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MSP-EXP430FR2355: Is there a way to disable EnergyTrace DC-DC converter and use the linear LDO regulator to power the target MCU?

Kevin Tomm
Prodigy 20 points
Part Number: MSP-EXP430FR2355
Other Parts Discussed in Thread: MSP430FR2355, , ENERGYTRACE, MSP-FET

I am developing a device that uses the Smart Analog Combo SAC and DAC features on the MSP430FR2355.

I have determined that the DC-DC converter on the MSP-EXP430FR2355 launchpad (used by EnergyTrace) is causing significant noise in my analog circuit.

The launchpad is also equipped with a linear LDO regulator option to provide VCC to the target, but I cannot find a way to disable EnergyTrace and switch to the LDO regulator for debug sessions in CCS-12.

Can anyone point me to a setting in Code Composer Studio 12 to allow me to do this?

I found a checkbox for EnergyTrace -> "Enable Auto-launch on target connect",  but I have confirmed the un-checking it does not disable the (noisy) DC-DC converter.

Thanks in advance!

Kevin

  • 0
    Guru 38800 points

    WHy not just pull the 3.3 V jumper and either put in some extra filtering or tap off the 5 V and put in your own LDO? I think the LDO on the LP is used for the XDS110.

  • 0 in reply to Keith Barkley
    Prodigy 20 points

    Hi Keith,

    Thanks for your reply. Both are good ideas.

    For now I pulled the 3.3V jumper and connected a fly-wire from the target VCC to the Linear regulator output (EZFET_VCC) on the debug portion of the Launchpad. That solves the noise problem for the short term, but I was hoping for a more elegant solution that does not involve modification of the Launchpad PCB. 

    Also, longer term (production PCB) I plan to use the MSP-FET for in-circuit debug.

    The Launchpad hardware supports selection of LDO or DC-DC to supply target VCC, so I am surprised there does not seem to be a way to choose the option in Code Composer IDE.

  • 0 in reply to Kevin Tomm
    TI__Mastermind 27785 points

    Hello Kevin,

    I don't know of anyway to do this.  I actually wasn't sure it was even an option, but I do see that in the MSP-Debugger UG that eZ-FET v2.x+ versions should support switching but this is news to me.  I wasn't even able to quickly confirm the version on this specific Launchpad.  

    I've only ever done it like Keith mentioned.  Disconnecting the supply and providing my own. 

    Thanks,

    JD 

  • 0 in reply to JD Crutchfield
    Guru 38800 points

    I took a dive into the schematic for a few Launchpads with Energy trace. The DUT is supplied via an analog switch that is controlled by two GPIOS from the EZ-FET, and it switches between the LDO and the DC-DC converter. So all the hardware is there...

  • 0 in reply to Keith Barkley
    Prodigy 20 points

    Hi Keith,

    Yes. Here is the specific Launchpad I am using. There is an analog switch provided by IC103:

       https://www.ti.com/lit/ug/slau680/slau680.pdf

    So, in theory, the CCS IDE should be able to control it. But I have had no joy finding a way to do that. I just wanted to make sure I did not miss anything. ...It would not be the first time :)

    If there is no way to control it in CCS, I will just use the fly-wire jumper to the LDO VCC supply for now. That way I can move forward with my firmware development.

    At least now I know the analog noise is coming from the DC-DC converter, so it should not be there in the final (battery powered) product.

    Thanks to you and JD for all your help!

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