Patent ID: 7378886

Claim:
A detection circuit for monitoring a first supply voltage level comprising: a voltage detection circuit having a first input operatively connected to the first supply voltage and a first output, wherein the voltage detection circuit is responsive to a first threshold, a current limiting load functionally connecting a second power supply to the first output, a voltage differencing circuit with one input operatively connected to the first output and a second input operatively connected to the first supply voltage, the voltage differencing circuit having a first difference output and a second difference output, the voltage differencing circuit responsive to a second threshold that is higher than the first threshold, the voltage differencing circuit powered from the second power supply, a latch circuit having a first latch input, a second latch input, a first latch output and a second latch output, wherein the first latch input is operatively connected to the first difference output and the second latch input operatively connected to the second difference output, wherein the latch circuit logic state is responsive to first and the second difference outputs, and wherein the latch logic state indicates that the first supply voltage is high enough to power a circuit when the first supply voltage exceeds the second, higher threshold, and wherein the latch logic state indicates the first supply voltage is not high enough to power a circuit when the first supply voltage falls below the first, lower threshold, the difference between the second and the first thresholds defining a hysteresis, and wherein the first latch output and the second latch output both are functionally connected to circuitry that is powered by the first power supply.