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Abstract

A monolithic integrated circuit generates a programmable time delay under control of a digital work. The delay is generated by comparing a ramp signal to a threshold determined by the value of the digital word and appears as a time difference between a trigger pulse and a pulse generated when the value of the ramp voltage equals the value of the threshold voltage. The ramp voltage is generated by a simple resistance/capacitance charging circuit whose time constant can be adjusted by the user. The threshold voltage is set by a digital-to-analog converter (DAC) and resistor circuit which converts the digital control word into a variable voltage. In order to stabilize the device against changes in temperature and power supply variations, a voltage coupling circuit forces the threshold voltage to track changes in the ramp voltage caused by temperature and power supply variations. The coupling circuit obviates the need for percision voltage sources or current mirrors conventionally used to compensate for temperature and power supply changes. Without the need for the latter device, the integrated circuit can be easily and inexpensively fabricated of transistors of a single bipolar type.

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First Claim