TLE8110EE datasheet(21/72 Pages) INFINEON

21 / 72 page

Data Sheet

Rev. 1.0, 2009-06-15

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 VDS(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.

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:

(1)

Following equation simplifies under the assumption of

L = 0:

(2)

The maximum energy, which is converted into heat, is limited by the thermal design of the component.

The Repetitive Clamping Energies

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 VBatt = 16V and an ambient temperature of

typically Ta = 125°C.

•

cold operation with a typical battery voltage of typically VBatt = 13.5V and an ambient temperature of

typically Ta = -40°C.

•

generator defect with a typical battery voltage of VBatt = 18V and an ambient temperature of typically Ta =135°C.

The Power Dissipation Pv is typically considered with Pv = 3W during normal operation. This power dissipation

changes during the other operating conditions according the thermal behaviour of

DSon and the load Resistance

L. The interaction of both, together with an assumed typical Rthja = 7.5K/W, the given average junction

temperature Tj is considered as the start temperature for the clamping process.

Due to the fact, that the maximum possible Repetitive Clamping Energy

AR varies with the Load Current ID,

partially optional operating points are specified within the scenarios. Those optional operating points are not

considered as cummulative clamping pulses to the scenario.

Vbat

DScl

OUT

GND

OutputClamp.vsd

EVDS(CL)

Vbatt V

–

DScl

-------------------------------- ln

⋅

RL IL

⋅

Vbatt V

–

DScl

--------------------------------

–







------

⋅⋅

---

LIL

VDScl

VDScl V

–

Batt

---------------------------------

⋅

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