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CPU-Power distribution

meet , 01-04-2017, 05:33 AM
Hello Team,

I am trying to understand the layout of lesson 5 for memory module. i was trying to understand the placement of decoupling capacitor.

As shown in attachment, i was not able to find the source for net (+1V2_VDD_ARM_CAP).
all I found is the decoupling capacitor and power plane in layer 7. i am not able to address, where this supply (+1V2_VDD_ARM_CAP) is generated.

Meet Payak
robertferanec , 01-04-2017, 06:49 PM
This is a very special power. If you have a look inside CPU datasheet, you will find there information about internal regulator. There is no external power source for this net.
meet , 01-04-2017, 09:25 PM
Thanks a lot Ferance for your reply... keep helping to learn the world of High speed design...

meet , 08-18-2017, 07:40 AM
Hello Robert,
I am doing lesson 2 with expert option. i m confused to place big value capacitor 22uF, where to place them .. 220nF i was successful to place, but not sure for 22uF. please refer the attachment.
can you please suggest for placement please.
Also i am curious to know, how far we can place small value capacitor or their is priority for signal and relaxed for others.
robertferanec , 08-18-2017, 11:18 AM
If you are not sure, the best way is to have a look at reference designs. You can download Altium projects of our http://www.imx6rex.com/ boards and have a a look at decoupling under BGA.

Basically, you would like to keep the capacitors with smallest values as close as possible to the pins. The bigger caps can be a little bit further - somewhere on the way to the smaller caps.
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