Manual Reset Input

Many µP-based products require manual reset capabil-

ity, allowing the operator, a test technician, or external

logic circuitry to initiate a reset. A logic low on MR

asserts the reset output, clears the watchdog timer,

and deasserts the watchdog output. Reset remains

asserted while MR is low and for the reset timeout peri-

Ω pullup

resistor allows MR to be left open if unused. Drive MR

with TTL or CMOS-logic levels or with open-drain/col-

lector outputs. Connect a normally open momentary

switch from MR to GND to create a manual reset func-

tion; external debounce circuitry is not required.

Connect a 0.1µF capacitor from MR to GND to provide

additional noise immunity when driving MR over long

cables or if the device is used in a noisy environment.

Adjustable Input Voltage (RSTIN)

The MAX6734/MAX6735 provide an additional high-

impedance comparator input with a 626mV threshold to

monitor a third supply voltage. To monitor a voltage

higher than 626mV, connect a resistive-divider to the

circuit as shown in Figure 2 to establish an externally

V

= 626mV

EXT_TH

×

+

()

RR

R

12

2

Single-/Dual-/Triple-Voltage µP Supervisory

Circuits with Independent Watchdog Output

_______________________________________________________________________________________

9

(MIN)

RSTIN

RST

WDO

MR

Figure 1. RST, WDO, and MR Timing Diagram

MAX6734

MAX6735

GND

RSTIN

R1

R2

Figure 2. Monitoring a Third Voltage