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TPS65987D: use with BQ24618 for battery powered dock

dugan yoon
Prodigy 130 points
Part Number: TPS65987D
Other Parts Discussed in Thread: TPS65982, BQ24618, , LM3489, USB-CTM-MINIDK-EVM

Tablet on UFP USB-C connector using TPS65982/7 for PD control.

Wall brick barrel connector and dock battery as power sources in addition to Tablet as UFP source.

Three power delivery modes
PD0. Tablet and Dock Individually Powered by their own batteries, i.e. no PD
PD1. Tablet Powered so that battery can be hot swapped
PD2. Wall Powered to charge both the tablet and the battery

Questions:

1. Control to the two switches that are used by the BQ24618 for adapter and battery appear to be mutually exclusive, and the device has a CE pin that can disable charging.  Can the TPS6598x GPIO be used to turn off both BQ24618 switches to implement PD1 (Tablet Powered mode) described above?

2. Is there a bettter choice for a charging chip for this application?

  • 0
    TI__Mastermind 30000 points

    Hello,

    Question 1:

    You can look through the GPIO events in the Host Interface Technical Reference manual to see if there is a GPIO event for the TPS65987D that matches your functionality for the CE connection. I'm not sure there is a GPIO event to meet this functionality but you can check there.

    https://www.ti.com/lit/ug/slvubh2b/slvubh2b.pdf

    Question 2:

    You will have to reach out to the charger team to see if they have any other recommendations (post similar question on E2E, but have BQ24618) be the part number you reference). Your overall architecture looks correct. One thing that I would suggest is to have the internal PPHV power path for the TPS65987D be a source only instead of bi-directional. Also you will need at least two GPIO's going from the TPS65987D to the LM3489. You can reference the TPS65987DEVM.

  • 0 in reply to Adam Mc Gaffin
    Prodigy 130 points

    More follow on questions.

    Question 3: 

    I looked at the GPIO Events in Table 3-74 of the Technical Reference manual.  Source_Sink_Event_Port1 looks interesting since it can drive the BQ24618 CE pin low when sinking current from the Tablet. Any comments on this usage?

    Question 4:

    A colleague did some testing of the USB-CTM-MINIDK-EVM acting as a UFP sinking from a Laptop. A Dell power brick was plugged into the barrel jack and it became the power source.  However, there are occasional brown outs when unplugging the barrel jack and the power path switches back to the Laptop as the source, even with no loads on the DFPs. Is this a known issue and are there any recommendations for fixing this issue?

    Thanks

  • 0 in reply to dugan yoon
    TI__Mastermind 30000 points

    Question 3:

    Yes, this could be a good GPIO event to use. The TPS65987D will drive this GPIO high when the TPS65987D is acting as the source, and drive the GPIO low when acting as a sink.

    Question 4:

    The test setup you are describing where the dock starts as the power source, but then transitions to a power sink without dropping VBUS is known as a power role swap. I'm not sure if the USB-CTM-MINIDK-EVM supports FRS capabilities. If this is something that you would like to support in your design, you can read the following white paper as well as the following app note.

    http://www.ti.com/lit/wp/slyy147/slyy147.pdf

    http://www.ti.com/lit/an/slvae20/slvae20.pdf