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BQ24172: Minimum current

Arkadi shap
Intellectual 660 points
Part Number: BQ24172

Hi,

What is the minimum current of BQ24172?

(I need a minimum current of 80mA).

From the graphs in the datasheet it seems that the current is 0.5A. 

However, i am sure that the current may be lower (of course the efficiency would be low...)

If i cant get 80mA, please advice a switching (not linear) battery charger for such currents.

Best Regards,

Arkadi

  • 0
    TI__Guru**** 165786 points
    Hi Arkadi,

    Because the current regulation accuracy is a function of voltage across the external sense resistor (Rsr) as seen by the Kxxx specs on datasheet page 7, it is theoretically possible to achieve regulation accuracy within the datasheet spec if you increase the Rsr resistor. However, for Icharge = 80mA, the Rsr will need to be 50mohm or larger to achieve Vsrn-srp = 4mV. Termination accuracy will suffer unless you increase the Rsr resistor even larger. TI has not tested this IC with larger Rsr resistors but, in theory, the device should function. Also, with the typical inductor value, the switching charger will operate in DCM, resulting in large output ripple, which will degrade accuracy as well. If you use the design spreadsheet, you can optimize the inductor and output capacitors for the charger to operate in CCM at low current.

    TI does not have a switching charger designed for optimal accuracy down to Icharge=80mA. Choosing one with external Rsr resistor is the best choice.

    Regards,
    Jeff.
  • 0 in reply to Jeff F
    Intellectual 660 points
    Hi,
    Thank you very much for your detailed answer!
    You mentioned a ‘design spreadsheet’ to optimize the inductor, where can I find it?

    Best Regards,
    Arkadi