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Original question:

TPS65981: TPS65981: HPD GPIO Configuration

TPS65981: Sink/Source role switching

Alen Barisic
Intellectual 1300 points
Part Number: TPS65981
Other Parts Discussed in Thread: TPS65982

Hello,

we are developing a device with an user interface to an iPad via USB-C . 

In that configuration, our device acts as a USB sink and iPad acts as a USB Host, and the iPad sees our device as if it was a External Ethernet interface through Linux USB NCM gadget driver on our SoM.

This configuration worked fine till now. But We had a new requirement that, when user wants (through a button or a switch for example) our device should start charging iPad without losing existing data connection. Here I think we need an USB PD which supports Fast Power Role change. Please see the block diagram below:

By default first default connection (when user fist plug the cable at both USB-C side) iPad will be SOURCE and our device will be SINK.

When the user press a button on the GPR side, GPR SOM should communicate through I2C lines with TPS65981 and send a kind of command to TPS65981 to switch the existing role from SINK to SOURCE. And when user press the same button again, it should be possible to switch from SOURCE to SINK role back.

 

Here are my questions:

1. Such a fast role switching from Sink to Source and Source to Sink is possible with TPS65981?

2. It should be possible for us to deliver power to the iPad at 20V and 1A. Is TPS65981 capable of giving such a power?

3. I didn't understand the differences between TPS65981,TPS65982 and TPS65986 clearly. Do all those parts fit into our requirement?

Thanks,

Alen

  • +1
    TI__Mastermind 23605 points

    Hi Alen,

    1. The GPR SOM is able to swap from Sink to Source and vice versa. Section 4 of the TRM provides information on commands that can be sent over I2C that can handle power role swaps (SWSr and SWSk)

    2. The TPS6581 PP_HV internal power path supports 20V up to 3A. The PD controller does not provide the power itself so there would need to be external circuits generating the 20V.

    3.  All parts should fill the requirements. They all run off of the same firmware. One of the main differences between 981 and 982 is the packaging, where 981 is qfm and 982 is bga. The 986 does not support external power paths while both the 981 and 982 support external power paths. 

    Thanks and Regards,

    Chris