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TPS25750EVM: TPS25750EVM behavior during testing

MarcS
Prodigy 70 points
Part Number: TPS25750EVM
Other Parts Discussed in Thread: TPS25750

Hi,

Recently I've been using the evaluation board TPS25750EVM. My goal is to achieve the following:

- EVM as a USB2.0 device

- EVM is sourcing power (through the USB-C)

As such, the EVM was configured initially with the default source only (5V,3A) configuration. In order to check the sourcing, I plugged a samsung galaxy tab to it. It worked, the system was drawing 0.6A.

This is a bit weird for me as the tablets are supposed to be able to handle up to 2A of sinking (which would fall into the capability of the EVM board).

Anyway, I started playing a bit with the advanced configurations. More precisely I changed the "Transmit Source Capabilities (0x32)" register, PDO1 (only 1 PDO enabled). I lowered the maximum current value (which lowered as well the current drawn), but I also tried to make it higher (7A typically) to see if the tablet would suddenly start to be able to draw more power.

As a result, the EVM is not providing power anymore, even if I revert to the default configuration (5V,3A). I do not doubt that I messed up either the HW of have put the system in a complicated configuration. I would only like to understand a bit better what I should have done/avoided.

The EVM is powered through cable connected to TP4 (SYS_PWR) and TP5 (GND) at 19V. All jumpers are in place in the default stock configuration.

Thanks for your help.

Best regards,

Marc

  • 0
    TI__Mastermind 25750 points

    Marc,

    When you set the source PDO, you are setting the amount of current that the source will supply, not the amount that the sink can consume.  A phone only taking 600mA is not unusual if it is nearly fully charged.  It would be expected to draw more if it were close to drained.

    There are some really good low cost market available  tools that will allow you to create loading conditions for your design.  Here is one that I use extensivly: https://store.avhzy.com/index.php?route=product/product&product_id=52  This load will allow you to see the voltage and set a load up to 3A and test your setup.  This way you can slowly increase the load until you see the current limit kick in and lower the voltage and ultimately turn off the port in a more controlled manner.

    Here is a debug sequence to go through before to see what is happening:

    1.  Measure the P3V3 and P5V0 voltages and ensure that they are correct

    2.  Measure the SYS_PWR voltage and make sure it matches you input voltage

    3.  Connect the EVM to your PC through the USB port and see if you can program the board

    If all three of these work, then I am concerned that the device may have been damaged during your testing process.  You should be able to get a replacement board through the TISTORE if that is where you purchased it through.

    Regards,

    Chuck

  • 0
    Prodigy 70 points

    Thanks a lot for your very well structured answer Chuck.

    I also figured it could be the tablet being charged too much. That's why I also wanted to try with low battery state one, Unfortunately the EVM stopped to work properly before that.

    As for the debug sequence proposed, unfortunately for me, everything works, except the EVM unable to provide power as previously mentioned.

    In any case, we already started our design with the TPS25750S. My only concern is about the power draw from a tablet being charged. I need to limit the current output to 0.7A max. If I am understanding it correctly, when the tablet connects through USB-C and if the TPS25750 PDO is configured with a max output at 0.7A, it should advertise such capability to the tablet and the latter will not draw more than said current.

    If this is confirmed, I have no more questions Slight smile

  • 0 in reply to MarcS
    TI__Mastermind 25750 points

    Mark,

    Happy to help