AN3151

Short-circuit protection

Doc ID 17051 Rev 1

29/34

Short-circuit protection is implemented by means of a simple external circuitry based on:

●

Low-power quad voltage comparator (LM339)

●

Quad 2 input AND gate(74HC08)

The sensing signal is compared with an external reference set by a voltage divider providing

an active low output on each string.

The four outputs are in AND in order to have a single FAULT signal, which is an input

managed by the microcontroller thanks to the TIM1_BKIN pin.

When TIM1_BKIN input (Figure 4) is active, with a programmable polarity, the output stage

control disables all channels in order to protect the hardware.

Figure 21

shows a short-circuit event managed by the TIM1_BKIN.

Figure 21.

Short-circuit event