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TMS320F28375S: Split or not split AGND and DGND

Former Member
Former Member

Part Number: TMS320F28375S

Customer's previous experience is that one ground is better than split ground because of ground current between AGND & DGND. However, customer has had success with split grounds as well, and TI’s recommendation is splitting ground in ‘SPRAAS1C 4.6.3’ too. Need to understand what is the recommended/best solution.

  1. What is recommendation of ground split for TMS320F2837x (not in general), and why?
  2. What happens if there is a voltage difference between AGND and DGND? (SPRAAS1C 4.6.3)
  3. How are Vss and Vssa physically connected in TMS320F2837x?
  • 0
    TI__Guru 60865 points
    Hi Brian,

    We'd recommend that you split the grounds on F2837x devices as well, but this isn't a hard requirement; good layout with a combined ground plane will likely give much better performance than bad layout, but with split planes.

    One key to splitting the planes is to ensure that analog signals are routed over the analog plane/in the analog section and digital signals likewise are referenced to the digital planes and stay in the digital section. This will maximize performance by physically separating the two types of signals and should ensure that there is minimal voltage difference between the planes.

    We'd recommend that you join the analog and digital ground planes with a 0-ohm resistor right under the center of the DUT. In the case a signal has a return path through both planes (this should be mostly avoided by good layout - no signal should be crossing the plane boundaries) the return current will have a path to flow through this common point.

    I believe these grounds are mostly separate internally, but I'll have to consult with the designers to get an exact answer.
  • 0 in reply to Devin Cottier
    TI__Guru 60865 points
    Both grounds share a substrate, but the power domains are otherwise isolated. You can think of this as having ~100 ohms resistance between the internal grounds.
  • 0 in reply to Devin Cottier
    Prodigy 60 points
    Thank you for the answer