Description

AN4407

6/19

DocID025572 Rev 1

Figure 5. Risk of short-circuiting the sensing resistor

Figure 6 shows that, as the connection to the ground of the push-pull buffer circuit grounds

the sensing source pin, and since the power source pin is shorted internally with it, the

connection creates a short circuit for the sensing resistor.

So, when a 4-pin package is used, special precautions must be applied in order to preserve

system functionality (Figure 6).

Figure 6. Network implementation to remove the risk of short-circuit

The following solution is implemented on the ST demo board:

•

In the system, the value of the sensing resistor Rs is 18 m

Ω (Figure 4).

•

When using a 4-pin MOSFET, the connection shown in Figure 7 is applied to remove

the possibility of creating a short-circuit on Rs.

GIPG211120131738FSR

GIPG271120131034FSR