AM335X need buffer for NAND?

Rajas Yaso

Other Parts Discussed in Thread: SN74LVC16T245, AM3359, AM3354

Hai

Few days back i started to learn the AM335X EVM Schematics.But i watch a thing immoderately in that design. In that schematics the MICRON NAND FLASH embeds with buffer (vge translator) IC named SN74LVC16T245.But in some other EVALUATION modules, They doesn't include that buffer IC not only for a nand and also for WIFI ,7 inch LCD etc.

For that am3359 ZCZ package were i'm using.so i need to know that above BUFFER ICs were compulsory in that circuit?

If i omit them what will happens? I need to know what are the purpose for those iCs SN74LVC16T245, SN74LVC32T245, SN74LVC4T245 in the circuit

Thankyou

over 13 years ago

0 Biser Gatchev-XID over 13 years ago

TI__Guru**** 393215 points

Hi Rajas,

If you refer to U2, U4, U5 and U7 in the GP EVM Daugtherboard schematics, these are used to isolate the GPMC bus in different EVM profiles (or use cases). If you connect only a NAND memory to the GPMC bus there is no need for any buffering (please refer to GP EVM Baseboard schematics, page 7, U9).

0 Rajas Yaso over 13 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

Thankyou Biser

Here,I use a NAND flash in my development kit not a NOR or any other General Purpose Memory device.i designed that circuit with buffer IC SN74LVC16T245. I use a GPMC bus of AM3359 processor to MICRON NAND alone with the above mentioned 16 bit buffer IC.May be Biser,It makes any problem to the function??

0 Biser Gatchev-XID over 13 years ago in reply to Rajas Yaso

TI__Guru**** 393215 points

There is no need for this buffer in your case. You can connect the NAND directly to the GPMC lines.

0 Rajas Yaso over 13 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

I understand that biser,If i connect that buffer along with NAND it makes anything wrong?

0 Biser Gatchev-XID over 13 years ago in reply to Rajas Yaso

TI__Guru**** 393215 points

It will introduce some delay, which could be up to 6-7ns according to the SN74LVC16T245 datasheet. This could eventually limit your maximum operating frequency on the GPMC. Other than that nothing adverse will happen if everything is connected correctly.

0 Rajas Yaso over 13 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

Oh Thankyou biser.Really Thankful to you.

Almost i completed my designing using AM3354 from the reference of AM335X EVM Schematics.In my next module i omit that buffer IC definitely.

Thankyou for Spending a rgt time with me.

Rajas Yaso

0 sviss over 13 years ago in reply to Biser Gatchev-XID

Expert 1530 points

Biser Gatchev-XID said:
There is no need for this buffer in your case. You can connect the NAND directly to the GPMC lines.

I doubt it is always true.

To connect 1.8v NAND to Sitara, to my humble understanding I need to add a level translators on a:

1) WP# (a resistor divider might be sufficient) if/because GPMC_WPN is an another power domain and could be 3V;

2) R/B#, because (if GPMC_WAIT0 is a 3V power domain) 1.8v NAND (ex: Micron 2Gb MT29xxx) R/B# is not 3V tolerant.

Please correct me if I'm mistaken.

Thanks.

0 Biser Gatchev-XID over 13 years ago in reply to sviss

TI__Guru**** 393215 points

I think we were discussing the case where evrything is on the 3.3V rail. Otherwise you are right.

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AM335X need buffer for NAND?