AM3352: DDR3 schematic design

Kz777

Expert 7895 points

Part Number: AM3352

Hi Champs,

We would like to confirm which is recommend design for around of DDR circuit.

These two circuit use difference register value .

Could you please which value is correct or both value is possible ?

And this VDDS_DDR pin use "PULL-UP". Datasheet didn't recommend "PULL-UP" Is this pin also better to use "PULL" UP ?

1) am335x General purpose EVM (am335x_schematic_rev1_6a.pdf) mentioned "10Kohm Pullup" for VDDS_DDR

2) tmdexice3359_schematic mentioned "1Kohm" Pull up for VDDS_DDR.

over 5 years ago

0 Biser Gatchev-XID over 5 years ago

TI__Guru**** 393215 points

Hi,

Any value from 1kOhm to 10kOhm is acceptable.

0 Kz777 over 5 years ago in reply to Biser Gatchev-XID

TI__Expert 7895 points

Do we have to set always"Pull up" for this pin ?

0 Biser Gatchev-XID over 5 years ago in reply to Kz777

TI__Guru**** 393215 points

If you place an external pullup there is no need to set the internal one.

0 Kz777 over 5 years ago in reply to Biser Gatchev-XID

TI__Expert 7895 points

Hi Champs,

I mean that we would like to confirm if "PULL UP" is necessary for Hard ware too.

Because, this requirement didn't mention on the data sheet. and not mentioned at AM3352 check list.

Firstly, customer thought this is better to use Pull down. because, CPU drive to VOL after releasing reset.

Could you please confirm if this hardware Pull up is necessary action ?

Regards,

Kz777

0 Biser Gatchev-XID over 5 years ago in reply to Kz777

TI__Guru**** 393215 points

Yes, it is highly recommended. we have a pullup on DDR_RESETn on all our AM335x reference designs. If you do not have this pullup DDR3 may be reset when it's placed in self-refresh mode and the processor is in low-power mode (Standby or Deepsleep).

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AM3352: DDR3 schematic design