Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - system monitor Reset/power-on reset SOT 143 4

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

reset signal whenever the V

supply voltage falls

below a preset threshold, and they keep reset asserted

for the pin-selected reset timeout delay after V

has

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

the correct state for V

down to 1V), while the

MAX822 has an active-high RESET output. The reset

comparator is designed to ignore fast transients on

. Reset thresholds suitable for operation with a vari-

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

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

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

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

Voltages

♦ 2.5µA Supply Current

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

♦ Guaranteed RESET Valid to V

= 1V (MAX821)

♦ Power-Supply Transient Immunity

♦ No External Components

♦ SOT143 Package

MAX821/MAX822

4-Pin µP Voltage Monitors with Pin-Selectable

Power-On Reset Timeout Delay

________________________________________________________________ Maxim Integrated Products 1

SRT

(RESET) RESET

GND

MAX821

MAX822

SOT143

TOP VIEW

( ) ARE FOR MAX822

Pin Configuration

MAX821

MAX822

RESET

(RESET)

RESET

INPUT

GND

µP

( ) ARE FOR MAX822

SRT

20ms

100ms

1ms

__________Typical Operating Circuit

19-1122; Rev 3; 12/05

PART

MAX821LUS-T

MAX821MUS-T 4.38

4.63

NOMINAL V

(V) 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.

Devices are available in both leaded and lead-free packaging.

Specify lead-free by replacing “-T” with “+T” when ordering.

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_ _

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Summary of content (7 pages)

PAGE 1
9-1122; Rev 3; 12/05 4-Pin µP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay The MAX821/MAX822 microprocessor (µP) supervisory circuits monitor power supplies in µP and digital systems. They provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with 5V-powered or 3V-powered circuits. The MAX821/MAX822 also provide a power-on reset timeout delay that is pin selectable to 1ms (max), 20ms (min), or 100ms (min).
PAGE 2
MAX821/MAX822 4-Pin µP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GND) VCC ......................................................................-0.3V to 6.0V All Other Inputs.......................................-0.3V to (VCC + 0.3V) Input Current, VCC, SRT......................................................20mA Output Current, RESET or RESET .......................................
PAGE 3
4-Pin µP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay (VCC = full range, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS SRT Input Capacitance (Note 3) (see Setting the Reset Timeout Delay section) VOL RESET Output Voltage (MAX821) MAX UNITS Internal 20 pF MAX821L/M/P only, ISINK = 3.2mA, VCC = VTH(MIN) 0.4 MAX821R/S/T/U only, ISINK = 1.2mA, VCC = VTH(MIN) 0.
PAGE 4
____________________________Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX82_L/M POWER-DOWN RESET DELAY vs. TEMPERATURE MAX82_R/S/T POWER-DOWN RESET DELAY vs.
PAGE 5
4-Pin µP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay If a brownout condition occurs (VCC dips below the reset threshold), RESET goes low. Any time VCC goes below the reset threshold, the internal timer resets to zero, and RESET goes low. The internal timer begins counting after VCC returns above the reset threshold, and RESET remains low for the reset timeout period. The MAX822 has an active-high RESET output that is the inverse of the MAX821’s RESET output.
PAGE 6
MAX821/MAX822 4-Pin µP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay Ensuring a Valid RESET Output Down to VCC = 0V When VCC falls below 1V, the MAX821 RESET output no longer sinks current—it becomes an open circuit. Therefore, high-impedance CMOS logic inputs connected to the RESET output can drift to undetermined voltages. This presents no problem in most applications, since most µP and other circuitry is inoperative with VCC below 1V.
PAGE 7
4-Pin µP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay SOT-143 4L.EPS PACKAGE OUTLINE, SOT-143, 4L 21-0052 E 1 1 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.