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TPS65982: UVP under a 5V PD contract (or no PD contract) as a Sink for the external power path

Pierre Fourcade
Prodigy 10 points
Part Number: TPS65982
Other Parts Discussed in Thread: TPS65981

Hello,

I have a question related to the under-voltage protection (UVP) trip point for the TPS65982 as a Sink under a 5V PD contract (or no PD contract) while using the external power path (PP_EXT).

To set the situation, we are using the TPS65982 as a Sink with the external power path always. Our Sink defines three different PDOs: 5V, 9V and 12V. We are trying to set a specific under-voltage protection, however I seem to be incapable of setting, as intended, the UVP under a 5V contract (or no PD contract).

The registers I am using to configure the UVP are the followings (taken from the "TPS65981, TPS65982, and TPS65986 Host Interface Technical Reference Manual", page 22):

By trying different configurations with those three registers I have noticed the followings:

  • When activating the "SetUvpTo4P5V", the under-voltage protection is correctly set to around 4.5V for all cases: 5V PD contract, no PD contract or a >5V PD contract.
  • When disabling the "SetUvpTo4P5V", under a >5V PD contract the "UvpUsageHV" is correctly interpreted and the measured UVP trip point matches the set percentages with respect to the extra 5% for fixed PDOs (our case) and the cable voltage drop offset (itself with respect to the operational current of the current contract).
  • When disabling the "SetUvpTo4P5V", under a 5V PD contract or no PD contract the "UvpTripPoint5V" percentage seems to have no effect on the UVP trip point and the shut down occurs with a VBUS around 3.75V. I assumed this was caused as the voltage is to low for a VBUS powered application as ours.

From those results I assumed that PP_EXT falls under the "high voltage" power path configuration, explaining why only "SetUvpTo4P5V" and "UvpUsageHV" registers have an impact on the UVP trip point. However, I then tried using the "UvpUsageHV" for a 5V PD contract or no PD contract and, despite lowering the operational current to have a significantly high UVP trip point, I still obtain a shut down around 3.75V.

Then, my question is: is there a way to set an UVP trip point for the external path of the TPS65982 under a 5V contract or no PD contract without using the "SetUvpTo4P5V" (which is too restrictive for us)? Or, am I missing/misunderstanding something on this and could you please clarify this for me?

In advance, thank you for your answer!

Best regards,

Pierre Fourcade