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DS1233
3.3V EconoReset
FEATURES
PIN ASSIGNMENT
§ Automatically restarts microprocessor after
power failure
§ Monitors pushbutton for external override
§ Internal circuitry debounces pushbutton
DALLAS
DS1233A
Econo
Reset
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
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1
§ 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
1 2 3
BOTTOM VIEW
TO-92 PACKAGE
See Mech.
Drawings Section
on Website
4
2
TOP VIEW
SOT-223 PACKAGE
See Mech.
Drawings Section
on Website
§ Operating temperature of -40°C to +85°C
PIN DESCRIPTION
PIN 1 GROUND
PIN 2 RESET
PIN 3 V
CC
PIN 4 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 (V
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.
). When an out-of-tolerance condition is detected, an internal power fail
CC
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
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.
RST signal is asserted. On power-up, RST is kept active
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DS1233A
OPERATION — PUSHBUTTON RESET
The DS1233A provides for a pushbutton switch to be connected to the RST output pin. When the
DS1233A is not in a reset cycle, it continuously monitors the RST signal for a low-going edge. If an edge
is detected, the DS1233A will debounce the switch by pulling the RST line low. After the internal timer
has expired, the DS1233A will continue to monitor the RST line. If the line is still low, the DS1233A will
continue to monitor the line looking for a rising edge. Upon detecting a release, the DS1233A 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
minimum capacitance of 500 pF should be used, along with a parallel external pull-up resistor of 1kW
minimum.
RST and ground. In applications where additional reset current is required, a
BLOCK DIAGRAM Figure 1
APPLICATION EXAMPLE Figure 2
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Page 3
PUSHBUTTON RESET Figure 3
POWER-UP Figure 4
DS1233A
POWER-DOWN Figure 5
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DS1233A
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 V
CC
DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; V
1.2 3.3 5.5 V 1
= 3.3V ± 10%)
DD
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
V
Low Level @ RST
Output Current @ 0.4V I
Operating Current I
VCC Trip Point 10% V
VCC Trip Point 15% V
Output Capacitance C
Pushbutton Detect PB
Pushbutton Release PB
Internal Pull-Up Resistor R
OL
OL
CC
CCTP1
CCTP2
OUT
DV
RD
P
+8 mA
2.80 2.88 2.97 V 1
2.64 2.72 2.80 V 1
0.8 2.0 V 1
0.3 0.8 V 1, 2
3.75 5 6.25
AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; V
0.4 V 1
50
mA
10 pF
kW
= 3.3V ± 10%)
CC
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Reset Active Time t
VCC Detect to RST
V
Slew Rate (2.85V - 2.3V) t
CC
VCC Slew Rate (2.3V - 2.85V) t
Pushbutton Debounce PB
VCC Detect to RST t
t
RST
RPD
F
R
DB
RPU
NOTES:
1) All voltages are referenced to ground.
2) With a 100pF to 0.01mF capacitor connected from
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250 350 450 ms
100 ns
300
ms
0ns
250 350 450 ms
250 350 450 ms
RST to ground.
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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
DS1233A
5V
3.3V
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
DS1833-5 4.5 4.625 4.75 N/A N/A
DS1233A-15 2.64 2.72 2.80 0.8 - 2.0
DS1233A-10 2.8 2.88 2.97 0.8 - 2.0
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