TPS65983: Doubt about VBUS connection of the PD negotiation

Picher Lu

Part Number: TPS65983

Hi there,

When I use TPS65983 to develop a dual role PD device, there are some doubt about PD negotiation.

I want to add a MOSFET switch between PD source and sink VBUS to control the transition time of 5V - 20V, and this transition time is about 100ms.

It means that PD source VBUS will different with PD sink VBUS in about 100ms. I want to know if this transition time will cause the PD negotiate fail.

Thanks,

Picher

over 6 years ago

0 Rahul Sharma16 over 6 years ago

TI__Expert 6430 points

Hi Picher,

By looking at this I can say that it's fiine. PD spec allows up-to 265ms of time for voltage raamp-up time. Therefore. this timeline would be ok.

Please click "This resolves my issues" if I was able to answer your question.

Thnks,
Rahul

0 Rahul Sharma16 over 6 years ago

TI__Expert 6430 points

As per the PD secification the VBUS can takes upto ~250 ms so this 100 ms is not a concern.
Thanks,
Rahul

0 Picher Lu over 6 years ago in reply to Rahul Sharma16

Prodigy 160 points

Hi Rahul,

Thanks for your answer.

As the circuit above, when the transition time is more than about 60 ms, PD negotiate almost fail. VBUS transition to 20V from 5V then TPS65983 turn off the PP_EXT switch. PD negotiate fail and repeat negotiation.

But if I control the transition time at the PP_EXT switch, VBUS between source and sink is connected directly as show in figure below, negotiation is always success.

So I doubt that if the PD controller VBUS should be connect directly and keep the same voltage.

Thanks,

Picher

0 Rahul Sharma16 over 6 years ago in reply to Picher Lu

TI__Expert 6430 points

Hi Picher,

I missed in you last post that the VBUS in not directly connected.

VBUS must be directly connected to the VBUS to the VBUS of pin of port partner.

Please use the connection scheme in you last post and it should work.

Thanks,
Rahul

0 Picher Lu over 6 years ago in reply to Rahul Sharma16

Prodigy 160 points

Hi Rahul,

"VBUS must be directly connected to the VBUS to the VBUS of pin of port partner".

It is the PD spec required or TPS65983 required?

Do you have any documents describe about this.

Thanks,
Picher

0 Rahul Sharma16 over 6 years ago in reply to Picher Lu

TI__Expert 6430 points

Hi Picher,

This is the requirement of TPS65983. 83 PD controllers measures the VBUS voltages through the VBUS pin and therefore it must be connected to the the PD controller or else it will think VBUS is not available and will keep retrying and will fail to work.

Refer datasheet for more details.

Thanks,
Rahul

0 Rahul Sharma16 over 6 years ago in reply to Rahul Sharma16

TI__Expert 6430 points

Hi Picher,

Do you have any other queries or can I close this post?

Please click "This resolves my issue" if yours issue is resolved.

Thanks,
Rahul

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TPS65983: Doubt about VBUS connection of the PD negotiation