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UCD3138A: UCD3138A Power GND connectiong to SGND

Ella KIM
Expert 3862 points
Part Number: UCD3138A

Hi Team,

Please advise on how to connect SGND (=AGND=DGND) with power GND. Most EVMs have control board with UCD3138A and power board with power stage. My customer will have one integrated board for UCD3138A and buck+pushpull power stage. When looking up SLUA779B, it's still unclear for me.

I'm thinking ① would be top layer and ② would be 2nd layer. And customer will place 3rd layer which is power ground plane. 

For the connection of 2nd layer and 3rd layer, 

(1) Should it be single point? Connection by only one via?

(2) Can via location be directly under the thermal pad of UCD3138A? Or should it be as far as possible to IC?

Sincerely,

Ella

  • 0
    TI__Genius 17090 points

    Ella, that question is out of my area of expertise, but I think that someone in Shenzhen can answer it.  I'll assign it to one of them.  

  • +1
    TI__Expert 3050 points

    Hello,

    (1) Should it be single point? Connection by only one via?

    --- yes, you must do it.

    (2) Can via location be directly under the thermal pad of UCD3138A? Or should it be as far as possible to IC?

    --- please don't connect the thermal pad to power GND.  typically, there is 3.3V buck converter/LDO which supply to UCD on the board. the 3.3V output capacitor minus belong to signal GND. the 3.3V output capacitor minus is selected as one end of singe connect point.  For the power Gnd end of single connect point, the main output capacitor minus is recommend.

    --- you mentioned that the power GND will be place at layer3,I also recommend you avoid signal GND copper and Power GND copper overlap even they haven't been connected by via.

    thanks