KLauS - a charge readout and fast discrimination chip for silicon photomultipliers (SiPMs)

KLauS is an ASIC chip in AMS 0.35μm SiGe Technology with 12 channels. It was developed in October 2010 for the Analog Hardonic Calorimeter (AHCal) of the International Linear Collider (ILC). SiPMs are used to read out the organic scintillator tiles in such a calorimeter. The chip is supposed to provide a readout solution for SiPMs with very low gain (2.75×10⁵). The total dynamic range of the chip is up to 200pC with an integral non-linearity of about 1%. The signal to noise ratio is better than 10 for single photon signals of such low gain SiPMs. The ASIC allows to tune the input voltage by 2V, which is meant to compensate the breakdown voltage variation of silicon photomultipliers. In addition to charge measurement, the chip also offers a very fast trigger signal with a tunable threshold. The threshold can be set even less than single photon signals, which guarantees single pixel triggering. The timing jitter is 52ps for a MIP signal with 15 pixels fired at the same time, which is the nominal MIP signal of the ILC AHCal. In addition, in order to cope with the special ILC clock pattern for power consumption reduction, the chip is able to do power pulsing with 1% “power-on” time of the total ILC period. The input bias voltage can be kept on the preset value with only 1% error of total over voltage of SiPMs in the whole power pulsing period. The total stand-by power is less than 2mW.