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Original question:

LM62460: Design Review

LM62460: Design verification

Vaishnavi P
Prodigy 190 points

Part Number: LM62460

Hi,
The design is updated as per your comments.
And, Can you please clarify that the 6th point you mentioned to use Electrolyte ESR Caps, is there any part number and value of the caps. Please recommend.
(Consider adding damping on the input filter stage to avoid unwanted overshoots caused by the ferrite bead and the Input filter capacitors coupling. You can calculate the Damping ESR required to be the characteristic impedance of the LC filter i.e; root(L/Cin_ceramics) in your case. )

And also confirm, the CBOOT, RBOOT with SW connection is proper or not.

And the Attached updated design for your review.
image.png

  • 0
    TI__Genius 14920 points

    Hello,

    1) The Rboot, Cboot and SW node connections are correct now and as per datasheet.

    2) Since the FB144 is a ferrite bead, you should use its impedance V/S Frequency graph to check what is its impedance at 1MHz as usually that is the least frequency provided in the plot. Then you can calculate the L of the Ferrite bead at 1MHz and find out the damping required.

    Mostly, the Impedance at 1MHz is around 1Ohms, so that makes the L equals ~ 1uH. Considering 50% derating on input ceramic capacitors, effective capacitance is ~21uF.

    So, the characteristic impedance is root (L/C_ceramic), which comes out to ~ 218mOhms.

    Therefore, any electrolytic capacitor with ESR over 200mOhms should be fine. You can use 22uF, 200mOhms electrolytic capacitor for example.

    What is R2445 used for?

    Regards,

    Sourish

  • 0
    Prodigy 190 points

    Hello Sourish,
    R2445 resistor is used to connect the Analog ground AGND and Digital Ground.
    Regards,
    Vaishnavi

  • 0 in reply to Vaishnavi P
    TI__Genius 14920 points

    Hello Vaishnavi,

    Ok looks fine.

    Regards,

    Sourish