STAR Pixel Detector Phase-1 testing

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.


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


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


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


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


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


Nominal bias settings

Digital test results from D1 sensor - pixels connected - darkn

orm

aliz

ed

no

rma

lize

d

1010

Bias Settings


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


D1 E3 F4

ICLP

DIS

CIB

ufB

ias

IPIX

– V

RE

F2

1212

Bias Settings


• 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


F4(nominal: IPIX=50, IBufBias=10, ICLPDISC=100) black plots(optimized: IPIX=60, IBufBias=5, ICLPDISC = 30) red plots

1414

Analog Outputs


Analog test results from D1 sensor - pixels connected - dark

• ENC = ~16 e-

Noise55Fe spectrum

1515

Analog Outputs


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

1616

Analog output threshold vs. internal discriminator threshold

(D1) Generating the discriminator transfer functions in analysis from the analog outputs.


Sensor D1 has 1 bad analog output=> 560 columns shown.

Arbitrary offset

Width of transfer function in each column => temporal noise

1717

LED tests


Sensor E34 consecutive frames with LED pulse (occurring just after frame 1 starts)

1818

Observations and Discussion


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.

1919

end


2020



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



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)

Documents

STAR Pixel Detector Phase-1 testing