REV. 0

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

Microprocessor

Supervisory Circuits

ADM8690–ADM8695

FEATURES

Upgrade for ADM690/ADM695, MAX690–MAX695

Specified Over Temperature

Low Power Consumption (0.7 mW)

Precision Voltage Monitor

Low Switch On-Resistance 0.7

Normal,

7

in Backup

High Current Drive (100 mA)

Watchdog Timer—100 ms, 1.6 s, or Adjustable

400 nA Standby Current

Automatic Battery Backup Power Switching

Extremely Fast Gating of Chip Enable Signals (3 ns)

Voltage Monitor for Power Fail

Available in TSSOP Package

APPLICATIONS

Microprocessor Systems

Computers

Controllers

Intelligent Instruments

Automotive Systems

FUNCTIONAL BLOCK DIAGRAMS

ADM8691

ADM8693

ADM8695

RESET AND

WATCHDOG

TIMEBASE

RESET

GENERATOR

WATCHDOG

TRANSITION DETECTOR

WATCHDOG

TIMER

1.3V

LOW LINE

RESET

RESET

WATCHDOG

OUTPUT (

WDO)

POWER FAIL

OUTPUT (

PFO)

OSC IN

OSC SEL

WATCHDOG

INPUT (WDI)

POWER FAIL

INPUT (PFI)

BATT ON

4.40V (ADM8693)

ADM8690

ADM8692

ADM8694

RESET

POWER FAIL

OUTPUT (

PFO)

WATCHDOG

INPUT (WDI)

POWER FAIL

INPUT (PFI)

4.40V (ADM8692)

200ms (ADM8694)

WATCHDOG

TRANSITION DETECTOR

(1.6s)

RESET

1.3V

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., 1997

GENERAL DESCRIPTION

The ADM8690–ADM8695 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 complete family provides a variety of configurations to sat-

isfy most microprocessor system requirements.

The ADM8690, ADM8692 and ADM8694 are available in

8-pin DIP packages and provide:

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

brownout conditions. The

RESET output remains opera-

2. Battery backup switching for CMOS RAM, CMOS

microprocessor or other low power logic.

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

toggled within a specified time.

4. A 1.3 V threshold detector for power fail warning, low battery

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

The ADM8691, ADM8693 and ADM8695 are available in

16-pin DIP and small outline packages (including TSSOP) and

provide three additional functions:

1. Write protection of CMOS RAM or EEPROM.

2. Adjustable reset and watchdog timeout periods.

3. Separate watchdog timeout, backup battery switchover, and

The ADM8690–ADM8695 family is fabricated using an ad-

vanced epitaxial CMOS process combining low power con-

sumption (0.7 mW), extremely fast Chip Enable gating (3 ns)

and high reliability.

low as 1 V. In addition, the power switching circuitry is de-

signed for minimal voltage drop thereby permitting increased

output current drive of up to 100 mA without the need of an

external pass transistor.