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BQ25886: Charging startup error

abarnas.see
Prodigy 55 points
Part Number: BQ25886

Hello,

I am looking for a hint debugging the BQ25866 charging circuit. After connecting the power adapter STAT diode blinks once about 1s and then starts blinking about 5Hz. After that goes black. And the battery isn't charging.

What is suspicious for me yesterday it worked. 

For me, it looks like VBUS overload but I don't know where to look for the short-circuit as far as it appears only when it is checking the power source. When I connect the power adapter without the battery connected, STAT goes low stable, I connect the battery then and it is charging but only 270mA. Yesterday it was ca. 1A.

Current and voltage settings:

ISET   R = 600R

ICHG  R = 8K2

VSET  R = 150K

Oscilograms:

STAT (Diode anode):

VBUS:

Best regards

Adrian Barnaś

  • 0
    Prodigy 55 points

    I did not mention it but I checked it with two different wall adapters and four different USB-C cables.

  • 0 in reply to abarnas.see
    TI__Guru**** 166416 points

    Hi Adrian,

    Can you post your schematic?

    This device is sensitive to input line resistance and inductance. If you use an oscope to measure VBUS and IBUS on each board, you will likely see that the bad boards show ringing of VBUS either above VBUS OVP or below VBUS UVLO or both.  If that is the case, then you may be able to prevent this by either clamping the input current lower than 3.0A using the ILIM pin or adding more capacitance at PMID.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 55 points

    Hello Jeff,

    I cannot post schematics here because of company policy. 

    Yes, there are oscillations present on the input line during startup as shown on the oscillograms I posted. I have 1u+10u PMID capacitance as DS suggested. I tried to increase capacitance by adding 22u cap. (all ceramic). I tried also a few different capacitances. But it is still not working.

    My VBUS trace is 15mm long and 3mm wide [except 3mm long connection to IC]. I was trying to use different USB cables 0.5 - 1.5m different adapters and eventually lab power supply (I have shorted D+/D- lines). So cable resistance/inductance shouldn't be an issue.

    Clamping input current does help but charging current is one of the most important design factors in this project. 

    Maybe I should change the Inductor? I am using SRN8040-1R0Y.

    Best regards

    Adrian

     

  • 0 in reply to abarnas.see
    TI__Guru**** 166416 points

    Hi Adrian,

    Changing inductor is not recommended.  I will friend request you.  Can you then post schematic and screen captures or pdf of your layout in private chat?  Adding more capacitance on PMID (up to 47uF) may be required.

    Regards,

    Jeff