DS1818
3.3V EconoReset with Pushbutton
www.maxim-ic.com
FEATURES
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Automatically restarts a microprocessor after
power failure
Monitors pushbutton for external override
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
Accurate 5%, 10% or 20% power monitoring
Low-cost TO-92 or space saving surface
mount SOT-23 packages available
Efficient open-drain output with internal
5.5 kW pull-up resistor
Operating temperature -40°C to +85°C
PIN ASSIGNMENT
DALLAS
DS1818
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 Low Reset Output
Power Supply
Ground
SOT-23
1
2
3
RST
V
CC
GND
Active Low Reset Output
Power Supply
Ground
DESCRIPTION
The DS1818 EconoReset uses a precision temperature-compensated 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.
The DS1818 also monitors a pushbutton on the reset output. If the reset line is pulled low, a reset is
generated upon release and the DS1818 output will be held in reset output low for typically 150 ms.
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041002
DS1818
OPERATION - POWER MONITOR
The DS1818 provides the functions of detecting out-of-tolerance power supply conditions and warning a
processor-based system of impending power failures. 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 (OPEN-DRAIN OUTPUT)
Figure 1
APPLICATION EXAMPLE
Figure 2
OPERATION - PUSHBUTTON RESET
The DS1818 provides a pushbutton switch for manual reset control. When the DS1818 is not in a reset
cycle, a pushbutton reset can be generated by pulling the
RST
pin low for at least 1
ms.
When the
pushbutton is held low, the
RST
is forced active low and will remain active low for about 150 ms after
the pushbutton is released. See Figure 2 for an application example and Figure 3 for the timing diagram.
TIMING DIAGRAM: PUSHBUTTON RESET
Figure 3
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DS1818
TIMING DIAGRAM: POWER-UP
Figure 4
TIMING DIAGRAM: POWER-DOWN
Figure 5
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DS1818
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 +5V
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
1.0
TYP
MAX
5.5
(-40°C to +85°C)
UNITS
V
NOTES
1
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Output Current @ 0.4 V
Voltage Input Low
Voltage Input High
Operating Current V
CC
< 5.5V
V
CC
Trip Point (DS1818-5)
V
CC
Trip Point (DS1818-10)
V
CC
Trip Point (DS1818-20)
Internal Pull-up Resistor
Output Capacitance
SYMBOL
I
OL
V
IL
V
IH
I
CC
V
CCTP
V
CCTP
V
CCTP
R
P
C
OUT
(-40°C to +85°C; V
CC
=1.2V to 5.5V)
MIN
+10
0.4
0.7
*V
CC
28
2.98
2.80
2.47
3.50
3.06
2.88
2.55
5.5
35
3.15
2.97
2.64
7.5
10
TYP
MAX
UNITS
mA
V
V
mA
V
V
V
kW
pF
NOTES
2, 3
1
1
4
1
1
1
7
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
Pushbutton Detect to
RST
Pushbutton Reset
SYMBOL
t
RST
t
RPD
t
F
t
R
t
RPU
t
PB
t
PBRST
(-40°C to +85°C; V
CC
=1.2V to 5.5V)
MIN
100
300
0
100
1
100
150
250
150
250
TYP
150
2
MAX
250
5
UNITS
ms
ms
ms
ns
ms
ms
ms
5
5, 6
8
NOTES
5
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DS1818
NOTES:
1. All voltages are referenced to ground.
2. Measured with V
CC
³
2.7V.
3. A 1 kW external pull-up resistor may be required in some applications for proper operation of the
microprocessor reset control circuit.
4. Measured with
RST
output open.
5. Measured with 2.7V
£
V
CC
£
3.3V.
6. t
R
= 5
ms.
7. V
OH
and I
OH
are a function of the value of R
P
and the associated output load conditions.
8. The t
F
value is for reference in defining values for t
RPD
and should not be considered a requirement for
proper operation or use of the device.
PART MARKING CODES
“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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