6 Replies Latest reply on Jun 8, 2015 7:53 AM by janos

    Inaccurate footprint drawing for BCM20737S

      Hi guys,

      I have trouble with the datasheet of the BCM20737S (Data Sheet - Preliminary), which I found in the document "20737S-DS100-R".

      The footprint drawing on page 25, Figure 15, is very inaccurate. It appears that the drawing is supposed to display two types of masks (two of copper, solder and cream i guess), but only one is visible. Also, there are duplicate measures on the one hand, and - more crucial - missing measures on the other.

      The document itself states that it is preliminary and confidential. Is there a chance to get a more accurate version of the documents, or even better, the footprint in some "open" format like the ultra librarian format? Also EAGLE and Altium Designer I would be very interested in.

      Cheers

      Janos

        • 1. Re: Inaccurate footprint drawing for BCM20737S
          BoonT_56

          From whom are you sourcing your module? Perhaps they can furnish you with a better footprint layout.

          • 2. Re: Inaccurate footprint drawing for BCM20737S

            I did find someone who posted a 20732S footprint. Just make sure to check it against the 20737S

             

            Sample BCM20732S PCB Layout

            • 3. Re: Inaccurate footprint drawing for BCM20737S
              BoonT_56

              Is this still an open issue?janos

              • 4. Re: Inaccurate footprint drawing for BCM20737S

                Thanks for the designs and data. I am still confused though, that Braodcom doesn't provide proper data themselves. From the data you linked, it is not even clear who/where it is coming from. And still, with regard to the inaccurate datasheet, it is not possible to complitely verify them with the BCM20737.

                 

                @boont this is still open, as my distributor also didn't have a complete datasheet. But you may close it as it looks like there is no help to this.

                • 5. Re: Inaccurate footprint drawing for BCM20737S
                  MichaelF_56

                  Figure 15 from Page 25 of the BCM20737S SIP module datasheet is attached below for easier reference:

                   

                  fig15-page25.png

                  Note that this is the only datasheet for the part, so ignore the preliminary reference.

                  Also note that your local distributor will not have a footprint available, we need to provide.

                   

                  Sorry for the confusion.  I personally do not understand the question, but will ask our PCB team (userc_6547, jota_1939431)   if they do and provide a response to the following:

                   

                  "It appears that the drawing is supposed to display two types of masks (two of copper, solder and cream i guess), but only one is visible. Also, there are duplicate measures on the one hand, and - more crucial - missing measures on the other."

                   

                  Also note that we do not normally provide PCB files in multiple formats.  Per a previous post, another one of our power users/consultants (frro_352456) converted the PCB files for the 20732S to Altium format, so that particular file is available here on the site.  From a HW perspective, the 20737S is identical, so this file should work, so the previous post is correct (only difference between these two parts is firmware).

                   

                  If you must use 20737S based PCB files, both WICED Sense and the iBeacon Reference design use this device:

                   

                  iBeacon BCM20737S Reference Design Allegro Layout File (Module)

                  WICED Sense Reference Design Mentor Graphics PCB Layout File

                  • 6. Re: Inaccurate footprint drawing for BCM20737S

                    Thanks for your explanation.

                    To clarify, see for example the 0.05 measure in the drawing. It looks like there are two masks involved in the drawing, which differ by that measure in size. This is usually copper-to-soldermask or copper-to-paste (over- or underprinting, usually underprinting). It is totally not clear, what is meant here.

                    Of course, with a bit of experiance, one can figure out some measures for a footprint, which will most likely work well. But the aim is to use exactly the dimensions that the manufacturer (broadcom) has made their best experience with, at least to start with. You guys have that data on your drives, so please make them accessible to us :-).

                    More serious though is the missing measure for the vertical position of the horizontally aligned pads, e.g. the pad that is labelled "A". This is infact a "bug". What is the vertical position of the pad "A"?

                    Normally additional CAD data for footprints is not necessary, but this only holds if a correct footprint drawing is available :-).