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11/19

Rev.0.3

Single-ChannelIsolatedGateDriver

BTD5350x

In order to prevent the output port voltage from overvoltage/overcurrent damage when the positive secondary-side

power supply voltage VCC2 becomes lower than the negative secondary-side power supply voltage VEE2, due to gate

oscillation on output terminals, the 5350M version is designed with a Miller clamp on the output port to effectively

suppress oscillations. However, to ensure the normal operation of the drive circuit, BASiC recommends to use Schottky

diodes at the gate to clamp the positive and negative power supplies respectively.

Figure8.OutputStage

9.4ProtectionFunctions

9.4.1UndervoltageLockout

The BTD5350x has undervoltage lockout (UVLO) function on the primary-side power supply and the secondary-side total

supply voltage to prevent the gate drive voltage from being insufficient. When the supply voltage drops below UVLO

threshold, the ASIC turns off the output to protect the power devices. When the supply voltage reaches the positive-going

negative-going threshold, the ASIC resumes the output. To prevent repeated action near the UVLO threshold, the ASIC

is configured with hysteresis. In order to avoid the uncertainty of the output state after power-on, the ASIC first enters an

UVLO state after power-on, keeps the output off until the supply voltage is established and then starts normal operation (see

Figure 9).

Figure9.UVLOFunctions

9.4.2MillerClamp

The active Miller clamp function is used to prevent the power devices from false turn-on of the power switched cause by

the Miller current. A low impedance path is added between the gate terminal and ground (VEE2) to sink the Miller cur-

rent. The Miller clamp function clamps the gate voltage of the power device to less than 2V when the output is in the off

state.

VEE2

OUTH

VCC2

Level Shifting and

Control Logic

OUTL

UVLO2

ROH

RNMOS

ROL

IN+

VCC1

VCC2

VOUT

tUVLO1-rec

VON1

VOFF1

IN+

VCC1

VCC2

VOUT

tUVLO2-rec

VON2

VOFF2

IN+

VCC1

VCC2

VOUT

tUVLO1-rec

VON1

VOFF1

IN+

VCC1

VCC2

VOUT

tUVLO2-rec

VON2

VOFF2