Analog limit on digitally set pulse widths

Abstract

A power switching device (e.g., a power MOSFET) drives relatively large surges of pulsed power through a laser emitter of a Time of Flight (TOF) determining system where both the power switching device and laser emitter are closely packed on a printed circuit board having further closely packed and temperature sensitive other components. Waveforms of pulse trains that control the power switching device are programmably defined and thus may include pulse durations that are unduly large or spacing between pulses that are unduly small such that overheating may occur. A pulse duration limiting circuit is provided having an analog integrator configured to integrate over time, the programmably defined pulses and a voltage triggered clamping device coupled to an output of the analog integrator. The voltage triggered clamping device has a predetermined threshold voltage at and above which it is switched from a relatively low transconductances mode to a substantially higher transconductances mode. The voltage triggered clamping device is coupled to a current supplying circuit branch of the system, the current supplying circuit branch being one that has an ability to supply current for switching on the power switching device.