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Below-ground voltage on the OUT pin

AN2785

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Doc ID 14785 Rev 1

Figure 35.

OUT below-ground voltage in transient conditions: limited boot

overcharging

9.4.3

Below-ground voltage spikes

As explained in the previous section, the dynamic contribution of the below-ground voltage

on the OUT pin does not have enough time to overcharge the bootstrap capacitor. This fact

usually excludes the risk of exceeding the recommended maximum value of 20 V for the

VBOOT -VOUT voltage, but on the other hand it increases the danger of pulling the BOOT pin

down below ground, then violating its absolute minimum rating. As mentioned above, for

safe operation of the IC gate driver, this phenomenon should be avoided. However, note that

applicative bench tests have shown that the L6393 also works with below-ground spikes on

the OUT pin that well exceed -50 V (see Figure 36).

VOUT

VCC

VBOOT

VBOOT - VOUT

VBO OT - VOUT

v irtual final v alue

in s t eady st ate

VBGV_stati c

VBGV_spike

VBOOT - VOUT

bef or ov erc harge

VOUT

VBOOT - VOUT

s afe operating

max imum range

(20V )

VBOOT - VOUT

real

overc harge

High side O FF time

HIN

HVG

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