Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
The MAX6821–MAX6825 are low-voltage microproces-
sor (µP) supervisory circuits that combine voltage mon-
itoring, watchdog timer, and manual reset input func-
tions in a 5-pin SOT23 package. Microprocessor super-
visory circuits significantly improve system reliability and
accuracy compared to separate ICs or discrete compo-
nents. These devices assert a reset signal whenever the
monitored voltage drops below its preset threshold, keep-
ing it asserted for a minimum timeout period after VCC rises
above the threshold. In addition, a watchdog timer monitors
against code execution errors. A debounced manual reset
is also available. The MAX6821–MAX6825 monitor voltag-
es from +1.8V to +5.0V. These outputs are guaranteed to
be in the correct state for VCC down to +1.0V.
Nine preprogrammed reset threshold voltages are
available (see the Threshold Suffix Guide). The
MAX6821, MAX6822, and MAX6823 all have a manual
reset input and a watchdog timer. The MAX6821 has
push-pull RESET, the MAX6822 has open-drain RESET,
and the MAX6823 has push-pull RESET. The MAX6824
has a watchdog timer and both push-pull RESET and
push-pull RESET. The MAX6825 has a manual reset
input and both push-pull RESET and push-pull RESET.
The Selector Guide explains the functions offered in
this series of parts.
●● Set-Top Boxes
●● Computers and Con-
●● Embedded Controllers
●● Intelligent Instruments
●● Critical µP Monitoring
(RESET) MAX6821 ONLY
Pin Configurations continued at end of data sheet.
Typical Operating Circuit appears at end of data sheet.
●● Monitors +1.8V, +2.5V, +3.0V, +3.3V, +5.0V Supplies
●● 140ms (min) Reset Timeout Delay
●● 1.6s Watchdog Timeout Period (MAX6821/MAX6822/
●● Manual Reset Input (MAX6821/MAX6822/MAX6823/
●● Three Reset Output Options
●● Guaranteed Reset Valid to VCC = +1.0V
●● Immune to Short Negative VCC Transients
●● No External Components
●● Small 5-Pin SOT23 Packages
MAX6821_UK-T -40°C to +125°C
MAX6822_UK-T -40°C to +125°C
MAX6823_UK-T -40°C to +125°C
MAX6824_UK-T -40°C to +125°C
MAX6825_UK-T -40°C to +125°C
*Insert the desired suffix letter (from the table below) into the
blank to complete the part number
Devices are available in both leaded and lead(Pb)-free packag-
ing.Specify lead-free by replacing “-T” with “+T” when ordering.
Threshold Suffix Guide
Note: Bold indicates standard versions. Samples are typically
available for standard versions only. All parts require a 2.5k
minimum order increment. Contact factory for availability.
Selector Guide appears at end of data sheet.
19-1868; Rev 3; 7/14