A precision monolithic time delay generator for use in automotive electronic fuel injection systems

A high-performance low-cost IC time-delay generator has been developed to be used as a building block for automotive electronic fuel injection systems. Time-delay accuracies are achieved by employing the IC to precisely control both the reset time and the initial ramp voltage of an external RC voltage sweep circuit by means of a gated voltage regulator. Reference information, derived from the rotating distributor shaft, triggers an input flip-flop that controls a reset generator to produce the required gating pulses. The resulting exponential voltage sweep is sensed at the input of three externally programmable voltage comparators that provide three separate time-delayed output signals within a /spl plusmn/1-percent accuracy from -40/spl deg/ to +125/spl deg/C. This technique is contrasted to a linear voltage sweep approach which offers less desensitivity to IC parameter variations.