APPLICATION INFORMATION

DEMAGNETIZATION OF INDUCTIVE LOADS

An internal zener diode, limiting the voltage

across the Power MOS to between 50 and 60V

inductive loads without external clamping devices.

The maximum energy that can be absorbed from

an

inductive

load

is

specified

as

1J

(at

°C).

To define the maximum switching frequency three

points have to be considered:

1) The total power dissipation is the sum of the

On State Power and of the Demagnetization

Energy multiplied by the frequency.

2) The total energy W dissipated in the device

during a demagnetization cycle (figg. 2, 3) is:

W

L

log







1

+







]

Where:

L = inductive load;

Vs = supply voltage;

3)

In normal conditions the operating Junction

temperature should remain below 125

°C.

If the demagnetization energy exceeds the rated

must be externally connected (see fig. 5).

value and significantly (at least 10V) higher than

the voltage that is externally supplied to pin 10,

i.e. than the supply voltage.

Alternative circuit solutions can be implemented

to divert the demagnetization stress from the

TDE1890/1, if it exceeds 1J. In all cases it is rec-

ommended that at least 10V are available to de-

magnetize the load in the turn-off phase.

A clamping circuit connected between ground and

the output pin is not recommended. An interrup-

tion of the connection between the ground of the

load and the ground of the TDE1890/1 would

leave the TDE1890/1 alone to absorb the full

amount of the demagnetization energy.

Figure 2: Inductive Load Equivalent Circuit

TDE1890 - TDE1891

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