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BQ27520-G4: NG samples doesn't send ACK for 0x55 address

Guru 29340 points
Part Number: BQ27520-G4
Other Parts Discussed in Thread: BQSTUDIO,

Hi Team,

My customer has produced their application with BQ27520-G4 and has seen some samples couldn't be programmed golden file (BQFS file) by bqStudio.
He found these NG samples doesn't send ACK for 0x55 address although most of other samples sent ACK.

When he sent 0x0B address to confirm if these samples stay in ROM mode, these NG samples sent ACK however high frequency pulse occurred as the following.
Have you ever seen the behavior?

CH2: SCL
CH3: SDA


Best Regards,
Yaita

  • Hello Yaita,

    I have not seen this behavior before, it looks like some high frequencies have coupled in with the line. Are there any high frequency traces near the communication lines?

    Sincerely,

    Wyatt Keller

  • Hi Wyatt-san,

    I apologize for late reply.
    I had my customer captured the waveform of VCC and REGIN, it seems VCC (Regulator output of BQ27520-G4) causes the issue because REGIN is relatively stable.
    I also heard there is no such high frequency (about 65MHz) traces near the communication lines.

    CH2: SCL
    CH3: SDA
    CH4: VCC


    CH2: SCL
    CH3: SDA
    CH4: REGIN


    I believe the NG sample is a defective part and it is better for us to send it to TI analysis.
    What do you think about it?

    Best Regards,
    Yaita

  • Hello Yaita,

    What is the occurrence rate of this? I am very doubtful that this is originating from the gauge, since the highest frequency on the gauge is the HFO at just above 8MHz, there's nothin on the gauge that could cause this kind of noise.

    Can you share the schematic of the system so we can review?

    Sincerely,

    Wyatt Keller

  • Hi Wyatt-san,

    I will request the schematic to my customer.
    Could you send me a private message for share the schematics if we get it?
    I would like to share it in off-line.

    Best Regards,
    Yaita

  • Hello Yaita-san,

    I have sent you a friend request.

    Sincerely,

    Wyatt Keller