Programmable delay element using differential technique

摘要

A programmable delay element is provided for delaying a digital input signal. The programmable delay element comprises a discharge capacitor adapted to be precharged to a predetermined voltage in response to a first transition of the digital input signal. A transistor switch of a first type is provided for precharging the discharge capacitor to a predetermined voltage. A discharge current source is connected via a sense node to the discharge capacitor for discharging the capacitor in response to a subsequent opposite transition of the digital input signal. A transistor switch of a second type is provided for connecting the discharge capacitor to the discharge current source and thereby discharging the discharge capacitor. A reference voltage source is provided for applying a reference voltage to a reference node. A comparator is provided having a first input connected to the sense node and a second input connected to the reference node, such that an output of the comparator generates a delayed version of the digital input signal such that the subsequent opposite transition is delayed by an amount equal to the time for the capacitor to discharge to a voltage equal to the reference voltage.