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122001
FEATURES
Automatically restarts microprocessor after
power failure
Monitors pushbutton for external override
Internal circuitry debounces pushbutton
switch
Maintains reset for 350ms after V
CC
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 -40C to +85C
PIN ASSIGNMENT
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
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 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 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 350ms after the power supply has reached the selected tolerance. This allows the power
supply and microprocessor to stabilize before
RST
is released.
DS1233A
3.3V 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
DS1233A
Econo
Reset
DS1233A
2 of 5
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 0.01
mF must be
connected between
RST
and ground. In applications where additional reset current is required, a
minimum capacitance of 500 pF should be used, along with a parallel external pull-up resistor of 1k
W
minimum.
BLOCK DIAGRAM
Figure 1
APPLICATION EXAMPLE Figure 2
DS1233A
3 of 5
PUSHBUTTON RESET
Figure 3
POWER-UP
Figure 4
POWER-DOWN Figure 5
DS1233A
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ABSOLUTE MAXIMUM RATINGS*
Voltage on V
CC
Pin Relative to Ground
-0.5V to +7.0V
Voltage on I/O Relative to Ground
-0.5V to V
CC
+0.5V
Operating Temperature Range
-40C to +85C
Storage Temperature Range
-55C to +125C
Soldering Temperature
260C 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
1.2
3.3
5.5
V
1
DC ELECTRICAL CHARACTERISTICS (-40
C to +85C; V
DD
= 3.3V
10%)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Low Level @
RST
V
OL
0.4
V
1
Output Current @ 0.4V
I
OL
+8
mA
Operating Current
I
CC
50
mA
V
CC
Trip Point 10%
V
CCTP1
2.80
2.88
2.97
V
1
V
CC
Trip Point 15%
V
CCTP2
2.64
2.72
2.80
V
1
Output Capacitance
C
OUT
10
pF
Pushbutton Detect
PB
DV
0.8
2.0
V
1
Pushbutton Release
PB
RD
0.3
0.8
V
1, 2
Internal Pull-Up Resistor
R
P
3.75
5
6.25
k
W
AC ELECTRICAL CHARACTERISTICS (-40
C to +85C; V
CC
= 3.3V
10%)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Reset Active Time
t
RST
250
350
450
ms
V
CC
Detect to
RST
t
RPD
100
ns
V
CC
Slew Rate (2.85V - 2.3V)
t
F
300
ms
V
CC
Slew Rate (2.3V - 2.85V)
t
R
0
ns
Pushbutton Debounce
PB
DB
250
350
450
ms
V
CC
Detect to RST
t
RPU
250
350
450
ms
NOTES:
1) All voltages are referenced to ground.
2) With a 100pF to 0.01
mF capacitor connected from
RST
to ground.
DS1233A
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ECONORESET SELECTION GUIDE
V
CC
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
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