Multiple_supply_fault_monitor

Published:2009/7/24 4:57:00 Author:Jessie | From:SeekIC

This circuit shows an overvoltage/undervoltage fault monitor for multiple supplies, using a single ICL7665S detector. Figure 9-15B shows the pin connections. The resistors are chosen such that the sum of the currents through R21A, R21B and R31 is equal to the current through R11 when the two input voltages are at the desired low-voltage detection point. The current through R11 at this point is equal to 1.3 V/R11. The voltage at the VSET input depends on the voltage of both supplies being monitored. The trip voltage of one supply (while the other supply is at the nominal voltage) will be different than the trip voltages when both supplies are below their normal voltages. The other side of the ICL7665S can be used to detect the absence of negative supplies. The trip points for OUT1 depend on both the negative supply voltages and the actual voltage of the +5-V supply.



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