General Description

The MAX821/MAX822 microprocessor (µP) supervisory

circuits monitor power supplies in µP and digital sys-

tems. They provide excellent circuit reliability and low

cost by eliminating external components and adjust-

ments when used with 5V-powered or 3V-powered cir-

cuits. The MAX821/MAX822 also provide a power-on

reset timeout delay that is pin selectable to 1ms (max),

20ms (min), or 100ms (min).

These devices perform a single function: they assert a

below a preset threshold, and they keep reset asserted

risen above the reset threshold. The only difference

between the two devices is that the MAX821 has an

active-low RESET output (which is guaranteed to be in

MAX822 has an active-high RESET output. The reset

comparator is designed to ignore fast transients on

ety of supply voltages are available.

Low supply current makes the MAX821/MAX822 ideal

for use in portable equipment. These devices come in a

4-pin SOT143 package.

________________________Applications

Bar-Code Scanners

Computers

Controllers

Intelligent Instruments

Critical

µP and µC Power Monitoring

Portable/Battery-Powered Equipment

Features

o Pin-Selectable, Precision Power-On Reset Delay:

1ms (max), 20ms (min), or 100ms (min)

o Precision Monitoring of +3V to +5V Power-Supply

Voltages

o 2.5µA Supply Current

o Guaranteed Over Temperature (-40°C to +125°C)

o Power-Supply Transient Immunity

o No External Components

o SOT143 Package

4-Pin µP Voltage Monitors with Pin-Selectable

Power-On Reset Timeout Delay

________________________________________________________________ Maxim Integrated Products

1

1

2

4

3

SRT

(RESET) RESET

GND

MAX821

MAX822

SOT143

TOP VIEW

( ) ARE FOR MAX822

Pin Configuration

MAX821

MAX822

RESET

(RESET)

RESET

INPUT

GND

GND

µP

( ) ARE FOR MAX822

SRT

20ms

100ms

1ms

__________Typical Operating Circuit

19-1122; Rev 1; 12/99

PART

MAX821LUS-T

MAX821MUS-T

4.38

4.63

TOP MARK*

AZ_ _

BA_ _

Ordering Information

* The first two letters in the package top mark identify the part,

while the remaining two letters are the lot-tracking code.

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.

MAX821PUS-T

4.00

BM_ _

MAX821TUS-T

3.08

BB_ _

MAX821SUS-T

2.93

BC_ _

MAX821UUS-T

2.78

BL_ _

MAX821RUS-T

2.63

BD_ _

MAX822LUS-T

4.63

BF_ _

MAX822MUS-T

4.38

BG_ _

MAX822TUS-T

3.08

BH_ _

MAX822SUS-T

2.93

BJ_ _

MAX822RUS-T

2.63

BK_ _

Note: These parts are offered in the SOT143-4 package, in the

extended temperature range (-40°C to +85°C).