DS1814 Datasheet, PDF (1/8 Pages) Dallas Semiconductor – 5V and 3.3V MicroMonitor

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DS1814/DS1819
5V and 3.3V MicroMonitor
FEATURES
§ Halts and restarts an out-of-control
microprocessor
§ Holds microprocessor in check during power
transients
§ Automatically restarts microprocessor after
power failure
§ Monitors pushbutton for external override
§ Accurate 5%, 10%, or 20% (3V only)
microprocessor power monitoring
§ Eliminates the need for discrete components
§ 20% tolerance for use with 3.0V systems
§ Pin- and function-compatible with the
MAX823/24/25 products
§ Low cost SOT-23-5 package
§ Industrial temperature range: -40°C to +85°C
DEVICE
RST ^RST PBRST ^WD
DS181xA
X
X
X
DS181xB
XX
X
DS181xC
XX
X
x = "DS1814" for 5V devices
x = "DS1819" for 3V devices
PIN ASSIGNMENT
32 1
4
5
SOT-23-5 PACKAGE
See Mech. Drawing
PIN DESCRIPTION
DS181xA
1 RST
2 GND
Active Low Reset Output
Ground
3 PBRST Pushbutton Reset Input
4 ST
5 VCC
Strobe Input
Power Supply
DS181xB
1 RST
2 GND
3 RST
4 ST
5 VCC
Active Low Reset Output
Ground
Active High Reset Output
Strobe Input
Power Supply
DS181xC
1 RST
2 GND
3 RST
Active Low Reset Output
Ground
Active High Reset Output
4 PBRST Pushbutton Reset Input
5 VCC
Power Supply
DESCRIPTION
The DS1814 5-Volt MicroMonitor and the DS1819 3.3V MicroMonitor monitor three vital conditions for
a microprocessor: power supply, software execution, and external override. First, a precision temperature-
compensated reference and comparator circuit monitor the status of V_CC. When an out-of-tolerance
condition occurs, an internal power-fail signal is generated which forces the reset(s) to an active state.
When V_CC returns to an in-tolerance condition, the reset signal is kept in the active state for a minimum of
140ms to allow the power supply and processor to stabilize.
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