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FEATURES
§ Automatically restarts a microprocessor after
power failure
§ 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
§ 20% tolerance for use with 3.0-volt systems
§ 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
PIN DESCRIPTION
TO-92
1 RST Active High Reset Output
2 VCC Power Supply
3 GND Ground
SOT-23
1 RST Active High Reset Output
2 VCC Power Supply
3 GND Ground
DESCRIPTION
The DS1817 EconoReset uses a precision temperature 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.
DS1817
Active High 3.3V EconoReset
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
DS1817
Econo
Reset
DS1817
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OPERATION - POWER MONITOR
The DS1817 provides the function of detecting out-of-tolerance power supply conditions and warning a
processor based system of impending power failure. 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 (CMOS OUTPUT) Figure 1
APPLICATION EXAMPLE Figure 2
DS1817
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TIMING DIAGRAM: POWER-UP Figure 3
TIMING DIAGRAM: POWER-DOWN Figure 4
DS1817
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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 0.0 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 Voltage @ 0-500 mAVOH VCC
-0.5V
VCC
-0.1V
V1
Output Current @ 2.4V IOH 350 mA2
Output Current @ 0.4V IOL +10 mA 2
Operating Current VCC < 5.5 ICC 28 35 mA3
VCC Trip Point (DS1817-5) VCCTP 2.98 3.06 3.15 V 1
VCC Trip Point (DS1817-10) VCCTP 2.80 2.88 2.97 V 1
VCC Trip Point (DS1817-20) VCCTP 2.47 2.55 2.64 V 1
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
VCC Detect to RST tRPD 25 ms
VCC Slew Rate
(VCCTP (MAX) to VCCTP (MIN))
tF300 ms6
VCC Slew Rate
(VCCTP (MIN) to VCCTP (MAX))
tR0ns
VCC Detect to RST tRPU 100 150 250 ms 4, 5
DS1817
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NOTES:
1. All voltages are referenced to ground.
2. Measured with VCC ³ 2.7V.
3. Measured with RST output open.
4. Measured with 2.7V ³ VCC ³ 3.3V.
5. tR = 5 ms.
6. 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%
SOT-23 PACKAGE
