LCFI meeting 19th August 2008

TESTING OF CPR2A

Mirek Havranek, Peter Murray, Konstantin Stefanov, Stephen Thomas

2LCFI meeting 19th August 2008

INTRODUCTION

CPR2A provides read-out for column parallel CCD

126 voltage channels & 123 charge channels (spread in 2 parts)

5-bit ADC

Cluster finding logic

7-bit digital threshold for each column

Should be able to work with 50 MHz clock (same like CCD clock)

Stand-alone testing possible

3LCFI meeting 19th August 2008

ADC CHARACTERISTIC OF V-CHANNEL

Response of ADC to step voltage input signal is linear

Missing codes are significant at low reference voltage level

3 mV corresponds to 2000 electrons

Noise level at VREF = 200 mV was ± 1 LSB

4LCFI meeting 19th August 2008

ADC CHARACTERISTIC CH-CHANNEL

Charge amplifiers work well - not like last version of the chip

Higher number of missing codes is given by low VREF (measured lower charge

compare to last slide)

100 mV input voltage corresponds to 1250 electrons

NOISE DISTRIBUTION

5LCFI meeting 19th August 2008

FLUCTUATION

Response of all channels to the same signal level (differs for voltage and charge channels)

1 – 126 are voltage channels and 127 – 249 are charge channels

Step in the middle of charge amp. region is correct – there is change of feedback capacitance

6LCFI meeting 19th August 2008

DIGITAL TEST OF CPR2A

Simulated input data can be sent to the scan register in CPR2A a processed

by on-chip cluster finding logic

Cluster finder looks after clusters 2 by 2 pixels and read data from pixels around

The smallest read-out area is 6 by 4 pixels (6 in vertical direction)

Dimensions of read-out area depends on cluster sum

Current version of decoder allows to reconstruct data from

frames with low occupancy

7LCFI meeting 19th August 2008

RECONSTRUCTED CLUSTERS

Cluster sum = 45, cluster threshold = 40

No errors found (even when the cluster is surrounded by noise -> look at the backup)

CPR2A input CPR2A output

8LCFI meeting 19th August 2008

RECONSTRUCTED CLUSTERS

High cluster sum relative to threshold

Cluster sum = 110, cluster threshold = 40

No errors found (even when the cluster is surrounded by noise -> look at the backup)

CPR2A input CPR2A output

9LCFI meeting 19th August 2008

SIMULATION DATA

Provided by Stephen Thomas

10LCFI meeting 19th August 2008

RECONSTRUCTED MATLAB DATA

Successfully reconstructed input data over threshold = 39

Various shapes of clusters are observed

CPR2A input CPR2A output

11LCFI meeting 19th August 2008

RECONSTRUCTED MATLAB DATA

At threshlod level = 15 most of clusters is reconstructed – unfortunatelly cluster decoder in

LabVIEW is not still fully compatible with output data

CPR2A input CPR2A output

12LCFI meeting 19th August 2008

SUMMARY

Analog test

- voltage and charge channels produce linear response with acceptable

amount of missing codes and low noise

- good functionality was verified at 1 MHz clock frequency

- at higher frequency (> 5 MHz) noise level has significant part of dynamic

range

- next problem are big fluctuations across all channels

Digital test

- digital test is still in progress

- cluster finding logic works well at low occupancy

- any significant mistake in cluster finding logic wasn’t find

LCFI meeting 19th August 2008

THANK YOU FOR ATTENTION

14LCFI meeting 19th August 2008

BACKUP

Reconstructed clusters with noise – clusters one time over threshold

Cluster sum = 45 , Cluster threshold = 40Note: to zero value in output correspond grey color instead of white – it was used for visualization purposes

15LCFI meeting 19th August 2008

BACKUP

Reconstructed clusters with noise – clusters two times over threshold

Cluster sum = 110 , Cluster threshold = 40

Note: to zero value in output correspond grey color instead of white – it was used for visualization purposes