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About ADP2389  Inductor&capacitor

Question asked by Yuya on Aug 2, 2017
Latest reply on Aug 10, 2017 by Yuya

Hi,

I would like to use ADP2389.

So, I used "ADP2389/90 BuckDesigner Tool.

However, a problem occurred.

 

When setting under the following conditions, the values of inductor and capacitor differed between my calculation and tool.

-----------------------------------------------------

Setting Conditions

Vin   = 5.0 V

Vout = 1.0 V

Iout  = 9.0 A

Vout ripple = 0.015 V

Fsw  = 400 kHz

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So, I have some questions.

 

#1   About Inductor.

       When I calculate under the above conditions, the inductor value becomes 0.75 uH, but in the tool it is 0.4 uH. What   is the reason for this difference?

 

#2   About Capacitor.

       In the tool, the output capacitor value was 220 uF.
  When I calculate based on output ripple voltage condition and load transient response,
  It became Cout ripple = 56 uF, Cout ov = 82 uF, Cout uv = 9.1uF.
       Therefore, I think that it is good to satisfy 82 uF for the value of the output capacitor,
       Why is 220 uF?

 

Best Regards,

Yuya

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