TPS62150 & TPS62130 FSW pin connection implications

shay cohen

Other Parts Discussed in Thread: TPS62150, TPS62130

Few of our LVPS circuits on one of our design are using TPS62150 & TPS62130 ICs

All of those circuits are set to FSW=1 (low frequency for better efficiency) by connecting FSW pin to VIN using a 20kohm pull up rather then connecting it to VOUT (as the datasheet suggests)

what are the implications of this connection ?

can it cause a chip damage? at mass production we encounter a few boards that those IC had been damaged and their input voltage appeared at their output ( VOUT=VIN ) - can this connection can be the root cause of it ?

Thanks

Shay

over 8 years ago

0 Chris Glaser over 8 years ago

TI__Guru**** 150750 points

Yes, this connection to Vin is prohibited since the voltage is above the abs max for the FSW pin. Connect it to Vout to register a logic high.

If you seeing that failure mode on your production line, I would check for solder shorts and other manufacturing mistakes. As well, take a unit which shows the short and solder it onto an EVM to see if the short is still there.

0 shay cohen over 8 years ago in reply to Chris Glaser

Prodigy 90 points

Hello chris

thanks for the fast response

the datasheets specifies a in-rush current issue when FSW=1 at start-up - what are the implications of this ?
by the way , connecting FSW pin vout was a recommendation in early TI's datasheets and then changed to mandatory , can you clarify the reason for that ?

Thanks

Shay

0 Chris Glaser over 8 years ago in reply to shay cohen

TI__Guru**** 150750 points

The issue is that Vin is too high a voltage to apply to the pin itself. See the footnote on page 10 of the TPS62130 D/S.

0 shay cohen over 8 years ago in reply to Chris Glaser

Prodigy 90 points

we've double check it and it seems that FSW pin voltage is not higher the 3.5V at any of our circuity .

is it possible that the in-rush currents mentioned in the datasheet (when connecting FSW to high at start-up) can damage the chips ?

thanks

shay

0 Chris Glaser over 8 years ago in reply to shay cohen

TI__Guru**** 150750 points

So, I assume your Vin is around 3.6 then? With a 20k pull-up, the FSW pin should basically be at Vin.

Can you post your PCB layout and schematic?

Did you check for shorts/opens that occurred during manufacturing?

0 shay cohen over 8 years ago in reply to Chris Glaser

Prodigy 90 points

I'm sorry , i guess i have mistakenly dropped a few resistors - it not only a 20k pull up to vin but a network of resistors that sets the FSW pin voltage to 0.2*Vin (which is 17volt at its max) - so it seems not to be the fail reason for this chip burns

BRG

shay

0 Chris Glaser over 8 years ago in reply to shay cohen

TI__Guru**** 150750 points

Thanks for confirming that the FSW pin voltage is held lower. Were you able to check for shorts or other manufacturing issues?

Power management

Power management forum

TPS62150 & TPS62130 FSW pin connection implications