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TCA9548A: TCA9548ARGER / TCA9548AMRGER thermal pad size

Fiona Macpherson7
Prodigy 106 points

Part Number: TCA9548A

I'm using TCA9548A on my design in the QFN package.

The datasheet show two part numbers with the same package type name...

TCA9548ARGER 

TCA9548AMRGER

And there are two drawings in the datasheet for the QFN, one has a 2.1mm thermal pad, the other 2.7mm.

I can't make out which is which. I need to ensure the pad on PCB matches the part number.

  • 0
    TI__Guru* 79271 points
    Hey Fiona,

    So funny story about the ARGER and AMRGER.... They are the same devices but the M version is rotated 90 degrees in the reel.

    Anyways, I had to dig around but I was able to find that both devices have a thermal pad of 2.1

    I 'think' the 2.7 could be a typo though the blue outline suggests it is a recommended stencil.....

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Prodigy 106 points

    Hi Bobby,

    OK. Good to know that they are in fact the same device.

    So just to be sure - if I make my PCB footprint&stencil match the one in the datasheet (with the 2.7mm thermal pad) it will be fine with the 2.1mm pad on the device??

    That seems a little odd to me I have to say.

    Thanks,

    Fiona

  • 0 in reply to Fiona Macpherson7
    TI__Guru* 79271 points

    Hey Fiona,

    I've been digging around on this matter trying to figure out what that page actually is and can't seem to get an answer. I don't think that is the recommended stencil as typically stencils should be smaller for a thermal pad...... (I think there is a stenciling standard which suggests around 80% of the exposed area where as this picture would suggest over 100% which doesn't make sense)

    I believe this to be the stencil:

    What I can tell you is by looking at the older revision (E) that 2.7mm page did not appear until the M version was added in this latest revision (F). The parts are the same so it should not actually change the stencil or pad area at all..... I am thinking this is actually some kind of editorial mistake and those pages you pointed out should not be there.

    Thanks,

    -Bobby

  • 0
    TI__Guru* 79271 points
    Hey Fiona,

    I was finally able to figure out where the 2.7mm thermal pad came from. Looks like our auto qualified TCA9548A-Q1 device got wrongly associated with the catalogue version. We are in the steps to try to unassociate this.

    Thanks,
    -Bobby