Detailed Description

Reset Output

The MAX6467 provides an active-low open-drain

RESET output. The MAX6468 provides an active-low

drops below the selected threshold or if a falling edge

voltage or is one-shot pulsed low for the MR timeout

period after a falling edge on MR.

Manual Reset Input

Many µP-based products require manual reset capability,

allowing the operator, a test technician, or external logic

circuitry to initiate a reset. A falling edge on MR asserts

RESET low. RESET is one-shot pulsed low for the MR

timeout period after a falling edge on MR. An internal

1.5k

nected if not used. MR can be driven with TTL or CMOS-

logic levels, or with open-drain/collector outputs. Connect

a normally open momentary pushbutton switch from MR

to GND to realize a manual reset function. External

debounce circuitry is not required, as the MAX6467/

MAX6468 respond to the first falling edge on MR and

ignore subsequent falling edges within the reset timeout

period and during the MR debounce period (see Figure

one-shot is ready to trigger a reset on the next MR falling

edge. Connect a 0.1µF capacitor from MR to GND when

using long cables to provide additional noise immunity

(Figure 2).

Microprocessor Supervisory Reset Circuits

with Edge-Triggered, One-Shot Manual Reset

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5

Pin Description

PIN

NAME

FUNCTION

1

GND

Ground

2

RESET

Reset Output. RESET is an active-low open-drain (MAX6467) or push-pull (MAX6468) output. RESET asserts

falling edge of the manual reset input. The open-drain output requires an external pullup resistor.

3

MR

Manual Reset Input. Drive MR low to initiate a reset output. MR controls an edge-triggered one-shot that

asserts RESET low for a fixed MR timeout period when MR is driven low. Internal timing circuitry ignores

switch close and open bounce to ensure proper one-shot reset timing.

GND

GND

MR

GND

RESET

SWITCH

BOUNCE

SWITCH

BOUNCE

SWITCH

BOUNCE

Figure 1. Timing Diagram