Understanding SDRAM configurations

[pixellon]

Hi Forums,

I am working on a project that would require me to have a 4GB SDRAM. I dont know to understand the configuration for this.

for example I have chosen the part https://www.digikey.co.uk/product-detail/en/micron-technology-inc/MT41K256M16TW-107-XIT-P/557-1757-ND/6036287 would this mean that i have to have 4 of these chips in parell for me to have 4GB of memory ? is there a easy way to understand this?

Sorry about the very basic question this is the first time I am designing a DDR based design.

-Pix

[bobc]

I can’t tell if you are talking bits or bytes.

Those chips are 4Gbit, so 4 give you 16Gbit. That is a total of 2Mbyte.

[pixellon]

Hi BOBC,

Thanks, Understood I am looking for gigabit. so for being not so clear.

-pix

[bobc]

In that case you should be looking for four chips each 1GB with 64Mx16 layout.

[pixellon]

Can I not have like a single chip for the entire 4GB ? it will avoid me some of the pitfalls of pcb routing, I am cautious as I would have to follow strict routing rules.

-Pix

[bobc]

@pixellon

Can I not have like a single chip for the entire 4GB ?

You can if you can find a chip with the required bus width, which you haven’t specified but by implication is 64 bits. I don’t know what memory controller you are using, since you haven’t told us.

I don’t make RAM chips, you should consult your supplier to see what is available Routing DDR has challenging rules, so you are going to have to tackle that anyway.

I would strongly advise finding someone who can supervise you, and also study some reference designs.

[pixellon]

Sorry I forgot to mention the info. I am planning to base the design on the beaglebone, instead of the am335x i am planning on upgrading it to am437x and make a dslr camera dolly with image capture using usb and image processing using ffmpeg.

I am planning on using emif which supports
– DDR3 and DDR3L: 400-MHz Clock (DDR800 Data Rate)
– 32-Bit Data Bus
– 2GB of Total Addressable Space
– Supports One x32, Two x16, or Four x8
Memory Device Configurations

I would strongly advise finding someone who can supervise you, and also study some reference designs.

Thanks I will try to find someone to help me with my supervision. I am using the am437xgpevm and beaglebone green schematic as a reference.

-Pix

[kpfleming]

The specs you quoted indicate a maximum of 2GB address space, so providing 4GB of RAM doesn’t sound like a good idea.

They also indicate that you can use a single x32 DRAM part, so a 512Mx32 part would provide 2GB in a single chip, if you can find one.

[pixellon]

thanks very much @kpfleming