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The ASIC PARISROC, which stands for ìPhotomultiplier ARray Integrated in SiGe Read Out Chipî, is a complete read out chip in AMS SiGe 0.35 µm technology. It integrates 16 independent channels to provide charge and time measurements.

The ASIC PARISROC has been developed as a SoC (system on chip) that processes the analog signals, self triggering and digitizing internally the data for array of 16 PMTs. The main chip specifications are:

  • An adjustable gain channel by channel in order to compensate the photomultiplier tube gain variation because of the common high voltage supply;
  • Auto-trigger on 1/3 of photoelectron (p.e.) (50 fC at PM gain of 106);
  • Charge measurement efficient for 1 p.e. (160 fC) and up to 300 p.e. (50 pC);
  • The time measurement is done in two steps: a coarse time with a 24 bit Counter at 10MHZ and a fine time on a 100 ns ramp to achieve a resolution less then 1ns;
  • Internal ADC (Analog to Digital Converter).
  • Serial data readout.

The chip integrates many functions as it needs to auto-trigger asynchronously on any single photoelectron and provides digitized time and charge data. The 16 channels work independently and are managed by a common digital part.

The ASIC is made of two parallel channels: for charge and time measurements. The charge channel is obtained by two gain paths (high and low) for small and large signals in order to obtain a good charge measurement precision. The charge channel is made by a voltage preamplifier and a slow shaper (with variable shaping time up to 200 ns) to shape the input signal. The two shaper signals (high and low gain) are then stored in two analog memories (each has a depth of two) and only the correct one is converted to digital data thanks to an internal ADC.

The time channel is made by the high gain preamplifier followed by a fast shaper (5 ns) and a discriminator. Thanks to a TDC (Time to Digital Converter), that converts the amplitude in time, the signal is saved in the analog memory, in parallel with the charge, and converted to digital data by the ADC. Two TDC ramps are sampled at the same time and an internal module tags the valid one: only the good time value is then converted.

A digital part manages all the acquisition, the conversion and the readout. It provides by a 24-bit counter the coarse time measurement.

Parisroc at a glance

ASIC name : PARISROC (PMT Array Read-Out Chip)
Current available version : 1 - 2 
Number of channel : 16
Polarity of input signal : negative
Detector read out : MA-PMT, PM, SiPM, MPPC 
noise : 7 fC
Gain : Variable channel by channel of a factor 4 on 8 bits.
Max input signal : 50 pC (300 p.e. at PM gain of 106)

Parisroc features


PIN name

PIN type

and direction

PIN description



inputs bus


Voltage sensitive analogue input

to be connected to the detector


Digital data


Serialized data output (51 bits) :




Channel number


Coarse time counter


Extra Coarse time


Fine time (TDC) used


Charge converted


Gain used


Fine time (TDC) converted



51 bits



Digital output


Provides a logical OR

of the 16 triggers.

T <0:15>

Output triggers

Provides channel output triggers


Parisroc capabilities


Autonomous front-end ASIC with 16 channels managed independently.  It provides charge and time measurements.

Parisroc characteristics

The ASIC PARISROC 2 allows a linear charge measurement up to 600 p.e. (100 pC). Trigger efficiency measurements have been performed showing that each channel can trigger down to 35 fC which corresponds to the 5s noise limit. Time measurements have shown a resolution of 1ns.

Parisroc in experiments

The ASIC PARISROC has been developed for the PMm≤ project, founded by the French national Agency for Research (ANR), which has proposed a new system of ìsmart photo-detectorsî composed by sensor and read-out electronics dedicated to next generation neutrino experiments. The project, considering the need of the future underground detectors to reach large dimensions (ten times the Super-Kamiokande detector), proposes to segment the large surface of photo-detection into macro pixels consisting of an array (2*2 m≤) of 16 PMTs of 12-inches. Each array is connected directly at its back to an autonomous front-end electronics which works in a triggerless data acquisition mode. The array is powered by a common high voltage and only one data cable for each one allows the connection by network to the central data event builder and filter.

The PARISROC ASIC is available to be used in physics experiments and tested in real detector. Different international experiments are interested by the ASIC.