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Regarding BQ24103 Why charge current is reducing in the CC Mode?

Jake Kim
Intellectual 680 points
Other Parts Discussed in Thread: BQ24103

I have a question about BQ24103.

When I was testing charging with it. Charge current is reducing in the CC Mode as you can find the graph in below image.

In the Datasheet, It doesn't have a variation like this in the CC mode. Would you explain this phenomenon?

 

 

 

 

  • 0
    Guru 22270 points

    Hello Jake,

    If I understand your question correctly, you want to know why your diagram isn't exactly the same as the one found on page 13 of the data sheet?

    From your graph, it looks like the device is operating correctly.  The graph on page 13 should be considered as an idealized representation of what is happening.  Depending on the battery condition, temperature, etc, I would think that it would be very unlikely that you would see a completely linear relationship between the charge current and voltage.  The change in charge current looks to me like it is regulating correctly, adjusting itself by ramping down near the end of the CC Mode.

    Thanks,

  • 0 in reply to Greenja
    TI__Mastermind 31120 points

    This is not typical, but are two reasons for it.

    It is typical for the current to start tapering once the Charger's output voltage nears 4.17V.

    Thus, if your design has an increased amount of resistance between the output pin of the charger IC and the battery, the battery might be at a much lower voltage but if the output of the charger is near 4.2V the current will taper.  Reducing this resistance will improve this case.

    The other reason is if the input voltage is near the battery voltage.  The FETs do drop a fair amount of voltage (>100mV), so if your input voltage is within 500mV of the battery voltage, one may start to see some roll off of the CC.  Try raising the input voltage 500mV or more and see if the issue goes away.

  • 0 in reply to Charles Mauney
    Guru 22270 points

    Well, I stand corrected.

    Thanks for putting me straight on the typical operations for this device.