Accurate low voltage analogue CMOS timer for mixed-signal integrated circuits

Abstract

An analogue timer which generates a constant time delay that relies only on device geometry ratios and the frequency of a reference clock signal is described. The timer uses the discharge of a capacitor by a constant current over an appropriate voltage span both determined by a special bias circuit driven by the clock in such a way as to eliminate the influence of supply voltage, process parameters and temperature. This circuit is suitable for low-voltage operation.