DS1817
Active High 3.3V EconoReset
DS1817
032598 1/5
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
123
TO–92 PACKAGE
See Mech. Drawings
123
12
3
SOT–23 PACKAGE
See Mech. Drawing
PIN DESCRIPTIONS
TO–92
1 RST Active High Reset Output
2V
CC Power Supply
3 GND Ground
SOT–23
1 RST Active High Reset Output
2V
CC 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 sig-
nal is kept in the active state for approximately 150 ms to
allow the power supply and processor to stabilize.
DS1817
032598 2/5
OPERATION – POWER MONITOR
The DS1817 provides the function of detecting out–of–
tolerance power supply conditions and warning a pro-
cessor 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 approxi-
mately 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
+
–
VCC
GROUND
VCC
TOLERANCE
BIAS
T.C.
REFERENCE
150 ms
DELAY RST
APPLICATION EXAMPLE Figure 2
DS1817
VCC
MICROPROCESSOR
RST
RESET
DS1817
032598 3/5
TIMING DIAGRAM: POWER UP Figure 3
tR
tRPU
VOL
V IN
RST
VCCTP
VCCTP(MAX)
VCCTP(MIN)
TIMING DIAGRAM: POWER DOWN Figure 4
tRPD
tF
VCCTP
VCC
RST
VCCTP(MAX)
VCCTP(MIN)
RST SLEWS WITH VCC
VOH
DS1817
032598 4/5
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 µA VOH VCC–0.5V VCC–0.1V V 1
Output Current @ 2.4V IOH 350 µA 2
Output Current @ 0.4V IOL +10 mA 2
Operating Current VCC < 5.5 ICC 28 35 µA 3
VCC Trip Point (DS1817–5) VCCTP 2.98 3.06 3.15 V 1
VCC T rip Point (DS1817–10) VCCTP 2.80 2.88 2.97 V 1
VCC T rip 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 2 5 µs
VCC Slew Rate
(VCCTP (MAX) to VCCTP (MIN)) tF300 µs 6
VCC Slew Rate
(VCCTP (MIN) to VCCTP (MAX)) tR0 ns
VCC Detect to RST tRPU 100 150 250 ms 4, 5
NOTES:
1. All voltages are referenced to ground.
2. Measured with VCC > 2.7V.
3. Measured with RST output open.
4. Measured with 2.7V > VCC > 3.3V.
5. tR = 5 µs.
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.
DS1817
032598 5/5
PART MARKING CODES
12
3
ABCD
SOT–23 PACKAGE
“A”, “B”, & “C” represents 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%
