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BQ25120: BQ25120A

Shlomi Yehezkia
Mastermind 6150 points
Part Number: BQ25120

Hi Team,

I facing few issues with the battery charger in terms of charging current and Vin range.

 

I set the device to I(ILIM) of 400mA and I(chag) of 300mA, VINDPM=4.2V,

Battery - Lithium-Pol Vbat_max=4.2V, capacity 400-550mAh.

 

I feeding the device (VIN) with external power supply 5V±8%.

 

During standard operation when VIN is above 4.7V the battery is charged at 280mA and the circuit (Isys @VSYS) consumes 120mA.

 

I facing a problem that when VIN reduced to 4.6V the charging current reduced to 200mA or less (Isys @VSYS consumes 120mA), when I increase the voltage by 0.1V to 4.7 the battery charge current increased to the required value of 280mA.

 

I disabled the VINDPM but it didn't change the charging current.

 

The battery voltage is 3.7-3.9V, PMID voltage is 4.55V so I don't understand why the device reduce the charging current at this state.

 

In order to overcome this problem, I thinking of feeding the device with 5.2-5.4V ±5%, but then I might have a problem with voltage above 5.5V that will activate the OVP.

Thanks,

Shlomi

BQ25120A.docx

 

 

  • 0
    TI__Genius 12485 points

    Shlomi,

    One other loop to remember is the VDPPM loop which is a function of VBATREG. 

    Can you lower your VBATREG resistor to say 4.0V and see if the current goes back up? Is VPMID 4.55V during this condition or at a different read point?

    Any other faults on I2C?

    Regards,

    gautham

  • 0 in reply to Gautham
    Mastermind 6150 points
    Hi Gautham,

    Reducing the Vbatreg to 4.0V increased the charging current, so it means that even when the VPMID is 4.55V Vbatreg can't provide 4.2V.

    The VD(PPM) according to the data sheets is 0.2V typical, can TI provide the max value, so I will be able to calculate the minimum voltage at PMID for Vbatreg of 4.2V?

    One more issue related to the data sheets is the t/CD_DGL parameter, the value listed is 100uS (Typ.), I would like to know if I can have the maximum value, I need to know how much time to wait between the rising edge of CD\ and the transition from "Hi-Z" to "Active Battery" in order to communicate with the device using the I2C.

    Thanks,

    Shlomi
  • 0 in reply to Shlomi Yehezkia
    Mastermind 6150 points
    Hi Gautham,

    Reducing the Vbatreg to 4.0V increased the charging current, so it means that even when the VPMID is 4.55V Vbatreg can't provide 4.2V.

    The VD(PPM) according to the data sheets is 0.2V typical, can TI provide the max value, so I will be able to calculate the minimum voltage at PMID for Vbatreg of 4.2V?

    One more issue related to the data sheets is the t/CD_DGL parameter, the value listed is 100uS (Typ.), I would like to know if I can have the maximum value, I need to know how much time to wait between the rising edge of CD\ and the transition from "Hi-Z" to "Active Battery" in order to communicate with the device using the I2C.

    Thanks,

    Shlomi