TPS65987DDJ: VBUS will drop and PD reconnect when change source PDO from 20V/5A to 20V/3.25A through MCU

Hi,

Is there any setting or workaround that we could do to aviod this OC event so that I can switch the Source PDO from 100W(20V/5A)to 65W(20V/3.25A)?

Thanks！

Hello,

   I am afraid I do not understand the question.  Do you want to limit the source capabilities to 3.25A or do you want to support 4A?

Thanks,
Chris

Hi

I hope that in the process of switching source capabilities from 5A to 3.25A, VBUS will not drop and PD will not reconnect. How can this be achieved? (An OC event is triggered during the actual switchover because sink still consumes much more than 3.25A when source capabilities are switched to 3.25A)

Thanks!

Hi,

I repeated the test with the current load of 2A and was able to switch 5A to 3.25A

But we are currently in a situation where when we switch from 5A to 3.25A, sink still consuming more than 4A, sink current cannot be lowered

instantaneously,so that OC is triggered and we cannot successfully switch from 5A to 3.25A without PD reconnection

Can I disable OC feature by PD FW?How do I disable OC feature?

or Can I set the OC trigger point to a higher fixed point (regardless of if PDO changes)? How do I set it?

Thanks!

Hi,

I tried to increasing the Peak Current value to 200% in the Source PDO

However, the OC is still triggered in the above scenario.

Hello,

Thank you again for testing the Peak Current.  I do not believe what you want to do is possible.

How long does it take for the sink to reduce the current consumption to 3.25A?

Regards,

Chris

Hi,

Thank you for your confirmation.

Sink will takes at least 1s to reduce the current consumption to 3.25A

Hi,

Can you set the delay for triggering OC to more than 15 seconds (for example, 2s) so that sink has enough time to reduce the current consumption to 3.25A

and therefore does not trigger OC in the preceding scenario?

Thanks!

Hello,

I do not believe so.  This would be a violation of the spec.  I will need to inquire internally to see if we can support this case and stay within the specification. 

Do you have any other means to communicate with the far end sink to prepare for the transition from the 5A to 3.25A loading?

Regards,

Chris

Hi,

Thank you!

I can communicate with the far end sink by UVDM to inform it to prepare for the transition from the 5A to 3.25A loading

But this method is only applies for a specific far end sink, not for all

Hi,

There is any result of your internal inquiry?

Can you support set the delay for triggering OC to 2s?

Or maybe you have another suggestion that could solve this issue?

Thanks!

Hello XF J, 

We will get back to you shorty on these question as TI Dallas is on Holiday. 

Regards,
Deepak 

Hello,

XF J said:

There is any result of your internal inquiry?

The result is the same.  The sink is supposed to transition its power consumption in 15ms, as defined in the specification: tSnkNewPower.

XF J said:

I can communicate with the far end sink by UVDM to inform it to prepare for the transition from the 5A to 3.25A loading

But this method is only applies for a specific far end sink, not for all

Do you have to comprehend all possible sinks or can you limit to only sinks which are compliant with the USB specification?

Hi,

sorry, I don't quite understand what you mean

My device is as TBT UFP,I think its dont need comprehend all possible sinks

but I cant limit to only sinks which are compliant with the USB specification.

Its must support PD3.0 spec,I need support up to 20V/5A.

Thanks!

Hi,

If we do not care specification, can we turn off OCP function or set OCP at a fixed high value (over 5A) in PD FW?

Hi,

If we do not care specification, can we turn off OCP function or set OCP at a fixed high value (over 5A) in PD FW?

--Please help to confirm whether this can be achieved

Hello,

XF J said:

If we do not care specification, can we turn off OCP function or set OCP at a fixed high value (over 5A) in PD FW?

No this cannot be achieved.

Regards,

Chris