An eight-channel charge ADC on a VME board

In a single width VME module has been housed an eight 12-bit Charge to Digital Conversion Channel. The basic structure of the circuit is composed by eight channels and each channel is built around a monolithic QAC (Charge to Amplitude Converter) developed in bipolar ASIC technology. The outputs of the eight QAC sections are multiplexed and subsequently converted by a fast 12 bit ADC module (1 μsec. conversion time). A Control Logic Circuit controls the conversion sequence. Many functions are software-selectable. The Full Scale Charge Range is 400 pC with a resolution of 0.1 pC; the maximum conversion time, obtained when all the 8 QAC values are in the range selected and therefore converted and stored in the output buffer, is 13 μsec