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Original question:

TPS7A88-Q1: Thermal Pads A1-A4

TPS7A88-Q1: Additional pad connection for the automotive part

Manuel de Dios
Prodigy 10 points
Part Number: TPS7A88-Q1
Other Parts Discussed in Thread: TPS7A88

Hi there,

As already asked by : On page 37 of the datasheet it shows 4 additional pads at the corner of the device marked A1 to A4.  I could not find in the datasheet anything about what they are connected to.  I assume that they would be the same as the main thermal pad.  Can you please confirm?

And answered by Kyle Van Renterghem: They are not internally connected so you are correct they can be tied to the thermal pad and GND.

I have this part on my desk and they're internally connected to the thermal Pad. So the Answer from TI is wrong and if you have vias on a corner position you can't use the TPS7A8801QRTJR as replacement for the TPS7A8801RTJR.

Hope this helps someone.

  • 0
    TI__Mastermind 41495 points

    Hi Manuel,

    I checked the bonding wire diagram to be sure and it looks like you are correct - it does show that the corner pads are connected to the thermal pad, although the connection is not as obvious on the diagram as I would normally expect so I see why it was mistaken that they are not connected. Just to be clear, if there are GND vias (i.e. thermal vias) near the corners of the package, there will be no issue using TPS7A8801QRTJR as a replacement for TPS7A8801RTJR. Only if they are another net besides GND will it be an issue. 

    Thanks for posting this.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    TI__Expert 3892 points

    Hi Nick,

    Please let me add two more question. 

    TPS7A88 and TPS7A88Q1 are in the same package (QFN(RTJ)|20) but actually they are different.

    1. What's the purpose of the corner pad on TPS7A88Q1? is it for a better thermal design in automotive application? but when I see thermal resistance, there's no improvement on TPS7A88Q1. 

    2. Can my customer use the same TPS7A88 CAD library for TPS7A88Q1. TPS7A88 CAD library does not have the corner pad. I wonder if they can just use it or they should recreate a library for TPS7A88Q1.

    Thank you for your help. 

  • 0 in reply to Ella KIM
    TI__Mastermind 41495 points

    Hi Ella,

    1) The extra pads in the corners are for mechanical reliability instead of thermal performance. 

    2) The only issue I can see is what was highlighted in this original post - the customer will need to be aware of the extra pads in the corners so that they can avoid having vias too close and potentially shorting them to GND. Hence I would recommend recreating the CAD model so that it is easily visible on their CAD layout. Note that the -Q1 package also has wettable flanks, although that does not affect the landing pad requirements. 

    Regards,

    Nick