Area efficient on-chip timeout generator with low temperature and low supply voltage dependency

Abstract

An area-efficient fully integrated BiCMOS analog time delay circuit with low-power supply requirements provides delays as long as two milliseconds. An ultralow PTAT current source comprises medium-value resistors to discharge an on-chip capacitor from a fixed zero-temperature coefficient voltage. The comparator monitors the capacitor voltage and changes stage from low to high when the capacitor is discharged below a reference voltage having a defined negative temperature coefficient. The temperature coefficient of the reference voltage generator and the PTAT current source are such that the timeout period is independent of temperature in the first-order. The generated timeout delay is independent of the supply voltage and can be used with a supply voltage as low as two volts.