Smart High-Side Power Switch
BTS5235-2L
Protection Functions
Data Sheet 16 Rev.1.1, 2008-09-01
6.2 Reverse Polarity Protection
In case of reverse polarity, the intrinsic body diode causes power dissipation. Additional power is dissipated by the
integrated ground resistor. Use following formula for estimation of total power dissipation
P
diss(rev)
in reverse
polarity mode.
(3)
The reverse current through the intrinsic body diode has to be limited by the connected load. The current through
sense pins IS1 and IS2 has to be limited (please refer to maximum ratings on Page 8). The current through the
ground pin (GND) is limited internally by
R
GND
. The over-temperature protection is not active during reverse
polarity.
6.3 Over Voltage Protection
In addition to the output clamp for inductive loads as described in Section 5.1.3, there is a clamp mechanism for
over voltage protection. Because of the integrated ground resistor, over voltage protection does not require
external components.
As shown in Figure 12, in case of supply voltages greater than
V
bb(AZ)
, the power transistor switches on and the
voltage across logic part is clamped. As a result, the internal ground potential rises to
V
bb
- V
bb(AZ)
. Due to the ESD
zener diodes, the potential at pin IN1, IN2 and SEN rises almost to that potential, depending on the impedance of
the connected circuitry.
Figure 12 Over Voltage Protection
6.4 Loss of Ground Protection
In case of complete loss of the device ground connections, but connected load ground, the BTS5235-2L securely
changes to or stays in off state.
diss(rev)
V
DS(rev)
I
L
⋅()
all channels
∑
V
bb
2
R
GND
--------------+=
OUT
VBB
OverVolt age .emf
V
OUT
R
GND
logic
GND
IN
IS
SEN
R
SEN
R
IN
ZD
ESD
ZD
AZ
internal ground
