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BQ25883: Sometimes can not enter into fast charging

Intellectual 830 points

Replies: 2

Views: 27

Part Number: BQ25883

Hi Team,

When using BQ25883, Sometimes the whole charging current is 70 ~ 100mA, sometimes it can enter the fast charging state.  I cannot loacte the problem. The following is the schematic and register configuration table. Could you please help to check whether something in these two parts are abnormal? Thank you very much.

Note: When using the OTG function, it is necessary to set 06h bit7 (EN_OTG) = 1 and bit3 (EN_CHG) = 0.

  • Guru 87660 points

    Hi Gene,

    Regarding your schematic, SYS cannot be left floating.  Even if you have no SYS load, you should put some capacitance on SYS.  I recommend splitting your 44uF on BAT to 22uF on SYS and 22uF on BAT.  With D+/D- floating, IINDPM auto sets to 500mA at startup.  The BTST to SW capacitor voltage rating is too low.  It holds REGN+V(SYS) voltage which is so close to the capacitor voltage rating that the capacitance value is likely less than 1/2 47nF. Also, a 900kohm pull down on /CE might produce a voltage from the pin leakage that is above the warrantied minimum.

    Regarding the register settings, if the host isn't writing to the watchdog timer every 40 s, some of the registers reset.  Can you reply back with the status flag and fault registers?

    Regards,
    Jeff

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  • In reply to Jeff F:

    Hi Jeff

    Thank you for the hints. I checked with the SYS voltage, and see the voltage wave, so I add cap as you said, it .seems to work fine now. Will keep tracking if anything wrong afterwards

    Thanks again!

    Gene

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