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Original question:

TPS65983B: Current limit of PPHV and PP_EXT

TPS65981: TPS65981: Current limit of PP_HV

Steve Schefter
Expert 1780 points
Part Number: TPS65981
Other Parts Discussed in Thread: TPS65983B

Hi.

In the TPS65981 datasheet under "Port Power Switch Characteristics", it lists the current limits for PP_HV for different settings.  However, I can't find the corresponding setting either in I2C-accessible registers or in the Application Customization Tool.

The E2E thread https://e2e.ti.com/support/interface/f/138/t/862719 indicates that the current limit is hardwired and cannot be set on the TPS65983B.  Is that also the case for the TP65981?  If not, how is it set?

In either case, can I determine what the setting is?

    Steve

  • 0
    TI__Genius 9630 points

    Hi Steve,

    The TPS65983B is only approved for use in Intel TBT device reference designs and on that specific the current limits cannot be changed.

    The TPS65981 on the other hand you can set the advertised current in the transmit source capabilities and transmit sink capabilities register, registers 0x32 and 0x33. The peak current percentage field in the Transmit Source Capabilities can be used to increase the OCP trip point.

    Regards,

    Emma

  • 0 in reply to Emma Hoying
    Expert 1780 points

    Thanks for the quick response Emma.

    I'm not quite following some details.

    From the description of register 0x32 in the TRM, it looks like you encode up to 7 x 32 bit PDO Source messages per the PD specification.  That would allow for arbitrary values.

    However, the datasheet, under Port Power Switch Characteristics, describes PP_HV limit having 16 settings of the current with specific min/typical/max values.

    How do the two relate?  Where is the selection from among the 16 settings made?

    Regards,
        Steve

  • 0 in reply to Steve Schefter
    TI__Genius 9630 points

    Hi Steve, 

    Though we can set anything in the GUI, the hardware is only capable of recognizing the listed data sheet buckets, so the firmware does its best to fit into the selected value into one. 

    When you select a current limit in the GUI, you can go into the datasheet and see which bucket it fits into. 

    Thanks,

    Emma

  • 0 in reply to Emma Hoying
    Expert 1780 points

    Thank you Emma.

        Steve