EXL/R3B Calorimeters- Readout from ASIC to DAQ Ian Lazarus STFC Daresbury Laboratory

Overview: 1.What makes ASICs “application specific”? 2.ASIC Readout Options 3.Using timestamps 4.Connections to DAQ 5.An example from AIDA (DeSpec) 6.Summary

What makes an ASIC “application specific”? Detector characteristics: –Geometry (pad pitch, channel count) –Detector Capacitance –Leakage current –Gain required –Signal processing required (shaping time depends on detector type and size) Other things can usually be standardised –readout (but can be analogue or digitised in ASIC) –triggering –slow control (e.g. I2C) –power supplies

ASIC Readout options Analogue –Shaper output (with or without peak detector)- 1 or 2 pads/channel –Multiplex to an external ADC; read peak detector outputs –Preamplifier output (for external Flash ADC) Digital –Multiplex to an internal ADC; read digital data Examples…

Analogue readout, 2 pads per channel. Example- FREDA. 16 channels Peaking times: ns Gain: x1,2,4 or 8 16 inputs 16 diff outputs Design is pad-limited. Aimed at gas detectors with Cdet in range 2- 80pF

Multiplex to ext. ADC; read peak detector outputs Example- Gassiplex (CERN) Peaking times: ns Gain: 4.9mV/fC 16 inputs 1 mux output Reads all 16 channels in turn (10 MHz max; CAEN V550 max is 5MHz)) Aimed at Si/gas detectors

Preamplifier output (for external Flash ADC) Example- AIDA ASIC. Octal Flash ADC 12/14 bit 50MHz 8 Spectroscopy ADC PSA

Multiplex to an internal ADC; read digital data Example- NUCAM 128 inputs, each with: Preamp Programmable Shaper Peak time measurement Discriminator Programmable leakage comp. Intelligent multiplexer Common ADC (12 bits 1MHz) 4 bit daisy chained readout Readout 32 bits/channel in 1us Read only active channels

Example of readout rates. Time to read 128 channels of which 3 are active. Assume 5MHz readout for analogue multiplexers ArchitectureReadout time for 3 active channels. Settling time for external ADC Mux only25.6us200ns Mux with “look at me”<1us200ns On chip ADC and mux with “look at me” 3us (energy and time)n/a

Using Timestamps. Multiplexers cause problems –either slow (read all channels) and timestamp at low rate. –or lose timing relationship with inputs Two possible solutions –Timestamp in ASIC before multiplexer Good timing correlation But, need clock in ASIC near detector so need careful layout to avoid noise problems. Also need to reconstruct full timestamp after ASIC (or read huge amounts of un-necessary data). –Use multi-channel FADC (e.g. octal AD9252) with FPGA to process one channel per pin ASIC preamps. Difficult for fast detectors due to limited speed of octal FADCs

Example of timestamp in an ASIC.

Readout from ASIC Requirements: –ADC: either external ADC matched to mux clock rate or Internal ADC in ASIC or ADC per output for non-muxed ASIC –Control logic (sequencing, clocks, ext ADC) –Timestamp control and logic –Fast Data path –NUSTAR Interfaces (slow control, timestamp, readout)

Usually control readout from FPGA (Field programmable gate array). Why? –Flexible (reprogrammable in situ to change function or fix bugs) –Fast (>1Gbyte/sec using multiple output paths) –Handles control logic and clocks easily –Handles data transfer easily and fast –Built in IP for Ethernet (Virtex 4) and PCIe (Virtex 5) –Reasonable expectation of common development (shared IP) for NUSTAR interfaces to slow control, readout and BUTIS timestamping.

Pk Det & Mux Preamp + shaper low/high gain. (16 channels) Octal FADC (serial out) 12/14bit 50MHz (2 per ASIC) Control Logic Part of FPGA Sliding Scale Spectroscopy ADC 14bits 1 to 5us conv. Octal FADC (serial out) 12/14bit 50MHz (2 per ASIC)

Virtex 4LX FPGA Virtex 4FX FPGA (or V5) Fibre Driver (Laser) 16 ch ASIC 128 detector signals in; 1 data fibre out (max 50Mbytes/sec) or multiple MGTs with PCIe or point-point 200Mbytes/sec PPC (Unix) Ethernet physical interface ADC Readout Timestamp control FADC PSA ASIC Control Slow Control Data Output ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs ASIC 1 SS ADC 16 FADCs 16 FADCs (12/14 bit) 1 Sliding Scale ADC (14bit) per ASIC Virtex 4LX FPGA ADC Readout Timestamp control ASIC Control Slow Control MGT (raw/PCIe)

Summary: Multiplexing is good for high channel counts, but makes timestamping more complex and slows down readout. For more simple timestamping consider high density FADC and pad per channel. DAQ links will use FPGAs for maximum flexibility and to take advantage of shared developments to NUSTAR standards (1G (10G?) Ethernet, PCIe)