DS1812
5V EconoReset with Active
High Push-Pull Output
www.maxim-ic.com
FEATURES
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Automatically restarts a microprocessor after
power failure
Maintains reset for 150 ms after V
CC
returns
to an in-tolerance condition
Reduces need for discrete components
Precision temperature-compensated voltage
reference and voltage sensor
Low-cost TO-92, or space saving surface
mount SOT-23 packages available
Push-pull active high output
Operating temperature -40°C to +85°C
PIN ASSIGNMENT
DALLAS
DS1812
Econo
Reset
3
1
2
1 2 3
1 2 3
BOTTOM VIEW
TO-92 PACKAGE
See Mech.
Drawings Section
On Website
TOP VIEW
SOT-23 PACKAGE
See Mech.
Drawings Section
On Website
PIN DESCRIPTION
TO-92
1
2
3
RST
V
CC
GND
Active High Reset Output
Power Supply
Ground
SOT-23
1
2
3
RST
V
CC
GND
Active High Reset Output
Power Supply
Ground
DESCRIPTION
The DS1812 EconoReset uses a precision temperature reference and comparator circuit 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 150 ms to allow the power supply and
processor to stabilize.
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041002
DS1812
OPERATION - POWER MONITOR
The DS1812 provides the function 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, the RST
signal is asserted. On power-up, RST is kept active for approximately 150 ms after the power supply has
reached the selected tolerance. This allows the power supply and microprocessor to stabilize before RST
is released.
BLOCK DIAGRAM (CMOS OUTPUT)
Figure 1
APPLICATION EXAMPLE
Figure 2
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DS1812
TIMING DIAGRAM: POWER-UP
Figure 3
TIMING DIAGRAM: POWER-DOWN
Figure 4
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DS1812
ABSOLUTE MAXIMUM RATINGS*
Voltage on V
CC
Pin Relative to Ground
Voltage on RST Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
*
-0.5V to +7.0V
-0.5V to V
CC
+0.5V
-40°C to +85°C
-55°C to +125°C
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
PARAMETER
Supply Voltage
SYMBOL
V
CC
MIN
0.0
TYP
MAX
5.5
(-40°C to +85°C)
UNITS
V
NOTES
1
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage @ 0-500
mA
Output Current @ 2.4 volts
Output Current @ 0.4 volts
Operating Current V
CC
< 5.5
V
CC
Trip Point (DS1812-5)
V
CC
Trip Point (DS1812-10)
V
CC
Trip Point (DS1812-15)
Output Capacitance
SYMBOL
V
OH
I
OH
I
OL
I
CC
V
CCTP
V
CCTP
V
CCTP
C
OUT
(-40°C to +85°C; V
CC
=1.2V to 5.5V)
MIN
V
CC
-0.5V
+10
30
4.50
4.25
4.00
4.62
4.35
4.13
40
4.75
4.49
4.24
10
TYP
V
CC
-0.1V
350
MAX
UNITS
V
mA
mA
mA
V
V
V
pF
NOTES
1
2
2
3
1
1
1
AC ELECTRICAL CHARACTERISTICS
PARAMETER
RESET Active Time
V
CC
Detect to RST
V
CC
Slew Rate
(V
CCTP
(MAX) to V
CCTP
(MIN))
V
CC
Slew Rate
(V
CCTP
(MIN) to V
CCTP
(MAX))
V
CC
Detect to RST
SYMBOL
t
RST
t
RPD
t
F
t
R
t
RPU
(-40°C to +85°C; V
CC
=1.2V to 5.5V)
MIN
100
300
0
100
150
300
TYP
150
2
MAX
300
5
UNITS
ms
ms
ms
ns
ms
4
NOTES
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DS1812
NOTES:
1. All voltages are referenced to ground.
2. Measured with V
CC
³
2.7 volts.
3. Measured with RST output open.
4. t
R
= 5
ms.
PART MARKING CODES
SOT-23 PACKAGE
“A”, “B”, &“C” represent the device type.
810
-
DS1810
811
-
DS1811
812
-
DS1812
813
-
DS1813
815
-
DS1815
816
-
DS1816
817
-
DS1817
818
-
DS1818
“D” represents the device tolerance.
A
-
5%
B
-
10%
C
-
15%
D
-
20%
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