BTS3028SDR Datasheet, PDF (17/22 Pages) Infineon Technologies AG – Smart Low Side Power Switch

HITFET - BTS3028SDR
Smart low side power switch
Protection Functions
6.2
Overvoltage Protection
When switching off inductive loads with low-side switches, the Drain-Source voltage V_D rises above battery
potential, because the inductance intends to continue driving the current.
Drain
Source
OutputClamp .emf
Figure 13 Output Clamp
The BTS3028SDR is equipped with a voltage clamp mechanism that prevents the Drain-Source voltage to rise
above V_D(Clamp) . See Figure 13 and Figure 14 for more details.
IN
5V
0
ID
Turn off due to
over temperature or short circuit
t
VD
t
VC lamp
Vbat
Figure 14 Switching an Inductance
t
InductiveLoad .emf
While demagnetization of inductive loads, energy has to be dissipated in the BTS3028SDR.
This energy can be calculated by the following equation:
E = V_D(Clamp) ⋅
V_{-----b--a---t---–----}V_{----D----(-C----l-a--m----p---)}
⋅
⎛
ln⎜1
–
-------------^R----^L----^â‹---^I---^L-------------
⎞
⎟
R_L
⎝ ^Vbat ^{– V}_D(Clamp) ⎠
+ I_L
⋅ --^L----
R_L
Following equation simplifies under assumption of R_L = 0
E
=
1_--
2
LI_L2
⋅
⎛
⎜1
⎝
–
----------------^V----^b--^a---^t---------------
V_bat – V_D(Clamp)
⎞
⎟
⎠
Figure 16 shows the inductance / current combination the BTS3028SDR can handle.
Datasheet
17
Rev. 1.0, 2009-12-06