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LM25085 switching frequency

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luiHS:
Hello.

I replaced the switched regulators XL4015 and XL4016 in all my circuits, for an LM25085. I used the Texas configurator, leaving the default value for the switching frequency at 454.966 Khz.

I have had a problem, although I think I have already found out the error. When connecting the circuit, to 12 volts of input, the voltage of the power supply began to vary, in addition when approaching the ear to the board a noise is heard, and although the output voltage is stable at 5 volts, it affects the operation of the circuit that feeds. If the input voltage goes up to 18 volts for another of my circuits, the problems practically disappear. Checking the scheme on the Texas web, in the input capacitor puts 15uF, but today seeing it carefully, I see that it puts 3 units, I mean 3 capacitors of 15uF in parallel and not one as I thought.

In my circuit I put 3 capacitors of 10uF, and that because in one of the calculations the capacitor was 22uF, with a lower switching frequency. As the ceramic capacitors in 0402 to 25v, they are not bigger than 10uF, I decided to put 3 thinking that I was still putting a larger capacity capacitor. The reality is that for this calculation the total capacitor should be 3 x 22uF, that is 66uF.

I have not tried to put a couple more capacitors in parallel, to get to 50uF, but I hope that is the solution to the problem.

One question:
The LM25085 can be configured for a switching frequency between 100Khz and 800Khz.

What is the ideal frequency, advantages and disadvantages of choosing a higher or lower value? What I see is that for higher frequencies the inductor is of a lower value, which means that it would be smaller and probably cheaper.

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