FUNCTIONAL BLOCK DIAGRAMS

WATCHDOG

TRANSITION

DETECTOR

WATCHDOG

INPUT (WDI)

POWER-FAIL

INPUT (PFI)

POWER-FAIL

OUTPUT (

PFO)

WATCHDOG

OUTPUT (

WDO)

RESET

*VOLTAGE REFERENCE = 4.65V (ADM705), 4.40V (ADM706)

ADM705/

ADM706

RESET &

WATCHDOG

TIMEBASE

RESET

GENERATOR

MR

250 A

WATCHDOG

TIMER

4.65V*

1.25V

1.25V

4.65V*

POWER-FAIL

INPUT (PFI)

POWER-FAIL

OUTPUT (

PFO)

RESET

*VOLTAGE REFERENCE = 4.65V (ADM707), 4.40V (ADM708)

ADM707/

ADM708

RESET

GENERATOR

MR

250 A

RESET

REV. B

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

Low Cost P

Supervisory Circuits

ADM705–ADM708

FEATURES

Guaranteed

RESET Valid with V

190

A Quiescent Current

Precision Supply-Voltage Monitor

4.65 V (ADM705/ADM707)

4.40 V (ADM706/ADM708)

200 ms Reset Pulsewidth

Debounced TTL/CMOS Manual Reset Input (

MR)

Independent Watchdog Timer—1.6 sec Timeout

(ADM705/ADM706)

Active High Reset Output (ADM707/ADM708)

Voltage Monitor for Power-Fail or Low Battery

Warning

Superior Upgrade for MAX705–MAX708

Also Available in MicroSOIC Packages

APPLICATIONS

Microprocessor Systems

Computers

Controllers

Intelligent Instruments

Critical

P Monitoring

Automotive Systems

Critical

P Power Monitoring

GENERAL DESCRIPTION

The ADM705–ADM708 are low cost

µP supervisory circuits.

They are suitable for monitoring the 5 V power supply/battery

and can also monitor microprocessor activity.

The ADM705/ADM706 provide the following functions:

1. Power-On Reset output during power-up, power-down and

brownout conditions. The

RESET output remains opera-

2. Independent watchdog timeout,

WDO, that goes low if the

watchdog input has not been toggled within 1.6 seconds.

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

battery detection or to monitor a power supply other than

5V.

4. An active low debounced manual reset input (

MR).

The ADM707/ADM708 differ in that:

1. A watchdog timer function is not available.

2. An active high reset output in addition to the active low

output is available.

Two supply-voltage monitor levels are available. The ADM705/

ADM707 generate a reset when the supply voltage falls below

4.65 V, while the ADM706/ADM708 require that the supply

fall below 4.40 V before a reset is issued.

All parts are available in 8-lead DIP and SOIC packages. The

ADM707 and ADM708 are also available in space-saving

microSOIC packages.

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

Tel: 781/329-4700

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

Fax: 781/326-8703

© Analog Devices, Inc., 2000