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2 X 16bit DDR3 interface with DM8148

kiran more2
Prodigy 30 points

Hello All,

I am thinking to interface two x16 DDR3 (2Gb each) devices with DM8148.

Can anyone suggest me the complications involved with DM8148 for interfacing two x16 DDR3 if any.

and can anyone suggest me the DDR3 part number which is working fine with this configuration for DM8148.

Regards,

Kiran

  • 0
    TI__Guru**** 393215 points
    Hi Kiran,
     
    For interfacing please check DM814X datasheet, section 8.13.4.2, for part numbers - section 8.13.4.2.4.3, Table 8-64.
  • 0 in reply to Biser Gatchev-XID
    Prodigy 30 points

    Thanks Biser,

    Sorry for late reply.

    I am facing  some queries regarding memory interface.

    1. I need to interface 4Gb DDR3, so is there any significant difference in using single x16 4Gb device or two X16 2Gb devices.

    2. I was referring to Mistral reference design for DM8148, In this for address and control signal termination, Datasheet has suggested only resistor termination to Vtt, but they have also used capacitors which are connected to Vddq(1.5V). So is it required or not, and what is its significant.

    Please suggest.

    Regards,

    Kiran

  • 0 in reply to kiran more2
    TI__Guru**** 393215 points
    Hi Kiran,
     
    1. Yes, there is a difference. First of all the DM8148 has two EMIF's. I understand that you want to use only one of them. This will decrease approximately by half the total possible DDR efficiency (if both EMIF's are used, they will work in interleaved mode). Second, if you connect one x16 device, this will again decrease approximately by half the DDR efficiency (you will use only one EMIF in 16-bit mode, approx. 25% of total possible DDR efficiency). If you use two 16-bit devices you will be able to use the EMIF in 32-bit mode.
     
    2. There has been quite a discussion about these capacitors, especially whether they have to be tied to VDDQ_1V5 or GND. The overall conclusion is that they are good to have, as they provide hi-speed bypassing on these lines termination. Whether they are tied to VDDQ_1V5 or GND, very much depends on the particular board layout. If you have a large and solid GND plane, and decouple to VDDQ, this will help the low-to-high transitions on address/control lines, and vice versa. The overall opinion is that the capacitors are good to have, that they need to be placed close to the termination resistors, and decoupling to GND or VDDQ remains designer's choice.
  • 0 in reply to Biser Gatchev-XID
    Prodigy 30 points

    Thanks Biser.

    Regards,

    Kiran