Amplificadores de Alta Velocidade Dicas e Truques Nas Aplicacoes de Video

8/2/2019 Amplificadores de Alta Velocidade Dicas e Truques Nas Aplicacoes de Video

1/56

High Speed Amplifiers

Video Tips and Tricks

Randy Stephens

Member Group Technical Staff


2/56

Agenda

Video Overview Analog Video But Everything is Digital, Right?

Standards

Video Signal What Does it Look Like?

Why Use a Filter?

Test Equipment

Solving Common Video Issues Measurement Discrepancies

Input Coupling AC or DC

Output Coupling AC or DC

Output Coupling Frequency Tweaks

A Few Solutions Think Outside the Box Comparison to Passive Filters

Questions


3/56

Analog Video is Everywhere

DVI/HDMI

Receiver

Tuner

VCR/DVDR

DDR SDRAM

Antenna/CableConnection

DTV, HDTV, CRT

AudioDAC Amp

AV Receiver

Digital AudioOutput Jack

CVBS

S-Video

ComponentYPbPr

1394Link &Phy

Media Interface Card

AudioA/D

TMDS341

Decoder /Video ADC

XDRMemory

Video Processor

High PerformanceClocking

Encoder /Video DAC

DVD Player

DSC

PVR Set Top Box

ProjectorDigi-Cam

PC

PMP

CameraPhone

MediaInterface

Logic

A

/V

Inputs

A/VO

utputs

CVBS

S-Video

ComponentYPbPr


4/56

Overview Resolution & Format

3DCombFilter

Tuner

VideoDecoder(TVP5160)

CloseCaption

V Chip

Tele Text

Micro-Processor

EEPROM

or Flash

Audio Processor

De-Interlacer

Class D Audio Amp

(TPA3100D2)

Scaler

A/DConverter

DVI/RxHDCP/HDMI LVDS Tx

TTL Output

OSDSDRAM

DVIPC-VGA

YPbPr

S Video

CVBS (Composite)

RF In

Audio

LVDS Rx

LCD GateDriver

LCDPanel

Lamp

Back LightConverter

SDTVCVBS

SDTVCVBS

SDTV/EDTV/

HDTV

Component

SDTV/EDTV/

HDTV

ComponentSDTVS-Video

SDTVS-Video

SD/ED/HDTVYCbCr

Digital RGB

SD/ED/HDTVYCbCr

Digital RGB

VGA/SVGA/XGA

SXGA/UXGA/QXGA

AnalogRGB

VGA/SVGA/XGA

SXGA/UXGA/QXGA

AnalogRGB

VGA/SVGAXGA

SXGA/UXGA/QXGA

DigitalRGB

VGA/SVGAXGA

SXGA/UXGA/QXGA

DigitalRGB

HDMIComponent

New : Display Port


5/56

Common Video StandardsSDTVStandard Definition Television:

CVBS (Composite Video Baseband Signal) - SMPTE 170M

S-Video

480i (NTSC) or 576i (PAL) Interlaced

EDTVEnhanced Definition Television:

480p (NTSC) or 576p (PAL)

Progressive - SMPTE 293M

HDTVHigh Definition Television:

720p Progressive - SMPTE 296M

1080i Interlaced - SMPTE 274M / ITU-R BT.709

1080p Progressive - SMPTE 274M / ITU-R BT.709

SMPTE = Society of Motion Picture and Television Engineers

ITU-R = International Telecommunication UnionRadiocommunication

ITU-R BT.1358

ITU-R BT.601 (Formerly

CCIR)


6/56

Color Signal Flow

R

G

B

Gamma

R

G

B

YNTSC/PAL/480ip/576ip = 0.299R + 0.587G + 0.114BY720p/1080ip = 0.2126R + 0.7152G + 0.0722B

PB 480ip/576ip = 0.5 (B -Y) / (1 0.114)

PB 720p/1080ip = 0.5 (B -Y) / (1 0.0722)

Luma (Y)

Blue Color Difference (PB)

PR 480ip/576ip = 0.5 (R -Y) / (1 0.299)

PR 720p/1080ip = 0.5 (R -Y) / (1 0.2126)

Red Color Difference (PR)

U = 0.492 (B -Y)V = 0.877 (R -Y)

NTSC/PAL

NTSC = 3.58MHz

PAL = 4.43MHz

Subcarrier

Modulator

PB

PR

ComponentOutput

Y

S

I = Vcos 33 - Usin 33Q = Vsin 33 + Ucos 33

S-VideoOutput

CVBS

++

Chroma (C)

Simplified Color Flow in Consumer Video System

S

ource


7/56

Video Signal Summary

SRMIN = 2 Pi Vpk (1Vpk) x 0.707 (-3dB) x 2 (to ensure no problems)

FormatStandard / Display

ResolutionSignal

Element

AnalogBandwidth

(MHz)

Ideal Min.SR

(V/us)

H. SyncWidth(us)

Max. VideoAmplitude

(Vpp)CVBS CVBS 4.2* ;


8/56

CVBS Video Signal = S-Video Y + C

NTSC 100 IRE = 714mV

40 IRE = 286mVGR

RD

BL

Wh Yel Cy Gr Mg Rd BL BLK

100

89

70

59

41

30

11

0

S-Video Y100% Saturation

IRE Units

+0.714V

-0.286V

-40

-20

0

20

10

100

80

60

40

+0.700V

-0.300V

NTSC PAL

82.8

NTSC S-Video C'100% Saturation

IRE Units

20

60

40

-60

0

-20

-40

117 117109.2 109.282.8

167.1

0

283.5240.7 60.7 103.5

347.1

40

0

0

0.7V

0.62V

0.49V

0.41V

0.29V

0.21V

0.08V

0V

PAL 100 IRE = 700mV

40 IRE = 300mV


9/56

100% Saturation Color Bars Screen Shots


10/56

Screen Shots NTSC & PAL

NTSC: S-Video Y C

CVBSPAL: S-Video Y C

CVBSNote : 100% Color Saturation causes CVBS Signal to be about 1.25Vpp

75% Color Saturation causes CVBS Signal to be 1Vpp

10uS / Div10uS / Div


11/56

Screen Shots 480i Component

480i YPBPR 480i GBR10uS / Div 10uS / Div

Notes : 1) Maximum Voltage Swing is 1Vpp on Channels with Sync2) HSync can also be found on Color Difference Signals


12/56

Screen Shots 480p / 576p Component

480p YPBPR 576p YPBPR4uS / Div 4uS / Div

Notes : 1) Maximum Voltage Swing is 1Vpp on Channels with Sync2) HSync can also be found on Color Difference Signals


13/56

Screen Shots 720p Component

720p @ 60HzYPBPR

720p @ 60HzGBR

4uS / Div 4uS / Div

Note : Maximum Voltage Swing is 1Vpp on Channels with Sync


14/56

Screen Shots 1080i / 1080p Component

4uS / Div 2uS / Div1080i @ 60HzYPBPR

1080p @ 60HzYPBPR

Note : Maximum Voltage Swing is 1Vpp on Channels with Sync


15/56

Screen Shot Computer Video (VGA)

1280 X 1024 @ 60Hz RGSB 1920 X 1440 @ 75Hz RGSB2uS / Div 1uS / Div

Notes : 1) Maximum Voltage Swing is 1Vpp on Channels with Sync2) HSync can also be found on All or None of these Signals


16/56

SDTV Video DAC

Every video DAC shows aliasing

artifacts.

Vertical or diagonal lines appearthroughout picture.

Remember this Signal Feeds into anADC in modern designs -> Aliasing.

Wh Fil DAC O ?


17/56

Why Filter DAC Output?Actual DVD Player Encoder (DAC) Output

-90

-80

-70

-60

-50

-40

-30

-20

000E+0 20E+6 40E+6 60E+6 80E+6 100E+6 120E+6

Frequency

Output-dB

-90

-80

-70

-60

-50

-40

-30

-20

000E+0 50E+6 100E+6 150E+6 200E+6 250E+6 300E+6 350E+6 400E+6

Frequency

Output-dB

Baseband

Signal

Nyquist

Zone 2 & 3

2Fs3Fs

4Fs5Fs 6Fs 7Fs 8Fs

9Fs 10Fs 11Fs 12Fs 13Fs 14Fs

Nyquist

Zone 4 & 5Nyquist

Zone 6 & 7 NyquistZone 8 & 9

Fs

Fs 2Fs3Fs

4Fs


18/56

No DAC Filter Gives Poor Video

Buffer ampwithout filter:

Videodisplay shows

DAC imageinterference

Standard VideoTest Patterns


19/56

Using DAC Filter Gives Good Video

THS7303 Bufferamp withfilter:

Videodisplay clean

Standard VideoTest Patterns


20/56

Low Pass Filters : Part 1 - Amplitude

VERY Hard to Achieve in Any System

SYSTEM Level Response Not justthe Amplifier or Filter Alone

Targeted for Broadcast QualitySystems (Many Systems in Series andthe effects are additive)

Consumer Video is More Relaxed !!!

Most Standards Show Requirements

Example

ITU-R BT.601(SDTV)

StandardShows:


21/56

5th-Order Filter Responses - Amplitude

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

100E+3 1E+6 10E+6 100E+6Frequency - Hz

Output-dB

0.5dB 10MHz Chebyshev

8.5MHz Modified Butterworth

Ex: Low Pass Filters - Amplitude

5th-Order Filter Responses - Ampli tude

-50

-40

-30

-20

-10

0

10

100E+3 1E+6 10E+6 100E+6Frequency - Hz

Output-dB



Look at a 5th-Order Filter Comparison:

Modified Butterworth at 8.5MHz

0.5-dB Chebyshev at 10MHz

Attenuation at 27-MHz :

Chebyshev = 57dB

Butterworth = 46dB

0.5dB Flatness Bandwidth :

Chebyshev = 10-MHz

Butterworth = 6-MHz


22/56

Low Pass Filters : Part 2 - Group Delay

ITU-R BT.601(SDTV)

StandardShows:

Do NOT Forget About Group Delay !!!

Group Delay is Defined as:Change in Phase (Degrees)

360 X Change in Frequency (Hz)


23/56

5th-Order Filter Responses - Group Delay

20

40

60

80

100

120

140

160

180

100E+3 1E+6 10E+6 100E+6Frequency

GroupDelay-ns

0.5dB 10MHz

Chebyshev


Ex: Low Pass Filters Group Delay

5th-Order Filter Responses - Phase

-405

-360

-315

-270

-225

-180

-135

-90

-45

0

45

100E+3 1E+6 10E+6 100E+6Frequency

Phase-Degrees

0.5dB 10MHz

Chebyshev

8.5MHz Modified

Butterworth

Typically only Concerned with Group Delay Variation at a SpecificFrequency (Relative to 100kHz typ)

Absolute Value of Group Delay is Generally not a Concern - Exceptfor Channel to Channel Timing Matching

Why is this Important ??? ...


24/56

Low Pass Filters Pulse Response

Remember:Video Signal Amplitude = Amount of Color,Brightness, etc. to Display on the Screen

If the Signal Goes from say Black to White

to Black (0V to 0.7V to 0V) in successivepixels, then overshoot and ringing must beavoided.

Otherwise smearing and other artifacts willbe seen on the display.


25/56

5th-Order Filter Responses - Pulse Response

0.951

0.965

0.979

0.993

1.007

1.021

1.035

1.049

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Time - us

OutputVoltage



Input

Low Pass Filters Pulse Response

5th-Order Filter Responses - Pulse Response

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Time - us

OutputVoltage


8.5MHz Modified ButterworthInput

Rule of Thumb : The more variation in Group Delay, Themore Overshoot and Ringing will Occur

1 IRE (~7mV) Settling Time: Chebyshev = 482nSButterworth = 217nS

C t C I t t d Filt P d t


26/56

Current Consumer Integrated Filter ProductsAll Utilize Butterworth Filters

VideoStandard

Fixed

Filter

SDTV :CVBS

S-Video480i / 576i

Selectable

LPF

HDTV :1080p501080p60

HDTV :720p1080i

1080p24/30

EDTV :480p576p

THS7303 / THS7353

3-Channels9/16/35MHz Filters

I2C Control

THS73143-Channels

8.5MHz Filters

THS7313

3-Channels8.5MHz FiltersI2C Control

THS73153-Channels

8.5MHz FiltersGain = 5.2V/V

Bypass Mode150MHz

THS73183-Channels

20MHz Filters3.5mA Total

WCSP

THS73163-Channels

36MHz Filters

OPA360 / 611-Ch / 9MHz Filter

2V/V / 5.2V/V

THS73744-Channels

9.5MHz Filters


27/56

Test Equipment for Video - Standard Definition

VM700TTHESD Video

Analyzer NTSC and PAL

CVBS, S-Video, Component

Differential Gain and Phase


28/56

CVBS Video Differential Gain and Phase

Differential Phase: dP Change in Phase (Hue) of the color modulation

(Chroma) due to a change in brightness (Luma)amplitude

Affects the actual color

Consumer Products > 0.5%

Professional Products target < 0.05%

Differential Gain: dG

Change in Amplitude (Saturation) of the colormodulation (Chroma) due to a change inbrightness (Luma) amplitude

Affects color Saturation Consumer Products > 0.5 Professional Products target < 0.05


29/56

VM700T Tests

Signal to Noise Ratio MeasurementK2T Pulse Test

Measures Potential Issues Before and Aftera Pulse


30/56

VM700T Tests

Short Time Distortion Test

Measures Potential Overshoot and SettlingTime Issues

Horizontal Sync + Color Burst Timing

Measures H-Sync Amplitude, Time, rise/falltimes, color burst amplitude and duration


31/56

VM700T Tests

Chroma and Luma Gain Delay

Measures Both Luma and Chroma Signalsfor Gain Errors and Relative Timing

Note Frequency Responses Can also be done, but a Network Analyzer isSignificantly Better than Video Analyzers


32/56

VM5000 Testing

VM5000 Just About Everything ElseNTSC and PAL Component Video (SD/ED/HD)

RGB, GBR

Recently Replaced by VM6000

Test Results are Not Graphical (like VM700T)

Test Results are Numbers Only

Examples:

SNR = 70.1dB

Y to Pb, Y to Pr, Pb to PrTiming Error = 1.1ns, 1.1ns, 0.5ns

Color Bar Amplitude : White = 698mV, Yellow

= 647mV, Cyan = 549mV, Green = 498mV..

Etc


33/56

VM5000 Test

Ex: Short Time Distortion Test


34/56

Measurement Issues

Key Issue Differences Between Bench Testing and

Customer Product Testing Bench Measurements

Uses Video Signal Generators (Ex: Tektronix TG700, Quantum Data802R, etc)

Many VM700T / VM5000 Tests can Calibrate Out the Video Generator +

Cables + VM700T / VM5000 Measurement Results with Amplifier in the Signal

Chain shows Only Amplifier Impact on the Video Signal

Calibrate Path MeasurementVideo Generator

DUT / EVM


35/56

Measurement Issues

Key Issue Differences Between Bench Testing and

Customer Product Testing Customer System Measurements

Uses Video Encoder/DAC/SOC as Signal Source

Uses SOC/Encoder/DAC On-Chip Signals, or

DVD/Sat/Cable/Ext. Input/etc. Signal Source (+ Decoding +

Processing + Encoder) Little or No Calibration done

Customer Shows Test Results of the System which Shows PossiblePerformance Issues

Measurement

Source(Cable/Sat/DVD/Gen)

System


36/56

Measurement Issues

How to Resolve Issue: Measure the Signal Before the Amplifier and then

After the Amplifier

Possible Solutions:

Many SOC/Encoders/DAC have some capability to tweak theprocessing. Usually a Register Setting.

If a Front-End Decoder is being used, maybe a tweak to aRegister on the Decoder can help.

If all else fails, Maybe some Tweaks to the Amplifier Can

Help the Customer.


37/56

Resolving Issues Common Solutions

Modify the Interface Between the DAC outputand the Amplifier.

Modify the Output Interface to the Line

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT

DAC /Encoder

+3.3V

1

2

3

4

CVBS

Y

C

CVBSOut

75

Y

Out

75

C

Out75+3.3V

75

75

SDTVCVBS

S-Video YS-Video C480i/576iYPBPR

GBR 75

S-Video

R

R

R

THS7314


38/56

Video Amplifier Signal Biasing Single Supply

DC Modes

AC Modes

DC

DC+SHIFT

ACSTC

ACBIAS

1.65V3.3V

AC BIAS

AC Sync Tip Clamp

250mV0V

DC + Level Shift

250mV

0V

DC

0V

Make Sure Input Signalis >50mV or OutputClipping May Occur

Allows Input Signal to go to 0Vwithout Output Clipping Problems

3.3V


39/56

Input Tweaks:

Sometimes the Interface is Wrong Current Sinking DAC is DC coupled to the Amplifier

Problem is DC Level is Typically too High for DC Coupling to OccurResulting in Saturation of the Amplifier

Solution AC Couple between the DAC and Amplifier

Utilize Sync Tip Clamp Function of the Amplifier for Video Signalswith Bottom-Level Sync (ex: CVBS, S-Video Y, Comp. Y)

Utilize Bias for all other signals (ex: S-Video C, Comp. Pb and Pr)

Resolving Issues Input Tweak

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT

DAC /Encoder

+3.3V

1

2

3

4

Y

PB

PR

+3.3V

SDTV480i/576iYPBPR

GBR

THS7314

0.1uF

22uF

+

R

+3.3V

R

+3.3V

R

+3.3V

0.1uF

0.1uF

0.1uF

3.01M

+3.3V

3.01M

+3.3V

Bias

STC


40/56

Resolving Issues Input Tweak

Input Tweaks:

DC Coupling is Generally Best Used with Current Source DACs with Output Voltage of Sync Signal

Approaching 0V (Most Common)

Ideal for Amplifiers with Internal Level Shift to Prevent Output Sat.

AC Coupling can also Work, but DC Coupling is Generally Better

No AC Coupled Tilt / Droop

No Abberations due to Sync Tip Clamp Function (Never Perfect)

Even if DC Coupling is Utilized, Tweaking the DAC Termination Resistor(and/or DAC Bias Setting Resistor) may Improve Performance

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT

DAC /Encoder

+3.3V

1

2

3

4

CVBS

Y

C

+3.3V

SDTVCVBS

S-Video YS-Video C480i/576iYPBPR

GBR

R

R

R

THS7314DC Coupling


41/56

Output Coupling AC or DC ???

AC Coupled

Legacy Way of Output Coupling

Universally Acceptable

Meets All Specifications for DC levels on Output

Possible Issues:

Line Tilt or Droop

Large Capacitor (330uF to 470uF typ) = Increased Cost andPCB Size

330uF

0.1uF

+

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT

DAC /Encoder

+3.3V

1

2

3

4

CVBS

Y

C

CVBSOut

75

Y

Out

75

C

Out75

+3V to 5V

75

75

SDTVCVBS

S-Video YS-Video C480i/576i

YPBPR

GBR 75

S-Video

R

R

R

THS7314330uF+

0.1uF

22uF

+


42/56

Output Coupling AC or DC ???

DC Coupled

New Way of Coupling No Capacitor = Lower Cost and Smaller PCB Area

No Line Tilt or Droop

Possible Issues:

Amplifier Offsets Cause a Current Flow.

EIA-770 Specification Requires Backporch Voltage = 0V +/- 1V atReceiver (0V +/- 2V at Amplifier Output).

Japan Specification EIAJ CP-1203 Requires Output Voltage = 0V +/-0.1V with No Video Signal.

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT

DAC /Encoder

+3.3V

1

2

3

4

CVBS

Y

C

CVBSOut

75

Y

Out

75

C

Out75+3.3V

75

75

SDTVCVBS

S-Video YS-Video C480i/576i

YPBPR

GBR 75

S-Video

R

R

R

THS7314

0V 1V

0.7V 1V

-0.3V 1V


43/56

Output Coupling - AC with SAG Correction

To See How it Works, Break it up into

Low-Frequency and High-FrequencyOperation:

DC : Zc = infinityAmp Gain = 1 + [(R1 + RF) / RG]

High Freq: Zc = 0

Amp Gain = 1+[((R1||R2) + RF) / RG)= 2 V/V (6 dB)

Choosing Proper Component Values willresult in the Amplifier Gain Increasing asthe Capacitors Impedance Increases

(which would normally result in Video

Output amplitude reduction).Thus the effects cancel each other outresulting in Low-Frequency Extensionwhile using Much Smaller Capacitors.

Out

SAG

47uF

33uF

75

75

VideoOut

+

-

RG RF

R1

R2

Input

-20

-15

-10

-5

0

5

10

15

20

1 10 100

Frequency - Hz

Gain-dB

47uF Only

Amp Gain

330uF

-20

-15

-10

-5

0

5

10

15

20

1 10 100

Frequency - Hz

Gain-dB

Amp Gain + 47uF = Same as 330uF + 6dB

SAG Correction Real Data


44/56

AC-Bypass Video Output Responses

-18

-15

-12

-9

-6

-3

0

3

1 10 100Frequency - Hz

Output-dB

47uF

100uF

330uF

47uF + 33uF SAG

Out

SAG

47uF

33uF

75

75

VideoOut

+

-

RG RF

R1

R2

Input

MeasurementPoint

AC-Bypass Amplifer Responses

0

3

6

9

12

15

1 10 100Frequency - Hz

Output-dB

AmplifierOutput

with SAG

SAG FeedbackPoint

Traditional AmplifierOutput (330uF)

SAG = 47uF + 33UF

Amp OutputMeasurement Point

SAG Correction Real Data


45/56

Resolving Issues Output Tweak

Modify the Source Termination Resistor

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT1

2

3

4

CVBSOut

75

Y

Out

75

C

Out75+3.3V

75

75 75

S-Video

THS7314

.07575

75IN

OUT

V

V

SNTERMI

NTERM

IN

OUT

RR

R

V

V

Traditional :

Ex: If Gain Needs to be Increased, Reducing Source ResistorIncreases System Gain.

While not an Ideal Solution, Testing (K2T Pulse) Shows thatReflections are not an Issue and all Other Tests Pass


46/56


Frequency Compensation

75

75+

-

R C

VOUT

VIN

275(2

)75(1

sC

sC

V

V

IN

OUT

Should Not Let R be less than 25-ohms as this can causeInstability to the Amplifier

Capacitive Load of Cable will Appear Directly on the Amplifier Outputwith no R.


47/56


75

75+

-

R C

VOUT

VIN

C = 180pF

R = Variable


48/56


75

75+

-

R C

VOUT

VIN

C = Variable

R = 75


49/56


THS7314 Bench Testing

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

1E+6 10E+6Frequency

Output-

dB

No Compensation

120pF

R = 75-Ohms

180pF

220pF

270pF

75

75+

-

R C

VOUT

VIN

Drawback An Increase in Group Delay Variation

Configuration Tweak CVBS From S-Video


50/56

Configuration Tweak CVBS From S-Video

Scenario: DAC only has S-Video Y and C Outputs. Need CVBS Output.Solution: THS7314 Low Cost 3-Channel SDTV Amplifier

330uF

0.1uF

+

5

8

7

6

VS+ GND

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT

DAC

/Encoder

+VD

1

2

3

4

Y

C

CVBS

Out75

Y

Out

75

C

Out75

+VA

75

75 75

S-VideoOPTIONAL - 1

RDAC

THS7314

330uF+

0.1uF

10uF

+

0.1uF

0.1uF

+VA

RPRDAC

OPTIONAL - 2

150

150

0.1uF

R C

Optional - 3

Optional 1 : Not Required. Only needed if DAC voltages are above 1.4V Max

Note : RP is not critical. Allowable value is from 3.1Mohm to 5.6Mohm Sets DC inputBias operating point and ultimately output DC operating point.

Optional 2 : Not Required for SMPTE/IEC/EIA standards. Can be used ifdesired or to meet EIAJ CP1203 Specification

Optional 3 : Not Required. Use to get a boost in the upper frequency area dueto 2 X filters for CVBS signal. Good starting point is R = 150 and C = 68 pF

Configuration Tweak - SCART


51/56

Configuration Tweak - SCARTScenario: System Needs to Support SCART output Cost IssuesSolution: THS7374 + Low Cost Switches

11

14

13

12

CH.4 IN CH.4 OUT

CH.2 IN

CH.3 IN

CH.1 IN

CH.3 OUT

CH.2 OUT

CH.1 OUT1

2

3

4

R

G

TV CVBS /Sync Out

75

75

75

+3Vto 5V

VideoSOC

/DAC

R1

R1

THS7374

TV R Out

TV G Out

B

5

6

7

10

9

8NC

BYPASSDISABLE

VS+GND

NC

R1

75

TV B Out

To GPIOController Or GND

TV

SCART330uF *+

330uF *

330uF *

330uF *

17

1918

20

13

1514

16

9

1110

12

5

76

8

1

32

4

17

1918

20

13

1514

16

9

1110

12

5

76

8

1

32

4

21*Optional

470

AudioLeft Out 47uF

470

AudioRight Out 47uF

N/C

N/C

N/C

N/C

N/C

75VCR CVBS /

Sync Out330uF *+

VCRSCART

N/C

N/C

N/C

N/C

N/C

75N/C

+12V

ABC

INHVEEVSS CD4053

CVBS /

SyncR1

Audio

Left

R2

Right

R2

22k

22k

100

47uF

100

47uF

100k

100k

470

AudioLeft Out 47uF

470

AudioRight Out 47uF

AmpLPFBias

0.1uF

220

75

10k

Fast BlankRGB / CVBS(From GPIO)

470

10k

1.5k

+12V

1.8k

Stby/TV(From GPIO)

10k

16:9 / 4:3

(From GPIO)

22k

AudioLeft In

AudioRight In

VCR Mode

VCR CVBS In

+Vbias

AmpLPFBias

21

NE5532DRV600DRV601

SOC

PCM17xx

Note:

This Example Does NotProvide ALL SCARTfeatures, but can work formany systems

Other circuit configurationsavailable that include morefunctions.

Passive vs Active Filters


52/56

Passive vs. Active Filters

Active Filter Passive Filter

Cost Very Low to High Very Low

ToleranceGood due to Element

Matching

Inductor15% to20%

Capacitor10% to15%

Corner Frequency +/- 10% typ+/-15% to +/-25%

(Depends on ComponentTolerances)

TemperatureTolerance

Good due to Matching andLow Coefficient Elements Poor

PCB Area Low to Mid Low to High

ImpedanceVariations

Small Input and OutputImpedance Variations

Significant Input andOutput Variations

Misc. Info Can Save System PowerInductors are Magnetic

Components


53/56

Active Filters Save Power ??? Yes they Can

VideoDAC / Encoder

75

3V

VIDEO OUT

75

26.6 mA

Active Current

Quiescent Current

26.6 mA

1V

1V

26.6 mA

No Buffer

With Buffer

DAC Quiescent Current = 2mA/Ch 6.6 mW/Ch

DAC Quiescent Current = 26.6mA/Ch 88 mW/Ch

3.3V 3.3V

3.3V

VideoDAC / Encoder

499

VIDEO OUT

75

75

x 2

2 mA

2 mA

1.5 mA

2V1V

13 . 3 mA

1V

Active Current 14.5mA (48mW)

Real Video Signals Result

in Buffer current of about

7mA RMS System

Savings of60mW/Ch

DAC Quiescent Current with ~1.24Vpp (100% CVBS) = 33mA/Ch 109 mW/Ch

DAC Quiescent Current with ~1.24Vpp = 2.5mA/Ch 8.3mW/Ch

P i Fil M C l A l i


54/56

Passive Filter Monte Carlo Analysis

DAC

75 150pF

2.2uH 2.2uH

75150pF470pF

Example: 5-Pole 8.5MHzButterworth Passive Filter

Monte Carlo Anaylsis

Inductors +/-15%

Capacitors +/-10%

Resistors +/-1%

Amplitude Variations

Group Delay Variations

P i Fil M C l A l i


55/56

Passive Filter Monte Carlo Analysis

DAC

75 150pF

2.2uH 2.2uH

75150pF470pF

Example: 5-Pole 8.5MHzButterworth Passive Filter

Monte Carlo Anaylsis

Inductors +/-15%

Capacitors +/-10%

Resistors +/-1%

Input and Output

ImpedanceVariations

Unit StepResponseVariations


56/56

Questions?

Amplificadores de Alta Velocidade Dicas e Truques Nas Aplicacoes de Video

Documents

Transcript of Amplificadores de Alta Velocidade Dicas e Truques Nas Aplicacoes de Video