AM625: 2 DDR4 two, 4GByte total

Cherry Zhou

Part Number: AM625

Hi team,

The customer did not find DDR4 with a single chip larger than 2GByte, so they consider using two 2Gx8bit DDR4 to form a total of 4GBbyte. Connections using sprad06.pdf figure2-2:

The DDR Manual is attached as follows:

https://e2echina.ti.com/cfs-file/__key/communityserver-discussions-components-files/120/MT40A1G16-16gb_5F00_ddr4_5F00_sdram.pdf

The schematic is as follows:

https://e2echina.ti.com/cfs-file/__key/communityserver-discussions-components-files/120/DDR4.pdf

Could you help check if it's possible and if there's any issues? Thanks.

Best Regards,

Cherry

over 2 years ago

0 JJD over 2 years ago

TI__Guru* 89705 points

Cherry, it looks like you are missing the VTT termination as shown in the diagram in the app note

Regards,

James

0 Cherry Zhou over 2 years ago in reply to JJD

TI__Mastermind 22235 points

Hi James,

Thanks for your support.

According to the design of the EVB board, the 16-bit DDR is also not VTT added, which appears to conflict with what is mentioned in sprad06.pdf. Which should be referenced?

Thanks and regards,

Cherry

0 JJD over 2 years ago in reply to Cherry Zhou

TI__Guru* 89705 points

Cherry, the EVM has only one DDR4 device, which only presents one load on addr/ctrl signals. Your design has 2 x8 devices and thus two loads, which would necessitate VTT termination because of the multiple loads. We are in the process of adding this detail to the app note. VTT-less design should only be used with one DDR device.

Regards,

james

0 Cherry Zhou over 2 years ago in reply to JJD

TI__Mastermind 22235 points

Hi James,

Thank you!

Is there any reference design available?

Thanks and regards,

Cherry

0 JJD over 2 years ago in reply to Cherry Zhou

TI__Guru* 89705 points

We don't have any reference designs with that specific topology. You can use the connection diagram in figure 2-2 of this app note: https://www.ti.com/lit/pdf/sprad06

And the AM64x EVM https://www.ti.com/tool/TMDS64GPEVM has an example of a connecting 1 DDR device with VTT. The AM64x uses the same DDR controller and PHY as AM62x

Regards,

James

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AM625: 2 DDR4 two, 4GByte total