LMG5200 Evaluation Board Layout

Lenny

Intellectual 700 points

I took a look at the layout and it looks like the ground planes are completely cleared out underneath the switch node.

What is the purpose behind this, it is not at all mentioned in any of the documentation.

over 9 years ago

0 Michael Seeman over 9 years ago

TI__Prodigy 50 points

Hi Leonid,

We remove the ground planes beneath the switch node to reduce capacitance between switch node and ground. With GaN's low output capacitance, any PCB capacitance may significantly increase the switch-node capacitance and cause additional switching loss.

regards,

Mike

0 Lenny over 9 years ago in reply to Michael Seeman

Intellectual 700 points

Mike,

How does this then affect EMC?

Also for higher currently what about replacing empty space with more switch node and stitching vias?

Thanks;
Leo

0 Michael Seeman over 9 years ago in reply to Lenny

TI__Prodigy 50 points

Hi Leo,

We have not evaluated the tradeoffs between switching loss and EMC. A potential compromise is to place a shield layer on the opposite side of the board (e.g. bottom layer) to minimize capacitance.

Regards,
Mike

0 Lenny over 9 years ago in reply to Michael Seeman

Intellectual 700 points

Thank you.

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LMG5200 Evaluation Board Layout