LMR23610: Cff selection

na na78

Guru 16770 points

Part Number: LMR23610

Cout = 47uF and Cff = 39pF is obtained from Webench simulation with Vin=24V, Vout=3.3V and Iout = 0.3A.

While, according to equation (17) and (18), Cff can be calculated as 58pF under following condition.

Vout = 3.3V,

Cout = 47uF (ceramic capacitor after derating)

RFBT = 51Kohm

If selected Cff is smaller than the result of calculation, what impact can be considered?

BestRegards

over 7 years ago

0 Eric Sato31 over 7 years ago

TI__Prodigy 480 points

Hi,

Based on my Webench simulations and what is mentioned in the datasheet, a Cff with 56pF will slightly affect the phase margin and gain margin of the bode plot. You can switch the capacitor in your Webench schematic to see the effect. I also attached my own Webench simulations in case you wanted to look at it. The comparison is made between a 56pF and a 47pF (default) capacitor.

webench_esim_5505615_19_1_805051357.pdf webench_esim_5505615_21_3_127105757.pdf

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LMR23610: Cff selection