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BQ24074: Maximum capacitance on OUT pin.

Robert Spoelstra
Prodigy 20 points
Part Number: BQ24074

Tool/software:

I'm designing a circuit with the BQ24074 charger and followed the datasheet's suggestion of adding a 4.7uF decoupling cap to the output. However the 3.3V LDO I plan to connect to the output also recommends a 10uF input cap and a DC boost converter I want to connect recommends a 4.7uF input cap.

This obviously adds up to much more than just the 4.7uF cap and I'm wondering whether I should worry about in rush current? I was hoping maybe the datasheet would give more information about the turn on time of Q2 (the FET that connects BAT to OUT). All the datasheet seems to mention is that 5A continuous current 9BAT -> OUT)  is allowed and that the output has short circuit protection.

Should I worry about potentially exceeding the max current rating of the BQ24074 because of inrush current generated by those caps?

  • +1
    TI__Mastermind 26110 points

    Hi Robert, 

    In the pin functions table on BQ24074 datasheet page 8 the OUT pin description mentions the recommended output capacitance should be in the range of 4.7uF to 47uF. Therefore, there should be no issue with adding 10uF + 4.7uF in addition to the original 4.7uF. 

    Please make sure at least the minimum recommended 4.7uF capacitor is placed near the OUT pin of the BQ24074. The additional input capacitors for other components can be placed near the input of said IC. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 20 points

    Hi Garrett,

    Wow I was so focused on the Electrical Characteristics table that I completely missed that!

    Thanks!