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TAD5242: Grounding and exposed thermal pad connection for TAD5242, TAD5142 and PCM1890

Ryu Yamashita
Genius 4465 points

Part Number: TAD5242
Other Parts Discussed in Thread: TAD5142,

Hi team,

Questions:
  1. TAD5242 / TAD5142
    1-1. For TAD5242 and TAD5142, is the pin named “VSSA” intended to be connected to the analog ground (AGND)?
    1-2. Is the pin named “VSS” intended to be connected to the digital ground (DGND)?
    1-3. For the exposed thermal pad (if present on these devices), should it be tied to AGND, DGND, or board ground in general?
    1-4. Are there any specific PCB layout recommendations regarding AGND/DGND partitioning and a single-point ground connection for these DACs?
  2. PCM1890
    2-1. For PCM1890, how should the exposed thermal pad be connected electrically?
    • To analog ground (AGND)?
    • To digital ground (DGND)?
    • To board ground (common GND plane)?
    • Any restrictions about connecting the pad to noisy digital ground

Best Regards,
Ryu.

  • +1
    TI__Mastermind 33601 points

    Hi Ryu, 

    I answer your questions regarding TAD52142 in one shot: Many  devices, they have separate AVSS and DVSS and VSS( Substrate ) . As the name implies, they are separate analog and digital grounds along with substrate that connects to thermal pad. On the board, these grounds should be connected to the same ground plane. Here there is not dedicated digital pin so the digital ground  internally is connected to VSS. At the end, on the board all the grounds come to each other . There is a section on layout hints in the datasheet where it tells to use  the same ground between VSS and VSSA to avoid any potential voltage difference between them.

    PCM1890 does not have separated supplies and all supplies are tied together and called VSS. In general the thermal pad is shorted to ground plane on the board. 

    Kind Regards,

    Arash