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Dynamically overwriting PDO in TPS65982 register

Masumi Saito
Intellectual 300 points
Other Parts Discussed in Thread: TPS65982

Can my customer dynamically overwrite PDO in TPS65982's register? This operation need to fill timer spec of USB-PD.

What they want to do:
1. Power Source(Our TPS65982) have some Fixed PDO.
2. Power Sink refer Source PDO. But every Source PDO don't match with Sink PDO. So Sink return RDO with Capability Mismatch.
3. Power Source refer Sink PDO and our system overwrite TPS65982's PDO which is same as Sink PDO.

Regards

Saito

  • 0
    TI__Mastermind 30280 points

    Saito-san,

    What you are describing is not ideal behavior. The Source is capable of delivering power based on the power circuitry designed in hardware.

    If you look at the EVM circuitry, it is capable of delivering 5V from PP_5V0, 12V from PP_HV, or 20V from PP_EXT. Therefore, it has 3 Fixed Source PDOs.

    It is not common for Source PDOs to be dynamically configurable to meet the needs of a specific Sink.

    Usually a Sink has a Variable voltage PDO which will accept a wide Source voltage range.

    If the Source power circuitry is dynamically configurable, it will involve a lot of interaction from a system EC (embedded controller) to change the Source capabilities and then update the TPS65982 Source PDOs dynamically.

    In conclusion, this implementation is possible but is very complex.

  • 0 in reply to Brian Berner
    Intellectual 300 points
    They understood your suggestion. they think it is very complex too.
    Certainly, the Sink PDO of a product which they checked has variable range.(e.g. 10.8V to 20V)
    Do you think what is the average voltage in sink's variable PDO?
    They are confusing because they cannot estimate expected voltage of Sink products in future.
    RegardsSaito
  • 0 in reply to Masumi Saito
    TI__Mastermind 30280 points

    It is our understanding that the majority of products will accept either a 12V (e.g. tablets) input or a 20V (e.g. laptops) input voltage to charge from the Type-C port.

    If the customer is going to only use the FET paths to deliver power as a Source, then we suggest you wire the board the same way as the EVM.

    The PP_HV node uses a 12V supply and delivers power to VBUS as a Source.

    The PP_EXT node uses a 20V supply and delivers power to VBUS as a Source.

    If either of these FET paths will be used as a Sink, then please reply with the requirements and we can propose a solution that uses a variable output voltage and a single FET path. At this time, we do not have a Reference Design that validates this proposal, but there is a reference design testing this solution at the moment.

  • 0 in reply to Brian Berner
    Prodigy 40 points
    We are looking at some of the same issues discussed here.

    In our case, we intend to use multiple TPS65982 to delivery at predominately 20V to a series of battery devices.

    We intend to use a System Policy Manager to override the individual Local Policy Managers on each port.

    Our objective is to be able to effective power switching,direction,duration, as well as to potentially craft custom PDO transfers between batteries. This is all in the interest of managing the battery packs as a pooled resource.

    Does the TPS65982 support the USB PD System Policy Manager and if so, what software mechanisms would be need in order to make that function as expected?

    Best Regards

    Chris