Dear E2E Design Support,
I have been using the TPS62130A in several designs, but recently I encountered a radiated emission issue with a new board which made me thinking about the right layout topology, especially how to connect the GND vias vertically in a 6+ layer board. Let's suppose I'm using exactly the same layout topology recommended in the datasheet and the regulator and surroundings are placed on the top layer and I have a 6-layer board with the following stackup:
Top / GND / Signal / Signal / Power / Bottom
There is an isolated and continuous GND copper on the top layer dedicated just to this buck regulator, The isolated GND copper includes the thermal pad of the TPS62130A, the AGND pin the passives around, the PGND pins and the GND pads of the input and output caps. There are two separate groups of GND vias, one group in the thermal pad and the other gropu at the GND pads of the input/output caps. The question is which internal layer(s) should I connect these GND vias for optimum emission? Each layer (except the power layer), does have GND copper pour. Options are as follows:
- Connect the vias in each layer (except the power layer).
- Connect the vias just in the continuous GND layer.
- Mixed solution for improved thermal performance: connect the thermal pad vias in each layer (again except the power layer) and connect the vias of the input/output caps just in the GND layer.
I'm considering to follow option#2. This way I can force the return current to flow just through the internal GND layer and so I expect to reduce radiated emission.
Is my train of thought correct? What is the recommended vertical connection pattern of the GND vias?
Thanks in advance:
Tom Ledeczi
