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LM3481-Q1: Input capacitor consideration for automotive industry.

Sergey Matkovsky
Prodigy 30 points
Part Number: LM3481-Q1

Hello,

We have a SEPIC design including the LM3481-Q1 controller.

According to the datasheet, Cin should be above 100uF.

However, the Powerbench suggests Cin to be tantalum 4.7uF.

The questions are:

1) Who should I follow, the datasheet or the Powerbench design?

2) 100uF tantalum or aluminum capacitors for automotive applications are not recommended. However, the LM3481-Q1 controller is for the automotive industry. Which capacitor do you recommend using as Cin in automotive applications? Is it, for example 4*22uF ceramic ones?

Awaiting your reply.

  • 0
    TI__Mastermind 22610 points

    Hi Sergey,

    Thanks for using the e2e forum.
    I would assume Webench is proposing the minimal required Cin capacitance, while the datasheet recommends a value with more safety margin and higher overall stability for the system.

    I would recommend ceramic caps, as they are rated for automotive and are generally lower ESR, which is better for filtering the switching noise.
    Using 4x 22uF ceramic caps actually should be a good recommendation here.

    Best regards,
    Niklas