LM5148: Use with GAN Device

Godziller

Part Number: LM5148

Tool/software:

Hello, I was wondering if I use the LM5148 as it is to drive GAN transistor with max Vgs of 5.5V. In case if it is possible what should I be carefull of? I was thinking about creating a 2.2MHz buck converter from 48V to 20V.

1 month ago

0 EricLee 1 month ago

TI__Guru 52021 points

Hello Godziller

Since LM5148 regulates VCC voltage which is the source of low-side MOSFET driver, at 5V+/-0.3V, the maximum V(LO-GND) voltage can be well regulated. But V(CBOOT-SW) which is the source of the high-side MOSFET, can be greater than V(VCC-GND) when the SW node negative spike is greater than one diode voltage drop. Please optimize the PCB layout in order to minimize the negative spike.

-EL

0 Godziller 1 month ago in reply to EricLee

Prodigy 120 points

Thanks for your reply, do you suggest using a Zener or something like that to clamp the voltage?

+1 EricLee 1 month ago in reply to Godziller

TI__Guru 52021 points

Hello Godziller

I am sure that the risk can be minimized by populating a Zener diode in parallel with boot capacitor.

-EL

0 Godziller 1 month ago in reply to EricLee

Prodigy 120 points

Just one more thing, this is my layout it good enough to minimize the negative voltage spikes? im also gonna add the zener diode.

0 EricLee 1 month ago in reply to Godziller

TI__Guru 52021 points

Hello Godziller

I forgot you will use GaN FETs. Because GaN has no body diode, the amount of negative spike will be dominated by the V_SD specification of your GaN FET. Means you need a Zener diode.

-El