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LM3150 Layout

Barrie Mullins
Prodigy 150 points
Other Parts Discussed in Thread: LM3150, CSD18504Q5A

Hi all, I’d like my LM3150 artwork reviewed please, just trying to avoid issues.  
6 layer board. Double sided assembly.
Schematic and layout attached.

Design has been simulated in web bench:
Input range 8.5-32v Dc, output 5v, 5amps.
Output caps, NICHICON RHS1A151MCN1GS: 150uF 10V, 3Amp ripple
Input caps, NICHICON UUD1H221MNL1GS: 220uF 50V
Input cap ceramic, TAIYO YUDEN #UMK325BJ106KM-T: 10uF 50V X5R
FETs, TI CSD18504Q5A: MOSFET N-CH 40V
Inductor, COILCRAFT #XAL1580-532MEB: 5.3uH 19.5A

Thanks, Barrie.

LM3150.PDF
  • 0
    Prodigy 150 points

    This is the schematic.

    Thanks again,
    Barrie


  • 0
    TI__Genius 15810 points

    Hello Barrie,

    Your component selection says you have one Nichicon cap and your schematics show two positions. As such you should be fine with one. The cap you have chosen seems to have about 25mohms of ESR (from Digikey website). According to Webench you should limit the ESR to 16mohms max. What happens is that with increasing ESR in the output cap and also presence of a Cff cap, there will be more than required ripple at feedback and it could cause your output to drift higher. Therefore I'd suggest adding a ceramic 10uF cap rated for the right voltage in parallel with your Nichicon cap. 

    A 19A inductor looks like overkill. Unless you have other large transients expected. Your layout also looks alright. Your input bypass ground and LS fet ground are right next to each other which is good. You sw node is also fat and wide and the feedback components seem to be a distance away from the inductor. I couldn't make out your Vout sense path to the top of the upper feedback resistor. I hope it is away from the inductor even if it is on an intermediate level. You might also want to think of adding some additional footprints on your output node for more high frequency ceramic caps. The right choise of HF ceramic caps can help eliminate switching noise and ripple from the output and make it a clean waveform. I hope this helps.

    Regards,
    Akshay

  • 0 in reply to Akshay Mehta
    Prodigy 150 points

    Hi Akshay thanks for taking the time to look at this, and providing some improvements, which I will make.

    “couldn't make out your Vout sense path to the top of the upper feedback resistor.” I’ve attached a snap which shows this net, it is well away from the inductor.

     

    Thanks again,

    Barrie