LMR33630-Q1: Output Capacitance equation

Ully Raihany

Part Number: LMR33630-Q1
Other Parts Discussed in Thread: LMR33630

Hi all

I found the LMR336 calculator from TI, I have checked from datasheet, but there is only one equation for Cout :

And when I try to do manual calculation, the result is different with calculator one.

I would like to know what formula is used for Calculated Output Capacitance and Calculated Minimum Output Capacitance in this calculator:

Attached are the datasheet and calculator that i found

8422.lmr33630-q1.pdf 4011.snvr484.zip

Thank you :)

over 1 year ago

+1 Hongjia-Wu over 1 year ago

TI__Expert 5250 points

Hi,

The equation used in the calculation tool is the same as in the datasheet. Put ΔIout=2A, Fsw=400k, ΔVout=250mV, k=0.3, D=5/12, you can get Cout=52uF. Assuming a 20% tolerance and a 10% bias de-rating, you can get Cout=52/0.8/0.9=72uF.

Regards,

Hongjia

+1 Ully Raihany over 1 year ago in reply to Hongjia-Wu

Intellectual 265 points

Hi Hongjia,

Thank you for your explanation,

I have check the equation and its work for both Calculated Output Capacitance and Calculated Minimum Output Capacitance.

But i would like to know for this calculation :Cout=52/0.8/0.9=72uF. You said we assuming a 20% tolerance and a 10% bias de-rating to get the cout, so where is 0.8 and 0.9 come from ?

Thank you

+1 Hongjia-Wu over 1 year ago in reply to Ully Raihany

TI__Expert 5250 points

Hi,

1-20%=0.8 and 1-10%=0.9.

Regards,

Hongjia

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LMR33630-Q1: Output Capacitance equation