CAT1232, CAT1832
5V and 3.3V Supply Monitor, Watchdog Timer,
Manual Reset, with Active High & Low Resets
FEATURES
Selectable reset voltage tolerance
— CAT1232LP for 5V supply
— CAT1832 for 3.3V supply
Selectable watchdog period:
150ms, 600ms or 1.2s
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
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 5V or 3.3V 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 5V supply and 10% or 20% for the
CAT1832 3.3V 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
250ms 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: 150ms, 600ms and 1.2s. If the ST input is
not strobed low before the watchdog time out period
expires, the reset signals become active for a
minimum of 250ms.
APPLICATIONS
Microprocessor Systems
Portable Equipment
Controllers
Single Board Computers
Instrumentations
Telecommunications
FUNCTIONAL DIAGRAM
V
CC
TOL
V
CC
Reference
40kΩ
PBRST
TD
ST
Push Button Debounce
Watchdog Timebase Selection
Watchdog Transition Detector
–
Tolerance Selection
+
RESET
(CAT1232LP)
RESET
RESET
(CAT1832)
Reset &
Watchdog Timer
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. MD-3018 Rev. D
CATALYST [ CATALYST SEMICONDUCTOR ]
