Power-Supply Monitor with Reset

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5

Interfacing to µPs with

Bidirectional Reset Pins

Microprocessors with bidirectional reset pins (such as

the Motorola 68HC11 series) can contend with the

MAX709 reset output. If, for example the MAX709

RESET output is asserted high and the µP wants to pull

it low, indeterminate logic levels may result. To correct

this, connect a 4.7k

Ω resistor between the MAX709

RESET output and the µP reset I/O (see Figure 3).

Buffer the MAX709 RESET output to other system com-

ponents.

R1

GND

MAX709

RESET

4.7k

GND

RESET

MAX709

GND

µP

BUFFER

BUFFERED RESET

TO OTHER SYSTEM

COMPONENTS

RESET

Figure 3. Interfacing to µPs with Bidirectional Reset I/O