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can any gurus help me with this schematic/pcb...?

  • 13-03-2010 6:22pm
    #1
    x in the city
    Closed Accounts Posts: 7,134 ✭✭✭


    Hi Lads,

    Trying to get this buck implemented on a pcb, I am finding it more difficult to layout as I thought it would, can anyone suggest changes I should do to the schematic as when I do a layout it wont route (properly), I want to have the bottom layer ground, and the top layers for signals.

    So can use vias to take all the ground signals to the bottom layer.

    also, the capacitors c2-c7 should be as close as possible to the pins on the IC, but I found this hard to do as it got too cluttered.?

    Finally, can anyone suggest any footprints for the headers, I would need smt ones, ant couldnt get any on altium, also I couldnt get a footprint for the inductors which was strange, there seemed to be none to accomodate it. (L 6.6 x W4.45 mm).

    Thanks .:)


Comments

  • #2
    DublinDilbert
    Registered Users, Registered Users 2 Posts: 5,401 ✭✭✭DublinDilbert


    Is there a recommended layout from the people who make the switcher? There usually is. For good EMC performance the layout is critical. It should nearly all be top side. The only thing that should be on the bottom side is ground plane and low current/freq signal lines (although this should be avoided if possible).

    As you said the decoupling caps should be as close as possible to the IC and not connected through any Via's to the IC ground.


  • #3
    x in the city
    Closed Accounts Posts: 7,134 ✭✭✭x in the city


    National Semi make the switching dc/dc buck.

    They had recommended caps alright, and I have footprints which I think are ok for them , the inductor seems more difficult, the one I sourced for the specs that National Recommend is relatively large (compared to the other parts) but its running at over 2Amps, obv the output of that buck is pretty high...

    I will have to place them caps closer to the pins so and re-route.

    I am getting lots of errors, will post back an update again.

    I only need to send my signals to headers so I can wire them onto my canbus board


  • #4
    delux
    Registered Users, Registered Users 2 Posts: 153 ✭✭delux


    Are you using an auto-route function? They are usually bad. I would route it manually for better results, and it's more fun too!
    A good tip is to change the direction of routing on either side of the board. For example route the tracks horizontal on the top and vertical on the bottom. It makes layout easier.
    If you're getting errors about spacings you may need to check your design rule settings(for minimum track width etc.).


  • #5
    FarmerGreen
    Registered Users, Registered Users 2 Posts: 1,134 ✭✭✭FarmerGreen


    http://www.national.com/an/AN/AN-1619.pdf
    Application Note 1619. Evaluation Kit for LP3907.


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