Forum Discussion
Altera_Forum
Honored Contributor
Honored ContributorDDR2/DDR3 SDRAM power decoupling circuitry design
Hello Usually when I place decoupling local capacitors for power supply pins I try to place a capacitor next to each power pin according to manufactor recomended sizing. I came to realize that ...
Altera_ForumHonored Contributor
Honored ContributorDecoupling became a very difficult matter at the frequencies that we use now. Using one capacitor per pin isn't recommended anymore at high frequencies, especially with BGA chips. It is better to connect the pins directly to the power planes, and put the capacitors around the chip between the power and ground planes. The number and values of the capacitors depend on the frequency/ies the system is running at, power consumption, inductance/resistance of the pins, etc...
You can search for documents about "power distribution networks" to have more information about the subject. For the Altera side, have a look here (http://www.altera.com/education/training/courses/opdn1100). Most of it should be applicable to the DDR chip too.
