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5

Detailed Description

Reset Output

A microprocessor’s (µP’s) reset input starts the µP in a

known state. The MAX6711/MAX6712/MAX6713 assert

reset to prevent code-execution errors during power-

up, power-down, or brownout conditions. They assert a

below a preset threshold, keeping it asserted for at

old. The MAX6713 uses an open-drain output, and the

MAX6711/MAX6712 have a push-pull output stage.

Connect a pull-up resistor on the MAX6713’s RESET

output to any supply between 0 and 6V.

Manual Reset Input

Many µP-based systems require manual reset capabili-

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

logic circuitry to initiate a reset. Reset remains asserted

while MR is low, and for at least 140ms after MR returns

high. This input has an internal 20k

Ω pullup resistor, so

it can be left open if it is not used. MR can be driven

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

lector outputs. To create a manual reset function, con-

nect a normally open momentary switch from MR to

ground; external debounce circuitry is not required. If

MR is driven from long cables or if the device is used in

a noisy environment, connecting a 0.1µF capacitor from

MR to ground provides additional noise immunity.

Applications Information

In addition to issuing a reset to the µP during power-up,

power-down, and brownout conditions, the MAX6711/

MAX6712/MAX6713 are relatively immune to short-dura-

Figure 1 shows typical transient duration vs. reset com-

parator overdrive, for which the MAX6711/MAX6712/

MAX6713 do not generate a reset pulse. The graph was

starting 0.5V above the actual reset threshold and end-

ing below it by the magnitude indicated (reset compara-

tor overdrive). The graph indicates the maximum pulse

causing a reset pulse. As the magnitude of the transient

increases (goes farther below the reset threshold), the

4-Pin SC70 Microprocessor Reset Circuits

with Manual Reset Input

R1

100k

GND

MR

MAX6711

RESET

2

RESET

(MAX6711/

MAX6713)

is below the reset threshold, and for at

reset threshold.

1

GND

Ground

PIN

NAME

FUNCTION

RESET

(MAX6712)

is below the reset threshold, and for at

reset threshold.

_____________________Pin Description

400

320

0

1

100

1000

160

80

240

10

°C

MAX671_L/M

MAX671_R/S/T/Z

Figure 1. Maximum Transient Duration Without Causing a

Reset Pulse vs. Reset Comparator Overdrive

3

MR

Manual Reset Input. RESET (RESET)

remains asserted as long as MR is low,

and for at least 140ms after MR is

deasserted. This active-low input has

an internal 20k

Ω (typ) pull-up resistor.

It can be driven from a TTL- or CMOS-

logic line, or shorted to ground with a

if unused.

4

Supply Voltage (+5.0V, +3.3V, +3.0V,

or +2.5V)