1 of 5 122001
FEATURES
§ 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 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 5kW pull-up resistor
§ Operating temperature of -40°C to +85°C
PIN ASSIGNMENT
PIN DESCRIPTION
PIN 1 GROUND
PIN 2 RESET
PIN 3 VCC
PIN 4 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 (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 DS1233 is pushbutton reset control. The DS1233
debounces a pushbutton closure and will generate a 350ms 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 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.
DS1233
5V EconoReset
www.maxim-ic.com
1 2 3
1 2 3
BOTTOM VIEW
TO-92 PACKAGE
See Mech.
Drawings Section
on Website
2
3
4
TOP VIEW
SOT-223 PACKAGE
See Mech.
Drawings Section
on Website
1
DALLAS
DS1233
Econo
Reset
DS1233
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OPERATION — PUSHBUTTON RESET
The DS1233 provides for a pushbutton switch to be connected to the RST output pin. When the DS1233
is not in a reset cycle, it continuously monitors the RST signal for a low going edge. If an edge is
detected, the DS1233 will debounce the switch by pulling the RST line low. After the internal timer has
expired, the DS1233 will continue to monitor the RST line. If the line is still low, the DS1233 will
continue to monitor the line looking for a rising edge. Upon detecting a release, the DS1233 will force the
RST line low and hold it low for 350ms.
NOTE:
For proper operation with an external pushbutton, a capacitor between 100pF and 0.01mF must be
connected between RST and ground. In applications where additional reset current is required, a
minimum capacitance of 500pF should be used, along with a parallel external pull-up resistor of
1kW minimum.
BLOCK DIAGRAM Figure 1
APPLICATION EXAMPLE Figure 2
DS1233
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PUSHBUTTON RESET Figure 3
POWER UP Figure 4
POWER DOWN Figure 5
DS1233
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ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC Pin Relative to Ground -0.5V to +7.0V
Voltage on I/O Relative to Ground -0.5V to VCC +0.5V
Operating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature 260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS (-40°C to +85°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Supply Voltage VCC 1.2 5.0 5.5 V 1
DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VDD = 5V ± 10%)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Low Level @ RST VOL 0.4 V 1
Output Current @ 0.4V IOL +8 mA
Operating Current ICC 50 mA
VCC Trip Point 5% VCCTP0 4.50 4.625 4.75 V 1
VCC Trip Point 10% VCCTP1 4.25 4.375 4.49 V 1
VCC Trip Point 15% VCCTP2 4.0 4.125 4.24 V 1
Output Capacitance COUT 10 pF
Pushbutton Detect PBDV 1.8 3.3 V 1
Pushbutton Release PBRD 0.3 0.8 V 1, 2
Internal Pull-Up Resistor RP3.75 5 6.25 kW
AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC = 5V ± 10%)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
RESET Active Time tRST 250 350 450 ms
VCC Detect to RST tRPD 100 ns
VCC Slew Rate (4.75V - 4.00V) tF300 ms
VCC Slew Rate (4.00V - 4.75V) tR0ns
Pushbutton Debounce PBDB 250 350 450 ms
VCC Detect to RST tRPU 250 350 450 ms
NOTES:
1) All voltages are referenced to ground.
2) With a 100pF to 0.01mF capacitor connected from RST to ground.
DS1233
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ECONORESET SELECTION GUIDE
VCC TRIP POINT PUSHBUTTON DETECT
MIN TYP MAX MIN TYP MAX
DS1233-15 4.0 4.125 4.24 1.8 - 3.3
DS1233-10 4.25 4.375 4.49 1.8 - 3.3
DS1233-5 4.5 4.625 4.75 1.8 - 3.3
DS1233D-15 4.0 4.125 4.24 N/A N/A
DS1233D-10 4.25 4.375 4.49 N/A N/A
DS1233D-5 4.5 4.625 4.75 N/A N/A
DS1833-15 4.0 4.125 4.24 N/A N/A
DS1833-10 4.25 4.375 4.49 N/A N/A
5V
DS1833-5 4.5 4.625 4.75 N/A N/A
DS1233A-15 2.64 2.72 2.80 0.8 - 2.0
3.3V
DS1233A-10 2.8 2.88 2.97 0.8 - 2.0
