Interleaved dual slope ADC for a diamond dosimeter ASIC

Monocrystalline diamond, grown with CVD techniques, is a very good base material for clinical dosimetry sensors. Diamond also shows good physical and electronic properties in term of tissue equivalence and very low dark currents. The sensor current readout is made by electrometers, these are expensive and bulky and, due to the need of shielded cables, can hardly be used for matrix sensor readout. In order to overcome these problems an ASIC, directly bonded to the sensor, could be the most suitable electronic readout. The ASIC should be capable of integrating currents smaller than the pA, with a serial interface to minimize interconnection cable volume, providing a compact and portable device. This paper describes the main functional ASIC blocks we designed. The ASIC has nine channels that will be able to operate in the clinical dosimetry current range, and one channel dedicated to dark currents integration. We present simulation results for every functional block and the final chip layout.