LM5141-Q1: Iin(rms) current calculations

Jared Becker

Genius 11845 points

Part Number: LM5141-Q1

Hi Team,

In the 5141 datasheet, equation 35 does not appear to match equation 36. Which one is the correct one to use?

Thank you,

Jared

over 4 years ago

0 Timothy Hegarty over 4 years ago

TI__Guru 73652 points

Hi Jared,

Thanks for the question. It appears there should be brackets around the D term in equation 36.

The input capacitor RMS current is more easily expressed as follows by ignoring inductor ripple current: Icin(rms) = Iout * SQRT [(D*(1 - D)]

Worst case is at D = 50%.

Regards,

Tim

0 Jared Becker over 4 years ago in reply to Timothy Hegarty

TI__Genius 11845 points

Hi Tim,

Thanks for the confirmation. It also appears that no matter how the math is done for equation 36, I believe the answer should not be 2.93A. I calculated 3.29A. Is that just a typo?

Best,

Jared

0 Timothy Hegarty over 4 years ago in reply to Jared Becker

TI__Guru 73652 points

Quite possibly.

The easiest way to approximate it is to use Icin-rms = Iout/2 (as worst case is at D = 0.5).

Regards,

Tim

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LM5141-Q1: Iin(rms) current calculations