CAT1232LP Datasheet, PDF (1/12 Pages) Catalyst Semiconductor – 5V and 3.3V Supply Voltage Monitor and Reset Circuit

CAT1232LP, CAT1832
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
V_CC
TOL
PBRST
TD
ST
Tolerance Selection +
V_CC
Reference
–
40kΩ
Push Button Debounce
Watchdog Timebase Selection
Watchdog Transition Detector
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 R¯¯E¯S¯E¯T¯ 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 S¯¯T input
is not strobed low before the watchdog time out period
expires, the reset signals become active for a
minimum of 250 ms.
RESET
(CAT1232LP)
Reset &
Watchdog Timer
RESET
RESET
(CAT1832)
© 2009 SCILLC. All rights reserved.
1
Characteristics subject to change without notice
Doc. No. MD-3018 Rev. F