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CC2650STK: Urgent - board short

A K
Intellectual 905 points

Part Number: CC2650STK

We have used CC2650STK gerbers to manufacture the same board but just populate external flash, humidity and light sensors. I am using TI RTOS 2.13, Stack 2.1.1 SensorTag project with below modifications:

  1. Frequency set to 24MHz in appBLE.cfg
  2. Changed bsp_spi.c frame format to POL0_PHA0 to reduce current draw by 0.05mA
  3. Advertising every 1.5s
  4. TX at 5 dBm
  5. Humidity and light sensors read every 60s
  6. LED blinked every 10s

POWER_SAVING is defined. FEATURE_OAD is not defined. At initialization self test code tests the external flash but is never accessed after that. With this setup, the board draws 0.025mA average current while advertising and standby/idle current is 4uA.

The board runs fine with CR2032 battery up to 2.5V. Below 2.5V the sensors stop but board runs fine until battery goes dead. Board runs again with a fresh battery.

We connected a Panasonic CR2477 battery with wires to BAT+ and BAT- terminals. The board runs fine up to 2.8V and suddenly starts drawing 6mA and more. Eventually the board shorts. I have removed R12, FL1, L1, U2, ext flash, humidity and light and the board still draws current when connected to power supply between BAT+/-.

I do not understand why it causes an irreversible damage to these boards with CR2477. I am very much short on time to figure this out so all help appreciated. Thanks!

  • 0
    Intellectual 905 points
    Forgot to mention that I have a board soldered to CR2477 through much longer wires that has been running fine for more than a month. The boards that are failing have much shorter wires. I am wondering if the humidity sensor gets affected because of the wire length and starts drawing more current eventually shorting the board. Would this be the cause?
  • 0 in reply to A K
    TI__Mastermind 36395 points
    AdtK,

    It does not really make too much sense, to really dig into this I would like to perform a schematic review for you. I will send you a direct email.

    Regards,
    /TA