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LT3759 exposed Pad

nikoly

I'm using a 2 Layer Board in Eagle .

The datasheet gives some info about the layout, advising me to add some  vias inside that Pad for heatsink problems.

I have opened Eagle tutorial "ti-launchpad" where there are  2 IC with Pads and vias on them (how in the image)p .image

Watching the DRC I have some overlap errors.

I can follow that way in order to design my board but I wonder if it's the right way to do this or not !

I have also seen someone to put arrays of pads instead of vias in order to get this!

 

Hope you can put me in the right direction!

Thanks a lot

Nico

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  • 0

    Ok Rachael,

    Thanks again.

    I usually draw a GND polygon on the TOP and BOTTOM layer after I have routed all the board that cover all the board dimension!

    Do you think that they should be enough after I have properly added the exposed  pad (with  right dimensions as the datasheet says) in the package editor ?or do I have to make another GND polygon just for that device and another for the rest of the board on the top layer?

    Sorry for the idiot question image

    Thanks  a lot again

    Nico

     

Reply
  • 0

    Ok Rachael,

    Thanks again.

    I usually draw a GND polygon on the TOP and BOTTOM layer after I have routed all the board that cover all the board dimension!

    Do you think that they should be enough after I have properly added the exposed  pad (with  right dimensions as the datasheet says) in the package editor ?or do I have to make another GND polygon just for that device and another for the rest of the board on the top layer?

    Sorry for the idiot question image

    Thanks  a lot again

    Nico

     

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  • 0 in reply to nikoly

    Hi Nico,

     

    So long as the polygon you add actually floods underneath the device and surrounds the thermal pad that would work. You'll need to make sure other component placement and/or routing hasn't isolated that area of your board from GND thereby stopping it flooding the area under the part with your GND fill. One thing you will probably find doing this though is that you won't want to turn thermal relief off for the entire GND polygon for the board or you might end up with a board that is really difficult to build. So you might need to put another small polygon underneath with the thermal relief turned off to surround the area around the pad plus a little more to cover up the thermal relief on the main GND polygon for that pad.

     

    Best Regards,


    Rachael