TLE8110EE Datasheet, PDF (21/72 Pages) Infineon Technologies AG – Smart Multichannel Low Side Switch with Parallel Control and SPI Interface

FLEX
Smart Multi-Channel Switch
Power Outputs
7.2
Description of the Clamping Structure
When switching off inductive loads, the potential at pin OUT rises to V_DS(CL) potential, because the inductance
intends to continue driving the current. The voltage clamping is necessary to prevent destruction of the device,
see Figure 10 for the principle clamping circuit. Nevertheless, the maximum allowed load inductance is limited.
V_bat
V _DScl
OUT
L,
I_D
R_L
V
DS
GND
OutputClamp.vsd
Figure 10 Principle Clamping Structure
Maximum Load Inductance
During demagnetization of inductive loads, energy has to be dissipated in the device. This energy can be
calculated with following equation:
E = V_DS(CL) ⋅
V_{-----b--a---t-t---}–_-----V_{----D---S---c--l}
⋅

ln1
–
---------^R----^L----^â‹---^I---^L---------


R_L
 ^V_batt ^{– V}_DScl 
+ I_L
⋅ --^L----
R_L
(1)
Following equation simplifies under the assumption of R_L = 0:
E
=
1_--
2
L
I_L2
⋅ ----------^V----^D----^S---^c--^l---------
V_DScl – V_Batt
(2)
The maximum energy, which is converted into heat, is limited by the thermal design of the component.
The Repetitive Clamping Energies E_AR as defined in the following Chapter 7.3, Item 7.3.4 (and following items)
are representing cummulated operating scenarios for one channel group with:
• normal operating condition with a typical battery voltage of V_Batt = 16V and an ambient temperature of
typically T_a = 125°C.
• cold operation with a typical battery voltage of typically V_Batt = 13.5V and an ambient temperature of
typically T_a = -40°C.
• generator defect with a typical battery voltage of V_Batt = 18V and an ambient temperature of typically T_a =135°C.
The Power Dissipation P_v is typically considered with P_v = 3W during normal operation. This power dissipation
changes during the other operating conditions according the thermal behaviour of R_DSon and the load Resistance
R_L. The interaction of both, together with an assumed typical R_thja = 7.5K/W, the given average junction
temperature T_j is considered as the start temperature for the clamping process.
Due to the fact, that the maximum possible Repetitive Clamping Energy E_AR varies with the Load Current I_D,
partially optional operating points are specified within the scenarios. Those optional operating points are not
considered as cummulative clamping pulses to the scenario.
Data Sheet
21
Rev. 1.0, 2009-06-15