DM355 EVM Layout

Amer Abufadel said:

1-In the schematics of Rev D2, page 22:

  How does one install L70, which is an inductor bridging the digital and analog ground planes? These planes are connected and the power source, so where would L70 go?  Also, can a separate layer be used for each ground plane?

This topic usually generates a debate on the right practice for ground planes as it relates to splitting the ground plane or not.  Regardless of the choice you use for your application and design rules, I would not suggest having split ground planes on a separate layer.

Amer Abufadel said:

2- In layer 3 of (page 7 of EVMDM355_Gerber_RevD.pdf), the traces have S like shapes.  These signal traces go between the DM355 and the DDR module I presume.  Is this typical for delay purposes or is it something else?  How does one calculate the length of the trace needed?

I would suggest you have a look at the Implementing DDR2/mDDR PCB Layout on the TMS320DM35x DMSoC (Rev. A) (SPRAAR3) Application Note for the TMS320DM355 which is available from the Product Folder.

BrandonAzbell said:

This topic usually generates a debate on the right practice for ground planes as it relates to splitting the ground plane or not.  Regardless of the choice you use for your application and design rules, I would not suggest having split ground planes on a separate layer.

Ok, so if I split the ground plane on the same laer as I think thats what they did in the evm, where would the inductor go? would it be close to the point joining the ground planes or would it be away?

It would need to be at the point joining the ground planes.

The layout database for the DM355 EVM is found on Spectrum Digital's support website.