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Question about reference schematics for bq24702 and bq24703

133770
Prodigy 110 points

I have some concerns with the circuit shown on page 10 of SLU553e.pdf when compared against the schematic shown on page 34 of sluu160a.pdf.

In slu553e.pdf, the output capacitor refdes is C11, and listed as optional in the notes at the bottom of the page. The output capacitor for a buck supply cannot be optional.

In sluu160a.pdf, the output capacitor for the switch mode power supply is listed as EEVFC1V220P, which has a ripple current rating of 140 mA at 100KHz according to datasheet pic_fc_series.pdf. The EVM spec'ed in sluu160a.pdf claims charge current up to 3A available. Considering a good estimate for ripple current/output current to be 0.3, the EEVFC1V220P can only handle provide 466 mA of charge current instead of the spec'ed value up to 3A.

 

  • 0
    TI__Guru 56650 points

    You are right. Thank you for catching that.

    C11 of application diagram is not an option. The note should be "For Value, See Application Notes".

    In SLUU160A, the electrolytic capacitor C11 should be parallelled by a small ceramic capacitor. The EVM is old and just a reference for customers. Customers could change components to fit their design.