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LM2674: Ceramic output capacitor, ESR values for stability

Ue
Genius 17175 points
Part Number: LM2674

Hi all

Can I use ceramic output capacitors with the LM2674 ?

In the Datasheet table 2 I find only electrolytic and tantalum capacitors.

What is the ESR-range to ensure loop stability ?

I have two designs with these specs:

24V => 12V/200mA

24V=>5V/300mA

Thank you and best regards

Ueli

  • 0
    TI__Mastermind 23845 points

    Hi,

    I believe for this part, the ESR value is less relevant in order to ensure stability. I have attached a sample design on webench to simulate your design specifications

    https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=D1504BC56DCAA777

    The reason being is because internally we have 2 zeros to compensate for the voltage loop created by the regulator

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    TI__Genius 17175 points

    Hi Arief

    Thank you for the quick reply and for providing the Webench example.

    The 390uH suggested by Webench is not a recommended value in the Datasheet Table 2.

    I want to use 150uH and 47uH as reommended in Table 2 for a 24V => 12V/0.2A design.

    If I simulate with Webench with these values the Bode-Plot indicates a design that is not stable.

    Can you clarify ? Is there a bug in the Webench model ?

    What output capacitor should I use with an

    150uH inductor for a stable design ?

    Best regards

    Ueli

  • 0 in reply to Ue
    TI__Mastermind 23845 points

    Hi,

    I will response on the email that you sent me, therefore I will close this thread for now

    Thanks

    -Arief