Datasheet

SPIKE NOM LOAD
L
V V I
C
= + ´
STRAIGHTWIRE
4 length
L 0.2 length ln 0.75
diameter
æ ö
æ ö
´
æ ö
@ ´ ´ -
ç ÷
ç ÷
ç ÷
ç ÷
è ø
è ø
è ø
( )
2
2
SPIKE NOM
LI
C
V V
=
-
TPS2458
SLUS916B –FEBRUARY 2009–REVISED MAY 2010 www.ti.com
Transient Protection
TPS2458 devices in deployed systems are not likely to have long, inductive feeds or long load wires. However, it
is always advised that an analysis be performed to determine the need for transient protection. When the
TPS2458 interrupts current flow any inductance on the input will tend to cause a positive voltage spike on the
input and any inductance on the output will tend to cause a negative voltage spike on the output. The following
equations allow the designer to make a reasonably accurate prediction of the voltage spike due to interruptions in
current.
where
• V
NOM
is the nominal voltage at terminal being analyzed
• L is the combined inductance of feed to RTN lines.
• C is the capacitance at point of disconnect.
• I
LOAD
is the current through terminal at T
DISCONNECT
• (9)
This equation can be used to calculate the capacitance required to limit the voltage spike to a desired level
above the nominal voltage.
(10)
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