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TPS65135: Is it possible to set the value of Co(POS),Co(NEG) to 1uF capacitor?

user5843555
Prodigy 40 points
Part Number: TPS65135

There is whistle occured in our PCBA and we changed the value of output cpacitor POS and NEG as below.

Case1:

Co(POS),Co(NEG):DNI

The whistle is disappeared, but occured strong ripple wave.

case2:

Co(POS),Co(NEG):1uF

The whistle is improved with acceptable level and the strong ripple wave in case1 is disappeared.

case3:Co(POS),Co(NEG):2.2uF or 4.7uF or 10uF
With above value the whistle occured.

So my question is that is it possible to use 1uF capacitors for Co(POS) and Co(NEG)?

In datasheet the recommanded value is from 4.7uF to 20uF.

By the way this IC is used for 5.5 LCD power circuit.

Thanks!

  • 0
    TI__Expert 6330 points
    Hi,

    I have notified our expert regarding this topic. Please expect a response by 10/15/18.

    Thanks,
    Aaron
  • 0 in reply to Aaron Goodson
    TI__Mastermind 18550 points
    Hello,
    It is not advisable to use lower than 4.7uF capacitance at VPOS and VNEG outputs. Using lower capacitance can cause poor load/line transient response and possible loop stability issues. Normally, audible noise is caused by piezo-electric effects of ceramic capacitors due to either excessive ripple or poor board layout. You can also try using capacitors from a different manufacturer as some are better in this respect than others.
    Kind Regards,
    Liaqat