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Inductor Selection of ADP5072 Datasheet

Category: Datasheet/Specs
Product Number: ADP5072

Hello

There is a problem when I am solving DUTY, Ton, and Inductance Value(L1) for Inductor selection.

I substituted the table 11 values in the ADP5072 Datasheet into the Inductor selection equation(in the ADP5072 Datasheet).

Table 11 values are Vin, Vpos, Iload1, and Frequency.

So, I got the L1 value from the equation.

But, The L1 value from the equation was not the L1 value from Table 11.

Please pay attention to Table 11 in the attached picture.

For example, Let's substitute the values of Vin = 5 V, Vpos = 9, Iload = 140 mA, Frequency = 1.2 MHz into the Inductor selection equation.

The picture above is the Inductor selection equation.

When Vdiode is as 0.2V, Duty = 0.45652% , Ton = 0.38043x10^-6, L1 = 24.61uH.

But, the L1 value of Table 11 is 3.3uH.

I want to know if I'm wrong with the calculation or if the equation is wrong.

Regards

Haks

Parents
  • Hello Haks,

    The recommended components on the datasheet covers a wide range of input and output voltages already. You may also notice from the table that the recommended 3.3uH is also applicable to different loads and switching frequency. On the other hand, the equation for L1 is only specific for a certain conditions of input, output, frequency, ripple, and load. If you want to compare your solution with respect to the recommended components, the appropriate equation to use is the computation for the minimum inductance on page 18. Using the given parameters on your question, you will see that the minimum inductance for stable current mode operation is 0.37uH, which aligns with the value provided on table 11 because 3.3uH>0.37uH. 

    Regards, 

    Fritz Cyrill Gonzales

Reply
  • Hello Haks,

    The recommended components on the datasheet covers a wide range of input and output voltages already. You may also notice from the table that the recommended 3.3uH is also applicable to different loads and switching frequency. On the other hand, the equation for L1 is only specific for a certain conditions of input, output, frequency, ripple, and load. If you want to compare your solution with respect to the recommended components, the appropriate equation to use is the computation for the minimum inductance on page 18. Using the given parameters on your question, you will see that the minimum inductance for stable current mode operation is 0.37uH, which aligns with the value provided on table 11 because 3.3uH>0.37uH. 

    Regards, 

    Fritz Cyrill Gonzales

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