DS1813.PDF

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DS1813
DS1813
5V EconoReset with Pushbutton
FEATURES
•
PIN ASSIGNMENT
Automatically restarts a microprocessor after power
failure
3
•
Monitors pushbutton for external override
•
Maintains reset for typically 150 ms after V CC returns
to an in–tolerance condition
1
2
•
Reduces need for discrete components
SOT–23 PACKAGE
•
Precision temperature–compensated voltage
reference and voltage sensor
•
Low–cost TO–92 or space saving surface–mount
SOT–23 packages available
123
•
Efficient open–drain output with internal 5.5K W
pull–up resistor
1 23
•
Operating temperature –40
°
C to +85
C
TO–92 PACKAGE
See Mech. Drawings
Section
PIN DESCRIPTIONS
TO –92
1 RST
Active Low Reset Output
2V CC
Power Supply
3 GND
Ground
SO T–23
1 RST
Active Low Reset Output
2V CC
Power Supply
3 GND
Ground
DESCRIPTION
The DS1813 EconoReset uses a precision temperature
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 sig-
nal is kept in the active state for approximately 150 ms to
allow the power supply and processor to stabilize.
The DS1813 also monitors a pushbutton on the reset
output. If the reset line is pulled low, a reset is generated
upon release and will be held in reset output low for typi-
cally 150 ms.
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°
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DS1813
OPERATION – POWER MONITOR
The DS1813 provides the functions of detecting out–of–
tolerance power supply conditions and warning a pro-
cessor–based system of impending power fai lure.
When V CC is detected as out–o f–tole rance, 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 t he p ower
supply and microprocessor to stabilize before RST is re-
leased.
OPERATION – PUSHBUTTON RESET
The DS1813 provides for a pushbutton switch for
manual reset control. When the DS1813 is not in a reset
cyc le, a pushbutton reset can be generated by pulling
the RST pin l ow for at least 1 m s. When the pushbutton is
held low, the RESET 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.
BLOCK DIAGRAM (OPEN–DRAIN OUTPUT) Figure 1
V CC
5.5K
W
RESET
MONITOR
RST
Vcc TOLERANCE
+
AND BIAS
150 ms
DELAY
–
GROUND
T.C. REFERENCE
APPLICATION EXAMPLE Figure 2
V CC
DS1813
RST
MICRO PROCESSOR
RESET
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DS1813
TIMING DIAGRAM: PUSHBUTTON RESET Figure 3
t PB
t RST
RST
V IH
V IL
TIMING DIAGRAM: POWER UP Figure 4
t R
V CCTP (MAX)
V CCTP (MIN)
V CCTP
V CC
t RPU
V OH
RST
TIMING DIAGRAM: POWER DOWN Figure 5
V CC
t F
V CCTP (MAX)
V CCTP
V CCTP (MIN)
RST
t RPD
V OL
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DS1813
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
0.0
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 volts
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 < 5.5
I CC
30
40
m A
4
V CC Trip Point (DS1813–5)
V CCTP
4.50
4.62
4.75
V
1
V CC Trip Point (DS1813–10)
V CCTP
4.25
4.35
4.49
V
1
V CC Trip Point (DS1813–15)
V CCTP
4.00
4.13
4.24
V
1
Internal Pull–Up Resistor
R P
3.50
5.5
7.5
K
6
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
300
ms
V CC Detect to RST
t RPD
2
5
m s
V CC Slew Rate
(V CCTP (MAX) – V CCTP (MIN))
t F
300
m s
7
V CC Slew Rate
(V CCTP (MIN) – V C CTP (MAX))
t R
0
ns
V CC Detect to RST
t RPU
100
150
300
ms
5
Push–button Detect to RST
t PB
1
m
s
Push–button Reset
t PBRST
100
150
300
ms
NOTES:
1. All voltages are referenced to ground.
2. Measured with V CC > 2.7 volts.
3. A 1K W external resistor may be required in some applications for proper operation of the microprocessor
reset control circuit.
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DS1813
4. Measured with RST output open.
5. t R = 5 m s.
6. V OH and I OH are a function of the value of R P and the associated output load conditions.
7. This 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
3
ABCD
1
2
“A”, “B”, &“C” represent the device type.
“D” represents the device tolerance.
810
. . . .
DS1810
A
. . . . . .
5%
811
. . . .
DS1811
B
. . . . . .
10%
812
. . . .
DS1812
C
. . . . . .
15%
813
. . . .
DS1813
D
. . . . . .
20%
815
. . . .
DS1815
816
. . . .
DS1816
817
. . . .
DS1817
818
. . . .
DS1818
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