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TDC1000-TDC7200EVM: Consumed Current when CPU is disconnected

Ramtin Massoumzadeh31
Prodigy 20 points
Part Number: TDC1000-TDC7200EVM
Other Parts Discussed in Thread: TDC1000, TDC7200

Hello,

I am trying to understand what draws current on the TDC1000-TDC7200EVM board. Even when the CPU is disconnected (jumper JP2 removed) I am seeing a consumption of ~40mA upon measuring which makes no sense to me. What components draw this much current? Is there a way to lower it significantly?

Sincerely,

Ramtin

  • 0
    TI__Mastermind 31655 points
    Hi Ramtin,

    This was something I looked into a while ago. It turns out that the CPU is still getting power even when JP2 is removed. You'll find that the CPU side of JP2 is sitting at about 2V even when the jumper isn't closed.

    The VBUS is connected to the CPU at all times, and this goes into an internal LDO in the MSP430. I don't know enough about the MSP430's internals to know for sure, but the input voltage could be going elsewhere and appearing at the VCC. In any case, the MSP430 will still be drawing current even when the JP2 is removed.

    In isolation, the TDC1000 and TDC7200 meet their specified current consumption numbers, so I would not be concerned about the current consumption of the EVM as a whole.

    Regards,
  • 0 in reply to Scott Cummins
    Prodigy 20 points

    Hi , thanks for the quick reply!

    The problem is that my team and I are using your PCB-layout as a reference when designing ours and we have difficulties determining where it is behaving incorrectly (i.e. drawing this much current). The MSP should not draw more than 0,29mA. The same thing goes for your GASEVM - it draws roughly 40mA in the same way.

    How do you suggest that we solve this?

    Sincerely,

    Ramtin

    EDIT: I've tried to supply the MSP430 with 3,3V through its jumper instead of having the board connected to the USB - this lowers the total consumption by ~10mA, which means that I am now seeing ~30mA so you were correct in that sense that the internal LDO of the MSP430 was consuming some energy. What else can we do?