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CAT1232LP, CAT1832
© 2015 SCILLC. All rights reserved. 1 Publication Order Number: CAT1232LP/D
January, 2015 – Rev. 7
Characteristics subject to change without notice
5 V and 3.3 V Supply Monitor, Watchdog Timer,
Manual Reset, with Active High & Low Resets
FEATURES
Selectable reset voltage tolerance
— CAT1232LP for 5 V supply
— CAT1832 for 3.3 V supply
Selectable watchdog period:
150 ms, 600 ms or 1.2 s
Two reset outputs
— Active high, push-pull reset output
— Active low, open-drain reset output
(CAT1232LP)
— Active low, push-pull reset output (CAT1832)
Debounced manual push-button reset
Compact SOIC and MSOP packages
For Ordering Information details, see page 11.
APPLICATIONS
Microprocessor Systems
Portable Equipment
Controllers
Single Board Computers
Instrumentations
Telecommunications
FUNCTIONAL DIAGRAM
DESCRIPTION
The CAT1232LP and CAT1832 microprocessor
supervisors can halt and restart a “hung-up” or
“stalled” microprocessor, restart a microprocessor
after a power failure, and debounce a manual/push-
button microprocessor reset switch. The devices are
drop in replacements for the Maxim/Dallas
Semiconductor DS1232LP and DS1832 supervisors
Precision reference and comparator circuits monitor
the 5 V or 3.3 V system power supply voltage, V
CC
.
During power-up or when the power supply falls
outside selectable tolerance limits, both the RESET
and RESET
¯¯¯¯¯¯
become active. After the power supply
voltage rises above the RESET threshold voltage, the
reset signals remain active for a minimum of 250ms,
allowing the power supply and system processor to
stabilize. The trip-point tolerance
input, TOL, selects
the trip level tolerance to be either 5% or 10% for the
CAT1232LP 5 V supply and 10% or 20% for the
CAT1832 3.3 V supply.
Each device has a push-pull, active HIGH reset
output. The CAT1232LP also has an open drain,
active LOW reset output while the CAT1832 also has
a push-pull, active LOW reset output.
A debounced manual reset input activates the reset
outputs and holds them active for a minimum period of
250 ms after being released.
Also included is a watchdog timer to reset a
microprocessor that has stopped due to a software or
hardware failure. Three watchdog time-out periods are
selectable: 150 ms, 600 ms and 1.2 s. If the ST
¯¯
input
is not strobed low before the watchdog time out period
expir
es, the reset signals become active for a
minimum of 250 ms.
ST
RESET
PBRST
40kΩ
TOL
V
CC
–
+
Reference
V
CC
RESET
TD
Push Button Debounce
Watchdog Timebase Selection
Reset &
Watchdog Timer
(CAT1232LP)
Watchdog Transition Detector
RESET
(CAT1832)
Tolerance Selection
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