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TPS568215: TPS568215RNN

Part Number: TPS568215

How to decide inductor value as in Equation 7 there are two unknown variable Lout and ILrms?

• Hi Arvind,

The inductor value is not calculated by Equation 7.

You can refer to Table 5 to decide the inductor value and the variable Lout here means the inductor value.

The Equation 7 here is used to calculate the ILrms which is a parameter of inductor to help to choose a suitable one.

• Thanks Athos,

Iout max for this IC is 8A. And if my requirement is 5A then Is there any circuitry which will decide my Iout as 5A?

• In Table 5 there is not any suggestion for Inductor for Vout as 5V, 1.8V, 0.9V or any other value. Then How we will decide the Inductor value?

• Hi Arvind,

The Table 5 is just for reference. If Vout is 5V you can refer to the 5.5V.

For more different condition, the inductor selection is decided by the limitation as follows:

a. Inductor current ripple: If current ripple is too large, the output voltage ripple will be too large.

b. Loop stability: If current ripple is too small, the loop may be not stable.

c. Ensure the peak current under the current limit condition.

So usually we choose inductance to let the inductor current ripple equal to N=20%-40% of max loading current. The inductance value can be derived as equation:

You can also use our simulation tool POWERSTAGE or WEBENCH to select the inductor.

https://www.ti.com/tool/POWERSTAGE-DESIGNER?keyMatch=POWER%20STAGE

https://www.ti.com/design-resources/design-tools-simulation/webench-power-designer.html?keyMatch=WEBENCH

Regarding the Iout, you can also use 8A for your calculation since the over current value is 8A.