Datasheet

Data Sheet 23 Rev. 2.1, 2011-09-01
PROFET™+ 12V
BTS5045-2EKA
Protection Functions
6.4 Reverse Polarity Protection
In case of reverse polarity, the intrinsic body diodes of the power DMOS 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 logic pins
has to be limited to the maximum current described in Chapter 4.1 with an external resistor. Figure 17 shows a
typical application.
R
GND
resistor is used to limit the current in the Zener protection of the device. Resistors R
DSEL
,
R
DEN
, and R
IN
are used to limit the current in the logic of the device and in the ESD protection stage. R
SENSE
is used
to limit the current in the sense transistor which behaves as a diode. The recommended value for
R
DEN
= R
DSEL
=
R
IN
= R
SENSE
= 4.7 kΩ. Z
GND
can be either a 150 Ω resistor or Schottky diode with 1 kΩ resistor in parallel.
In case the overvoltage is not considered in the application,
R
GND
can be replaced by a Schottky diode and 1kΩ
resistor in parallel. Optionally a capacitor in parallel is recommended for EMC reasons.
During reverse polarity, no protection functions are available.
Figure 17 Reverse Polarity Protection with External Components
6.5 Overload Protection
In case of overload, such as high inrush of cold lamp filament, or short circuit to ground, the BTS5045-2EKA offers
several protection mechanisms.
6.5.1 Current Limitation
At first step, the instantaneous power in the switch is maintained at a safe value by limiting the current to the
maximum current allowed in the switch
I
L(SC)
. During this time, the DMOS temperature is increasing, which affects
the current flowing in the DMOS. The current limitation value is
V
DS
dependent. Figure 18 shows the behavior of
the current limitation as a function of the drain to source voltage.
INx
DEN
IS
ZD
ESD GND
OUTx
V
S
-V
S(REV)
Z
D(AZ)
LOGIC
DSEL
Reverse Polarity.vsd
Z
DS(AZ)
IN0
R
IN
R
DEN
R
DSE L
R
SENSE
R
IS
V
DS(REV)
Micro controller
protection diodes
Z
IS(AZ)
Z
GND