Nonvolatile_power_supply_malfunction_detector

Published:2009/7/24 5:19:00 Author:Jessie | From:SeekIC

This circuit detects and stores the fact that an out-of-operating-range supply-voltage condition has occurred-even when the supply drops to 0. The circuit works on both high and low supply malfunctions so that the circuit can detect when a low supply voltage might have caused a volatile memory loss, or when an overvoltage might have damaged components, or any similar transient/intermittent power failure. The circuit operates with any supply range between 2 and 30 V. Figure 9-23B shows the output states as a function of supply voltage.Figure 9-21B shows the equations to calculate resistor values. The ICL8212 detects voltage V2, which is the upper limit of the operating voltage range. The ICL8211 detects the lower voltage limit of range V1. Hysteresis is used with the ICL8211 so that the output can be stable in either state over the operating voltage range from V1 to V2 by making V3 (the upper trip point of the ICL8211) much higher in voltage than V2. The ICL8212 output forces the ICL8211 output into the on-state above V2 Thus, there is no value of supply voltage that will result in the output of ICL8211 charging from the on-state to the off-state. This can be achieved only by shorting out R3 for values of supply voltage between V1 and V2.



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