• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 34 subscribers
  • Views 591 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TPS65981: TPS65981EVM + DP-EXPANSION-EVM unstable settings

TPS65981: TPS65981EVM + DP-EXPANSION-EVM unstable settings

Mario Michel95
Prodigy 160 points
Part Number: TPS65981
Other Parts Discussed in Thread: LM3489, , CSD87501L, TPS6598X-CONFIG

Hello TI Team,

coming back to the discussion we had some time ago about our problem, unstable behavior with the TPS65981EVM. After a while being blocked with other tasks I picked up our Type-C PD project again and I've noticed that the current limit of the LM3489 is set to less than 1A inductor peak. Taking the ripple current into consideration the load current limit will be quite low (approx 500-600mA) causing the unstable behavior when sourcing higher demands. I've changed Radj to 24K (approx 2.8A load current) and now I can charge a Powerbook for example. Anyway, when sourcing 20V loads we use the external FET path now.

Btw, the EVM user's guide is telling that the board can power up to 60W (20V/3A). Why isn't possible to provide up to 100W by using the external path FET?

Thanks and Regards

Mario

  • 0
    TI__Genius 10370 points

    Hi Mario,

    Welcome to e2e! The TPS65981 can do 100W (20V/5A) but one must make sure to choose external FET's that have a strong SOA curve. The current EVM has external FET's that can handle 3A/20V, but not 5A/20V. Hence why the EVM can only handle 60W (FET limited). Stronger FET's can handle 5A/20V :-)

    I hope this helps and If this answers your question, PLEASE select  This resolved my issue 

  • 0 in reply to Aramis P. Alvarez
    Prodigy 160 points
    Hi Aramis P. Alvarez,

    thanks for the information.
    My EVM currently is using the CSD87501L FET, which is on board and in the TI EVM BOM. This FET is advised in the TPS65981 datasheet for 20V/5A.

    Chapter 10.2.1 Fully-Featured USB Type-C and PD Charger Application

    Can you clarify this?

    Kind Regards

    Mario
  • 0 in reply to Mario Michel95
    TI__Genius 10370 points

    Hi Mario,

    Sorry for the confusion, let me clarify: I had thought that the user's guide stated this FET can handle 20V/3A, but this seems not to be the case. This FET should be able to handle 20V/5A but this all depends on multiple variables in your design (Ambient Temp., Board Layout, Heat Sink, etc.) One should always take into account these calculations to de-rate the SOA curve of the FET, for a particular application.

    With that being said, you can use the Application Customization Tool (GUI) to set a 20V/5A PDO. You can download this tool here (TPS6598x-CONFIG): http://www.ti.com/tool/tps6598x-config.

    One last thing, even if the Source and Sink boards have the capabilities for a 20V/5A PD contract, the current will be limited by the type-c cable. Make sure to purchase a 5A rated Type-C active or e-marked cable. If not, the PD contract will be limited to 20V/3A because of the cable :-)

    If this answers your question, PLEASE select  This resolved my issue