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TPS65981: Two TPS65981 in one device - one acting as Source and one acting as Sink

Mario Michel95
Prodigy 160 points
Part Number: TPS65981
Other Parts Discussed in Thread: TPS65988, TPS65982

Hello TI Team,

we are using two TPS65981 PD controller in one device. One TPS65981 is a power sink, the other one is powered by the sink controller and acting as a power source. Buspowerz at the sink device is pulled-down by a resister to enable PP_EXT as input power path to power the entire system. Buspowerz at the source device is pulled-up by a resister to LDO_3V3 for disabling power from VBUS. That works! The normal operating voltage is set to 20V via PP_EXT only. I have two questions:

1. During first negotiation the sink controller provides 5V via PP_EXT to the entire system until the 20V contract is established. That will cause an over-current because of the quite high inrush current caused by some DCDC converters used. Is there any possibility to switch the external FET (PP_EXT) only when the 20V contract is established?

2. Both TPS65981 do have dedicated SPI flash memory. Is there a way to use the same flash image and just switch the configuration type (sink or source, etc) by a TPS65981 GPIO?

Thanks and Regards

Mario

  • 0
    TI__Expert 6430 points

    Hi Mario,

    Answers to your queries are as follows:

    1. It's possible, you can configure PP_HV for 5V contract and use PP_EXT for 20 V contract. Alternatively, you can have a GPIO which goes high when 20V contract is negotiated and you can control the DC-DC converters depending on the state of this GPIO.
    2. It's not possible. However, you can have a look at TPS65988 which can manage 2 ports together and can probably solve your issue.

    Please click "This resolves my issue" if I was able to answer your query.

    Thanks,

    Rahul

  • 0 in reply to Rahul Sharma16
    Prodigy 160 points

    Hi Rahul,

    > It's possible, you can configure PP_HV for 5V contract and use PP_EXT for 20 V contract.

    you mean to change the status of the BUSPOWERZ pin externally? It is my understanding that the voltage level on that pin decides between PP_HV or PP_EXT.

    Thanks and Regards

    Mario

  • 0 in reply to Mario Michel95
    TI__Expert 6430 points
    Hi Mario,

    Yes, use buspowerz to use one of the switch and later when 20 V PDO is negotiated then send SRDY command from the EC of the system and pick the right switch PP_HV or PP_EXT. Please refer TPS65981, TPS65982 and TPS65986 Host Interface Technical Reference Manual for more details on SRDY command.

    Thanks,
    Rahul