1 of 5
111999
FEATURES
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 k
=pull-up resistor
Operating temperature -40
°
C to +85
°
C
PIN ASSIGNMENT
PIN DESCRIPTION
TO-92
1
RST
Active Low Reset Output
2 V
CC
Power
Supply
3 GND Ground
SOT-23
1
RST
Active Low Reset Output
2 V
CC
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 (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.
DS1818
3.3V EconoReset with Pushbutton
www.dalsemi.com
1
2
3
SOT-23 PACKAGE
1 2 3
1 2 3
TO-92 PACKAGE
See Mech.
Drawings Section
DS1818
2 of 5
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
µ
s. 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
3 of 5
TIMING DIAGRAM: POWER-UP Figure 4
TIMING DIAGRAM: POWER-DOWN Figure 5
DS1818
4 of 5
ABSOLUTE MAXIMUM RATINGS*
Voltage on V
CC
Pin Relative to Ground
-0.5V to +7.0V
Voltage on
RST
Relative to Ground
-0.5V to +5V
CC
+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
V
CC
1.0
5.5
V
1
DC ELECTRICAL CHARACTERISTICS (-40
°
C to +85
°
C; V
CC
=1.2V to 5.5V)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Output Current @ 0.4 V
I
OL
+10
mA
2, 3
Voltage Input Low
V
IL
0.4
V
1
Voltage Input High
V
IH
0.7
*V
CC
V
1
Operating Current V
CC
< 5.5V
I
CC
28
35
µ
A
4
V
CC
Trip Point (DS1818-5)
V
CCTP
2.98
3.06
3.15
V
1
V
CC
Trip Point (DS1818-10)
V
CCTP
2.80
2.88
2.97
V
1
V
CC
Trip Point (DS1818-20)
V
CCTP
2.47
2.55
2.64
V
1
Internal Pull-up Resistor
R
P
3.50
5.5
7.5
k
7
Output Capacitance
C
OUT
10
pF
AC ELECTRICAL CHARACTERISTICS (-40
°
C to +85
°
C; V
CC
=1.2V to 5.5V)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
RESET Active Time
t
RST
100
150
250
ms
5
V
CC
Detect to
RST
t
RPD
2
5
µ
s
V
CC
Slew Rate
(V
CCTP
(MAX) to V
CCTP
(MIN))
t
F
300
µ
s
8
V
CC
Slew Rate
(V
CCTP
(MIN) to V
CCTP
(MAX))
t
R
0
ns
V
CC
Detect to
RST
t
RPU
100
150
250
ms
5, 6
Pushbutton Detect to
RST
t
PB
1
µ
s
Pushbutton Reset
t
PBRST
100
150
250
ms
5
DS1818
5 of 5
NOTES:
1.
All voltages are referenced to ground.
2.
Measured with V
CC
2.7V.
3.
A 1 k
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
µ
s.
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%
PDF 
ZIP