SC589_EZ-BOARD uses DDR3 with series termination, Why?

Hi,

For DDR3/3L, VTT termination is recommended by JEDEC, as this mitigates signal reflection. 

The primary purpose of a VTT island is to prevent reflections at the memory device. Removing the VTT termination results in signal reflections. The removal can lead to higher than nominal voltages at the memory address or command input pins, which can damage or reduce the lifetime of the memory. Check with the appropriate memory vendor for device specific information.

VTT termination does not play a major role for the ADSP-2159x/SC59x SHARC+® Processor, it’s only a requirement for the memory device.

As you have already aware of EE-434, Please follow the board design guidelines for DMC.

Regards,
Nandini C

Thank you for your reply.

However, my main questions are:

(1) Why does the SC584 document EE-387 not mention VTT?

(2) Why does the SHARC Audio Module (ADSP-SC589) not use VTT termination?

(3) Are there differences in the electrical characteristics of the DMC between SC58x and SC59x?

I would appreciate it if you could answer these points.

Regards.

Hiro

Hi Hiro,

VTT termination is a guideline from the memory vendors/ JEDEC, so we are just passing them along. VTT termination is recommended at higher frequency, hence we follow and recommend the same.

Customers of Griffin and GL could use VTT termination if they feel so.

Customers of 2156x/SC59x processors could also use series termination and not VTT if they perform satisfactory simulations and compliance on their board.

Regards,
Nandini C