TPS65987D: Cable testing

Darren Jenkins

Part Number: TPS65987D
Other Parts Discussed in Thread: TPD6S300

TPS65987D support,

Our customer is working with TPS65987D on their own board. The DFP is either a laptop or the TPS65987D EVM.

They can negotiate to 20V all the time with a short cable with no emarker. With a 6 foot cable, they very rarely get 20V working and usually see Legacy mode indicated on the DFP EVM Sink Trace. With a 10 foot cable, the 20V Vbus is established about 1/3 times.

What is meant by the Legacy Mode?

What should we investigate next to figure out why this is happening?

Thanks,
Darren

over 3 years ago

0 Prajith Cheerakkoda over 3 years ago

TI__Expert 7700 points

Hello,

Legacy means non-PD mode. PD messaging would be failing due to higher cable loss. You can capture scope trace at various cable lengths and compare the signal quality.

Please click "This resolved my issue" button if I answered your query.

Thanks

Prajith

0 Darren Jenkins over 3 years ago in reply to Prajith Cheerakkoda

TI__Genius 10526 points

Prajith,

The waveforms look the same when it connects and when it doesn't.

Is there a way to configure the TPS65987D so it never goes into Legacy Mode?

Is there a way to configure a GPIO so it goes high/low/toggles when entering Legacy Mode?

Thanks,

Darren

0 Prajith Cheerakkoda over 3 years ago in reply to Darren Jenkins

TI__Expert 7700 points

Hi,

Could you share PD log for legacy mode connection? legacy mode entry happens when PD communications fails. I think the failure is due to higher cable loss.

No, there is no GPIO event for Legacy mode.

Thanks

Prajith

0 Darren Jenkins over 3 years ago in reply to Prajith Cheerakkoda

TI__Genius 10526 points

Hi Prajith,

It appears the problem was caused by damaged TPD6S300. Thank you for the guidance here. This problem is now resolved.

Thanks,

Darren

0 Prajith Cheerakkoda over 3 years ago in reply to Darren Jenkins

TI__Expert 7700 points

Hi,

Glad to know that the issue is resolved. Could you click "This resolved my issue" to close this thread ?

Thanks

Prajith

Interface

Interface forum

TPS65987D: Cable testing