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TPS65987D: Voltage on VBUS line

sameer kunte
Prodigy 170 points
Part Number: TPS65987D

Hi TI,

we are using TPS65987D in our design. Please find attached block diagram. Our design takes power supply from two ways i) from USB type C adapter and ii) from battery.

We are using 'SWITCHING LOGIC' (MOSFET) to operate our system from outside supply (from USB type C) when it is present otherwise from battery voltage. For that voltage at point A must be greater than what is at B (which is 9V fixed from booster output).When this condition is fulfilled then A to C path is ON otherwise B to C will be ON.

In the datasheet of TPS65987D, section 9.2.1. "Under normal conditions, all high power PD contracts should start at 5 V and then transition to a higher voltage." is written. So,for my case Voltage at point A will be less than 9 V.

i)How it will scale up to a higher voltage? ii) Is this Voltage scale up dependent on system load? iii) Is there any way so that output of TPS65987D will be 12V after plugging in the supply  from USB connector.

Thanks for reading.

  • 0
    TI__Expert 6430 points

    Hi Sameer,

    Answers to your queries are as follows:

    i) How it will scale up to a higher voltage?

    Ans: As per the PD specification, a PD connection always starts with 5V contract and then can go upto 20V contract depending on the PD adaptor and the PD controller's configuration. The PD picks a higher VBUS voltage only if both the power adaptor and TPS65987D are configured to support higher voltages and negotiate for it.

    ii) Is this Voltage scale up dependent on system load?

    Ans: As I explained earlier the voltage at the VBUS only depends on the PD negotiation, it has nothing to do with the system load.

    iii) Is there any way so that output of TPS65987D will be 12V after plugging in the supply  from USB connector?

    Ans: Again it depends on the PD adator and the configuration settings of TPS65987D.

    Please click "This resolves my issue" if this answers your query.

    Thanks,

    Rahul