AN2785 Datasheet, PDF (8/51 Pages) STMicroelectronics – L6393 half bridge gate driver

UVLO function
3
UVLO function
AN2785
The L6393 supply voltage V_CC is continuously monitored by an under-voltage lock-out
(UVLO) circuitry, which turns off the IC outputs when the supply voltage goes below the
V_{CC_thOFF} threshold (see L6393 datasheet for values) and turns on the device when the
supply voltage goes above the V_{CC_thON} voltage. A hysteresis of about 1.5 V is provided for
noise rejection purposes. The high voltage floating supply BOOT is also provided with a
similar under-voltage lock-out circuitry. When the L6393 is in a UVLO condition, both gate
driver outputs are set to low, setting the half-bridge power switches to high impedance.
Figure 3 shows the I-V characteristics of the output buffers at different V_CC values.
Figure 3. L6393 gate driver outputs in UVLO condition
ILVG/HVG
(mA)
100
90
L6393 output buffer characteristic in UVLO condition
VCC = 15V
VCC = 9V
VCC = 7V
VCC = 6V
80
VCC = 5V
70
60
50
VCC = 4V
40
30
VCC = 3V
20
10
VCC = 2V
VCC = 0V ^{VCC = 1V}
0
1
2
3
4
NOTE: when VCC < VLVG/HVG
the body diode of the p-channel (source)
turns ON and clamps the VLVG/HVG voltage
5
VLVG/HVG
(V)
GATE DRIVER
OUTPUT BUFFER
(LS/HS)
p-channel
(source)
OFF
ON
n-channel
(sink)
TEST CIRCUIT
VCC/BOOT
LVG/HVG
ILVG/HVG
A₊
+
VLVG/HVG
VCC
GND/OUT
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Doc ID 14785 Rev 1