LM3708/LM3709 Microprocessor Supervisory Circuits with Low Line Output, Manual Reset and
Watchdog Timer
June 2002
LM3708/LM3709
Microprocessor Supervisory Circuits with Low Line
Output, Manual Reset and Watchdog Timer
General Description
The LM3708/LM3709 series of microprocessor supervisory
circuits provide the maximum flexibility for monitoring power
supplies and battery controlled functions in systems without
backup batteries. The LM3708/LM3709 series are available
in a 9-bump micro SMD package.
Built-in features include the following:
Reset: Reset is asserted during power-up, power-down, and
brownout conditions. RESET is guaranteed down to V
CC
of
1.0V.
Manual Reset Input: An input that asserts reset when pulled
low.
Low Line Output: This early power failure warning indicator
goes low when the supply voltage drops to a value which is
2% higher than the reset threshold voltage.
Watchdog Timer: The WDI (Watchdog Input) monitors one of
the 碌P鈥檚 output lines for activity. If no output transition occurs
during the watchdog timeout period, reset is activated.
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Custom Reset Threshold voltages: For other voltages
between 2.2V and 5.0V in 10mV increments, contact
National Semiconductor Corp.
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No external components required
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Manual-Reset input
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RESET (LM3708) or RESET (LM3709) outputs
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Precision supply voltage monitor
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Factory programmable Reset and Watchdog Timeout
Delays
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Available in micro SMD package for minimum footprint
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鹵
0.5% Reset threshold accuracy at room temperature
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鹵
2% Reset threshold accuracy over temperature
extremes
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Reset assertion down to 1V V
CC
(RESET option only)
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28 碌A(chǔ) V
CC
supply current
Applications
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Embedded Controllers and Processors
Intelligent Instruments
Automotive Systems
Critical 碌P Power Monitoring
Features
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Standard Reset Threshold voltage: 3.08V
Typical Application
20011703
漏 2002 National Semiconductor Corporation
DS200117
www.national.com