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Altera_Forum's avatar
Altera_Forum
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13 years ago

Cyclone IV GX, DDR decoupling

Hi, I'm actually doing schematics using the cyclone Iv gx evaluation board. I placed the same DDR2( Mircon MT47H16M16) but I wonder why there are only 40 caps (10x4 CN caps) when micron says t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

These caps are placed to keep Vref plane as much clean as possible. You should add a cap near every termination resistor, but since You're probably using resistor networks (at least I did), then place at least one cap per resistor network. The common approach is to place 3 caps near one resistor network with values: 100nF, 10nF, 1nF.