AN2785 Datasheet, PDF (44/51 Pages) STMicroelectronics – L6393 half bridge gate driver

Below-ground voltage on the OUT pin
AN2785
Figure 33. L6393 safe operating range when OUT pin is below ground voltage (in
steady state)
Vcc
Vboot
0V
Vout
Vcc-Vboot
Vboot > - 0.3V
Vboot-Vout < 20V
below ground
voltage on Vout
9.4
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Functionality of L6393 outputs in below-ground condition
The L6393 IC gate driver makes use of a level shifter in order to send the set-reset
information to the high-side floating section. The level shifter, shown in Figure 34, is mainly
composed of two high-voltage switches, for set/reset signals, driven by the low-voltage
section and linked to two pull-up resistors connected to the BOOT pin.
Figure 34. Driver functionality in below-ground voltage condition on OUT pin
Vcc
Vboot
Vcc-Vboot
Vboot-Vout
Vboot > 5V
for full
functionality
of level shifter
Vcc
Vboot
Level
Shifter
Low Side
section
set
reset
Vboot
High Side
floating
section
HVG
0V
Vout
gnd
below ground voltage on Vout
gnd
Vout
The two level-shifted signals are then fed into a logic latch in the high-side floating section,
providing the logic state for the high-side gate driver (HVG output).
Doc ID 14785 Rev 1