Can we use the circuit similar to what is referred in "Quick Fundas: Op-amp# 3" to build an over-voltage monitoring circuit, which shall latch an over-voltage condition, i.e. even if the over-voltage occurs temporarily, the circuit should be able to continue driving the over-voltage shutdown trigger? The Op-amp should work with single +12V supply. The circuit should have provisions to adjust the threshold voltage levels for over-voltage detection (the voltage monitored could be different than the supply voltage to the Op-amp).
Ans:
There could be different ways to do it. The circuit below also should work. The circuit monitors the voltage "VMON" and drives "VOUT" to its positive rail when VMON goes above ~6.8V. The output VOUT gets latched even when VMON comes back to its nominal value. The latching feature is sometimes required for the user to understand an over-voltage condition has occurred. Changing R2, R3, R1 etc., the voltage threshold level could be adjusted.
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| Figure 1: Over-voltage latch circuit diagram |
The simulated waveforms are shown below:
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| Figure 2: Simulated waveform |
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