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CC2640R2F: Unintentional power through programming pins

Rick
Prodigy 140 points

Part Number: CC2640R2F

Hello,

I have a custom board. I am trying to evaluate impact to RSSI from different battery voltages using SmartRF Studio.

I've adapted a LAUNCHXL board to be the programming interface for the board and it works great.

When I remove power from Vin and reconnect the custom board to the lauchpad, the device boots up.

The only electrical connections are through pogo pins that connect to TMSC, TCKC, TDO, TDI and RESET.

I get ~2.8v measured on my custom board Vin pins.

Am I getting leakage through TCKC and its powering the device?

TCKC is around 3.3v

RESET is less then 2.8v

And if I am getting leakage through there, how do I mitigate the system powering up through that pin.

I appreciate the help on this head scratcher.

  • 0
    TI__Mastermind 38575 points

    Hi Rick,

    Yes you're right. You are powering the other pins from the parasitic voltage generated due to the ESD protection diodes on the chip. Is it your goal for the system to not power up when you connect it to the JTAG (The TMCS/TCK/TDO/TSI/RST pins)? I don't believe you'll be able to program it if you do so.

  • 0 in reply to Nathan Block
    Prodigy 140 points

    Hi Nathan,

    Thanks for the insight.

    My goal is to power the device through the battery connector on my device with ~1.9v-3.0 to observe the performance of the system with SmartRF Studio. 

    The issue occurs when I try and test an input voltage lower then the parasitic voltage. The power rails stay higher then the voltage I want to test.

    I've also ran into issues where if I connect the JTAG interface before hooking power to the device, SmartRF tells me either the debug interface is locked or that the device is unresponsive/unknown.

    Powering the device first, then installing into the programming rig allows SmartRF to connect to it, the system voltage will only go as low as the parasitic voltage tho.

    Does this clarify? I can try adding more information as needed.

    -Rick 

  • 0 in reply to Rick
    Prodigy 140 points

    It looks like I have my problem resolved with moving jumper P10 to "Exten Power" on the dev kit.

    Thanks for the confirmation of the parasitic voltage Nathan!