SCUBA2 Systems Review MultiChannel Electronics Hilo Hawaii June
SCUBA-2 Systems Review Multi-Channel Electronics Hilo, Hawaii June 19 -23, 2006
MCE Overview w Each MCE reads signals from a 41× 32 pixel sub-array. w 4 readout cards (RC) that each read 8 output lines through 14 -bit 50 MHz ADCs. w One address card (AC) that asserts each of 41 addresses at ~850 k. Hz. w One clock card (CC) that interprets the commands and synchronizes all the cards.
MCE Interfaces
Synchronizer Box w Commands get_Status enable DV-outputs disable DV-outputs RTS mode (external DV supplied) fn n set frame num. to n fr n set free-run counter to n < 4095 nr n set num. of rows to n < 63 rl n set row_len to n < 4095 re reset ps power status dpa disable power for all 8 MCEs dpu n disable power for MCE(n) ? go st rt w Status Mancho_Enable = ON DV_Mode = FRUN_DV FRUN_COUNT = 47 row_len = 64 num_row = 41 ACDCCU_onoff = 0 X 00
Output of Synchronizer to MCE 39 33 1 0 Fr. No. DV sync
Cold Electronics Warm Electronics (MCE) TES Bias 14 b SQ 1_FB D/A BC 2 data_mode 2: filtered 2 n LPF SA_BIAS 2 m 15 kΩ PID (110 Ω) SQ 1 A=195 Dout A/D 14 b + data_mode 0: error - SQ 2 data_mode 1: feedback ADC_OFFSET RCn 0. 1 Ω data_mode 3: raw SA_OFFSET RCn SA_FB BC 1 SQ 2_BIAS (SB) BC 3 SQ 2_FB BC 2 SQ 1_BIAS (RS) AC (110 Ω)
Squid Characterization Using MCE w 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. 1. Sweep Series-Array(SA) feedback n 2. Sweep SQ 2 feedback and adjust SA feedback n 3. 5. Choose SQ 2_BIAS, SA_FB Sweep SQ 1 feedback and adjust SQ 2 feedback n 4. Choose SA_BIAS, target voltage Choose SQ 1_BIAS, SQ 2_FB, SQ 1_FB Turn on the servo loop Sweep through TES_bias
• bias and feedback for SQ 1 and SQ 2 are set to 0 • Curves are near Icmax for all 8 channels • Choose points at Maximum d. Vout/DIin
Squid characterization Using MCE w Linux shell scripts that call C functions to issue commands to MCE w Areas of improvement: n n Implementation in C RTL PC reliability: l l l 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)
Science Data Mode w In normal data mode the first-stage squid feedback signal, which is read at 20 k. Hz, is low-pass filtered and reported at every data valid pulse (DV), approximately at 200 Hz. w The filter is a 4 -pole Butterworth filter with a cutoff frequency of ~50 Hz. w For each DV pulse, the MCE reports 41 8 4 32 -bit values plus a header.
Engineering Readout Modes In addition to ‘Science Data Mode’ we have a number of readout modes to help diagnose performance. w Internal DV pulses up to 1. 4 k. Hz. Normal format. w Combined Feedback and Error signals in 32 b words w 41× 8 pixels sampled at 50 MHz, in a burst. w Reduced array area at a rate > 1. 4 k. Hz w Error Signals only (ie not the Feedback signal) Combinations of these options are possible. Question: Can the Data Pipeline handle any of these?
MCE Power Shutdown MCE shuts itself down only if: n n 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.
- Slides: 12