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LAUNCHXL-F28379D: Problem powering the launchpad from external power supply

Damiano Rullo
Prodigy 230 points
Part Number: LAUNCHXL-F28379D
Other Parts Discussed in Thread: TL082

Tool/software:

Hello,

I am working on a project where I need to power the Launchpad from external power supply.

I removed the jumpers JP1, JP2, JP3 to isolate xds100v2 and added JP6 to activate internal step-up, then I applied GND and 3.3V, from external power supply, on connector J10.

It didn't  work.

Sometimes it does not power on at all, sometimes seems to boot but with a stange behavior (for example i see pwm signal appearing and diappearing, SCI1 emitting strange characters on the terminal, and so on).

I am using an external bench dual power supply (because i have to deal with negative signals, between +5V and -5V, and a few TL082 op amps), so I powered the launchpad by connecting J10 between virtual GND and 3.3V using a 3V3 LDO placed bewteen virtual GND and 5V.

I also tried to detach launchpad from the LDO and give 3.3V directly from the power supply.

Tried to physically disconnect the serial port (which is trough FT232RL).

In any case the result did not change.

Do you have any hint?

Can I power the launchpad by populating jumpers JP2,JP3 and  applying 5V on connector J16,  when usb cable is disconnected, to route 5V trough TPS62162DSGT and get the 3.3V out, or do I risk to damage the XDSV100?

Note the launchpad returns fully functional if I place jumpers back in the original position and power from USB, so i would tend to exclude damages to the board.

Thanks in advance

Damiano Rullo

ITALOGIC

  • 0
    TI__Genius 14161 points

    Hi Damiano,

    When you supply power through your lab bench, how much current is being pulled?

    If you can provide a picture of the board in the external voltage supply setup that can more easily help me to identify any potential issues with the setup

    Regards,

    Peter

  • 0 in reply to Peter Luong1
    Prodigy 230 points

    Hi Peter,


    I set the current limit of the power supply up to 500 mA.
    Finally I got it to work by providing both 5V and 3.3V from external Power supply on connectors J10 andJ16.

    When running, it drains about 90 mA.

    No way to get it to work using internal step-up on jumper J6 and providing 3.3V only.

    Regards

    Damiano

  • 0 in reply to Damiano Rullo
    TI__Genius 14161 points

    Hi Damiano,

    Glad that you got it working but that seems weird. Since you are providing both 3.3V and 5V, then you want to disable the onboard 5V boost converter so that you do not have any contention on the 5V rail. But I have suspicions that your 5V boost may not be working properly. Can you check the voltage on the 5V rail when supplying just 3.3V? 

    Note that lack of 5V will not cause the device to not operate properly since only 3.3V is required. Are you running your own project or simply an example file? Maybe you can try testing some of the example files in your project and reporting on the functionality of those examples?

    Regards,

    Peter

  • 0 in reply to Peter Luong1
    Prodigy 230 points

    Yes of course I disabled the boost.
    But if I remove the +5V from the power supply and use the boost I can measure the 5V, but the MCU seems to have problem booting.

    For now I gave up trying to use the boost because the project, which is a pid controller, have a dedaline, and both 3.3V and 5V are available in the final design.

    If I have have the time I will further investigate after the end of the project.

    Thank you

  • 0 in reply to Damiano Rullo
    TI__Genius 14161 points

    Hi Damiano,

    Thanks for the update. I will close the thread for now, please re-open it once you have more time to debug this issue

    Regards,

    Peter