Digital-analog current converter

Abstract

A digital-analog current converter receives, at input, a succession of bits of a binary signal and delivers, at output, sampled by a clock signal, a positive or negative current depending on the state of the input bit. The converter comprises at least one circuit to control the build-up time of the output current of the converter, comprising a capacitor and a circuit to charge this capacitor controlled by the clock signal. The build-up time is controlled by the charging of a capacitor at a constant current up to a reference voltage. The circuit to control the build-up time of the output current may comprise at least two reference voltages, the capacitor being charged and then discharged between these two voltages. The build-up time of the output current is then the sum of the time taken to charge the capacitor and the time taken to discharge the capacitor. The charging and discharging current of the capacitor can be sent directly into the output load of the converter by means of selector switches and current mirrors. Two capacitors are used and are they are charged and discharged. While one of the capacitors gets charged, the other gets discharged. The disclosure can be applied especially to sigma-delta type digital-analog converters.

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