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DS1818
3.3V EconoReset with Pushbutton
FEATURES
Automatically restarts a microprocessor after
power failure
Monitors pushbutton for external override
Maintains reset for 150 ms after VCC 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 k=pull-up resistor
Operating temperature -40°C to +85°C
PIN ASSIGNMENT
3
12
SOT-23 PACKAGE
123
123
TO-92 PACKAGE
See Mech.
Drawings Section
PIN DESCRIPTION
TO-92
1 RST
2 VCC
3 GND
Active Low Reset Output
Power Supply
Ground
SOT-23
1 RST
2 VCC
3 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 (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 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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DS1818
OPERATION - POWER MONITOR
The DS1818 provides the functions of detecting out-of-tolerance power supply conditions and warning a
prowcwewss.Doart-abSaheseetd4Us.cyosmtem of impending power failures. When VCC 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 µs. 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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TIMING DIAGRAM: POWER-UP Figure 4
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TIMING DIAGRAM: POWER-DOWN Figure 5
DS1818
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ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC Pin Relative to Ground
Vowltwawg.eDaotanShReSetT4UR.coemlative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
-0.5V to +7.0V
-0.5V to +5VCC +0.5V
-40°C to +85°C
-55°C to +125°C
260°C for 10 seconds
DS1818
* 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
SYMBOL MIN TYP
Supply Voltage
VCC 1.0
(-40°C to +85°C)
MAX UNITS NOTES
5.5 V
1
DC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
Output Current @ 0.4 V
IOL
Voltage Input Low
VIL
Voltage Input High
VIH
Operating Current VCC < 5.5V
VCC Trip Point (DS1818-5)
VCC Trip Point (DS1818-10)
VCC Trip Point (DS1818-20)
Internal Pull-up Resistor
Output Capacitance
ICC
VCCTP
VCCTP
VCCTP
RP
COUT
(-40°C to +85°C; VCC=1.2V to 5.5V)
MIN TYP MAX UNITS NOTES
+10 mA 2, 3
0.4 V
1
0.7 V 1
*VCC
28 35
µA
4
2.98 3.06 3.15
V
1
2.80 2.88 2.97
V
1
2.47 2.55 2.64
V
1
3.50 5.5
7.5
k
7
10 pF
AC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
RESET Active Time
tRST
VCC Detect to RST
tRPD
VCC Slew Rate
(VCCTP (MAX) to VCCTP (MIN))
tF
VCC Slew Rate
(VCCTP (MIN) to VCCTP (MAX))
tR
VCC Detect to RST
tRPU
Pushbutton Detect to RST
tPB
Pushbutton Reset
tPBRST
(-40°C to +85°C; VCC=1.2V to 5.5V)
MIN TYP MAX UNITS NOTES
100 150 250
ms
5
2 5 µs
300 µs 8
0 ns
100 150 250 ms 5, 6
1 µs
100 150 250
ms
5
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NOTES:
1. All voltages are referenced to ground.
DS1818
2. wMwwe.DasautarSehdeewt4Uit.hcoVm CC 2.7V.
3. A 1 kexternal 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 VCC 3.3V.
6. tR = 5 µs.
7. VOH and IOH are a function of the value of RP and the associated output load conditions.
8. The tF value is for reference in defining values for tRPD 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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