Vbb disconnect with charged external
inductive load
4
high 3 IN
Vbb
OUT 6
1
ST
PROFET
OUT 7
D
5 IS
GND
2
RL
L
Vbb
If other external inductive loads L are connected to the PROFET,
additional elements like D are necessary.
Inductive Load switch-off energy
dissipation
E bb
=
Vbb
3 IN
1 ST
5 IS
4
Vbb
PROFET
GND
2
E AS
OUT 6
OUT 7
ELoad
EL
ER
Energy stored in load inductance:
EL = 1/2·L·I2L
While demagnetizing load inductance, the energy
dissipated in PROFET is
EAS= Ebb + EL - ER= VON(CL)·iL(t) dt,
with an approximate solution for RL > 0 Ω:
EAS=
2IL·R· LL·(Vbb
+
|VOUT(CL)|)·
ln
(1+
IL·RL
|VOUT(CL)|
)
BTS 640 S2
Semiconductor Group
Page 10
2003-Oct-01