LM61440-Q1: why inductor value is so large in datasheet

Elec Cheng

Part Number: LM61440-Q1

Hi Expert,

I see in LM61440-Q1 datasheet, that the recommended inductor value is quite large. Actually via calculation =1000*(1-Vout/Vin)*K/(Fsw*K*Iout), the calculated value is about 5.46uH instead of 8.2uH. May you help explain why we set the value in datasheet? Thanks.

BR,

Elec Cheng

over 1 year ago

0 Elena Gao over 1 year ago

TI__Genius 13735 points

hi, Elec,

Both 5.46uh and 8.2uh could used for 3.3V output, we choose 8.2uh for recommend is because this will get much less current ripple ,and could also share same BOM when change to 5V output, what's more 8.2uh will be better for 3.3V application in light load.

Elena

0 Elec Cheng over 1 year ago in reply to Elena Gao

TI__Expert 7055 points

Hi Elena,

Elena Gao said:
what's more 8.2uh will be better for 3.3V application in light load.

Could you please share more details about the impact to light load? How does the inductor affect? Thanks.

BR,

Elec Cheng

0 Elena Gao over 1 year ago in reply to Elec Cheng

TI__Genius 13735 points

I means if application is ~mA for example, the inductor ripple could be less than use a smaller inductor .

0 Elec Cheng over 1 year ago in reply to Elena Gao

TI__Expert 7055 points

Hi Elena,

Do you have test result or calculation table that shows the specific difference between the large inductor value and small inductor value? That would be very clear and straightforward. Thanks.

BR,

Elec Cheng

0 Elena Gao over 1 year ago in reply to Elec Cheng

TI__Genius 13735 points

Elec,

I don't have a bench test data, but the webench tool simulation ,you could change the different inductor value and check the results.

Elena

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LM61440-Q1: why inductor value is so large in datasheet