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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 kW pull-up resistor
§ Operating temperature -40°C to +85°C
PIN ASSIGNMENT
PIN DESCRIPTION
TO-92
1 RST Active Low Reset Output
2 VCC Power Supply
3 GND Ground
SOT-23
1 RST Active Low Reset Output
2 VCC Power Supply
3 GND 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.
DS1818
3.3V EconoReset with Pushbutton
www.maxim-ic.com
12
3
TOP VIEW
SOT-23 PACKAGE
See Mech.
Drawings Section
On Website
1 2 3
1 2 3
BOTTOM VIEW
TO-92 PACKAGE
See Mech.
Drawings Section
On Website
DALLAS
DS1818
Econo
Reset
DS1818
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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 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 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
DS1818
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TIMING DIAGRAM: POWER-UP Figure 4
TIMING DIAGRAM: POWER-DOWN Figure 5
DS1818
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ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC Pin Relative to Ground -0.5V to +7.0V
Voltage on RST Relative to Ground -0.5V to +5VCC +0.5V
Operating Temperature -40°C to +85°C
Storage Temperature -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 VCC 1.0 5.5 V 1
DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC=1.2V to 5.5V)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Output Current @ 0.4 V IOL +10 mA 2, 3
Voltage Input Low VIL 0.4 V 1
Voltage Input High VIH 0.7
*VCC
V1
Operating Current VCC < 5.5V ICC 28 35 mA4
VCC Trip Point (DS1818-5) VCCTP 2.98 3.06 3.15 V 1
VCC Trip Point (DS1818-10) VCCTP 2.80 2.88 2.97 V 1
VCC Trip Point (DS1818-20) VCCTP 2.47 2.55 2.64 V 1
Internal Pull-up Resistor RP3.50 5.5 7.5 kW7
Output Capacitance COUT 10 pF
AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC=1.2V to 5.5V)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
RESET Active Time tRST 100 150 250 ms 5
VCC Detect to RST tRPD 25 ms
VCC Slew Rate
(VCCTP (MAX) to VCCTP (MIN))
tF300 ms8
VCC Slew Rate
(VCCTP (MIN) to VCCTP (MAX))
tR0ns
VCC Detect to RST tRPU 100 150 250 ms 5, 6
Pushbutton Detect to RST tPB 1ms
Pushbutton Reset tPBRST 100 150 250 ms 5
DS1818
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NOTES:
1. All voltages are referenced to ground.
2. Measured with VCC 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 £ VCC £ 3.3V.
6. tR = 5 ms.
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%
