LM3709 Datasheet, PDF (1/11 Pages) National Semiconductor (TI) – 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 µP’s output lines for activity. If no output transition occurs
during the watchdog timeout period, reset is activated.
Features
n Standard Reset Threshold voltage: 3.08V
n Custom Reset Threshold voltages: For other voltages
between 2.2V and 5.0V in 10mV increments, contact
National Semiconductor Corp.
n No external components required
n Manual-Reset input
n RESET (LM3708) or RESET (LM3709) outputs
n Precision supply voltage monitor
n Factory programmable Reset and Watchdog Timeout
Delays
n Available in micro SMD package for minimum footprint
n ±0.5% Reset threshold accuracy at room temperature
n ±2% Reset threshold accuracy over temperature
extremes
n Reset assertion down to 1V V_CC (RESET option only)
n 28 µA V_CC supply current
Applications
n Embedded Controllers and Processors
n Intelligent Instruments
n Automotive Systems
n Critical µP Power Monitoring
Typical Application
© 2002 National Semiconductor Corporation DS200117
20011703
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