AN2785 datasheet(8/51 Pages) STMICROELECTRONICS

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UVLO function

AN2785

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Doc ID 14785 Rev 1

UVLO function

The L6393 supply voltage VCC is continuously monitored by an under-voltage lock-out

(UVLO) circuitry, which turns off the IC outputs when the supply voltage goes below the

VCC_thOFF threshold (see L6393 datasheet for values) and turns on the device when the

supply voltage goes above the VCC_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 VCC values.

Figure 3.

L6393 gate driver outputs in UVLO condition

VLVG/HVG

(V)

L6393 output buffer characteristic in UVLO condition

ILVG/HVG

(mA)

VCC = 0V

VCC = 1V

VCC = 2V

VCC = 3V

VCC = 4V

VCC = 5V

VCC = 6V

VCC = 7V

100

VCC = 9V

VCC = 15V

LVG/HVG

GND/OUT

VCC/BOOT

GATE DRIVER

OUTPUT BUFFER

(LS/HS)

n-channel

(sink)

p-channel

(source)

OFF

VCC

VLVG/HVG

ILVG/HVG

NOTE: when VCC <

VLVG/HVG

the body diode of the p-channel (source)

turns ON and clamps the

VLVG/HVG voltage

TEST CIRCUIT

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