Specifications

OUT
VS
Vol,off
FAULT
OPEN LOAD
VBAT
ST/CS
Rpu
TPS1H100-Q1
www.ti.com SLVSCM2A –OCTOBER 2014–REVISED JANUARY 2014
Figure 36. Open Load Detection Circuit
8.3.4.3 Short to Battery Detection
Short to battery has the same detection mechanism and behavior as open load both in the on-state and off-state.
Refer to the fault truth table, Table 1, for more details. In the on-state, the reverse current flows through the FET
instead of the body diode, leading to less power dissipation. Thus, the worst case for off-state is when reverse
current occurs. In the off-state, if V
OUT
– V
S
< V
F
, short to battery can be detected. (V
F
is the body diode forward
voltage and typically 0.7 V.) However, the reverse current will not occur. If V
OUT
– V
S
> V
F
, short to battery can
be detected, and the reverse current should be smaller than I
rev2
to ensure the survival of the device. TI
recommends switching on the input for lower power dissipation or the reverse block circuitry for the supply. Refer
to Reverse Current Protection for more external protection circuitry information.
8.3.4.4 Reverse Polarity Detection
Reverse polarity has the same detection mechanism and behavior as open load both in the on-state and off-
state. Refer to the fault truth table, Table 1, for more details. In the on-state, the reverse current flows through
the FET instead of the body diode, leading to less power dissipation. Thus, the worst case off-state is when
reverse current occurs. In off-state, the reverse current should be smaller than I
rev1
to ensure the survival of the
device. Refer to Reverse Current Protection for more external protection circuitry information.
8.3.4.5 Thermal Protection Behavior
Both the absolute temperature thermal shutdown and the dynamic temperature thermal swing diagnostic and
protection are built in to the device to increase the max reliability of the power FET. Thermal swing is active
when the temperature of the power FET is increasing sharply, that is ΔT = T
DMOS
– T
Logic
> T
sw
, then the output is
shut down, and the ST pin goes low, or the CS pin is pulled up to V
CS,h
. It auto-recovers and clears the fault
signal until ΔT = T
DMOS
– T
Logic
< T
sw
– T
hys
. Thermal swing function improves the device’s reliability against
repetitive fast thermal variation, as shown in Figure 37. Multiple thermal swings are triggered before thermal
shutdown happens. Thermal shutdown is active when absolute temperature T > T
SD
. When active, the output is
shut down, and the ST pin goes low, or the CS pin pulled up to V
CS,h
. The output is auto-recovered when T <
T
SD
– T
hys
; the current limit is reduced to I
lim,tsd
, or half of the programmable current limit value, to avoid repeated
thermal shutdown. However, the thermal shutdown fault signal and half current limit value are not cleared until
the junction temperature decreases to less than T
SD,rst
.
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