A system clock precision frequency to code converter for low power supply dependence ROIC

This paper presents the frequency-to-code converter for a low power consumption ReadOut Integrated Circuit (ROIC). It allows conditioning and acquiring capacitive sensors signals that complements the front-end of the acquisition platform with very high resolution. The design consists of a temperature compensated voltage reference circuit (bandgap) coupled to a low power relaxation oscillator that adjusts the input signal of the Capacitive-toFrequency converter (CtoF). The bandgap, ensures the correct power supply dependence compensation of the CtoF. This sensing acquisition board, conforms the front-end of the frequency to digital processing architecture developed for this ROIC. For this circuitry, a novel frequency to code converter with very high precision conversion and low relative quantification error has been designed. Moreover, a Microblaze embedded processor has been used in this architecture in order to linearize the CtoF response and to control the whole acquisition process. Finally the output of the processing board is transmitted to an external monitoring unit via an internal UART.