[Gb-ccb] CCB ADC delay optimization
Martin Shepherd
mcs at astro.caltech.edu
Tue Oct 4 16:14:19 EDT 2005
Here are the results of optimizing the ADC clock delay for the minimum
noise levels.
The test program that I have written assumes that nothing is connected
to the CCB inputs (in such conditions the inputs float to mid scale).
The program performs one dump-scan for each combination of input port
(J1 to J16) and ADC delay (0 to 9), and collects consecutive 16384 ADC
samples per dump-scan. It then computes the mean and RMS scatter of
the samples in each dump frame, and use these RMSs as estimates of the
noise levels, as a function of port number and ADC clock delay. In
verbose mode the program displays all of the mean and RMS values
acquired in this manner, then displays a table of noise level as a
function of delay and port number, and then finally displays which ADC
clock-delay results in the lowest noise levels, first per port, and
then globally.
The output of the program is as follows:
Port ADC Delay Mean ADC count Standard deviation Samples
---- --------- -------------- ------------------ --------------
J00 0 8189.3558 0.521 16383 of 16383
J00 1 8189.3518 0.518 16383 of 16383
J00 2 8189.3573 0.520 16383 of 16383
J00 3 8189.3521 0.520 16383 of 16383
J00 4 8189.3350 0.517 16383 of 16383
J00 5 8189.3107 0.513 16383 of 16383
J00 6 8189.3038 0.510 16383 of 16383
J00 7 8189.3063 0.517 16383 of 16383
J00 8 8189.2932 0.515 16383 of 16383
J00 9 8189.2890 0.511 16383 of 16383
J01 0 8189.2466 0.503 16383 of 16383
J01 1 8194.0240 0.487 16383 of 16383
J01 2 8194.0219 0.490 16383 of 16383
J01 3 8194.0250 0.490 16383 of 16383
J01 4 8194.0284 0.494 16383 of 16383
J01 5 8194.0020 0.481 16383 of 16383
J01 6 8194.0266 0.489 16383 of 16383
J01 7 8194.0277 0.488 16383 of 16383
J01 8 8194.0087 0.487 16383 of 16383
J01 9 8194.0124 0.479 16383 of 16383
J02 0 8191.5344 0.535 16383 of 16383
J02 1 8191.5439 0.534 16383 of 16383
J02 2 8191.5548 0.535 16383 of 16383
J02 3 8191.5324 0.535 16383 of 16383
J02 4 8191.4831 0.533 16383 of 16383
J02 5 8191.4971 0.534 16383 of 16383
J02 6 8191.4972 0.535 16383 of 16383
J02 7 8191.4760 0.532 16383 of 16383
J02 8 8191.5199 0.537 16383 of 16383
J02 9 8191.4346 0.527 16383 of 16383
J03 0 8186.9843 0.492 16383 of 16383
J03 1 8186.9733 0.493 16383 of 16383
J03 2 8186.9612 0.488 16383 of 16383
J03 3 8186.9385 0.494 16383 of 16383
J03 4 8186.9283 0.500 16383 of 16383
J03 5 8187.0079 0.487 16383 of 16383
J03 6 8186.9838 0.485 16383 of 16383
J03 7 8186.9678 0.489 16383 of 16383
J03 8 8187.0236 0.495 16383 of 16383
J03 9 8186.9503 0.491 16383 of 16383
J04 0 8178.7546 0.504 16383 of 16383
J04 1 8178.7614 0.505 16383 of 16383
J04 2 8178.7497 0.511 16383 of 16383
J04 3 8178.7612 0.502 16383 of 16383
J04 4 8178.7857 0.498 16383 of 16383
J04 5 8178.7119 0.514 16383 of 16383
J04 6 8178.6816 0.519 16383 of 16383
J04 7 8178.7381 0.510 16383 of 16383
J04 8 8178.7591 0.504 16383 of 16383
J04 9 8178.7800 0.504 16383 of 16383
J05 0 8184.6703 0.506 16383 of 16383
J05 1 8184.6632 0.509 16383 of 16383
J05 2 8184.6780 0.509 16383 of 16383
J05 3 8184.6827 0.505 16383 of 16383
J05 4 8184.7059 0.498 16383 of 16383
J05 5 8184.6809 0.508 16383 of 16383
J05 6 8184.6767 0.504 16383 of 16383
J05 7 8184.6583 0.509 16383 of 16383
J05 8 8184.6745 0.505 16383 of 16383
J05 9 8184.6930 0.498 16383 of 16383
J06 0 8185.6919 0.505 16383 of 16383
J06 1 8185.6999 0.505 16383 of 16383
J06 2 8185.7225 0.506 16383 of 16383
J06 3 8185.7363 0.500 16383 of 16383
J06 4 8185.7019 0.503 16383 of 16383
J06 5 8185.7162 0.505 16383 of 16383
J06 6 8185.7041 0.506 16383 of 16383
J06 7 8185.7005 0.508 16383 of 16383
J06 8 8185.7280 0.504 16383 of 16383
J06 9 8185.7272 0.500 16383 of 16383
J07 0 8180.0396 0.478 16383 of 16383
J07 1 8180.0414 0.480 16383 of 16383
J07 2 8180.0435 0.478 16383 of 16383
J07 3 8180.0218 0.483 16383 of 16383
J07 4 8180.0137 0.479 16383 of 16383
J07 5 8180.0678 0.488 16383 of 16383
J07 6 8180.0229 0.480 16383 of 16383
J07 7 8180.0381 0.483 16383 of 16383
J07 8 8180.0446 0.477 16383 of 16383
J07 9 8180.0225 0.487 16383 of 16383
J08 0 8192.6691 0.517 16383 of 16383
J08 1 8192.6600 0.525 16383 of 16383
J08 2 8192.6449 0.524 16383 of 16383
J08 3 8192.6600 0.522 16383 of 16383
J08 4 8192.6527 0.522 16383 of 16383
J08 5 8192.6164 0.528 16383 of 16383
J08 6 8192.6047 0.525 16383 of 16383
J08 7 8192.6028 0.521 16383 of 16383
J08 8 8192.6162 0.524 16383 of 16383
J08 9 8192.6545 0.517 16383 of 16383
J09 0 8201.0079 0.468 16383 of 16383
J09 1 8200.9655 0.478 16383 of 16383
J09 2 8200.9788 0.475 16383 of 16383
J09 3 8200.9791 0.480 16383 of 16383
J09 4 8200.9830 0.480 16383 of 16383
J09 5 8200.9681 0.479 16383 of 16383
J09 6 8200.9713 0.473 16383 of 16383
J09 7 8200.9572 0.472 16383 of 16383
J09 8 8200.9766 0.480 16383 of 16383
J09 9 8200.9851 0.473 16383 of 16383
J10 0 8189.3256 0.510 16383 of 16383
J10 1 8189.3114 0.506 16383 of 16383
J10 2 8189.3153 0.506 16383 of 16383
J10 3 8189.2972 0.502 16383 of 16383
J10 4 8189.3379 0.512 16383 of 16383
J10 5 8189.3222 0.508 16383 of 16383
J10 6 8189.3243 0.509 16383 of 16383
J10 7 8189.3170 0.505 16383 of 16383
J10 8 8189.3236 0.504 16383 of 16383
J10 9 8189.3248 0.507 16383 of 16383
J11 0 8177.1512 0.472 16383 of 16383
J11 1 8177.1846 0.479 16383 of 16383
J11 2 8177.1680 0.473 16383 of 16383
J11 3 8177.1541 0.475 16383 of 16383
J11 4 8177.1455 0.472 16383 of 16383
J11 5 8177.2299 0.488 16383 of 16383
J11 6 8177.1688 0.469 16383 of 16383
J11 7 8177.1507 0.474 16383 of 16383
J11 8 8177.2004 0.482 16383 of 16383
J11 9 8177.1542 0.473 16383 of 16383
J12 0 8189.5818 0.546 16383 of 16383
J12 1 8189.5608 0.546 16383 of 16383
J12 2 8189.5506 0.552 16383 of 16383
J12 3 8189.5554 0.549 16383 of 16383
J12 4 8189.5504 0.551 16383 of 16383
J12 5 8189.5514 0.548 16383 of 16383
J12 6 8189.5296 0.549 16383 of 16383
J12 7 8189.4664 0.552 16383 of 16383
J12 8 8189.5379 0.547 16383 of 16383
J12 9 8189.5395 0.552 16383 of 16383
J13 0 8189.5231 0.549 16383 of 16383
J13 1 8184.9023 0.474 16383 of 16383
J13 2 8184.8967 0.475 16383 of 16383
J13 3 8184.9304 0.457 16383 of 16383
J13 4 8184.9828 0.464 16383 of 16383
J13 5 8184.9418 0.470 16383 of 16383
J13 6 8184.9241 0.471 16383 of 16383
J13 7 8184.9423 0.470 16383 of 16383
J13 8 8184.9213 0.470 16383 of 16383
J13 9 8184.9487 0.469 16383 of 16383
J14 0 8177.6974 0.525 16383 of 16383
J14 1 8177.6432 0.529 16383 of 16383
J14 2 8177.6507 0.530 16383 of 16383
J14 3 8177.6621 0.524 16383 of 16383
J14 4 8177.6217 0.533 16383 of 16383
J14 5 8177.7037 0.523 16383 of 16383
J14 6 8177.6676 0.530 16383 of 16383
J14 7 8177.6219 0.535 16383 of 16383
J14 8 8177.6504 0.526 16383 of 16383
J14 9 8177.6485 0.533 16383 of 16383
J15 0 8202.2865 0.500 16383 of 16383
J15 1 8202.2564 0.493 16383 of 16383
J15 2 8202.5534 0.529 16383 of 16383
J15 3 8202.2384 0.488 16383 of 16383
J15 4 8202.2849 0.500 16383 of 16383
J15 5 8202.2813 0.499 16383 of 16383
J15 6 8202.2448 0.488 16383 of 16383
J15 7 8202.2484 0.490 16383 of 16383
J15 8 8202.3542 0.508 16383 of 16383
J15 9 8202.3457 0.507 16383 of 16383
Noise levels (counts) as a function of delay and input-port:
Delay
--------------------------------------------------------------------
Port 0 1 2 3 4 5 6 7 8 9
---- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----
J01: 0.521 0.518 0.520 0.520 0.517 0.513 0.510 0.517 0.515 0.511
J02: 0.503 0.487 0.490 0.490 0.494 0.481 0.489 0.488 0.487 0.479
J03: 0.535 0.534 0.535 0.535 0.533 0.534 0.535 0.532 0.537 0.527
J04: 0.492 0.493 0.488 0.494 0.500 0.487 0.485 0.489 0.495 0.491
J05: 0.504 0.505 0.511 0.502 0.498 0.514 0.519 0.510 0.504 0.504
J06: 0.506 0.509 0.509 0.505 0.498 0.508 0.504 0.509 0.505 0.498
J07: 0.505 0.505 0.506 0.500 0.503 0.505 0.506 0.508 0.504 0.500
J08: 0.478 0.480 0.478 0.483 0.479 0.488 0.480 0.483 0.477 0.487
J09: 0.517 0.525 0.524 0.522 0.522 0.528 0.525 0.521 0.524 0.517
J10: 0.468 0.478 0.475 0.480 0.480 0.479 0.473 0.472 0.480 0.473
J11: 0.510 0.506 0.506 0.502 0.512 0.508 0.509 0.505 0.504 0.507
J12: 0.472 0.479 0.473 0.475 0.472 0.488 0.469 0.474 0.482 0.473
J13: 0.546 0.546 0.552 0.549 0.551 0.548 0.549 0.552 0.547 0.552
J14: 0.549 0.474 0.475 0.457 0.464 0.470 0.471 0.470 0.470 0.469
J15: 0.525 0.529 0.530 0.524 0.533 0.523 0.530 0.535 0.526 0.533
J16: 0.500 0.493 0.529 0.488 0.500 0.499 0.488 0.490 0.508 0.507
Optimal ADC delays (modulo 10) per port:
Port: J1 J2 J3 J4 J5 J6 J7 J8 J9 J10 J11 J12 J13 J14 J15 J16
Delay: 6 9 9 6 4 9 9 8 9 0 3 6 0 3 5 6
Noise levels averaged across all ports, as a function of delay (modulo 10):
Delay: 0 1 2 3 4 5 6 7 8 9
Noise: 0.5082 0.5038 0.5064 0.5016 0.5034 0.5044 0.5025 0.5034 0.5042 0.5017
The optimal delay for noise levels averaged over all ports = 3
Clearly the ADC clock delay doesn't appear to affect the noise level
very much, although there is a weak correlation. If I run the program
repeatedly, the deduced optimal port number is generally either 2 or
3, which happens to match the value of 2 that I suggested in my
firmware documentation.
I haven't decided whether it is worth repeating this test with
multiple frames of integrated data, instead of multiple samples of raw
data.
Martin
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