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CBM705/CBM706/CBM707/CBM708

OPERATION INSTRUCTION

MONITORING ADDITIONAL SUPPLY LEVELS

It is possible to use the power fail comparator to monitor a second supply as shown in Figure

20. The two sensing resistors, R1 and R2, are selected so the voltage on PFI drops below 1.25V at

the minimum acceptable input supply. PFO can connect to MR so a reset is generated when

the supply drops out of tolerance. In this case, if either supply drops out of tolerance, a reset is

generated.

MICROPROCESSOR WITH BIDIRECTIONAL RESET

To prevent contention for microprocessors with a bidirectional reset line, a current limiting

resistor must be inserted between the CBM705/ CBM706/ CBM707/ CBM708 RESET output pin

and the microprocessor RESET pin. This limits the current to a safe level if there are conflicting

output reset levels. A suitable resistor value is 4.7kΩ. If the reset output is required for other uses,

it must be buffered, as shown in Figure 21.

Figure 21. Bidirectional Input/Output RESET