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LCFI meeting 19th August 2008
TESTING OF CPR2A
Mirek Havranek, Peter Murray, Konstantin Stefanov, Stephen Thomas
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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
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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
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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
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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
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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
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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
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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
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9LCFI meeting 19th August 2008
SIMULATION DATA
Provided by Stephen Thomas
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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
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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
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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
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LCFI meeting 19th August 2008
THANK YOU FOR ATTENTION
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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
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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