DS1233A
3.3V EconoReset
www.maxim-ic.com
FEATURES
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PIN ASSIGNMENT
Automatically restarts microprocessor after
power failure
Monitors pushbutton for external override
Internal circuitry debounces pushbutton
switch
Maintains reset for 350ms after VCC returns to
an in-tolerance condition or pushbutton
released
Accurate 10% or 15% microprocessor 3.3V
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 5kW pull-up resistor
Operating temperature of -40°C to +85°C
DALLAS
DS1233A
Econo
Reset
1
1 2 3
1 2 3
BOTTOM VIEW
TO-92 PACKAGE
See Mech.
Drawings Section
on Website
2 4 3
TOP VIEW
SOT-223 PACKAGE
See Mech.
Drawings Section
on Website
PIN DESCRIPTION
PIN 1
PIN 2
PIN 3
PIN 4
GROUND
RESET
VCC
GROUND (SOT-223 ONLY)
DESCRIPTION
The DS1233A 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 (VCC). When an out-of-tolerance condition is detected, an internal power fail
signal is generated which forces reset to the active state. When VCC returns to an in-tolerance condition,
the reset signal is kept in the active state for approximately 350ms to allow the power supply and
processor to stabilize. The second function of the DS1233A is pushbutton reset control. The DS1233A
debounces a pushbutton closure and will generate a 350ms reset pulse upon release.
OPERATION — POWER MONITOR
The DS1233A provides the functions of detecting out-of-tolerance power supply conditions and warning
a processor-based system of impending power failure. When VCC 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 350ms 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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