TPS54335A: Recommendation for better thermally performing part in inverting buck configuration

Hi Steven,

Just a curious question, have you given a chance to resolve the thermals from layout perspective instead of looking for an alternate part? 

Regards,

Gautam

Hi Gautam,

Thanks for your reply. Yes we have spend a significant amount of effort to copy the layout guide. We are able to achieve our target current / power but at a cost of a general temperature rise on the PCB that is affecting sensitive components.

Regards,

Steven

Steven, for recommendation on devices can you please share your requirement apart from 9Vin & -4V/3A output?

Hi Gautam, the temperature rise should be at least 40% lower than the current part. I have done some searching myself by looking at the high side / low side Fet resistances but the problem is the inverting buck requirement - I am not sure which parts I could potentially use. Thanks again.

Hi Steve, another input I need is: which package are you currently using? Also, are you flexible with other packages?

Hi Gautam,

Ideally it would be a similar package (we are currently using VSON) but we are relatively flexible. I would like to avoid packages like BGA where the pads are directly underneath if possible.

Thanks,

Steven

Hi Steven, 

If 9V is the max Vin and -4 is max Vout then you can very well use 17V-3A SOT part.

AC/DC & DC/DC converters (integrated FET) product selection | TI.com

You can convert these to Inverting Buck using these App note:

Using the TPS5430 As An Inverting Buck Boost Converter (Rev. A

https://www.ti.com/lit/an/snva856b/snva856b.pdf

Let me know if you're still inconclusive. 

Regards,

Gautam

Hi Gautam, thanks for your recommendation. The TPS5430 internal mosfet resistance of 110 milliohm seems to be similar to the TPS54335A. Would that not mean a similar temperature rise?

Steven