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a

ADM691A/ADM693A/ADM800L/M

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

World Wide Web Site: http://www.analog.com

Fax: 617/326-8703

© Analog Devices, Inc., 1996

Microprocessor

Supervisory Circuits

FUNCTIONAL BLOCK DIAGRAM

CHIP ENABLE

OUTPUT

CONTROL

OSC IN

OSC SEL

WATCHDOG

INPUT (WDI)

POWER FAIL

INPUT (PFI)

ADM691A/ADM693A

ADM800L/ADM800M

1.25V

WATCHDOG

TIMER

RESET &

WATCHDOG

TIMEBASE

RESET &

GENERATOR

BATT ON

LOW LINE

RESET

RESET

WATCHDOG

OUTPUT (

WDO)

POWER FAIL

OUTPUT (PFO)

WATCHDOG

TRANSITION DETECTOR

FEATURES

Low Power Consumption:

Precision Voltage Monitor

2% Tolerance on ADM800L/M

Reset Time Delay—200 ms, or Adjustable

1

A Standby Current

Automatic Battery Backup Power Switching

Fast Onboard Gating of Chip Enable Signals

Also Available in TSSOP Package (ADM691A)

APPLICATIONS

Microprocessor Systems

Computers

Controllers

Intelligent Instruments

Automotive Systems

Critical

P Power Monitoring

GENERAL DESCRIPTION

The ADM691A/ADM693A/ADM800L/ADM800M family of

supervisory circuits offers complete single chip solutions for

power supply monitoring and battery control functions in

microprocessor systems. These functions include

µP reset,

backup-battery switchover, watchdog timer, CMOS RAM write

protection, and power-failure warning. The family of products

provides an upgrade for the MAX691A/93A/800M family of

products.

All parts are available in 16-pin DIP and SO packages. The

ADM691A is also available in a space-saving TSSOP package.

The following functionality is provided:

1. Power-on reset output during power-up, power-down and

brownout conditions. The circuitry remains operational with

2. Battery backup switching for CMOS RAM, CMOS micro-

processor or other low power logic.

3. A reset pulse if the optional watchdog timer has not been

toggled within a specified time.

4. A 1.25 V threshold detector for power fail warning, low bat-

tery detection, or to monitor a power supply other than +5 V.

CMOS

RAM

OSC IN

OSC SEL

BAT

ON

LOW LINE

RESET

RESET

PFO

WDI

WDO

I/O LINE

NMI

A0–A15

µP

POWER

µP

ADDRESS

DECODE

ADM691A

ADM693A

ADM800L

ADM800M

GND

PFI

BATTERY

0.1µF

+5V

NC

R2

R1

INPUT

POWER

7805

SYSTEM

STATUS

INDICATORS

Figure 1. Typical Application