LMG5200: pin-out / layout

Dave-o

Prodigy 110 points

Part Number: LMG5200

Is there a good reason why HS and HB are on the opposite side of the device to the SW pin?

over 6 years ago

0 Serkan Dusmez over 6 years ago

TI__Intellectual 805 points

Hi Dave,
Inside the module, the location of HS and HB are close to the high side GaN FET, which minimizes the bootstrap loop inductance. The SW pin is routed to the bottom for easiness of external routing. PIN and PGND are closer so that the bypass caps can be placed very close to the module in a standard 2Layer pcb. In this way, switch node power plane does not have to intersect with high voltage (PIN) or ground (PGND) planes.

Regards,
Serkan

0 Dave-o over 6 years ago in reply to Serkan Dusmez

Prodigy 110 points

Fair enough, life is full of little compromises, for the greater good.

How robust is the HB clamp?

thanks

0 Serkan Dusmez over 6 years ago in reply to Dave-o

TI__Intellectual 805 points

We haven't seen any issues with the clamping function. The clamp circuitry limits the bootstrap refresh operation to ensure that the high-side gate driver overdrive does not exceed 5.4 V. On the other hand, the low side FET has no clamping function.

Hope this helps.

Regards,

Serkan

0 Dave-o over 6 years ago in reply to Serkan Dusmez

Prodigy 110 points

Oh, think I have blown it up. I need the high side powered continuously in my application.

0 Serkan Dusmez over 6 years ago in reply to Dave-o

TI__Intellectual 805 points

Hi Dave,
You need to drive the high side with PWM so that bootstrap capacitor replenishes charge. To power high side continuously, you need provide an isolated 5V to the HB and HS with local decoupling capacitor.
Regards,
Serkan

0 Dave-o over 6 years ago in reply to Serkan Dusmez

Prodigy 110 points

In a fit of enthusiasm I tried a current source from 12v above my Vin of 2.5 mA, the max value from the data sheet. It seemed to work for a few seconds, but now I think the top fet is blown, it measures 170 ohm between Vin and SW. I measured about 9 volts between Hb and Hs. In retrospect 150uA would be more appropriate for the current source, i think , and I will put a zener across Hb to Hs. Going to try that today.

0 Serkan Dusmez over 6 years ago in reply to Dave-o

TI__Intellectual 805 points

Hello Dave,
If you are connecting 12V between HS and HB, it will damage the part. Please check Abs max table and you'll see that max input voltage between these pins are 6V. The driver is integrated so you should supply 5V rather than converting to current.

Regards,
Serkan

0 Dave-o over 6 years ago in reply to Serkan Dusmez

Prodigy 110 points

Hi,

I don't think you understand what I wrote. It is possible I shorted something.

I think I have sorted it now. The HS HB does not behave in quite the same way as I was expecting.

Thanks

Power management

Power management forum

LMG5200: pin-out / layout