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BQ25120F3A: RESET output pin is always low after powering with battery or VIN

PSG_4
Intellectual 570 points
Part Number: BQ25120F3A
Other Parts Discussed in Thread: BQ25120A

Hi, 

It seems BQ25120F3A  RESET output pin  is always low  after powering with battery or  VIN. Because of this issue , not able to program MCU. 

Let me know what may be reason for BQ25120F3A  RESET  is always low. Need any initialization  through I2C to  disable any feature because of factory settings ? 

Few history about PCB

++++++++++++++

Out design started with BQ25120A in first revision PCB and all interfaces are working perfectly.   Later replaced few board with BQ25120F3A and all are working in first revision PCB. 

once we started with second revision PCB, we used BQ25120F3A straight away in PCB but it seems always low. 

Regards

Sudheer

  • 0
    TI__Genius 11885 points

    Hi Sudheer,

    For more context can you please answer the following:

    -Can you please confirm VIN, VBAT, VPMID, and VSYS when this happens?

    -Additionally, can you please share your schematics?

    -Can you describe any changes related to the BQ or RESET net that may have changed between PCB revisions?

    Best Regards.

  • 0 in reply to Juan Ospina
    Intellectual 570 points

    Hi, 

    Pleas find my answer below.   Let us know BQ25120F3A factory settings for  RESET signal   causing any issues ? It it requires a programming ? 

    1. -Can you please confirm VIN, VBAT, VPMID, and VSYS when this happens?

    Ans: VIN =5 , stable 

    VBAT = Detecting battery . Battery voltage is okay

    VPMID = 5V, stable

     VSYS  = 1.8V , stable

    2. -Additionally, can you please share your schematics?

    Attached Schematic . 

    BQ25120F3AYFP.pdf

    3. -Can you describe any changes related to the BQ or RESET net that may have changed between PCB revisions?

    Between PCB revisions , below changes are made:

    1.   BQ25120A replaced with  BQ25120F3A . But few samples of BQ25120F3A received from TI and mount on first revision PCB and all are working well. 

    2.  GPIO connected to MR# pin in second revision  has changed with another GPIO. There is no pull up for GPIO in second revision (MCU side) . In first revision , there was pull up for GPIO in first revision ( MCU side) 

    Regards

    Sudheer G

  • 0 in reply to PSG_4
    Intellectual 570 points

    Hi ,

    Any update please ..

    Regards

    Sudheer

  • 0 in reply to PSG_4
    TI__Genius 11885 points

    Hi Sudheer,

    Looking at the schematic there doesn't seem to be an issue that would result in the /RESET pin being held low. Is MR voltage being pulled low?

    Alternatively, is there anything that might be pulling the /RESET pin low outside of the BQ?

    Best Regards,

    Juan Ospina

  • +1 in reply to Juan Ospina
    Intellectual 570 points

    Hi Thanks for the detailed reply.

    After debugging more PCBs, it is noted that the issue is with one batch of MCU not with BQ chip. 

     Moreover, I had replaced the non-working MCU in one board with a working batch MCU. The board is working fine after the MCU replacement.

     Thanks for support.

    Regards

    Sudheer