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TPS65983B: What is the need of having I2C Port 2

Alice Ng
Intellectual 330 points
Part Number: TPS65983B

Hi, 

My design follow Intel Apex Creek ATX Reference Design. The I2C_SDA2 & SCL2 are connected from Primary TPS65983B & Secondary TPS65983B. I probed on these pins & not able to capture any communication on these I2C2 lines. May I know...

1. what is the need of having I2C2?

2. In what scenario, I2C2 will have communication?

Thanks,

Alice

  • 0
    TI__Expert 4455 points

    Hi Alice,

    The primary device can act as the I2C master in certain scenarios .

    One is if the Source Policy Manager is set up in Master mode. It can control a slave 83B using I2C.

    Regards,

    Scott

  • 0 in reply to Scott T
    Intellectual 330 points

    Hi Scott,

    Can you please guide me how to set source policy manager to master mode? 

    How can I check when will the primary device is a master?

    Thanks,

    Alice Ng

  • 0 in reply to Alice Ng
    TI__Expert 4455 points

    Hi Alice,

    I double checked and the default Apex Creek project with Dynamic charging has Source Policy Master enabled.

    When either the master or slave port enters a PD contract as a Source with CapabilityMismatch, then the master requests the Sink Capabilities from its port partner.

    If an extra allocation can be made then there will be I2C communication between devices.

    Regards,
    Scott

  • 0 in reply to Scott T
    Intellectual 330 points

    Hi Scott, 

    Thanks for the further explanation. Would like to confirm my understanding is correct...

    "When either the master or slave port enters a PD contract as a Source with CapabilityMismatch, then the master requests the Sink Capabilities from its port partner." means:

    When a Host is not capable of providing 15W to all ports, a Host will implement a source policy manager to dynamically allocate power across its USB Type-C ports. E.g. if the first connection is a 15W device, the source policy manager may reduce the power advertisement on the 2nd port to 4.5W. And this communication between both PD controller is through I2C_2. 

    If above is correct, does this ONLY related to host? From my understanding, self powered device is required to support 15W for each port. 

    Thanks & Regards,

    Alice Ng

  • 0 in reply to Alice Ng
    TI__Expert 4455 points

    Hi Alice,

    The policy master should check if Master or Slave port has entered PD with ‘Capabilities Mismatch’ Bit Set.

    Regards,

    Scott