Datasheet

BTS4175SGA
Power Stage
Data Sheet 11 Rev.1.0, 2008-04-29
5.3 Inductive Output Clamp
When switching OFF inductive loads with high side switches, the voltage V
OUT
drops below ground potential,
because the inductance intends to continue driving the current. To prevent the destruction of the device due to
high voltages, there is a voltage clamp mechanism implemented that keeps the negative output voltage at a certain
level (
V
S
-V
DS(AZ)
). Please refers to Figure 6 and Figure 7 for details. Nevertheless, the maximum allowed load
inductance is limited.
Figure 6 Output clamp
Figure 7 Switching in inductance timing
Maximum Load inductance
During demagnetization of inductive loads, energy has to be dissipated in the BTS4175SGA. This energy can be
calculated with following equation:
Following equation simplifies under the assumption of
R
L
= 0Ω.
V
BAT
V
OUT
I
L
L, R
L
V
S
OUT
V
DS
LOGIC
IN
V
IN
Output clamp.vsd
GND
IN
V
OUT
I
L
V
S
V
S-
V
DS(AZ)
t
t
t
Switching an inductance.vs
d
t
peak
EV
D
S
AZ()
L
R
L
------- -
×
V
S
V
DS AZ()
–
R
L
----------------------------------------
R
L
I
L
×
V
S
V
DS
AZ()
–
----------------------------------------
⎝⎠
⎛⎞
ln I
L
++×=