3 V, Voltage Monitoring

Microprocessor Supervisory Circuits

ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T

Rev. C

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibilityis assumedbyAnalogDevicesforitsuse,norforanyinfringementsof patentsorother

rightsofthirdpartiesthatmayresultfromitsuse.Specificationssubjecttochangewithoutnotice.No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.

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

Tel: 781.329.4700

www.analog.com

Fax: 781.461.3113

©1995–2008 Analog Devices, Inc. All rights reserved.

FEATURES

Precision supply voltage monitor

2.63 V (ADM706P, ADM706R, ADM708R)

2.93 V (ADM706S, ADM708S)

3.08 V (ADM706T, ADM708T)

100 μA quiescent current

200 ms reset pulse width

Debounced manual reset input (MR)

Independent watchdog timer

1.6 second timeout (ADM706x)

Reset output

Active high (ADM706P)

Active low (ADM706R, ADM706S, ADM706T)

Both active high and active low (ADM708R, ADM708S,

ADM708T)

Voltage monitor for power-fail or low battery warning

Superior upgrade for MAX706P/R/S/T, MAX708R/S/T

APPLICATIONS

Microprocessor systems

Computers

Controllers

Intelligent instruments

Critical microprocessor monitoring

Battery-operated systems

Portable instruments

FUNCTIONAL BLOCK DIAGRAMS

WATCHDOG

TRANSITION

DETECTOR

WATCHDOG

INPUT (WDI)

POWER-FAIL

INPUT (PFI)

POWER-FAIL

OUTPUT (PFO)

WATCHDOG

OUTPUT (WDO)

RESET,

(P = RESET)

*VOLTAGE REFERENCE = 2.63V (P/R), 2.93V (S), 3.08V (T)

ADM706P/ADM706R/

ADM706S/ADM706T

WATCHDOG

TIMER

RESET AND

WATCHDOG

TIMEBASE

RESET

GENERATOR

MR

70μA

1.25V

Figure 1. ADM706P/ADM706R/ADM706S/ADM706T

1.25V

INPUT (PFI)

* VOLTAGE REFERENCE = 2.63V (R), 2.93V (S), 3.08V (T)

POWER-FAIL

RESET

RESET

GENERATOR

MR

70μA

RESET

POWER-FAIL

OUTPUT (PFO)

ADM708R/ADM708S/

ADM708T

Figure 2. ADM708R/ADM708S/ADM708T

GENERAL DESCRIPTION

The ADM706P/ADM706R/ADM706S/ADM706T and the

ADM708R/ADM708S/ADM708T microprocessor supervisory

circuits are suitable for monitoring either 3 V or 3.3 V power

supplies.

The ADM706P/ADM706R/ADM706S/ADM706T provide

power-supply monitoring circuitry that generate a reset output

during power-up, power-down, and brownout conditions. The

Independent watchdog monitoring circuitry is also provided.

This is activated if the watchdog input has not been toggled

within 1.6 seconds.

In addition, there is a 1.25 V threshold detector for power-fail

warning, low battery detection, or to monitor an additional power

supply. An active low debounced MR input is also included.

The ADM706R, ADM706S, and ADM706T are identical except

for the reset threshold monitor levels, which are 2.63 V, 2.93 V, and

3.08 V, respectively. The ADM706P is identical to the ADM706R in

that the reset threshold is 2.63 V. It differs only in that it has an

active high reset output.

The ADM708R/ADM708S/ADM708T provide similar functio-

nality as the ADM706R/ADM706S/ADM706T and only differ

in that a watchdog timer function is not available. Instead, an

active high reset output (RESET) is provided in addition to the

active low (RESET) output.

All parts are available in narrow 8-lead PDIP and 8-lead SOIC

packages.