Low Voltage Supervisory Circuits with
Watchdog & Manual Reset in 5-Lead SOT-23
Preliminary Technical Data
ADM6821–ADM6825


Rev. PrA
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FEATURES
Precision Low Voltage Monitoring down to 1.8V
9 Reset Threshold Options:
1.58V to 4.63V
140ms (Min) Reset Timeout
Watchdog Timer with 1.6s Timeout
Manual Reset Input
Reset Output Stages
Push-Pull Active-Low
Open-Drain Active-Low
Push-Pull Active-High
Low Power Consumption (3µA)
Guaranteed Reset Output valid to VCC=1V
Power Supply Glitch Immunity
Specified from -40°C to +125°C
5-Lead SOT-23 Package

APPLICATIONS
Microprocessor Systems
Computers
Controllers
Intelligent Instruments
Portable Equipment


GENERAL DESCRIPTION
The ADM6821-ADM6825 are supervisory circuits which
monitor power supply voltage levels and code execution
integrity in microprocessor-based systems. As well as 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 means of 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.
FUNCTIONAL BLOCK DIAGRAM

X52X45X53X45X54
X47X45X4EX45X52X41X54X4FX52
X4DX52 X44X45X42X4FX55X4EX43X45
X47X4EX44
X52X45X53X45X54
X56
X43X43
X56
X52X45X46
X56
X43X43
X41X44X4DX36X38X32X31
X57X41X54X43X48X44X4FX47
X44X45X54X45X43X54X4FX52
X57X44X49









Each part is available in a choice of 9 reset threshold options
ranging from 1.58V to 4.63V. The reset and watchdog timeout
periods are fixed at 140ms (min) and 1.6s (typ), respectively.
The ADM6821-ADM6825 are available in 5-lead SOT-23
packages and typically consume only 3µA, making them
suitable for use in low power portable applications.


Table 1. Selection Table

Output Stage
Part No. Watchdog Timer Manual Reset
RESET

RESET
ADM6821 Yes Yes - Push-Pull
ADM6822 Yes Yes Open-Drain -
ADM6823 Yes Yes Push-Pull -
ADM6824 Yes - Push-Pull Push-Pull
ADM6825 - Yes Push-Pull Push-Pull