ANALOG DEVICES ADM9690 Data Sheet
Summary
The ADM9690 is a dedicated monitoring circuit designed for microprocessors in critical applications, such as computers and industrial controllers. It provides comprehensive hardware oversight by continuously checking both the local power supply voltage and system activity via an integrated watchdog timer. If the processor stalls or if the voltage drops outside specified tolerance levels, the unit generates precise reset signals (RESET(1) and RESET(2)). This ensures maximum reliability, safeguarding your systems from power-fail conditions or software freezes.
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Power Supply and Watchdog Timer
Monitoring Circuit ADM9690 FEATURES FUNCTIONAL BLOCK DIAGRAM
Precision Voltage Monitor (4.31 V) Watchdog Timeout Monitor
Selectable Watchdog Timeout—0.75 ms, 1.5 ms, 12.5 ms, 25 ms
ADM9690
Two RESET Outputs
APPLICATIONS Microprocessor Systems RESET(1)
RESET(1)
OSC SEL1 TIMER
Computers WATCHDOG OSC SEL2 TIMEBASE
Printers RESET(2) RESET(2) TIMER
Controllers Intelligent Instruments WATCHDOG
WATCHDOG
TRANSITION
INPUT (WDI)
DETECTOR
GENERAL DESCRIPTION The watchdog timer monitoring circuit is designed to monitor The ADM9690 contains a voltage monitoring comparator and a the activity on the WDI input. This input is normally connected watchdog timer monitor. It is designed to monitor the 5 to an output line on the µP. Its function is to check that the power supply to a microprocessor and the microprocessor opera- microprocessor has not stalled in an infinite loop. If there is a tion via a watchdog function. period of inactivity for the watchdog timeout period, both reset
outputs are activated. As above, RESET(1) remains low for
The voltage monitoring comparator monitors the voltage on
www.BDTIC.com/ADI 50 ms while RESET(2) remains low for an additional 10 ms.
VMON. If it drops outside tolerance, as will happen during a
The watchdog timer is restarted when RESET(1) goes inactive.
power-fail, two reset signals are generated. Both reset signals go
The actual watchdog timeout period is adjustable using two
active (low) simultaneously. They will remain active while
select inputs SEL1 and SEL2.
VMON is below the threshold, and for 50 ms (RESET(1)) or 60 ms (RESET(2)) after VMON climbs above the reset thresh- The ADM9690 is available in an 8-lead SOIC package. It is old. RESET(1) is intended to provide a power-on reset signal specified over the industrial temperature range. for the µP while RESET(2) is used to hold additional circuitry in a reset state until the µP has regained control following a power-up. The voltage monitoring circuitry remains operational with VCC as low as 2 V.
REV. 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. which may result from its use. No license is granted by implication or Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
otherwise under any patent or patent rights of Analog Devices. Fax: 781/326-8703 © Analog Devices, Inc., 2000
Page Summary Contents For ANALOG DEVICES ADM9690 Data Sheet
Manual Details
| Brand | Analog Devices |
|---|---|
| Pages | 6 |
| File Size | 80.36 KB |
| Published | June 15, 2026 |
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Frequently Asked Questions
What conditions cause the ADM9690 to trigger a reset?
It triggers if the voltage drops outside tolerance, or if the microprocessor stalls for the set timeout period.
How do I adjust the watchdog timer's expected delay?
The actual watchdog timeout period is adjustable using two select inputs (SEL1 and SEL2).
What is the primary function difference between RESET(1) and RESET(2)?
RESET(1) handles power-on reset for the µP, while RESET(2) holds additional circuitry until control is restored.
What is the required operating voltage range?
The ADM9690 must operate on a supply voltage ranging from 4.3 V to 5.5 V.