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5

Detailed Description

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

known state. The MAX803/MAX809/MAX810 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 MAX803 uses an open-drain output, and the

MAX809/MAX810 have a push-pull output stage.

Connect a pullup resistor on the MAX803’s RESET out-

put to any supply between 0 and 6V.

Applications Information

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

power-down, and brownout conditions, the MAX803/

MAX809/MAX810 are relatively immune to short-duration

Figure 1 shows typical transient duration vs. reset com-

parator overdrive, for which the MAX803/MAX809/

MAX810 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

maximum allowable pulse width decreases. Typically, for

100mV below the reset threshold and lasts 20µs or less

will not cause a reset pulse. A 0.1µF bypass capacitor

additional transient immunity.

Ensuring a Valid Reset Output

no longer sinks current—it becomes an open circuit.

3-Pin Microprocessor Reset Circuits

2

RESET

(MAX803/

MAX809)

is below the reset threshold, and for at

reset threshold.

1

GND

Ground

PIN

NAME

FUNCTION

RESET

(MAX810)

is below the reset threshold, and for at

reset threshold.

3

Supply Voltage (+5V, +3.3V, +3.0V, or

+2.5V)

Selector Guide

TOP MARK

PART/SUFFIX

RESET THRESHOLD (V)

OUTPUT TYPE

SOT

SC70

MAX803L

4.63

OPEN-DRAIN RESET

⎯

AAZ

MAX803M

4.38

OPEN-DRAIN RESET

⎯

ABA

MAX803T

3.08

OPEN-DRAIN RESET

⎯

ABB

MAX803S

2.93

OPEN-DRAIN RESET

⎯

ABC

MAX803R

2.63

OPEN-DRAIN RESET

⎯

ABD

MAX803Z

2.32

OPEN-DRAIN RESET

⎯

ABE

MAX809L

4.63

PUSH-PULL RESET

AAAA

AAN

MAX809M

4.38

PUSH-PULL RESET

ABAA

AAO

MAX809J

4.00

PUSH-PULL RESET

CWAA

⎯

MAX809T

3.08

PUSH-PULL RESET

ACAA

AAP

MAX809S

2.93

PUSH-PULL RESET

ADAA

AAQ

MAX809R

2.63

PUSH-PULL RESET

AFAA

AAR

MAX809Z

2.32

PUSH-PULL RESET

⎯

AAS

MAX810L

4.63

PUSH-PULL RESET

AGAA

AAT

MAX810M

4.38

PUSH-PULL RESET

AHAA

AAU

MAX810T

3.08

PUSH-PULL RESET

AJAA

AAV

MAX810S

2.93

PUSH-PULL RESET

AKAA

AAX

MAX810R

2.63

PUSH-PULL RESET

ALAA

AAW

MAX810Z

2.32

PUSH-PULL RESET

⎯

AAY

Pin Description