• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 202 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25886: STAT pin goes high right after VBUS applied.

Chase Jeong
Mastermind 7365 points
Part Number: BQ25886

Dear TI experts,

my customer tests BQ25886 on their own PCB.

During the test, they found that STAT pin goes high right after VBUS applied, and goes to low after 380ms.

please see the schematic and waveform.

As you can see, they control 2 LEDs using 1 stat pin. so if they apply VBUS by adapter, greed LED turns on for 380ms and then red LED turns on.

my customer wants to reduce this 380ms to 0s.

Is there any way to reduce this time to zero? making additional circuit is fine.

Please check this issue. Thanks.

Best regards,

Chase

  • 0
    TI__Mastermind 40305 points

    Hello Chase,

    Can you please clarify your setup and which waveforms are which? When I apply ~7.6 V VBAT first with 8.4 V VREG on BQ25886 EVM followed by attaching ~5 V VBUS I see VBUS come up and then STAT go low 400 ms later. The battery starts charging then. STAT is high before I plug VBUS in when only battery is attached.

    Please keep in mind that before the converter starts there is a minimum of 220 ms to power on REGN, not to mention poor source qualification and input source qualification which take additional time. I believe this is the prescribed time.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Mastermind 7365 points

    Dear Mike,

    Thank you for your support.

    waveform 1 is VBUS, waveform 2 is STAT pin.

    Please keep in mind that before the converter starts there is a minimum of 220 ms to power on REGN, not to mention poor source qualification and input source qualification which take additional time. I believe this is the prescribed time.

    -> So, 220ms is initial time to power on REGN after VBUS applied. and during this 220ms, STAT pin goes to high. Am I right?

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Mastermind 40305 points

    Hi Chase,

    In our EVM we use pullup for STAT as output of LDO from BAT. This means the pullup rail will always be present on battery only. With your setup you pull STAT up through VBUS. This makes sense that before VBUS is applied STAT is low because VBUS is low. Next, during the initialization process, STAT has not yet turned on to indicate converter running. In my circuit this keeps STAT high, in your circuit STAT is pulled high from VBUS. After initialization for both, STAT goes low.

    The timing is correct.

    Regards,

    Mike Emanuel