FlexToT - Current mode ASIC for readout of common cathode SiPM arrays

A comparative study of the time performance between NINO and FlexToT ASICs

“…Moreover, the FlexToT ASIC also provides a low power consumption of 11 mW per channel. The amplitude of the charge pulses at its inputs is encoded as duration of output pulses with linearity better than 5% for peak input currents ranging from 2.5 mA to 18 mA [2].…”

“…The characterization of the first version of FlexToT and an evaluation of its performance on the readout of scintillator matrices for PET imaging has been performed, with results showing a trigger jitter better than 45 ps rms for a signal equivalent to single photon, coincidence time resolution (CTR) of 269 ps (FWHM), energy resolution of 9.6% (FWHM) at 511 keV and reconstructed spatial resolution of 1.9 mm (FWHM) for a 0.25 mm diameter 22 Na point source [2,9,10].…”

“…We selected the single photo-electron events by calculating the area of the analog SiPM signal after its corresponding amplification. For the FlexToT v2 measurements [2], the selection was done by observing the width of the time signal provided by the trigger output, since the ToT (energy) channel is not sensitive enough for detecting photons at single photon flux. The single photon events (1 pe in figure 2, -3 -right) are intrinsically discriminated by the FlexToT v2 ASIC.…”

“…For fast timing electronics, an alternative solution consists in detecting the transition of the current signal using a current mode input stage [2,3]. In this case, a valid event is detected when the current pulse exceeds a certain threshold regardless of the integrated charge.…”

“…In this paper we report on precise timing measurements with two ASICs (described in 2.2) based on different schemes, the FlexTOT v2 ASIC [2] and the NINO ASIC [5]. We have performed comparative SiPM single-photon time resolution (SPTR) and coincidence time resolution (CTR) measurements between both ASICs.…”