Datasheet

TPS2480
TPS2481
SLUS939B –APRIL 2010–REVISED DECEMBER 2010 www.ti.com
The TPS2480/81 responds rapidly to the short circuit as seen in Figure 15. The falling OUT voltage is the result
of the external FET and C
O
currents through the short circuit impedance. The internal GATE clamp causes the
GATE voltage to follow the output voltage down and subsequently limits the negative V
DS
to 1.2 V. The rapidly
rising fault current overdrives the GATE amplifier causing it to overshoot and rapidly turn the external FET off by
sinking current to ground. The external FET slowly turns back on as the GATE amplifier recovers; the external
FET then settles to an equilibrium operating point determined by the power limiting circuit.
Figure 15. Current Limit Onset
Minimal input voltage overshoot appears in Figure 15 because a local 100-mF bypass capacitor and very short
input leads were used. The input voltage would overshoot as the input current abruptly drops in a typical
application due to the stored energy in the input distribution inductance. The exact waveforms seen in an
application depend upon many factors including parasitics of the voltage distribution, circuit layout, and the short
itself.
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