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BQ25886: STAT charge indicator LOW status delayed couple seconds or minutes

Jonathan Navor
Genius 9475 points
Part Number: BQ25886


Hello Team,

Good day! We need your help with our customer's concern below.

We use the BQ25886 standalone, works well, except for 2 problems we cannot fix it.

1, If the 5V standard USB-c charger is connected, the STAT pin goes LOW after a lot of delays (more seconds, even more minutes if the circuit is not warmed up.)

2, The battery charging current is sometimes below the configured value and does not charge properly but the STAT pin is LOW. In this case, the only solution is to disconnect and reconnect the USB connector.

 

Configuration:

Charge current limit: 1.8 A

Input current limit: 2.8 A

Charge voltage: 8.4V (VSET floating)

OTG disabled

 

The battery pack we tried: 2S3P and 2S2P 7800mAh, 9000mAh.

The issue is independent of USB-c charger type / NTC value, independent from current limit configurations, and independent from battery pack type, all is 8.4V maximum charged voltage.

We cannot figure out what part is responsible for these issues. I attached the circuit diagram with the USB connector wiring.

Please see attachment

  attachments (2).zip

Best regards,

Jonathan

  • 0
    TI__Expert 4285 points

    Hi Jonathan,

    I suspect device got confused during USB D+/D- detection. Have you tried other type of adapters?

    When it "worked", what's the charge current? Can you elaborate "does not charge properly"?

    Best Regards,

    Linhong

  • 0 in reply to Linhong Qin
    TI__Genius 9475 points

    Hi Linhong, 

    Thank you for the response. Here is the customer's answer to your question.

    We have tried 5 types of adapters with different cables or connected to notebook USB, and always the same result. The STAT HIGH -> LOW is delayed 2 seconds after the usb cable is connected. Sometimes there is much more delay, but this is a very rare case.
    The normal charging current is between 1500-1800mA, and 700-900mA if not charging properly. This issue probability is around 1-2% when the USB cable is plugged in. If the charging current is low, the only way is to unplug and plug again the USB cable.
    This issue is noticed on all prototype circuits, with different battery packs.
    PCB stack is 4 layers: signal / gnd / signal / gnd.
    USB D+/D- wiring is very short on PCB.
    All USB connector pins connected properly, D+, D-, GND, VBUS.
    CC1, CC2 via 5.1k to GND.
    TX, RX pins are floating, SHIELD is floating.
    Best regards,
    Jonathan
  • 0 in reply to Jonathan Navor
    TI__Expert 4285 points

    Hi Jonathan,

    Normally D+/D- detection won't take more than a few hundreds of msec. It takes another 200msec or so to bring up LDO or V_REGN. Then charger will start to turn on converter. To better debug this, we need to track VBUS, D+/D-, V_REGN, and IBAT, to see where is the biggest delay.

    Best Regards,

    Linhong