TPS65150-Q1: FBP pin=1.518V which is higher than the normal value 1.214V

Sherry Liang

Part Number: TPS65150-Q1

Dear team,

When testing the device, the customer found that the voltage of FBP is 1.518V, but in our datasheet this value should be 1.214V. In addition, the voltage at the DRVP pin is 0V. And the VGH(positive charge pump output) is 27V while the setting value should be 22V. The schematic is as below, Vs=11.6V

When change the diode in the red box to BAV99(larger voltage drop and smaller leakage current compared to the old diode), then the VGH becomes normal. At this time the voltage of DRVP is 0.8V.

Could you please help analyze this problem?

Thanks & Best Regards,

Sherry

over 4 years ago

0 Grant Falkenburg over 4 years ago

TI__Intellectual 1965 points

Hi Sherry,

Let me contact the engineer who supports this part. You can expect a response by 10/22/19 (edited from 10/19/19 since it is on a weekend).

Best,

Grant

0 Liaqat Khan over 4 years ago

TI__Mastermind 18550 points

Hi Sherry,

I just wanted to let you know that I tried to reproduce this problem in my EVM today with the same settings as customer design but so far I am not able to. I am continuing to do more experiments and will get back to you with any findings.

Kind Regards,

Liaqat

0 Liaqat Khan over 4 years ago in reply to Liaqat Khan

TI__Mastermind 18550 points

Hi Sherry,

I think what is going on is that in the charge pump tripler mode (two stages of charge pump as shown in the customer schematics), the charge pump can not regulate to a voltage lower than the output of the first stage (i.e. doubler) which is ~23V. That is why DRVP is at 0v or not switching to achieve the minimum possible duty cycle. When diodes with higher voltage drop are substituted, the doubler mode output becomes lower than the target regulated output of 22V, hence the DRVP starts switching and voltage gets regulated to proper level. You can also verify that by slightly reducing Vvs to say 10.6V and in that case the charge pump tripler will regulate to proper 22V without having to use the higher voltage drop diodes. Hope this explanation helpful.

Kind Regards,

Liaqat

0 Sherry Liang over 4 years ago in reply to Liaqat Khan

TI__Genius 10255 points

Hi Liaqat,

Thanks for your explanation which is helpful!

I can also disconnect D4 and Vs and use an external smaller voltage to supply the first stage, right?

Thanks & Best Regards,

Sherry

0 Liaqat Khan over 4 years ago in reply to Sherry Liang

TI__Mastermind 18550 points

Hi Sherry,

I would suggest to just lower the Vvs setting slightly (change resistor divider) instead of connecting an external supply because the device may shutdown due to power sequencing if you use an external supply.

Kind Regards,

Liaqat

0 Sherry Liang over 4 years ago in reply to Liaqat Khan

TI__Genius 10255 points

Hi Liaqat,

Ok, got it! Thank you!

Thanks & Best Regrads,

Sherry

0 Liaqat Khan over 4 years ago in reply to Sherry Liang

TI__Mastermind 18550 points

You are welcome!

Kind Regards,

Liaqat

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TPS65150-Q1: FBP pin=1.518V which is higher than the normal value 1.214V