I am looking at the ADSP-SC589 EZ board layout.
The DSP DDR Reference 34R resistor is Located under the DDR RAM Chip next to the 240R resistor to the DDR3 ZQ Pin. These are separate nets not connected in any way . Is the correct?
I can only assume that they wanted to be at the same GND point.
Hi Brett,Please note that the 34Ohms is recommended value for processor and 240Ohms is recommended value for memory for RZQ. As per the note:2 under the DDR/LPDDR/DDR2/DDR3 Feature Comparison(Page No: 2 / 31) in the application note(EE-387), an external resistor (240Ω±1%) is inserted between the DRAM ZQ pin and GND for reference.For more information, please refer the application note (EE-387) which talks about "Interfacing DDR3/DDR2/LPDDR Memory to ADSP-SC58x/2158x Processors". You can find the application note from below link,www.analog.com/.../ee387.pdfRegards,Lalitha.S
In terms of DMC_RZQ resistor placement, Engineering note does not clearly indicates where to place this DMC_RZQ resistor in the design. I would assume DMC_RZQ resistor to be placed close as possible to the Processor pin. In the reference design gerbers this resistor placed right under the DDR3 next to DDR3 ZQ pin. Is it required to put this resistor close as possible to DDR3 in order to accurately calibrate the processor Driver Impedance and ODT due to the distance between processor and DDR3?
Hi Brett,Apologies for the delay in getting back to you.It is recommended to place the DMC_RZQ resistor close to the processor and the DDR3 ZQ resistor close to the memory.Regards,Lalitha.S