Snubber design considerations

AN280

10/15

Doc ID 1703 Rev 3

When the snubber network is installed in the application the voltage transients on the

terminals of the L6203 are greatly reduced, as shown in Figure 11. The drawback of a

snubber network of this type is that a current spike flows into the transistor when it is

switched on as the capacitor is discharged. The theoretical peak value of this spike is given

by the equation:

Equation 4

Figure 10.

Supply voltage with snubber

Figure 11.

This peak current flowing in the snubber is added to the load current when the device is

turned on and the total peak current in the transistor is the sum of the snubber circuit current

plus the load current. In practice, the peak current measured is usually much less than the

calculated peak, due to the capacitors internal resistance and the resistor inductance.

Figure 12 and Figure 13 show the peak current in the snubber network in the design

example.

I

V

smax

R

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

42V

7.5ohm

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

5.6 A

==

=

AM15177v1

AM15178v1