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LMR54410: Inductor Selection and Max. Output Capacitance

Shashank K S
Prodigy 115 points
Part Number: LMR54410

Tool/software:

Hi Team,

I wished to design a module which supports 3.3V, 5V 12V and 24V output voltage with minimal design variants. As per the datasheet and webench, inductor values suitable are,

Output Voltage Inductor Value (Datasheet) Inductor Value (WeBench)
3.3V 10uH 8.2uH
5V 15uH 12uH
12V 33uH 22uH
24V  - 22uH

Input Voltage: 34V ~ 36V

Kindly provide some insights into the following,
1) Is 15uH Inductor suitable for 3.3V and 5V output ?
2) Is 22uH Inductor suitable for 12V and 24V output ?
3) What is the Max. supported output capacitance ?

Regards,

Shashank

  • 0
    TI__Expert 4650 points

    Hi,

    1) Yes, you can use 15uH for both the case/

    2) can you please provide switching frequency? this is required to calculate current ripple.

    3) Cout is chosen based on the transient specification you want .

    Thanks

    Pramanik

  • 0 in reply to Pramanik Patel
    Prodigy 115 points

    Hi,

    So just to confirm, 15uH inductor would be suitable for 3.3V, 5V, 12V and 24V?

    Switching frequency is 1.1MHz for LMR54410.
    I want to know the max. supported output capacitance for LMR54410. 

    Regards,
    Shashank

  • 0 in reply to Shashank K S
    TI__Expert 4650 points

    Hi,

    Yes, you can use 15uH for all outputs.

    For the max output capacitor, as capacitor increases you will have to go for electrolytic caps and electrolytics caps have a ESR that varies from manufacturer to manufacturer. I think you can use the below attached quick start calculator and populate the specs according to your need and vary the output cap and see what max capacitor gives you at least PM = 45.

    SLURB07 Calculation tool | TI.com

    Thanks

    Pramanik