TPS25947: PGTH pin issue

Bryan Chang

Part Number: TPS25947

Tool/software:

Dear Sir,

PGTH pin could be opened ? what will happen if this pin is opened? It can cause any damage for following circuit design ?

PS, When AC Adapter pug in (20V) , TPS25947 VIN PIN ; V0UT PIN ; PGTH pin , three pins are damaged.

( Only one M/B was happened )

If this pin can not let open , what R4&R5 values are recommend ? ( VIN 20V; VOUT 20V)

Thanks and best regards,

Bryan

TPS259474A.pdf

9 months ago

+1 Arush Gupta 9 months ago

TI__Mastermind 38645 points

Hi Bryan,

If PG is not being used, PG can be left floating and PGTH can be grounded. Even if PGTH is left floating, it shouldn't get damage. It is just an input to a comparator.

Bryan Chang said:
( Only one M/B was happened )

what is the fail rate? is the product in main production stage? What does M/B stands for?

Best Regards,
Arush

0 Bryan Chang 9 months ago in reply to Arush Gupta

Prodigy 50 points

Okay, I got it.

The fail rate is very low, there are 3 NB Models ( about over hundrens pcs of M/B) .

Just only one Model one pcs of M/B which had damaged issue.

M/B (Mother board) for NB

Thanks for your reply.

Bryan

+1 Bryan Chang 9 months ago in reply to Arush Gupta

Prodigy 50 points

Hi Arush,

By the way I have another question:

We have checked two Models:

When JDC_AC (Adaptor) plug in via LM5050 Vout VA2(20V) which connect to U79(TPS259474A) PIN 6 VOUT

There is a leakage voltage about 0.36V on U79(TPS259474A) PIN 5 (VIN)

Is there any solution to fix this issue?

Thanks and best regards,

Bryan

+1 Arush Gupta 9 months ago in reply to Bryan Chang

TI__Mastermind 38645 points

Hi Bryan,

There will be some uA leakage from Vout to Vin and there is around 210kOhms or resistance due to resistive ladder for EN. Most likely this is causing 0.36V at the Vin.

If this is indeed the cause of this voltage build up, you can reduce the overall resistance to reduce this voltage build up.

Best Regards,
Arush

+1 Bryan Chang 9 months ago in reply to Arush Gupta

Prodigy 50 points

Hi Arush,

you can reduce the overall resistance to reduce this voltage build up.

---You mean that I can try to change PR466 from 10K to 1K ; PR465 change from 100K to 10K , is that right?

Thanks and best regards,

Bryan

+1 Arush Gupta 9 months ago in reply to Bryan Chang

TI__Mastermind 38645 points

Hi Bryan,

I was thinking of leakage current causing voltage buildup due to OVLO pin resistive divider.

You can verify this by just removing pull up resistor to see if this is causing the voltage buildup or not.

Best Regards,
Arush

+1 Bryan Chang 9 months ago in reply to Arush Gupta

Prodigy 50 points

Hi Arush,

I had removed the pull up resistor PR468 (200K) , PIN 5 (VIN) voltage change from 0.36V to 0.46V

Do you have any other solutions that I could try to test again.

Thanks and best regards,

Bryan

+1 Bryan Chang 9 months ago in reply to Bryan Chang

Prodigy 50 points

Hi Arush,

Please let me know , if this Vin pin leakage voltage ( cause by leakage current from Vout to Vin ) could not be fixed.

Thanks and best regards,

Bryan

+1 Arush Gupta 9 months ago in reply to Bryan Chang

TI__Mastermind 38645 points

Hi Bryan,

The Vout to Vin leakage cannot be reduced. It will remain in uA order and I suspect this will buildup the input voltage to the level which you are seeing.

This leakage cannot be reduced.

Best Regards,
Arush

+1 Bryan Chang 9 months ago in reply to Arush Gupta

Prodigy 50 points

Hi Arush,

OK, I got it.

Thanks and best regards,

Bryan

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TPS25947: PGTH pin issue