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BQ24190: Recommendations for maximum SYS capacitance

Bart
Expert 6460 points
Part Number: BQ24190

Team,

do we have guidelines about the maximum recommended capacitance on SYS voltage marked below?

Is it fine to put 1000uF?

The reason is that we have excessive consumption on board and sudden drops in power voltages caused by GSM module - need energy reserve when these sudden drops appear. I would like to put 1000uF on output from charger, which is also the input of a buck-boost dc/dc (which tolerates high capacitance at its input, as far as 15F range).

Thank you.

  • 0
    TI__Mastermind 25800 points

    Hey Bart,

    In section 10.2.2.3 Output Capacitor of the datasheet, you will find a output filter (LC) resonant frequency range that will limit the min and max values of SYS output capacitance. Based on using a 2.2-uH inductor, you will find max acceptable is ~60uF of output capacitance.

    In general for a voltage-mode controlled buck converter like this, too much capacitance will not lead to instability as much as having too little capacitance. However, I feel that 1000uF is too much for this converter and may well induce instability. 

    I would likely stick to 100-220uF if you are going to push the capacitance that far. If you need more capacitance, drop your inductance value to 1-uH and double the capacitance and you may be fine. 

    Regards,

    Joel H