V Decoupling of the internal pixel reference voltage +5V
VDDHPX 9 SUPPLY +10V Decoupling of the internal pixel reference voltage +10V
VDDCP 11 SUPPLY +12V Filter capacitor pin for the charge pump circuit +12V
VDDBS 6 SUPPLY -3V Power supply: Bias voltage -3.0V
VDDT 3 DIN +5V Connect to +5V.
GND 21 SUPPLY --- Ground for digital circuitry +1.8V
GNDA 22 SUPPLY --- Ground for analog circuitry, charge pumps and +5V I/O circuit
GNDPLL 24 SUPPLY --- Ground for PLL
GNDLED 23 SUPPLY --- Ground for LED driver
GNDM 4 DIN +5V Connect to GND.
NC1 18 +5V Attention: Do not connect this pin
NC2 1 +5V Attention: Do not connect this pin
NC3 13 +5V Attention: Do not connect this pin
Table 4: Pin function descriptions
Abbreviations to 4:
VSC Supply class for matching components and I/O voltage levelsDOUT Digital outputDIN Digital inputAOUT Analog outputAIN Analog input
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
6 / 25 Datasheet epc600 - V0.3www.espros.ch
Layout information (all measures in mm,
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CSP-24 Package
0.125
0.450
0.200
0.450
0.20
0
2.65
0 ±0
.1
2.650 ±0.1
1.325
1.32
50.
050
0.23
0 ±0
.023
Photosensitive areaon the backside of the chip
Circuit side (Frontside)
Pin 1
Solder ballsSn97.5Ag2.5
0.320
0.45
00.
450
0.32
0
0.450 0.150
0.4
50
2.6
50
±0
.1
2.650 ±0.1
Pin 1
∅ 0.3000.450
no solder stop inside this area
Via GNDmin. ∅ 1.00
Solder stop∅ 1.40
Hole∅ 0.50 - 0.60
0.4
50
0.2
00
0.200
Figure 7: Mechanical dimensions Figure 8: Layout recommendation
Recommendations for a strong ground connection and for reliable soldering of solder balls:
■ Use a pad layout similar to 8. Notice all tracks should go underneath the solder mask areas.
■ To keep the noise floor low in the sensitive receiver path of the chip, a low ohmic and low inductive connection to the supply ground is needed. 8 suggests a recommended grounding of the chip (if a ground plane is not feasible):Feed all grounds into a central viahole with a drill diameter 0.5 - 0.60mm.
■ Do not connect to any pins inside of the opening of the solder mask.
■ Open vias underneath the chip must be covered with a solderstop lid, to prevent ascending solder during the soldering process.
■ If the conductors are with a Ni-Au surface finish, then the preferred landing pad design for the solder balls covers the round landing pad with a gold surface finish as a solderable area only.
Design precautions: EMC shielding
The sensitivity of the sensor area is very high in order to achieve a long operational range of the range-finder. Thus the epc600 device is very sensitive to EMI. Special care should be taken to keep the chip away from the IR LED signal tracks and other sources which may in -duce unwanted signals. It is strongly recommended to cover the device and all passive components around the chip with a metal shield (refer to 9). The shield should be well connected to the GND on the PCB board. A hole in the front is the opening window for the sensor area. The corresponding backside area of the PCB shall be a polygon, connected to GND to shield the circuit from the backside as well.
Figure 9: EMC shield example
Ambient Light (Backlight)
A DC or AC photo-signal can be generated by ambient light, e.g. sunlight, or by cross-talk from the IR-LEDs. Refer to chapter 1.3.3: Ambi-ent-light suppression. However, if this is above the stated maximum value, then the sensor or the input electronics are saturated. This blocks the detection of the AC modulation signal.
Reflow Solder ProfileFor infrared or conventional soldering, the solder profile has to follow the recommendations of IPC/JEDEC J-STD020C (revision C and later) for PB-free assembly. The peak soldering temperature (T L) should not exceed +260°C for a maximum of 4 sec.
Packaging Information (all measures in mm)
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
7 / 25 Datasheet epc600 - V0.3www.espros.ch
Tape & Reel Information
The devices are packaged into embossed tapes for automatic placement systems. The tape is wound on 178mm (7inch) or 330mm (13inch) reels and individually packaged for shipment. General tape-and-reel specification data are available in a separate data sheet and indicate the tape size for various package types. Further tape-and-reel specifications can be found in the Electronic Industries Association EIA-Standard 481-1, 481-2, 481-3.
LST 27.07.2011
Page 1
File: This document is confidential and protected by law and international trades. It must not be shown to any third party nor be copied in any form without our written permission.
Raster 2.5mm2.5mm
4mm
8m
m
Pin 1 / Solder balls bottom side
Figure 10: Tape dimensions
epc does not guarantee that there are no empty cavities in the tape. Thus, the pick-and-place machine should check the presence of a chip during picking.
Ordering informationOrder number: epc600-CSP24
Package: All types are with CSP24 housing.
Packaging method: Delivery in tape on reel.
RoHS compliance: All types are compliant with EN RoHS regulations.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
8 / 25 Datasheet epc600 - V0.3www.espros.ch
Functional DescriptionThis manual is arranged in following sections:
■ OperationThis general description of the operation and the functionalities is based on the user and application level.
■ Hardware DesignAll informations regarding hardware design aspects are covered here.
■ Instruction SetContains detailed description of the data communication and the command set.
■ Optic DesignThe chapter where the user finds some design guidelines for developing appropriate optics and illumination for the device.
1. Operation1.1. Introduction
The epc600 chip is based on the 3D-TOF principle. Modulated light is sent out by a transmitter. This light is reflected by the object to be detected. The returning light is sampled by a photosensitive sensor. The receiver compares the phase difference between the emitted and the received light and computes the time difference of the “time-of-flight”. This value multiplied by the speed of light (ca. 300'000km/sec) and divided by 2 corresponds directly to the distance.
epc600device Backscattered light with a time delay
dependent on the distance between the object and the device
Object
Figure 11: The time-of-flight principle
1.2. General overview
The epc600 chip is designed to enable simple and cost effective system designs. Together with a tiny microprocessor e.g. PIC 10F206 and few external components, a very low cost but fully functional TOF sensor system can be built (refer to 12).
The epc600 system-on-chip contains:■ A full data acquisition path with a power driver for the LED, the photo-receiver, the signal conditioning, the A/D converter and the signal
processing.■ An on-chip controller managing the data acquisition and the data communication.
■ A 2-wire serial interface for the command and data communication.
■ A supply-voltage power management unit.
Microprocessore.g. PIC10F206
IR LED
epc600-pic
LED
LEDF
SCLK
SDATA
< 180mACCDSCLK
SDATA
2-wire interface
OUTDIST
Figure 12: Basic application
The measurement functionality supports distance and ambient light measurement with variable integration times, on-chip temperature measurement and LED current feedback for drift compensation.
The sensitivity of the receiver can be adjusted on the fly to the object reflectivity, the object distance and the ambient light conditions by means of integration time. The longer the integration time, the higher the sensitivity.In cases where the illumination power of the built-in driver is not sufficient, the epc600 chip can also be used with an external LED driver. This allows longer operational ranges or faster measurements, resulting in a faster response time and reduced ambient light sensitivity.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
9 / 25 Datasheet epc600 - V0.3www.espros.ch
1.3. Operational mode
This chapter lists the available features for the epc600-device.
The range-finder works in combination with a tiny microprocessor. It operates according to a single shot principle. A command sent by the microprocessor sets the user parameters in the chip and stimulates the measurement. The device executes the requested task standalone and sends back the answer (data) according to 13.
Measurement n
Response:Read data
measurement cycle time tCYCLE
Calculation n-1Distances & Quality
Measurement n-1
Measurement n
Measure n
Measure n-1 Measure n+1
Calculation nDistances & Quality
Command:Set parametersTrigger capture
Command:Set parametersTrigger capture
Command:Set parametersTrigger capture
Response:Read data
Response:Read data
measurement time tMEAScommunication time tCOM
Figure 13: Basic distance measurement
The microprocessor controls the parameter settings for the measurement and the start. It computes from the read-out data the final dis-tance, quality, ambient-light and temperature data. This also includes applying the necessary correction algorithms and to adapt the epc600 settings to the useful operational range and present scenery conditions.
The epc600 chip supports range finding as a single spot distance measurement, ambient-light measurement (similar to a Luxmeter) and temperature metering.
1.3.1. Distance measurement
The distance measurement is done by single shots following the protocol in 14, first section.
Request measurement:- Select type- Select integration time- Send command
Wait for response
Read measurement data
Set measurement typeSet integration time
Do measurement
Send data
Idle
IdleCalculate result
Request data:- Send command Tx
Wait for response
Read data
Fetch data
Send data
Rx
Idle
Idle
epc600Microprocessor 2-wire interface
Tx
Rx
Figure 14: 2-wire communication sequences Measurement and data reading
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
10 / 25 Datasheet epc600 - V0.3www.espros.ch
A command, including the measurement type and integration time, sent by the microprocessor to the 2-wire interface, sets the epc600-chip configuration and triggers the measurement. The device operates standalone to perform the distance measurement. When it is finished, the chip responds by sending the results: a distance and quality value. Based on this data, the microprocessor computes the final mea-surement result in regards to the necessary correction factors e.g. offset, ambient-light, and temperature drift. The actual result must be read first before starting the next capture cycle. The detailed method of communication and the instruction set are described in chapter 3: Instruction Set.
The epc600 range-finder uses the time-of-flight principle. It is implemented with a repeating, continuous-mode modulation signal during the measurement phase (refer to 15). Consequently, only signals returning within the maximum time slots can be detected unambiguously. This corresponds for the epc600 to a maximum operating range of 15m. Strongly reflected signals outside of this range may therefore in -terfere with the measurement.
1.3.2. Sensitivity, integration time and operating range
The operational range of the complete system is limited by the sensitivity of the receiver as well as by the illumination power emitted by the modulating light source (e.g. LED).
Integration time t INT
Time
Ambient-light DC SDC
Modulated light SAC-PP(peak-to-peak)
LightIntensity
Figure 15: The light detected by the receiver
The system sensitivity consists of two factors: The hardware sensitivity SAC of the photo-sensor (refer to chapter:Timing and optical Char-acteristics) and the exposure time (integration time t INT).
The measurement evaluation is done by computing the distance out of 4 samples caught in one measurement cycle tMEAS. A sample is the collected power of the receiving light signal during the integration time (refer to SAC in 15). This means the sensitivity corresponds to the in-tegration time: The longer the integration time, the more sensitive the measurement.
The formula for the sensitivity is a function of the integration time and is calculated from the references S AC-REF and tINT-REF in the chapter “Timing and optical Characteristics“:
SAC =t INT-REF
t INT
⋅SAC-REF
SAC is the the sensitivity corresponding to the used integration time t INT.
Illumination power, remission of the object (reflectivity), sensitivity of the sensor together with the integration time are limiting the distance operating range. For more detailed information, refer to epc's application note: AN02 Reflected power calculation.
It will probably not be possible to cover the full operational range within one integration time step due to the dynamic range of the re-ceiver's electronics. The possibilities to extend the operating range or to influence the reaction time are:
■ to adapt the integration time correspondingly to the necessary sensitivity as demonstrated in 16.
■ or alternatively: use an additional, external LED driver to adjust the illumination to the needed sensitivity level (refer to chapter1.3.8: Extended operating range).
The easiest way is to adapt the exposure time to the current illumination situation (e.g. in 16). With the command formats, which allows ad-justing of the exposure time, it is easy to do. It is simple to change the exposure time on the fly, because every capture is initiated by a command sent to the chip.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
11 / 25 Datasheet epc600 - V0.3www.espros.ch
rangen-1
operationalrange
n
rangen+1
rangen+2
rangen-2
Distance R
Exposure time (Integration time)
R0
2√2
R0
2
R0
√2R0 R0⋅√2 R0⋅2
2⋅T0
T0
0.5⋅T0
0.25⋅T0
4⋅T0
Figure 16: Operating ranges as a function of distance and exposure timebased on doubling the light power to the sensor
1.3.3. Ambient-light suppression
An important function of the range-finder is the ability to separate the self emitted and reflected modulated light S AC from the ambient illumi-nation SDC. The ambient-light suppression SDC allows suppression of the DC or low frequent signal distortions caused by foreign light sources e.g. sunlight, daylight, room illumination, etc. Refer to 3 for example values as a function of the wavelength and compared to sun-light.
Similar to the sensitivity is the ambient-light suppression as a function of the integration time. The longer the integration time, the more the measurement is sensitive to the ambient-light.
SDC is the the ambient-light corresponding to the used integration time t INT, based on the references SDC-REF and tINT-REF of the chapter “Tim-ing and optical Characteristics“:
SDC =t INT-REF
t INT
⋅SDC-REF
1.3.4. Quality of the measurement result
The epc600 provides, in the read-out data, information on the quality of the received optical signal. It reflects the confidence level of the measurement result. The better the received signal, the better and more precise the distance measurement will be.
Each distance measurement has a corresponding quality rating, which is read as one data word together with the distance data. This 4 bit quality indicator helps to interpret the validity of the measured data.
5 lists the possible combinations for the quality values, gives an interpretation of the data and advises how to react to the situation:■ Generally: The higher the quality value, the better the quality level of the received signal, the better the accuracy of the reading and the
lower the noise. ■ The best operating level is 10.
The illumination is in a comfortable range and not too close to any limitations. The signal amplitude is inside the range 20% - 200% to the best working point for the illumination and integration time.
■ Numbers above indicate a too high illumination in the scenery. A reduction of the integration time for the next measurement is suggested.
■ Lower numbers indicate a low or too low intensity of the reflected, modulated light.A increase of the integration time (or illumination) is suggested.
■ Quality level = 0 and distance value = maximum signal:There is no usable receiver signal or a lack of signal. Possible reasons are:Regular operation: Absence of an object in the operating range.Fault conditions: - Object has too little remission (reflectivity).
- It is too far away.- There is too much ambient-light. Measure and check the ambient-light level.- The illumination is too dim. Too little modulation signal is emitted.
■ Quality level 15 or Quality level = 0 and Distance value = minimum signal:Suggests there is an object, but it is out of the usable operating range.Fault conditions: - The object has a too high remission (reflectivity).
- It is too close to the sensor.- There is too bright illumination or too much modulation signal is emitted.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
12 / 25 Datasheet epc600 - V0.3www.espros.ch
■ All other quality levels:These levels indicates that the epc600 chip has detected undefined conditions during the measurement sequence caused by, e.g. a moving object. The correctness of the result is questionable and a repeat of the measurement is suggested.
Quality value Measurement result Illumination What to do?
Object Accuracy
Quality value = 0 and Distance value = 3'000d
no --- no signalRepeat measurement
with an increased integration time
1 detected bad too low (<7%)Repeat measurement
with an increased integration time
2 detected reduced low (7 – 20%)Measured value okay.
For the next measurement, use an increased integration time
10 detected good good (20 – 200%)Measured value okay.
For the next measurement, use the same integration time
Quality value = 15 or
detected signal saturation too high (>200%)Repeat measurement
with a decreased integration timeQuality value = 0 and Distance value = 0d
others --- --- undefined conditions Repeat measurement
Table 5: Quality levels
1.3.5. Ambient-light measurement (“Luxmeter”)
Instead of reading distance data, the epc600 chip can measure the ambient-light level. Functions of this feature are:■ Use to compensate deviations in the distance measurement caused by the presence of ambient light.
■ Monitor the ambient-light level during the distance measurement to prevent faulty conditions.
■ Use the ecp600 as a “Luxmeter” e.g. for brightness control.
■ or in combination e.g. where the presence or absence of an object in the environmental illumination needs to be controlled.
1.3.6. Temperature metering
An on-chip temperature sensor gives back temperature readings. This allows for the compensation of the signal drifts caused by changing thermal conditions in the light source and the sensor. The data access follows the protocol in 14, second section. For the calculation of the value, refer to 3.2.4: Response: Temperature.
1.3.7. Calibration and compensations
Due to the fact that the range-finder chip does not know its surrounding environment and the phase-shifts caused by the electronic imple-mentation and also due to manufacturing tolerances, a calibration of the sensor is necessary.
Whereas a simple light barrier doesn't need the same accuracy as a range-finder, the compensation and and calibration is dependent on the application.
Influencing variables for various attributes are:
■ Distance: Offset, Slope scaling, Linearity, Reflectivity, Ambient-light, Integration time, Temperature.
■ Reflectivity of the object: Quality, Ambient-light.
■ Ambient-light: Offset, Slope scaling, Linearity, Integration time, Temperature.
■ Temperature: Offset, Slope scaling, Linearity.
These compensations are necessary for the microprocessor to correct the raw distance data in the final measurement.
1.3.8. Extended operating range
The epc600 is a range-finder designed as a system-on-chip for minimum part count circuits. Therefore, a LED driver is integrated on-chip.
In cases where the illumination, achieved with the built-in driver, is not sufficient to detect near and far objects in the expected operational range or in the necessary reaction time, the epc600 chip can be used with a more powerful external LED driver (refer to chapter 2.4 Exter-nal LED driver).
1.3.9. Measurement sequence
A basic possible measurement flow is given in 17:■ Execute a distance measurement and check the quality of the signals. If action is needed, do it accordingly.
■ If the camera operates in thermally changing conditions, from time to time read the temperature for compensation.
■ Calculate, based on the correction data, the final distance value – or whatever is needed.
■ Optional: After START or if needed, check the ambient-light level to evaluate the maximum proper exposure time (or if possible, set the correct modulated illumination power compared to environmental condition).
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
13 / 25 Datasheet epc600 - V0.3www.espros.ch
MEASUREMENTdistance
Quality = 1 or(Quality = 0 and
Distance = 3000d)
Quality = 15 or(Quality = 0 andDistance = 0d)
quality?
Quality = 2 or 10
quality?
Quality <> 0, 1, 2, 10, 15
all other
READtemperature
Calculatetemperature
Calculatedistance
continue?
no
yes
quality?
Quality = 2
Quality = 10
increaseintegration time
ENDmeasurement
decreaseintegration time
STARTmeasurement
Figure 17: Principle measurement flow
This flow is not only for detecting objects. It is also possible to observe and track the object (once captured).
1.3.10. Multi range-finder application
Light barriers are not always operating in a single sensor application. In some applications, more than one sensor is deployed to partially or entirely cover the same observation field. The epc600 range-finder uses signal-processing based on the sinus modulation theory of the time-of-flight principle.The LEDs are modulated with 10MHz square-wave and a duty cycle of 1:1. There is no coding in the modulation sig-nal to make each device unique. To date, in multi range-finder applications, cross-talk between the signals of closely placed individual sen-sors can occur.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
14 / 25 Datasheet epc600 - V0.3www.espros.ch
2. Hardware Design2.1. General Hardware Configuration
The general hardware configuration section covers all design aspects for an epc600 circuit.
2.2. Power Supply, Clock and Mode setting
The external voltage supplies are +8.5V DC as a main supply and -3.0V DC as a bias voltage. Both supplies need to be well regulated and with a low level of noise and ripple voltage, because the epc600 chip is a sensitive, highly amplifying device.
All other necessary voltages are generated on-chip. The internally generated voltage levels VSC (see 4) have to be taken into consideration in order to choose the right components for the design.
All necessary power supply decouplings and the supply of the external reference clock have to be designed according to 18 and 6. Capaci-tors C3 – C8 are used for decoupling of the internally generated voltages.
Schottky diode D1 is vital to ensure a correct power-up of the device.
C3
LED
NC3
LEDF
VREF
VDDIO
VDDHPX
VDDPX
VDDCP
VDDBS
XTAL1
XTAL2
GNDM
VDDT
SDATA
SCLK
NC2
NC1
VDDPLL
VDDCORE
GNDLEDGNDPLLGNDAGND
VDD
epc600
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21 22 2324
C6
C8
C4
C5
C7
C9
+
C2
C1
VDD +8.5V
GND
D1
C10
C11
Y1
VDDBS -3.0V
Figure 18: Main power supply decoupling and clock supply
Part No. Pin Pin No. Component value
Min. Nom. Max. VSC Type
C1 VDD 10 10μF +8.5V
C2 VDD 10 1μF +8.5V Ceramic X7R
C3 VDDCORE 2 1μF 1μF 3.3μF +1.8V Ceramic X7R
C4 VDDPLL 17 1μF 1μF 3.3μF +1.8V Ceramic X7R
C5 VDDIO 7 3.3μF 3.3μF 10μF +5V Ceramic X7R
C6 VDDPX 8 3.3μF 3.3μF 10μF +5V Ceramic X7R
C7 VDDPXH 9 3.3μF 3.3μF 6.8μF +10V Ceramic X7R
C8 VDDCP 11 10nF 100nF 100nF +12V Ceramic X7R
C9 VDDBS 6 10nF 10nF 20nF -3V Ceramic X7R
C10 XTAL1 15 27pF +1.8V Ceramic X7R
C11 XTAL2 16 27pF +1.8V Ceramic X7R
Y1 XTAL1 & XTAL2 15 & 16 4 MHz Crystal-oscillator
D1 VDD & VDDCP 10 & 11 Schottky diode
Table 6: Component values
Leave open pins NC1, NC2, NC3 and VREF. They don't require any termination.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
15 / 25 Datasheet epc600 - V0.3www.espros.ch
2.3. On-chip LED driver
A feature for the minimum part count system is the on-chip LED driver. 19 & 20 show examples for possible circuitries. The design has to take in consideration that these LEDs are switched very fast (10MHz) and with high power (<180mA). Suggested are high speed LEDs with short switching times e.g. Stanley DNK5306, Osram SFH4059, Vishay VMB2000. The layout needs to be well decoupled and with low Z conductors.
Note: Take care that the voltages at LED and LEDF do not exceed their specified operational range of maximum +5V.
Short range application design
The circuit in 19 drives two power IR LEDs. The LED output LED is driven by an open source switching transistor. The illumination intensity of the LEDs is defined by the current flowing through the resistors R1. For output LED = on, the current of resistor R1 is <180mA. In order to have safe voltage operating conditions for output LED and input LEDF, there is a minimum current of <1mA flowing through the LED diodes in the off-state. This also gives the advantage of enhanced switching performance for the LEDs. This off-current is set by the resis-tor R2. The LEDF feedback input is used by the ep600 to adjust the signal correlation for the delay to the real phase conditions of the LEDs, influenced by the design, temperature and aging. C3 and C4 are the charge capacitors to supply the LEDs. In order to support the required fast switching, C3 shall be of a ceramic type. The decoupling of the supply of the epc600 is done by C1 and C2 (ceramic type). The resistor R3 decouples the LED feeding circuit from the ep600 supply. Whereas the voltage drop of the diodes D1A and D1B adjust the voltage supply level to the LED supply level. The advantage of this concept is that it gives a good decoupling between the epc600- and the LED-supply.
For the LED power dissipation calculation, refer to chapter 3.3.6: Cycle times & reaction time.
epc600
LEDF
LED
GND
VDD
GND
VDD = 8.5V
LED1SFH4059
LED2SFH4059
R24k7
R122R
C3100nF
+C110μF
GND
C2100nF
+
C410μF
R315R D1A
BAV99
D1BBAV99
Low Z, fast switching connection
GNDLED
epc600
LEDF
LED
GND
VDD
GND
VDD = 8.5V
LED1SFH4059
LED2SFH4059
LED3SFH4059
R34k7
R418R
C3100nF
+C110μF
GND
C2100nF
Low Z, fast switching connection
GNDLED
Figure 19: Short range application with decoupled LED supply
Figure 20: Mid range application with minimum part count circuit
Mid range application design
The circuit of 20 is a minimum part count design for a more powerful illumination (3 LEDs are equal to 50% more illumination energy).
The design considerations are exactly the same as before. The difference is the additional third LED3, which replaces the diodes D1A and D1B, in order to have more powerful illumination. As it is used as a minimum part count design, the decoupling between the LED supply circuit and the epc600 supply is not of the same quality as in the short range example before. Therefore, the layout design regarding the noise and ripple voltage has to be done very carefully.
2.4. External LED driver
For a more powerful, sensitive or fast system application with an epc610 chip, the use of an external LED driver is an option. The design has to take into consideration that the LEDs are modulated at high frequencies (10MHz) and with high power. So far, the layout needs to be well decoupled and with low Z conductors. The schematic has to follow the correct signal inversions as given in 21. This is important in order to have the correct phase for the feedback signal at input LEDF.
Note: The voltages at LED and LEDF must not exceed their specified operational range.
epc600 LED's output LED pin is driven by an open source switching transistor. The pull-up termination resistor R1 to the V_LOGIC supply guarantees safe voltage operating conditions for the output LED. The modulation signal of output LED feeds a fast inverting digital buffer IC1. It drives the fast switching transistor T3. T3 switches the current through LED-1LEDn on/off to modulate the light. Output LED = low corresponds to light = on. The voltage divider R7+R8 attenuates the modulation signal to the correct maximum voltage and input-swing level for the phase feedback to the input LEDF.
As opposed to the on-chip driver, such a design can have additional light levels as the circuit in 21 shows. A I/O port of the microprocessor switches the intensity to the LOW or HIGH level. The illumination (current through LED1-LEDn) is controlled by R5 for the low (LED LOW), and with the sum of the currents through R4 and R5 for the bright (LED HIGH) illumination level. The level-shifter T1, R2, R3 brings the control signal from I/O port to the switch T2. I/O port = low corresponds to level LED LOW.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
16 / 25 Datasheet epc600 - V0.3www.espros.ch
T3IC1
R6
R7
R1
LED1
LEDn
R2
T1
T2
R5R4
R3
+C2 C3
epc600
LEDF
LED
GND
VDD
GND
C2100nF
VDD +8.5V
V_LOGIC
GND_LED
V_LED
GND_LOGIC
GND_LOGIC
Low Z, fast switching connection
Microprocessor
SCLK
SDATA
SCLK
SDATA
2-wire interface
LOW / HIGH
GNDLED
Figure 21: Long range or fast response application
Advantages of this circuit are the free design of the illumination power (number of LEDs), additional selectable light levels for extending the operation range, the independent voltage supply for the LEDs and the strong decoupling of the epc600 supply and LED circuitry.
What performance can be achieved?
A typical example of an application is a very small, single spot distance gauge (refer to 23). In this example, a range of up to 4m can be expected on white targets when using two SFH4059 LEDs directly driven by the LED pin with a collimator lens of 17mm focal length, a receiver lens of approx. 15x15mm with a focal length of 17 mm using an integration time t int of 410µs.
The response time in this application is t resp. = 4 * tint + 255µs = 1.859ms.
LED1
NC3
LEDF
VREF
VDDIO
VDDHPX
VDDPX
VDDCP
VDDBS
XTAL1
XTAL2
VDDT
GNDM
SDATA
SCLK
NC2
NC1
VDDPLL
VDDCORE
GNDLEDGNDPLLGNDAGND
VDD
epc600
1
2
3
4
5
6
7
8
9
10
11
12
13
14
17
18
19
20
21 22 2324
VDD +8.5V
D1BAS40
C9
C8
C7
C6
C5
C4
C3
10n
100n
1μ
3μ3
3μ3
3μ3
1μ
LED1SFH4059
LED2SFH4059
R24k7
R118R
C12100n
GND Low Z, fast switching connection (as short and wide conductors as possible)
15
16
C1127p
C1027p
Y14MHz
C21μ
C110μ
GND
SDATA
SCLK
+
D1ABAV99
D1BBAV99
VDDBS -3.0V
Figure 22: Minimum part count application
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
17 / 25 Datasheet epc600 - V0.3www.espros.ch
epc600 chipwith IR filter on topIllumination LEDs
Figure 23: Low power, high performance distance gauge. Figure 24: Chip on PCB board
2.5. 2-wire interface
All data communication to and from the epc600 chip goes over the two lines SDATA and SCLK of the 2-wire serial interface (refer to 25).
LED
NC3
LEDF
VREF
VDDIO
VDDHPX
VDDPX
VDDCP
VDDBS
XTAL1
XTAL2
GNDM
VDDT
SDATA
SCLK
NC2
NC1
VDDPLL
VDDCORE
GNDLEDGNDPLLGNDAGND
VDD
epc600
GND
VDD
Microprocessore.g. PIC 10F206
VDD +8.5V
GNDGND
+5.0V
I/O1
I/O22-wire interface
R1(optional)
+5.0V
Figure 25: 2-wire interface wiring
SCLK line
SCLK is the serial clock signal. It is unidirectional and always driven by the microprocessor.
The maximum 'HIGH' pulse length is not defined. The maximum 'LOW' pulse length must be < 1ms.
ERROR handling: A 'LOW' pulse > 1ms will reset the epc600 chip.
SDATA line
SDATA is the serial data line. It is used in a bidirectional way. Depending on the communication direction, it is either driven by the micro-processor or the epc600 chip (refer to 25). A “wired-OR” compatible I/O circuitry on either side is used to handle unexpected error situa-tions. It avoids permanent damage of each party in case they drive opposite logic values.
The microprocessor can achieve the Wired-OR connection by using programmable open-drain I/O pads, or writing a permanent logic low to the output and switching the line between the high-Z and transparent modes. A pull-up resistor to +5.0V will terminate the line to logic high during the high-Z state. By default, the epc600 device enables an internal pull-up resistor to +5.0V on the SDATA pin. If the rise time of the SDATA line is not steep enough, the user may either enable an embedded pull-up resistor in the microprocessor or add an external one (R1) in parallel.
ERROR handling: If the epc600 device detects a communication error, it will pull the SDATA line permanently to low until the interface will be reset.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
18 / 25 Datasheet epc600 - V0.3www.espros.ch
3. Instruction SetThe 2-wire serial interface allows the user to communicate with the epc600 chip. The description of the hardware is in chapter 2.5: 2-wireinterface. The graph of the principle communication flow is in 14.
Starting a measurement, reading the result and setting the correct user parameters for operation are the main functions. All configurations are set at run-time, are loaded immediately and are not stored in the chip.
3.1. 2-wire serial interface
The interface is for single slave use. It is targeted to operate up to a 10MHz clock frequency. Only 2 wires, one bidirectional data transmis -sion and a clock line, are needed. This allows the use of a tiny microprocessor as a controller for the chip. Based on a handshake protocol the chip is either receiving or transmitting data during active clock cycles. The general waveform definition and timing are listed in 26 and 7.
In the idle state, the SCLK and SDATA lines are in the high state (outputs in tristate mode terminated with a pull-up resistor). The transmis-sion is always initiated with a start bit on the SDATA line: SDATA = low. This forces the microprocessor to clock the SCLK line with the nec -essary number of cycles for sending or reading the data. The falling edge of the clock puts the data to the SDATA line. At the time of the rising edge, the data is valid and readable. After the last rising clock edge the sender unlocks the SDATA line and both lines remain in the high state.
tDR
tDH
tH
CLK1 CLK2 CLKnSCLK
SDATA
trfSCLK
trfSCLK
tL
tSCKL
MSB LSBS
tS
tLSBH
Sender pulls SDATA to low:Hand-shake signal for WRITE
Sender changes mode:from WRITE to IDLE
Idle Sender writes to SDATA Idle
IDLE IDLE
≈≈
≈
Figure 26: General waveforms for 2-wire transmission (telegram)
Symbol Parameter Min. Typ. Max. Unit
SCLK 2-wire serial clock
SDATA Serial data, bidirectional transmission
tSCLK Cycle time of SCLK 100 ns
tH High period of SCLK 50 ns
tL Low period of SCLK (refer to ERROR handling) 50ns 1.0ms
trfSCLK Rise or fall time of SCLK (20% - 80% of signal amplitude) 10 ns
tS First negative SCLK edge after negative edge of SDATA 100 ns
tDR Data ready before positive SCLK edge 50 ns
tDH Data hold after positive SCLK edge 0 ns
tLSBH Data hold after positive SCLK edge of last bit transmitted (LSB) 0 ns
Table 7: General timing 2-wire transmission
3.2. Commands & responses
The epc600 device works on a task principle: The chip is in a idle state and performs a single measurement or a read-out on command only (refer to 14).
The microprocessor sends a command to the chip. It is processed immediately. The tasks are: Execute a measurement or read data. When the processing of the instruction is finished, then the chip sends back the answer to the controller by default. Refer to 13 and 14.
The command format always has 8 bits, including 4 bits for command itself (C0-C3) and 4 bits to set the integration length (I0-I3). Bit 7 (MSB) is transmitted first, bit 0 (LSB) last.
The response format is always 16 bits. Bit 15 (MSB) is transmitted first, bit 0 (LSB) last.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
19 / 25 Datasheet epc600 - V0.3www.espros.ch
3.2.1. Command: Commands & Integration times
Name: Command & Integration time
Bit 7 6 5 4 3 2 1 0
C3 C2 C1 C0 I3 I2 I1 I0
Description CMD [3:0] INT [3:0]
CMD: Command to start the measurement with a defined integration time or to read data.
Description CMD INT epc600 response Waiting time
Read temperature 0101 0000 Temperature tACC = 1.5 μs
Measurement of distance and quality 1000 see INT Distance & quality tMEAS
Measurement of ambient-light level 1101 see INT Ambient-light level tMEAS
Don't use OthersINT: Sets the integration time for the measurement. The measurement time is tMEAS = 4x integration time + 255 μs.
Note: A doubling of the integration time is equal to a doubling of the illumination in the scenery.The integration times below in the table are for a LED modulation frequency of 10MHz.
Time INT Time INT Time INT Time INT
1.60 μs 0000 25.6 μs 0100 408 μs 1000 6.56 ms 1100
3.20 μs 0001 51.2 μs 0101 818 μs 1001 13.2 ms 1101
6.40 μs 0010 103 μs 0110 1.64 ms 1010 26.3 ms 1110
12.8 μs 0011 205 μs 0111 3.28 ms 1011 52.5 ms 1111
3.2.2. Response: Distance & Quality
Name: Distance & Quality
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Q3 Q2 Q1 Q0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Description QUAL [3:0] DIST [11:0]
QUAL: Quality value. Generally the higher the value, the better the quality level of the received signal, the better the accuracy of the reading and the lower the noise. The best operating level is 10. Here, the illumination is in a comfortable range and not close to any limitations. A detailed description is in chapter 1.3.4: Quality of the measurement result .
DIST: Distance value, without corrections (@ 10MHz LED modulation frequency).1 LSB = 0.5 cm. Minimum DIST = 0d ≙ 0m. Maximum DIST = 3'000d ≙ 15m.Note: Distance values are valid as long as Quality value >0.
The basic calculation formula is D [cm] = DIST [11:0]⋅1500cm3000
⋅DCORR⋅+ DOFFSET
D Adjusted distance in centimeters
DCORR Scaling of the slope
DOFFSET Offset compensation
DCORR and DOFFSET need to be evaluated by a calibration of the sensor. Refer also to chapter Calibration and compensations.
© 2012 ESPROS Photonics CorporationCharacteristics subject to change without notice
20 / 25 Datasheet epc600 - V0.3www.espros.ch
3.2.3. Response: Ambient-light level
Name: Ambient-light level
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Q1 Q0 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Description 0 0 AMBIENT [13:0]
AMBIENT: Ambient-light value (“Luxmeter”). Output range: signed (0d – 8188d)
The basic calculation formula is SDC =ABS (AMBIENT [13:0])
4⋅SDC-CORR⋅+ SDC-OFFSET
SDC Scaled value of ambient-light level
SDC-CORR Scaling of the slope (necessary only for high accuracy measurements)
SDC-OFFSET Offset compensation (necessary only for high accuracy measurements)
SDC-CORR and SDC-OFFSET need to be evaluated by calibration of the sensor.
3.2.4. Response: Temperature
Name: Temperature
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Q3 Q2 Q1 Q0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Description 0 0 0 0 TEMP [11:0]
TEMP: Temperature value.
The basic calculation formula isTemp [deg C] =
(TEMP [11:0]⋅ 40002048)− 2100
7.2
Temp Scaled value of the temperature in degrees Celsius.
For high accuracy measurements, exact correction factors need to be evaluated by a calibration of the sensor.
3.3. Communication tasks
3.3.1. Measurement sequence (Distance or ambient-light)
27 shows the communication during a measurement sequence:■ The microprocessor initiates the communication with a start bit on the SDATA line followed by actively clocking the line SCLK and the
command transmission.■ After completion of the command the epc600 chip is starting the measurement. Meanwhile, the microprocessor waits for a response.
■ The epc600 chip sets the start bit on SDATA when the measurement is executed and the data are ready ( tMEAS).
■ Now the microprocessor can read out the the data by active clocking.
3.3.2. Read sequence (Temperature)
The sequence is identical to the above except for the waiting time of the response of the chip ( tACC).28 shows the communication during a read sequence:■ The microprocessor initiates the communication with a start bit on the SDATA line followed by actively clocking the line SCLK and the
command transmission.■ After completion of the command, the epc600 chip fetches the data. Meanwhile, the microprocessor waits for a response.
■ The epc600 chip sets the start bit on SDATA when the data are ready ( tACC).
■ Now the microprocessor can read out the the data by active clocking.
3.3.3. Error detection by the microprocessor
Before the microprocessor tries to set a start bit, it first checks the SDATA line according to 29. SDATA = low indicates an ERROR. This means that the epc600 chip signals an error status or the interface is faulty.
3.3.4. Reset sequence
Whenever necessary, the microprocessor can reset the epc600 chip . The reasons for the reset are either due to an error detection during the transmission or in order to resynchronizing the interface. The epc600 interprets a low signal > 1ms on the SCLK line as a reset com -mand for the chip (29). After reset, the communication has to restart.
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SCLK
SDATA C2 C1 C0 I3 I2 I1 I0 Q3 Q2 Q1 Q0 D11 D10 D1 D0
LSB
C3
MSB MSB LSB
uP polls SDATAepc600: idle
Idle
epc600 pulls SDATA to low as soon measurement is finished:Data ready hand-shake signal to uP
tMEAS
SS
Response: epc600 writes SDATA uP reads SDATA
Command: uP writes SDATA epc600 reads SDATA
uP checks SDATA:high = continue; low = error
uP pulls SDATA to low:Command hand-shake signal to epc600
epc600 measures
Idle
≈≈ ≈
≈≈
Figure 27: Measurement sequence
SCLK
SDATA C2 C1 C0 I3 I2 I1 I0 Q3 Q2 Q1 Q0 D11 D10 D1 D0
LSB
C3
MSB MSB LSB
uP polls SDATAepc600: idle
Response: epc600 writes SDATA uP reads SDATA
Command: uP writes SDATA epc600 reads SDATAIdle Idle
uP checks SDATA:high = continue; low = error
epc600 pulls SDATA to low as soon data are ready:Data ready hand-shake signal to uP
tACC
SS
uP pulls SDATA to low:Command hand-shake signal to epc600
≈≈ ≈
≈≈
Figure 28: Read sequence
SCLK
SDATA C2 C1C3
MSB
Command: uP writes SDATA epc600 reads SDATAIdle
uP checks SDATA:detects error
S
uP pulls SDATA to low:Command hand-shake signal to epc600
≈
uP checks SDATA:high = continue; low = error
Reset by uP Idle
tRST
tREC
normal operation ...
Figure 29: Error detection by the uP and the reset sequence
SCLK
SDATA
Response: epc600 write cycle uP reads SDATA
Command: uP write cycle epc600 reads SDATA
MSB
Command: uP write cycle epc600 reads SDATAError
uP checks SDATA:detects error
uP pulls SDATA to low:Command hand-shake signal to epc600
≈
≈
uP checks SDATA:high = continue; low = error
Reset by uP Idle
normal operation ...≈≈
≈
≈≈≈
a) epc600 detects error: writes low to SDATA
MSBMSB LSB LSB
SCLK
SDATA
MSB
Error
uP checks SDATA:detects error
uP pulls SDATA to low:Command hand-shake signal to epc600
≈
≈
uP checks SDATA:high = continue; low = error
Reset by uP Idle
normal operation ...≈≈
≈
≈≈≈
b) epc600 detects error: writes low to SDATA
MSBMSB LSB LSB
Command: uP write cycle epc600 reads SDATA
Response: epc600 write cycle uP reads SDATA
Command: uP write cycle epc600 reads SDATA
≈
uP polls SDATAepc600: idle
uP polls SDATAepc600: idle
S
S S
S
S
Figure 30: Error detection by epc600
Symbol Parameter Min. Typ. Max. Unit
tMEAS Measurement duration. Depends on the selected integration time 1.60 52'427 μs
tACC Propagation delay of the epc600 after command transmission 1.5 μs
tRST Reset signal to the epc600. The time SCLK must be pulled low. 1.0 ms
tREC Recovery time after reset of epc600 4.0 ms
Table 8: Timing of the measurement, read and reset sequence
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3.3.5. Error detection by the epc600 chip
The epc600 chip detects if there are more falling clock edges than necessary for the transmission (see 30). If it happens, the communica-tion is erroneous and the device puts the interface in an ERROR condition by pulling down SDATA = 0. To leave this state, the micropro-cessor has to reset the epc600 chip.
3.3.6. Cycle times & reaction time
For a common understanding, we distinguish between the cycle and the reaction times.
The following examples uses:■ 10MHz modulation frequency at the LED pin.
■ the reference integration time of 103μs from the chapter: Timing and optical Characteristics.
■ a data transmission rate of 1Mbit/s.
Integration time tINT
Integration time t INT (or exposure time) is the timeframe in which the light is sampled by the sensor (refer to chapter 3.2.1: Command: Com-mands & Integration times). It is equal the exposure time (where a shutter is open for passing the light to the sensor).
Duty cycle of the modulation signal
The ratio of on to off for light power emission of a modulated signal (e.g. 50% for a modulation duty cycle 1:1).
Measurement time tMEAS
The time the epc600 device needs to execute a measurement from the point of receiving the command until it responds.
tMEAS = 4⋅t INT + 255μ s e.g. 663μs = 4⋅102μs + 255μs
Communication time tCOM
The period from the end of the measurement until the next start in a continuous mode manner (refer to 13). It is the real communication time used by the 2-wire interface and all the additional time the microprocessor needs to send the next command to the chip.
Example: Command write: 1 check bit + 1 start bit + 8 command bits
Read response: 1 check bit + 1 start bit + 16 data bits
Data rate: 1Mbit/s
Communication time tCOM e.g. 28μs = 10⋅1μs + 18⋅1μs
Measurement cycle time tCYCLE
The measurement cycle time tCYCLE includes the duration to execute a complete measurement cycle until the next cycle propagation is pos-sible (refer to 13).
tCYCLE = tMEAS + tCOM e.g. 691μs = 663μs + 28μs
Data processing time tPROCESS
The period needed by the microprocessor for the final result: “calculation distance & quality” (refer to 13)
Reaction time tREACTION
The reaction time denotes the necessary time interval to change the distance output DIST of the microprocessor from one state to the other (refer to 12). The maximum reaction time tREACTION of the range-finder system is given by
tREACTION = 2⋅ tCYCLE + tPROCESS e.g. 1'482μ s = 2⋅691μs + 100μs
LED on-time tLED-ON and LED duty cycle
For the power dissipation estimation of the emitter LED (at pin LED), the LED on-time and the duty cycle are of importance. The following time periods have to be taken in consideration:
■ tINT : during the integration period, the LED outputs are active for 50% of the time.
■ tMEAS : there are 4 integration periods t INT per measurement cycle tMEAS.
■ tCOM : during the communication time the LED outputs are not active.
The formula for the LED on-time is: tLED−ON = 4⋅t INT
2+ 15μs e.g. 219μs = 4⋅102μs
2+ 15μ s
Duty cycle DCLED-ON for LED on-time is DCLED−ON =tLED−ON
tCYCLE
e.g. 32% = 219μs691μs
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4. Optical DesignThe purpose of this section is to give some important guidelines to the optical designer to help him choose the appropriate optics design for his application.
Photosensitive area
The optical free area which has to be covered well by the illumination optics. This is the relevant surface for calculating the light sensitivity of the chip.
Signal sensitivity
The signal sensitivity is defined by the minimum and maximum detectable AC modulation signal (reflected light). It is defined by the light power (Watt/m2) in relation to:
■ the photo-sensitive area of the sensor.
■ the operating integration time t INT .
■ the operating wavelength λ.
■ the angle of interest (or reflectance of the sensor surface). Refer to 3.
It is independent of■ the modulation frequency
Ambient-light suppression
The ability to suppress DC or low-frequency modulation parts of the received light signal. It is defined by the light power (Watt/m 2) in rela-tion to:
■ the photo-sensitive area of the sensor.
■ the operating integration time t INT.
■ the operating wavelength λ.
■ the angle of interest (or reflectance of the sensor surface). Refer to 3.
Refer also to chapter 1.3.3: Ambient-light suppression.
Operating range
The maximum non-ambiguity distance is < 15m for a modulation frequency of 10MHz @ the pin LED. It is given by the modulation fre-quency and the time-of-flight.
The operating range (dynamic range) of the epc600 receiver for a certain illumination level is given by the photosensor and its electronics:■ the AC signal sensitivity for the modulated light.
■ the capability of the ambient-light suppression.
■ the level of illumination.
Depending of the optical design, these ranges do not match. The optical engineer has to plan the optical design and the light power in a way that matches the application best.
For more detailed information refer to epc's application note AN02 - Reflected power calculation.
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