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MAX6711S

4-Pin SC70 Microprocessor Reset Circuits with Manual Reset Input

Maxim Integrated 

4-Pin SC70 Microprocessor Reset Circuits

with Manual Reset Input

_____________________Pin Description

PIN NAME

1

GND

RESET

(MAX6711/

MAX6713)

2

RESET

(MAX6712)

3

MR

4

VCC

FUNCTION

Ground

RESET output remains low while VCC

is below the reset threshold, and for at

least 140ms after VCC rises above the

reset threshold.

RESET output remains high while VCC

is below the reset threshold, and for at

least 140ms after VCC rises above the

reset threshold.

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 20kΩ (typ) pull-up resistor.

It can be driven from a TTL- or CMOS-

logic line, or shorted to ground with a

switch. Leave open or connect to VCC

if unused.

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

or +2.5V)

400

TA = +25°C

320

240

160

MAX671_L/M

80

MAX671_R/S/T/Z

0

1

10

100

1000

RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)

Figure 1. Maximum Transient Duration Without Causing a

Reset Pulse vs. Reset Comparator Overdrive

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

reset signal whenever the VCC supply voltage declines

below a preset threshold, keeping it asserted for at

VCC

MAX6711

RESET

MR

R1

GND

100k

Figure 2. RESET Valid to VCC = Ground Circuit

least 140ms after VCC has risen above the reset thresh-

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 20kΩ 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

Negative-Going VCC Transients

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-

tion negative-going VCC transients (glitches).

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

generated using a negative-going pulse applied to VCC,

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

width a negative-going VCC transient can have without

causing a reset pulse. As the magnitude of the transient

increases (goes farther below the reset threshold), the

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