STAR Pixel DetectorPhase-1 testing
22
Testing interrupted
LBNL-IPHC 06/2009 - LG
Lena Weronika Szelezniakborn on May 30, 2009 at 10:04 am
weighing 3.23 kg measuring 50 cm
proud parents Joanna & Michal
LBNL-IPHC 06/2009 - LG 3
Talk Outline• Testing plan.• Test structures and DAC linearity.• Measuring discriminator transfer functions.• Effect of bias settings on discriminator transfer
functions.• Analog output measurements.• Analog output threshold vs. internal discriminator
threshold.• Observations and discussion.
44
Testing planWe generated testing plans significantly in advance of receiving the sensors. The initial testing and implementation plans for testing with the new RDO hardware are linked below.
The testing of the Phase-1 sensors is also the testing of the new RDO system which is all new hardware, firmware and software. We anticipated that we would need some time to get all of the RDO system working reliably to adequately test the Phase-1 sensors.
We have concentrated on assembling a scripted testing system that will allow for automated testing of sensors. Our testing of Phase-1 is not yet complete, we will show the results that we have generated thus far.
LBNL-IPHC 06/2009 - LG
http://rnc.lbl.gov/hft/hardware/docs/Phase1/m22_phase1_ultimate_sensor_testing.pdf
http://rnc.lbl.gov/hft/hardware/docs/Phase1/phase1_testing_plan_2009_01_18.doc
55
Testing Plan Goals
LBNL-IPHC 06/2009 - LG
http://rnc.lbl.gov/hft/hardware/docs/Phase1/m22_phase1_ultimate_sensor_testing.pdf
http://rnc.lbl.gov/hft/hardware/docs/Phase1/phase1_testing_plan_2009_01_18.doc
Our goals are:
• Validate sensor digital control / JTAG function, digital outputs.• Assess the bias settings.• Validate and characterize the analog pixel function.• Validate and characterize the discriminator function.• Make a preliminary assessment of the fabrication yield.•Assess the sensor characteristics of noise, S/N, efficiency, etc.
66
Current Testing Scope
LBNL-IPHC 06/2009 - LG
We have mounted 5 sensors onto individual test boards and are performing initial tests.
D1 D2
E3 E4
F4
77
Test structures and DAC linearity
Threshold as a function of DAC value
LBNL-IPHC 06/2009 - LG
y = 0.0003x - 0.0433
y = 0.0003x - 0.0255
y = 0.0002x - 0.0351
y = 0.0003x - 0.0296
y = 0.0003x - 0.0253
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
0 50 100 150 200 250 300
IVDREF1 DAC
VR
EF
1 (V
)
D2
D1
E4
F4
E3
Linear (D1)
Linear (E4)
Linear (F4)
Linear (D2)
Linear (E3)
Crossing points:D2=>110D1=>170E4=>100F4=>140E3=>100
• Measured value = design value = 250 uV / DAC count• Linearity is good• Some dispersion is observed in the 5 sensors ranging from 100 to 170
DAC counts.• Other DACs show good agreement with design values.
88
Discriminator Transfer Functions
LBNL-IPHC 06/2009 - LG
Digital test results from D1 sensor - internal test mode(pixels disconnected)
Nominal bias settings
no
rma
lize
d
no
rma
lize
dAll tests at ~ 36 C
99
Discriminator Transfer Functions
LBNL-IPHC 06/2009 - LG
Nominal bias settings
Digital test results from D1 sensor - pixels connected - darkn
orm
aliz
ed
no
rma
lize
d
1010
Bias Settings
LBNL-IPHC 06/2009 - LG
D1 E3 F4 parameter scan test results• Comments:
– A summary of scans for• Row 1 - ICLPDISC• Row 2 – IBufBias• Row 3 – IPIX that is adjusted together with VREF2
– In all plots, the plot title shows the values used for parameter scan (“_0” is just part of the name)
– Colors in plot are in the following order:• Black, red, green, blue, yellow, purple
1111
Bias Settings
LBNL-IPHC 06/2009 - LG
D1 E3 F4
ICLP
DIS
CIB
ufB
ias
IPIX
– V
RE
F2
1212
Bias Settings
LBNL-IPHC 06/2009 - LG
• Analysis of discriminator transfer functions:– Calculate derivative of the transfer function– Fit the resulting curve with a Gaussian function
• Mean – FPN• Sigma – temporal noise
– On the following slide:• Left column shows distribution of means (FPN)
– The figure of merit is the RMS of the distribution of means
• Right column shows distribution of std (temporal noise)– The figure of merit is the MEAN of the distribution of sigmas
1313
Bias Settings
LBNL-IPHC 06/2009 - LG
F4(nominal: IPIX=50, IBufBias=10, ICLPDISC=100) black plots(optimized: IPIX=60, IBufBias=5, ICLPDISC = 30) red plots
1414
Analog Outputs
LBNL-IPHC 06/2009 - LG
Analog test results from D1 sensor - pixels connected - dark
• ENC = ~16 e-
Noise55Fe spectrum
1515
Analog Outputs
LBNL-IPHC 06/2009 - LG
Run(sampling time)
Pedestal Noise Peak Peak sigma
ENC
27 (2,22) IPIX=30
3.45 (0.78 RMS)
2.67 324 -11.3 13.5
26 (2,22) IPIX=40
3.26 (0.75 RMS)
2.63 314 10.5 13.8
25 (2,22) IPIX=45
3.17 (0.75 RMS)
2.58 307 10.4 13.8
24 (2,22) IPIX=50
3.08 (0.75 RMS)
2.55 302 9.6 13.8
23 (2,22) IPIX=55
3.08 (0.77 RMS)
2.52 296 10.3 14.0
20 (2,22) IPIX=60
3.05 (0.78 RMS)
2.49 291 11.0 14.0
21 (2,22) IPIX=70
2.86 (0.74 RMS)
2.48 282 13.1 14.4
22 (2,22) IPIX=80
2.88 (0.79 RMS)
2.42 275 14.0 14.4
Sensor E3 as a function of IPIX bias.
Sensor F4 ENC = 14.6 IPIX = 70
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Analog output threshold vs. internal discriminator threshold
(D1) Generating the discriminator transfer functions in analysis from the analog outputs.
LBNL-IPHC 06/2009 - LG
Sensor D1 has 1 bad analog output=> 560 columns shown.
Arbitrary offset
Width of transfer function in each column => temporal noise
1717
LED tests
LBNL-IPHC 06/2009 - LG
Sensor E34 consecutive frames with LED pulse (occurring just after frame 1 starts)
1818
Observations and Discussion
LBNL-IPHC 06/2009 - LG
Yield – All 5 sensors tested have fully functional JTAG and digital interfaces. One sensor has a dead analog output channel. All other analog output channels are functional. This is a small sample – we are loading 5 more test boards with Phase-1 sensors. We will test and report.
Questions: • External voltage reference for comparators – we can not get it to work. This is under
investigation with IPHC. Christine has suggested a possible fix. We will test this soon and report.
• Internal comparator reference (pixels not connected) – why is there a larger variation in offsets than with pixels connected?
• When pixels are connected, are the observed magnitude of the offsets in the discriminator switching voltage what is expected?
• The first ~300 columns seem to have difference bias responses than the rest of the sensor, is this expected?
• The sensor chip used for the latch-up testing appears to have become non-responsive. We will investigate and report.
What can be done?• Analysis of design in the way voltage references are distributed, or other reason to
explain the comparator switching voltage differences.• 1 threshold per output?• Probe test pad for temperature sensor.
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end
LBNL-IPHC 06/2009 - LG
2020
Test structures and DAC linearity
LBNL-IPHC 06/2009 - LG
y = 0.0107x + 0.0173
y = 0.0103x + 0.0122
y = 0.0105x + 0.0009
y = 0.0101x + 0.0059
y = 0.0102x + 0.0003
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250
IKIM
O (
V)
IKIMO DAC
D2
D1
E4
F4
E3
Linear (D2)
Linear (D1)
Linear (E4)
Linear (F4)
Linear (E3)
2121
Test structures and DAC linearity
LBNL-IPHC 06/2009 - LG
y = 0.0108x + 0.0231
y = 0.0106x + 0.0111
y = 0.0107x + 0.0112
y = 0.0103x + 0.0201
y = 0.0103x + 0.0035
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250
VR
EF
2 (
V)
IVDREF2 DAC
D2
D1
E4
F4
E3
Linear (D2)
Linear (D1)
Linear (E4)
Linear (F4)
Linear (E3)
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