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Supervisory Circuits with Watchdog and
Manual Reset in 5-Lead SC70 and SOT-23
ADM823/ADM824/ADM825
Rev. A
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FEATURES
Precision 2.5 V to 5 V power supply monitor
7 reset threshold options: 2.19 V to 4.63 V
140 ms (minimum) reset timeout
Watchdog timer with 1.6 sec timeout (ADM823, ADM824)
Manual reset input (ADM823, ADM825)
Push-pull output stages
RESET
(ADM823)
RESET
, RESET (ADM824/ADM825)
Low power consumption (5 μA)
Guaranteed reset output valid to V
CC
= 1 V
Power supply glitch immunity
Specified over automotive temperature range
5-lead SC70 and SOT-23 packages
APPLICATIONS
Microprocessor systems
Computers
Controllers
Intelligent instruments
Portable equipment
FUNCTIONAL BLOCK DIAGRAM
ADM823
V
CC
V
CC
MR
GND WDI
RESET
RESET
GENERATOR
WATCHDOG
DETECTOR
DEBOUNCE
V
REF
04534-001
Figure 1.
GENERAL DESCRIPTION
The ADM823/ADM824/ADM825 are supervisory circuits
which monitor power supply voltage levels and code execution
integrity in microprocessor-based systems. In addition to
providing power-on reset signals, an on-chip watchdog timer
can reset the microprocessor if it fails to strobe within a preset
timeout period. A reset signal can also be asserted by an
external push-button, through a manual reset input. The three
parts feature different combinations of watchdog input, manual
reset input, and output stage configuration, as shown in
Table 1 .
Each part is available in a choice of seven reset threshold
options ranging from 2.19 V to 4.63 V. The reset and watchdog
timeout periods are fixed at 140 ms (minimum) and 1.6 sec
(typical), respectively.
The ADM823/ADM824/ADM825 are available in 5-lead SC70
and SOT-23 packages and typically consume only 3 μA, making
them suitable for use in low power, portable applications.
Table 1. Selection Table
Output Stage
Part No. Watchdog Timer Manual Reset
RESET
RESET
ADM823 Yes Yes Push-Pull –
ADM824 Yes – Push-Pull Push-Pull
ADM825 – Yes Push-Pull Push-Pull
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