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OPA2677: HSOIC (DDA) package CAE fooprint differs from datasheet recommendation

Daniel Ka
Intellectual 527 points
Part Number: OPA2677

Hello,

the TI page for OPA2677 provides design resources, see here:

www.ti.com/.../OPA2677

This page offers links to download CAD/CAE symbols and footprints for all available packages. I'm interested in the HSOIC (DDA) package. The link on the TI page leads to:

vendor.ultralibrarian.com/.../

The footprint there looks like this:

As you can see, the GND pad below the package is not extending beyond the thermal pad on the package. At least not in the footprint which I downloaded for EAGLE/Fusion 360.

However, the datasheet shows that the metal for the GND pad should extend under the solder mask:

I wonder why the footprint provided by the linked resource does not follow the recommendation in the datasheet? I assume that the thermal characteristics presented in the datasheet ( θJA = 55 °C/W) only hold true when one sticks to the recommended footprint.

Thanks.

Dan

  • 0
    TI__Expert 6050 points

    Hi Dan,

    As you have mentioned, the thermal characteristics are characterized assuming the footprint recommended in the datasheet. For example, having a ground plane that does not extend past the thermal pad of the package will reduce thermal performance due to the smaller dissipation area.

    I do not have Eagle/Fusion 360 so I am not currently able to check the footprint for that application. However, the footprint in Altium appears to have the ground plane that extends past the thermal pad of the OPA2677.

    Can you share what the footprint looks like when downloaded for Eagle/Fusion 360? I will also check with the team to see why it is different for the PCB design application you are using.

    Thanks,

    Nick

  • 0 in reply to Nick Nauman
    Intellectual 527 points

    Hello  ,

    if I open the *.lbr file for Fusion360 (downloaded from ultralibrarian.com) one of the three available footprint looks like this:

    The footprint above largely matches the preview on ultralibrarian.com. To see the preview, follow the link in my first posting.

    I extended the GND plane below the EPAD as follows:

    After placing the device, I will add the vias as recommended in the datasheet.

    Best regards,

    Dan

  • +1 in reply to Daniel Ka
    TI__Expert 6050 points

    Hi Dan,

    Thank you for the additional details. I will bring this to the attention of the team so that it can be fixed. 

    In the meantime, as you mentioned, manually extending the ground plane and adding the vias will work. Measurements for the size of the ground plane and vias are included in the datasheet footprint drawing.

    Please let me know if any questions arise.

    Thanks,

    Nick