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DDR_VREF reference for decoupling signal

RNJ
Prodigy 67 points


In the datasheet of AM335x (document SPRS717D - Revised may 2012) page 150 we can see a decoupling guide for the DDR2 reference level voltage.

When you read the tag B, saying "place the divisor and capacitors near the DDR_VREF pin" should not this mean to VREF pin? (DDR2 Device PIN) .

In DDR2 datasheets from Micron they recommended like that. Who is wrong?

  • 0
    TI__Guru**** 393215 points
    Hi Ricardo,
     
    You can download the new datasheet (Rev. E). It's available on the product page now. Actually Note B says: "One of these capacitors (meaning the VREF decoupling capacitors - my comments) can be eliminated if the divider and its capacitors are placed near a DDR_VREF pin." This means either processor or memory VREF pin. You can place the divider whereever it's most convenient. Distances are usually short enough on AM335X memory configurations, and if you follow the recommendation for 20mils trace width for VREF everything should be OK.