CAUTION
Do NOT ignore a FAULT signal when using the LMG342XEVM-04X. Turn off both top and bottom
devices if any device generates a FAULT signal. The device under a fault condition may operate
in the undesired third-quadrant mode and can overheat or become damaged due to the high source-
drain voltage drop if the other device is still switching.
2.1.2 Power Pins
There are some high frequency decoupling capacitors on the LMG342XEVM-04X from VDC to PGND to
minimize voltage overshoot during switching, but more bulk capacitance is required to hold up the DC voltage
during operation. TI recommends preventing any overlap and parasitic capacitance from VSW to VDC, PGND,
and any logic pins. The two ground PGND and AGND pins are functionally isolated from each other on the
LMG342XEVM-04X.
2.1.3 Bootstrap Mode
The LMG342XEVM-04X card can be modified to operate in bootstrap mode, where the 12-V bias voltage is used
to power both LMG342XR0X0 devices. This mode can be achieved by the following modifications to the EVM:
1. Remove R1.
2. Place a 2-Ω resistor on R2.
3. Place a 600-V SOD-123 diode on D1, such as UFM15PL-TP.
4. Adjust Rdrv resistor for the low side to be above 70 kΩ, which corresponds to a slew rate below 60 V/ns for
the low side.
2.1.4 Heat Sink
The heat sink is installed to help with heat dissipation of the LMG342XR0X0. Exposed copper pads are attached
to the die attach pad (DAP) on the high-side and low-side devices to provide a low thermal impedance point
for the heat sink. The two copper pads have a high-voltage potential difference between them, therefore an
electrically isolated thermal interface material (TIM) is required.
For optimal thermal dissipation and board level reliability, recommendation for thermal via pattern and
solder paste example are provided in the
LMG342xR030 600-V 30-mΩ GaN FET With Integrated Driver,
Protection, and Temperature Reporting
. In this daughter card design, 'S05MZZ12-A' heatsink
and 'GR80A-0H-50GY', thermal interface material has been used. More details on thermal performance and
comparison between different TIM are shown in
Thermal Performance of QFN 12x12 Package for 600-V GaN
.
Figure 2-2. Front Side View of the EVM
Introduction
SNOU176A – OCTOBER 2020 – REVISED JANUARY 2022
LMG342XEVM-04X User Guide
7
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