DS1233
5V EconoReset
www.dalsemi.com
FEATURES
Automatically restarts microprocessor after
power failure
Monitors pushbutton for external override
Internal circuitry debounces pushbutton
switch
Maintains reset for 350 ms after V
CC
returns
to an in-tolerance condition or pushbutton
released
Accurate 5%, 10% or 15% microprocessor 5V
power supply monitoring
Reduces need for discrete components
Precision temperature-compensated voltage
reference and voltage sensor
Low-cost TO-92 package or surface-mount
SOT-223 package
Internal 5k鈩?pull-up resistor
Operating temperature of -40掳C to +85掳C
PIN ASSIGNMENT
DALLAS
DS1233
Econo
Reset
1
1 2 3
1 2 3
TO-92 PACKAGE
See Mech.
Drawings Section
2 4 3
SOT-223 PACKAGE
See Mech.
Drawings Section
PIN DESCRIPTION
PIN 1
PIN 2
PIN 3
PIN 4
GROUND
RESET
V
CC
GROUND (SOT-223 ONLY)
DESCRIPTION
The DS1233 EconoReset monitors two vital conditions for a microprocessor: power supply and external
override. A precision temperature compensated reference and comparator circuit are used to monitor the
status of the power supply (V
CC
). When an out-of-tolerance condition is detected, an internal power-fail
signal is generated which forces reset to the active state. When V
CC
returns to an in-tolerance condition,
the reset signal is kept in the active state for approximately 350 ms to allow the power supply and
processor to stabilize. The second function of the DS1233 is pushbutton reset control. The DS1233
debounces a pushbutton closure and will generate a 350 ms reset pulse upon release.
OPERATION - POWER MONITOR
The DS1233 provides the functions of detecting out-of-tolerance power supply conditions and warning a
processor-based system of impending power failure. When V
CC
is detected as out-of-tolerance, as
defined by the tolerance of the part selected, the
RST
signal is asserted. On power-up,
RST
is kept active
for approximately 350 ms after the power supply has reached the selected tolerance. This allows the
power supply and microprocessor to stabilize before
RST
is released.
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