DS1814/DS1819
5V and 3.3V MicroMonitor
www.maxim-ic.com
FEATURES
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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擄C to +85擄C
RST
PIN ASSIGNMENT
3
2
1
4
5
SOT-23-5 PACKAGE
See Mech. Drawing
PIN DESCRIPTION
DS181xA
1
RST
2 GND
PBRST
3
4
ST
5 VCC
DS181xB
1
RST
2 GND
3 RST
4
ST
5 VCC
DS181xC
1
RST
2 GND
3 RST
4
PBRST
5 VCC
Active Low Reset Output
Ground
Pushbutton Reset Input
Strobe Input
Power Supply
DEVICE
RST
PBRST
WD
X
X
DS181xA
X
DS181xB
X
X
DS181xC
X
X
x = "DS1814" for 5V devices
x = "DS1819" for 3V devices
X
X
Active Low Reset Output
Ground
Active High Reset Output
Strobe Input
Power Supply
Active Low Reset Output
Ground
Active High Reset Output
Pushbutton Reset Input
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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