AM623: >2Gb LPDDR Support for AM6234?

Hi Nick, sorry for the confusion.  The device itself can support up to 4GB LPDDR4, however this has to be with one rank.  Dual rank with LPDDR4 is not supported because that would require a data bus T topology on the board (to connect both LPDDR4 x16 channels).  We only support point to point routing on the data bus.  

Practically, i've only ever seen max 2GB single rank package in the market.  If there ever did exist a single rank 4GB x16 package (or even a dual rank 4GB x16 package), AM62x could support that.  You could also choose a dual rank device that supports 4GB on each rank, and connect only half of the data bus, but then you'd be wasting half the memory. 

If you need more than 2GB, we would suggest to use DDR4, which can support up to 8GB with two ranks AM62x.

Hope this clears it up.  

Regards,

James

Hi,

Thanks for getting back. I've scoured the datasheets/suppliers for single die LPDDR4s at 4G with 16 bits addressing, but not sure, as there's a confusion between the terms of 'rank or die' within a memory package in the datasheets... Would any of these work?

MT53E256M16D1DS-046
www.mouser.co.uk/.../MT53E256M16D1DS-046-AATB

AS4C256M16MD4-062BAN
www.mouser.co.uk/.../AS4C256M16MD4-062BAN

IS43QR16256B-075UBLI
www.mouser.co.uk/.../IS43QR16256B-075UBLI

IS43LQ16256B-062BLI
www.mouser.co.uk/.../IS43LQ16256B-062BLI

Regards,

Nick

Hi Nick,

sorry, i think i mis-interpreted your original question.  If you are looking for 4Gbit (ie, 512MBytes), then the devices you quote should work.  Note the IS43QR* is a DDR4, while the other three are LPDDR4.  All 4 would be supported by AM62x

Please check our DDR layout app note during board design:  https://www.ti.com/lit/pdf/sprad06 

Also,  your software team needs to use our DDR Register Configure tool  https://dev.ti.com/sysconfig/?product=Processor_DDR_Config&device=AM62x to properly configure the DDR Controller/PHY for your memory.

Regards,

James

Hi,

Thanks for the extra info, I had obtained a copy of the DDR PCB layout guide for myself (had some experience successfully laying out DDR3L previously) and will be pointing SW at the DDR Reg Config Guide.

Back to the memory question... The difference between B and b is indeed a confusing one.... And I did mean Gigabytes.

OK, as far as I can find with the 16bit bus and one 'rank/mem chip' limitation, is this... https://www.mouser.co.uk/ProductDetail/Kingston/D1611PM3BDGUI-U?qs=jRuttqqUwMT4kPcx6wc8HQ%3D%3D

Will the above work?

Do you have any suggestions in LPDDR4 land that would give even more capacity? (We'll look at DDR if we really have to, but want t sound out LPDDR4 first)

Regards,

Nick

Yes, the single channel version of the Kingston memory should work, but that only gives you 16Gbit (2GByte).  As mentioned earlier, this is the practical max for LPDDR4 with AM62x, as i have never seen a single rank 4GByte LPDDR4.  You could use an 8GByte dual rank device and only connect half of it, but that's not practical, unless i guess cost is not a concern. 

If you need to go greater than 2GByte, you would have to use DDR4.  These give you more options since the come in x16 and x8 flavors.

Just curious why the preference for LPDDR4?  Is it cost? power? routing?

Regards,

James