SCUBA-2 Systems Review Multi-Channel Electronics

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SCUBA-2 Systems ReviewMulti-Channel Electronics

• Hilo, Hawaii
• June 19-23, 2006

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MCE Overview

• Each MCE reads signals from a 4132 pixel
  sub-array.
• 4 readout cards (RC) that each read 8 output
  lines through 14-bit 50MHz ADCs.
• One address card (AC) that asserts each of 41
  addresses at 850kHz.
• One clock card (CC) that interprets the commands
  and synchronizes all the cards.

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MCE Interfaces
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Synchronizer Box

•  Commands
• ? get_Status
• go enable DV-outputs
• st disable DV-outputs
• rt RTS mode
• (external DV supplied)
• fn n set frame num. to  n
• fr n set free-run counter to n lt 4095
• nr n set num. of rows to n lt 63
• rl n set row_len to n lt 4095
• re reset
• ps power status
• dpa disable power for all 8 MCEs
• dpu n disable power for MCE(n)

• Status
• Mancho_Enable ON
• DV_Mode FRUN_DV
• FRUN_COUNT 47
• row_len 64
• num_row 41
• ACDCCU_onoff 0X00  

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Output of Synchronizer to MCE
0
1
33
39
sync
DV
Fr. No.
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Cold Electronics
Warm Electronics (MCE)
TES Bias BC2
data_mode 2filtered
14b
?2n
D/A
SQ1_FB
LPF
SA_BIAS
?2m
data_mode 1feedback
15 kO
PID
(110 O)
14b
SQ1
data_mode 0 error

A/D
A195
Dout
-
SQ2
ADC_OFFSET RCn
0.1 O
data_mode 3 raw
SA_OFFSET RCn
(110 O)
SA_FB BC1
SQ2_BIAS (SB) BC3
SQ2_FB BC2
SQ1_BIAS (RS) AC
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Squid CharacterizationUsing MCE

• Sweep the feedback current of each stage across
  its full range and adjust the lower-stage
  feedback to keep the series-array output voltage
  constant.
• Sweep Series-Array(SA) feedback
• Choose SA_BIAS, target voltage
• Sweep SQ2 feedback and adjust SA feedback
• Choose SQ2_BIAS, SA_FB
• Sweep SQ1 feedback and adjust SQ2 feedback
• Choose SQ1_BIAS, SQ2_FB, SQ1_FB
• Turn on the servo loop
• Sweep through TES_bias

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• bias and feedback for SQ1 and SQ2 are set to 0
• Curves are near Icmax for all 8 channels
• Choose points at Maximum dVout/DIin

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Squid characterization Using MCE

• Linux shell scripts that call C functions to
  issue commands to MCE
• Areas of improvement
• Implementation in C
• RTL PC reliability
• More reliable PCI card with additional diagnosis
  features
• More robust Operating System e.g., Fedora
• Modular architecture (e.g., PCI Card driver
  independent of DRAMA and DAS)

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Science Data Mode

• In normal data mode the first-stage squid
  feedback signal, which is read at 20 kHz, is
  low-pass filtered and reported at every data
  valid pulse (DV), approximately at 200 Hz.
• The filter is a 4-pole Butterworth filter with a
  cutoff frequency of 50 Hz.
• For each DV pulse, the MCE reports 41?8?4 32-bit
  values plus a header.

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Engineering Readout Modes

• In addition to Science Data Mode we have a
  number of readout modes to help diagnose
  performance.
• Internal DV pulses up to 1.4 kHz. Normal format.
• Combined Feedback and Error signals in 32b words
• 418 pixels sampled at 50 MHz, in a burst.
• Reduced array area at a rate gt 1.4 kHz
• Error Signals only (ie not the Feedback signal)
• Combinations of these options are possible.
• Question Can the Data Pipeline handle any of
  these?

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MCE Power Shutdown

• MCE shuts itself down only if
• Unacceptable high voltages/currents are detected.
  
• Unacceptable high temperatures inside the MCE are
  detected.
• MCE status prior to auto-shutdown is recorded
  into an EEPROM.
• AC/DC unit shuts down if over temperature is
  detected.