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CBM705/CBM706/CBM707/CBM708

OPERATION INSTRUCTION

POWER FAIL COMPARATOR

The power fail comparator is an independent comparator that can monitor the input power

supply. The comparator inverting input is internally connected to a 1.25V reference voltage. The

noninverting input is available at the PFI input. This input can monitor the input power supply via

a resistive divider network. When the voltage on the PFI input drops below 1.25V, the

comparator output (PFO) goes low, indicating a power failure. For early warning of power failure,

the comparator monitors the preregulator input by choosing an appropriate resistive divider

network. The PFO output can interrupt the processor so a shutdown procedure is implemented

before power is lost.

pin with a Schottky diode to the RESET pin as shown in Figure 15. This helps clamping the PFI

pin voltage during device power up and operation.

Figure 15. Power Fail Comparator