Dallas Semiconductor DS1818R-5-T-R, DS1818R-20-T-R, DS1818R-10-T-R, DS1818-5, DS1818-20 Datasheet
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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 kΩ=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 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 (VCC). When an out-of-tolerance condition i s detected, an intern al
power-fail signal is generated which fo rces reset to the acti ve 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
12
3
SOT-23 PACKAGE
1 2 3
1 2 3
TO-92 PACKAGE
See Mech.
Drawings Section
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, th e RST
signal is asserted. On power-up, RST is kept active for a pproximately 150 ms after the power suppl y has
reached the selected tolerance. This allows the power supply and microprocessor to stabilize befor e 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 µs. 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
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