Adjustable timer circuit

摘要

An adjustable timer circuit capable of producing accurate pulse outputs having a wide range of periods. The timer circuit includes a timing capacitor and an associated current source for producing a reference current having a magnitude which is derived from a reference voltage. A current divider is used to divide the reference current down to a smaller current used for charging the timing capacitor. A comparator circuit is provided for comparing the voltage produced across the timing capacitor with a comparison voltage also derived from the reference voltage. The timing capacitor is discharged in response to the comparator output so that subsequent output pulses can be produced. The current divider is adjustable in response to a mode control signal so that different magnitude charging currents can be produced which results in different magnitude pulse width outputs.