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LM4549B Ground Layout Reference

NY
Expert 3040 points
Other Parts Discussed in Thread: LM4549B

Hi Team,

My customer selcted our device, LM4549B for Audio Codec and asked me there is any reference ground layout. 

9.3.1 in datasheet stated keeping analog and digital grounds separate, and connecting them together in only one place.

But no layout image in datasheet. so, please support. 

Best Regards,

Naoki Yada

  • 0
    TI__Guru** 102045 points
    Hi Yada-san,

    Unfortunately there is no layout example for this device.
    I your customer is planning to use a single layer for GND, they can split it and place the division below the device in order to allow the GND pins to be connected to the indicated ground. And then only connect both GND in one point of the division with a 0-Ohm or a jumper.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    TI__Expert 3040 points
    HI Ivan,
    Thank you very much.
    Customer will use four layers. They understand inner layers shall be separate analog and digital ground, however, how about top layer under device? I can see the # 1- 12 pins (and 45,46 also?) are digital pins, so those pin's ground should be digital ground, correct?

    Best Regards, Naoki Yada
  • 0 in reply to NY
    TI__Guru** 102045 points
    Hi Yada,

    Yes, those pins are digital pins so they should be referenced to digital ground.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    TI__Expert 3040 points
    OK. Thank you very much
  • 0
    Genius 3945 points

    "9.3.1 in datasheet stated keeping analog and digital grounds separate, and connecting them together in only one place."

    Don't do that -- that suggestion is obsolete.

    Instead, use one ground plane, but consider carefully how you route your signals. Imagine a "partition" at the chip. Keep all digital signals on one side and all analog signals on the other, and don't allow a digital signal to cross into the analog "domain."

    See the work by Henry Ott, among others.