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
V
CC
250H9262A
V
CC
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
V
CC
250H9262A
V
CC
RESET
REV.B
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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 H9262P
Supervisory Circuits
ADM705–ADM708
FEATURES
Guaranteed RESET Valid with V
CC
= 1V
190 H9262A 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 H9262P Monitoring
Automotive Systems
Critical H9262P 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-
tional with V
CC
as low as 1 V.
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