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BQ76PL455EVM: BQ76PL455EVM WAKEUP PROBLEM

Sevval Yorulmaz
Prodigy 10 points
Part Number: BQ76PL455EVM

Hello,

1- I have a bq76PL455EVM. It connects with microcontroller. At the first power-up, the D22 led seems to turn on as soon as the Wake signal is gone, but it flickers and the EVM does not wake up. I connect BAT16 and BAT0 before Vsense inputs. Since I use a single structure, I feed the VP pin from the microcontroller. But in no way does the EVM wake up. When I look at the Wakeup test point with the oscilloscope, I see that it suddenly drops from 5V to 2V.
2- By the way, I am testing for 6 cells and the led of the last cell is constantly on, even though there is no power.
What could be the problem, can you help?

  • 0
    TI__Prodigy 50 points

    Hi Sevval Yorulmaz,

    1. Based on your description, the D22 led flickering indicates that the device is not properly regulating power. You mentioned that you are feeding the microcontroller to the VP pin. However, VP is meant to regulate 5.3V supply for the chip’s digital logic. You can reference the EVM user guide for more information on the schematics and pin connections. The improper connection by the microcontroller to the VP is probably causing the wakeup problem. To properly connect the microcontroller, you can reference figure 36 in the datasheet using pins: VIO, WAKEUP, FAULT_N, RX, and TX. (GPIOS optional)
    2. If the led of the last cell is constantly on without power, then it could suggest that the cell balancing is active for the last cell. Could you check whether the cell balancing for BAT 6 is on? You could check by measuring across Q6 FET in the Figure 43 schematic in the EVM user guide.

    Hopefully this helps!

    Best regards,

    Anthony

  • 0 in reply to Anthony Zhang
    Prodigy 10 points

    Hi Anthony, I made a mistake, I meant VIO instead of VP. 

  • 0 in reply to Sevval Yorulmaz
    TI__Prodigy 50 points

    Hi Sevval,

    Could you send us a scope shot of  RX, TX, VIO, and WAKEUP pin during wakeup? Also, are you using the example code with the TI microcontroller or are you using your own custom microcontroller? Can you try it with our example code and microcontroller?

    Can you also tell us the BAT16 voltage that you are working with to power the EVM?

    Best regards,

    Anthony