Datasheet

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Overdrive (mV)
Max Transient Duration (Ps)
LM3722, LM3723, LM3724
www.ti.com SNVS154E –MAY 2001–REVISED MARCH 2013
NEGATIVE-GOING V
CC
TRANSIENTS
The LM3722/LM3723/LM3724 are relatively immune to short negative-going transients or glitches on V
CC
.
Figure 14 shows the maximum pulse width a negative-going V
CC
transient can have without causing a reset
pulse. In general, as the magnitude of the transient increases, going further below the threshold, the maximum
allowable pulse width decreases. Typically, a V
CC
transient that goes 125 mV below the reset threshold and lasts
40 µs or less will not cause a reset pulse. A 0.1 µF bypass capacitor mounted as close as possible to the V
CC
pin
will provide additional transient rejection.
Figure 14. Maximum Transient Duration without Causing a Reset Pulse vs. Reset Comparator Overdrive
INTERFACING TO µPS WITH BIDIRECTIONAL RESET PINS
Microprocessors with bidirectional reset pins, such as the Motorola 68HC11 series, can be connected to the
LM3722 RESET output. To ensure a correct output on the LM3722 even when the microprocessor reset pin is in
the opposite state, connect a 4.7kΩ resistor between the LM3722 RESET output and the µP reset pin, as shown
in Figure 15. Buffer the LM3722 RESET output to other system components.
Typical Application Circuits
Figure 15. Interfacing to Microprocessors with Bidirectional Reset I/O
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Product Folder Links: LM3722 LM3723 LM3724