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DDR3 selection

Jishor Emmanuel
Prodigy 70 points

Hi 

I am building a custom  board based on AM335x processor. While selecting DDR3 RAM. 

I am finding it difficult to match the clock rate mentioned in AM335x datasheet , which says 303 - 400Mhz.

But all the DDR3 chips in Micron are operating from 667/800Mhz. 

Can we use these chips and can run with a lower speed? , I am new with DDR memories.

Can you suggest any DDR3 device which supports AM335x, with 512Mx8 or 512Mx16?

Similarly, I want to use 1 Giga Byte DDR3 RAM, as that is the maximum supported by AM355x. 

Can i use a single chip 512M x16 device (MT41K512M16TNA-125) with two chip select , which both i can tie  together and feed to AM335x. 

Isn't it similar to using two 512Mx8 device ?

 

  • 0
    TI__Mastermind 25235 points

    Hi,

    Our hardware engineer is currently on vacation, so I'll forward this to the factory team.

    Best regards,
    Miroslav

  • 0
    TI__Genius 9625 points

    Each of the Memory parts you specify should operate between 303MHz - 400MHz clock rate if they are compliant to JEDEC specification. Per JEDEC all speed grades are required to operate at a max. TCK of 3.3ns (303 MHz).

    Please review the AM335x data sheet. The Section 7.7.2.3 has details about DDR3 memory configurations. Possible Device configurations are listed in Table 7-57/7-58. Figure 7-47/7-48/7-49 show the schematic connectivity with supported memory topologies.

    AM335x does not support 2 chip selects. So, you have to use 2 x8 512Mb  devices to get a total density of 1GB. Most of the standard memory vendors do have 2 x8 512Mb parts.

    2 x8 512Mb will have 1 unit load on the data bus. Using a twin die x16 part will have 2 unit loads on the data bus in addition to requiring 2 CS. So, they are not equivalent.

    Regards, Siva

     

  • 0 in reply to sivak
    Prodigy 70 points

    Hi Siva, 

    Thanks for the information.

    Do you have any reference schematic with Two DDR3 chips connected with AM335x ?

    Thanks 

    Jishor