Datasheet

BTS4175SGA
Protection Mechanisms
Data Sheet 15 Rev.1.0, 2008-04-29
In the case the supply voltage is in between of
V
S(SC) max
and V
DS(AZ)
, the output transistor is still operational and
follow the input. If the channel is in ON state, parameters are no longer warranted and lifetime is reduced
compared to normal mode. This specially impacts the short circuit robustness, as well as the maximum energy
E
AS
the device can handle.
6.4 Reverse Polarity Protection
In case of reverse polarity, the intrinsic body diode causes power dissipation. The current in this intrinsic body
diode is limited by the load itself. Additionally, the current into the ground path and the logical pins has to be limited
to the maximum current described in Chapter 4.1, sometimes with an external resistor. Figure 10 shows a typical
application. The
R
GND
resistor is used to limit the current in the zener protection of the device. Resistors R
IN
and
R
ST
is used to limit the current in the logic of the device and in the ESD protection stage. The recommended value
for
R
GND
is 150Ω, for R
ST 0/1
= 15kΩ. In case the over voltage is not considered in the application, R
GND
can be
replaced by a Shottky diode.
Figure 10 Reverse polarity protection with external components
6.5 Overload Protection
In case of overload, or short circuit to ground, the BTS4175SGA offers two protections mechanisms.
Current limitation
At first step, the instantaneous power in the switch is maintained to a safe level by limiting the current to the
maximum current allowed in the switch
I
L(LIM)
. During this time, the DMOS temperature is increasing, which affects
the current flowing in the DMOS.
Thermal protection
At thermal shutdown, the device turns OFF and cools down. A restart mechanism is used, after cooling down, the
device restarts and limits the current to
I
L(SCR)
. Figure 11 shows the behavior of the current limitation as a function
of time.
Micro controller
(e.g. XC22xx)
GND
OUT
IN
V
S
V
BAT
R
ST
ST
R
IN
R
GND
Z
dbody
ZD
ESD
Reverse Polarity single with diag.vs
d
-V
DS(REV)
I
L(nom )
R
STPU
VccµC