Short-circuit protection

AN1882

12/30

Doc ID 10209 Rev 4

4

Short-circuit protection

The device is provided by two limiting current circuitries, one on the high side and a second

on the low side MOSFET.

Due to the peak current mode architecture, the peak current flowing through the high side

switch is accurately sensed. When this current reaches the peak current limit threshold, the

circuit, the peak current could further increase because the intervention of the high side

limiting current is not fast enough. In this case, the valley current limits eliminate the risks of

device failure. To better understand this concept, it's useful to read the below considerations

on the current variation through the inductor during the ON and OFF time.

Equation 4

Equation 5

time. Therefore the current will increase step by step during each cycle In order to

understand when this phenomenon will end, some real parameter must be considered.

Figure 9.

Equivalent circuits during the ON time

ΔI

ON

V

IN

V

OUT

–

()

L

---------------------------------- T

ON

⋅

=

(ON time slope)

ΔI

OFF

V

OUT

L

-------------- T

OFF

⋅

=

(OFF time slope)