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BQ25892: Charge current (ICHGR) does not match actual current in warm and cool temperature

Vitor Sousa32
Prodigy 50 points
Part Number: BQ25892
Other Parts Discussed in Thread: BQ25890

Hi,

When temperature is at "TS WARM" or "TS COOL", the "ICHRG" don't correspond to  real current of charge. The current presented by the "ICHRG" is much higher  than in reality.

Some settings that I always have by default:

- JEITA_ISET:  0 – 50% of ICHG

- JEITA_VSET: 1 – Set Charge Voltage to VREG during JEITA high temperature

- ICHGR: 1536mA

- IINLIM: 500mA

ICHG: 600mA who is this value possible just for cool and warm temperatures? 

  • 0
    TI__Mastermind 25800 points
    Hey Vitor,

    There are a few things to note here:

    1) In TSCOOL, we ramp back the current to 50% of the ICHG current.

    2) In TSCOOL, we ramp back the battery regulation voltage.

    3) When the part is in IINDPM (i.e. when attempting to pull > IINDPM (500mA) from the input), the charge current will be reduced as such to maintain that IINDPM value at the input. If further load the charger (through PMID or VSYS), you will further have the charge current further reduced.

    I'm guessing ICHGR = 1536mA is the register setting, correct? And ICHG: 600mA is what you are measuring into the battery, correct?

    If so, it seems like the part is running into IINDPM, and preventing the charge current from being sufficiently large such that the input current limit is exceeded.

    Try increasing your IINDPM setting (if possible as spec'ed by your input power supply power rating), and see if the charging current goes to 1536mA*50% when in TCOOL.

    When in TWARM, make sure the charge will enter CV charging mode at when the battery voltage is at VBATREG - 0.200V.



    Regards,
    Joel H
  • 0
    TI__Guru**** 166626 points

    Hi Vitor,

    With INLIM=500mA and VBUS=5V, maximum input power is 2.5W.  Assuming 95% efficiency, you have 2.375W available output power.  At VBAT=4.1V (just before CV mode and expected current taper down), maximum charge current is 2.375W/4.1V = 0.579A due to restricted input current limit.

    In JEITA_COOL at 50% of ICHG, charge current would be restricted to 1536mA*50% if not already reduced by input current limit.

    In JEITA_WARM with Charge Voltage = VREG, there should be no reduction in charge current compared to normal temperature operation.

  • 0 in reply to Joel Hernandez II
    Prodigy 50 points
    Hi Joel H,

    Thanks for your answer!

    My real problem is that ADC doesn't match the charge current, I can only have 500mA and 5V at maximum input power for VBUS. In this test I don't have nothing in sys, so all current is for batteries. But, as the batteries are already quite charged the charge current in the batteries is 300mA (in this case, it decrease the more charged they are), whereas ICHGR (ADC conversion of Charge Current) is 600mA. This charging current doesn't match the actual charging current in TS COOL!

    Best regards,
    Vitor
  • 0 in reply to Jeff F
    Prodigy 50 points
    Hi Jeff,

    Thanks for your answer!

    My real problem is that ADC doesn't match the charge current, I can only have 500mA and 5V at maximum input power for VBUS. In this test I don't have nothing in sys, so all current is for batteries. But, as the batteries are already quite charged the charge current in the batteries is 300mA (in this case, it decrease the more charged they are), whereas ICHGR (ADC conversion of Charge Current) is 600mA. This charging current doesn't match the actual charging current in TS COOL!

    Best regards,
    Vitor
  • 0 in reply to Vitor Sousa32
    TI__Guru**** 166626 points

    Vitor,

    This is a known issue.  During JEITA Cool, when REG07[0] = 0, actual charge current = REG12[6:0] / 2 and when REG07[0] = 1, actual charge current ~= REG12[6:0] * 4.  During JEITA Warm, the ADC ICHRG should read correctly.  Keep in mind that in JEITA Warm, VBATREG is lowered.   If the battery is close to full charge, then goes into JEITA warm, the charge current will reduce further.

  • 0 in reply to Jeff F
    Prodigy 50 points
    Jeff,

    Thanks for your answer!


    When the bq25892 uses the termination current, does it use the actual charge current (Ichg) or the ADC charge current to compare with the ITERM and then terminate the charging?


    Does bq25890 also have the same problem reading ADC charge current to TS COOL?


    Best regards,
    Vitor