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PMP22650: Stackup | Number of Power Layers

Subrahmanyam V
Intellectual 470 points
Part Number: PMP22650

Dear all, 

I have a curious query to which I often get the answer as "Based on experience"!

I wanted to know the below - 

1. How do we decide on the number of power layers in a design?

2. Is there a methodical way to arrive at this number? Say, 3 layers, 4 layers, etc

For example, for a 1 kW, how many power specific layers are required?

For a 6 kW, how many power specific layers are required? What is the math behind that number of layer selection?

Can you please explain with a detailed example?

Warm regards,

Siri

  • 0
    TI__Mastermind 40425 points

    Hi Siri,

    I can start the conversation and maybe others in the industry who read this post can also chime in with their tips.

    Unfortunately, from my experience, I particularly have NOT nor from working with other engineers needed to 'calculate' the number of layers based on power. For me it comes down to complexity of the converter topology (and usually this is proportional to the power level), thermal capability (sometimes there are  better heat sinking availability in some systems than others - liquid cooling, fan, etc), EMI/noise requirements (adding more layers help trace paths that reduce the critical loops), and PCB fab cost (I've seen requirements where lowest cost daughter cards need to be implemented and so we designed with only two layers). I've seen designers start out with 4 layers and jump to 6 layers after doing a parts placement and trying to optimize for any of the above. A lot of times an engineer will look into what has been done successfully (or working) first using TI's reference design library, to get a good idea of how involved the layout was as an example. If specs are similar and the test report shows similar performance to your targets, then that reference design layout would be a good start. Then you can adjust for any of the above I mentioned. 

    https://www.ti.com/reference-designs/index.html

  • 0 in reply to Darwin Fernandez
    Intellectual 470 points

    Noted, Darwin.

    That's well explained. May be the initial designs are taken from reference designs and the next projects usually leverage the existing proven designs.

    This way, a designer in many cases, may not use his brain to decide on the number of power layers as one has already experimented and documented in their reference designs. 

    If anyone reading this post has any suggestions, please chime in.

    Thank you, 

    Warm regards,

    Siri