The ALTRO chip: a 16-channel A/D converter and digital processor for gas detectors

Abstract

Abstract-The ALTRO (ALICE TPC Read Out) chip is a mixedsignal integrated circuit designed to be one of the building blocks of the readout electronics for gas detectors. Originally conceived and optimized for the time projection chamber (TPC) of the ALICE experiment at the CERN LHC, its architecture and programmability make it suitable for the readout of a wider class of detectors. In one single chip, the analog signals from 16 channels are digitised, processed, compressed, and stored in a multi-acquisition memory. The analog-to-digital converters embedded in the chip have a 10-bit dynamic range and a maximum sampling rate in the range of 20-. After digitization, a pipelined Data Processor is able to remove from the input signal a wide range of perturbations, related to the nonideal behavior of the detector, temperature variation of the electronics, environmental noise, etc. Moreover, the Data Processor is able to suppress the pulse tail within 1 s after the peak with 1‰ accuracy, thus narrowing the pulses to improve their identification. The signal is then compressed by removing all data below a programmable threshold, except for a specified number of pre-and post-samples around each peak. This produces nonzero data packets. Eventually, each data packet is marked with its time stamp and size -so that the original data can be reconstructed afterwards -and stored in the multi-acquisition memory that has a readout bandwidth of 300 Mbyte/s. This paper addresses the algorithms of the implemented digital functions and the performance of the ALTRO chip.Index Terms-Analog-digital conversion, CMOS mixed analogdigital integrated circuit, data processing, digital filter, gas detector.

Upgrades of the ALICE TPC Front-End Electronics for Long Shutdown 1 and 2

“…• A charge sensitive amplifier/shaper • A 10-bit 10 MSps low power Analog Digital Converter (ADC) • A digital circuit that contains a tail cancellation, baseline subtraction and zero-suppression filter, and a multiple-event buffer The amplifier stage is contained in a single chip named PASA (PreAmplifier and ShAper) [8], while the ADC and digital circuits are contained in the ALTRO (ALICE TPC ReadOut) [9] chip. Each chip handles 16 input channels for a total of 128 channels per front-end card, where each channel corresponds to a single pad on the TPC detector.…”

L0 trigger for the EMCal detector of the ALICE experiment

“…This is done to allow the TRU to fake the 10-bit data format of the ALTRO [15] chip (FALTRO) used on the FEE boards, so that the TRU board data can be read out as if it were FEE data. The data is pedestal subtracted, but not timeintegrated.…”

Development of the data acquisition system of a large TPC for the ILC

“…The readout electronics of the ILC large TPC prototype is based on the ALICE [2] ALTRO [3,4] ADC chip in combination with a newly developed charge pre-amplifier, PC16, which is programmable with respect to shaping time, gain, decay time and polarity. The preamplifier was specially developed as a first step towards the final electronics for the ILC TPC.…”