Data Sheet

17

Rev. 1.0, 2008-10-30

TLE7239GS

Power Stages

6.3

Inductive Output Clamp

When switching off inductive loads with low-side switches, the potential at pin OUT rises to

V

because the inductance intends to continue driving the current. For the high-side channels, the potential at pin

OUT drops below ground potential to

V

device, see Figure 5 for details. Nevertheless, the maximum allowed load inductance is limited by the max.

clamping energy

E

Figure 5

Output Clamp Implementation

Maximum Load Inductance

During demagnetization of inductive loads, energy has to be dissipated in the TLE7239GS. This energy can be

calculated with following equations:

Low-side

(1)

High-side

(2)

These equations simplify under the assumption of

R

Low-side

(3)

High-side

(4)

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

OutputClamp.emf

high side

channel

GND

L,

I

S

VBB

OUT

low side

channel

L,

R

L

I

D

OUT

V

S(CL)

GND

–

D(CL)

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

⋅

1

⋅

–

D(CL)

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

–







+

L

------

⋅⋅

=

–

()

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

⋅

1

⋅

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

–







+

L

------

⋅⋅

=

E

1

2

---

2

1

–

D(CL)

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

–







⋅

=

E

1

2

---

2

1

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

–







⋅

=