LMZ23603: wrong solution on equation (12) in the datasheet

Benjamin Brammer36

Part Number: LMZ23603

Hello,

as I am designing a new circuit involving the LMZ23603, I want to choose the input bulk capacitance according to your EQ (12) in the datasheet. Either is your equation wrong or the presented example solution is. With your provided equation i don't get 22,3µF as a minimum value for oyur example. I get about 3,1µF .

So could you please check on that? either I am completely losing my math skills or something is quite wrong in this datasheet.

best regards

Benjamin

over 6 years ago

0 JohnTucker over 6 years ago

TI__Guru**** 191445 points

In the example, they call out 120 mV ripple, then use 240 mYV in the calculation.if you use 240 mV, then I do get the same result, as you. 3.07 uF. Let's see what the module team has to say about it.

0 Benjamin Brammer36 over 6 years ago in reply to JohnTucker

Prodigy 200 points

with 120mV you get about 6,1µF . So there is something wrong. thanks for your fast reply!

0 Jimmy Hua over 6 years ago in reply to Benjamin Brammer36

TI__Mastermind 47060 points

Hi Benjamin,

Thank you for pointing this discrepancy out in the datasheet. I will get someone to fix this.

Given the following conditions

deltaV = 0.120V
Fsw = 812khz

Equation = 3A * (3.3V / 12V) * (1 - 3.3V / 12V) / (812000 * 0.12) > 6.138uF

Regards,

Jimmy Hua

0 Benjamin Brammer36 over 6 years ago in reply to Jimmy Hua

Prodigy 200 points

thx!

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LMZ23603: wrong solution on equation (12) in the datasheet