AM437x GP EVM Vtt termination resistor value and IO impedance control settings

j-breeze

Hi Champs,

AM437x GP EVM VTT termination resistor on the address and control signals is 47 ohm.
And, the IO Impedance Control is set to 0.88*Rext (41.36 ohm = 0.88*47) in the GEL file.
I think that both values are not within Zo value range which AM437x datasheet requires.

So, could you please let me know why AM437x GP EVM use the value and the setting?

Thank you in advance for your cooperation.

Best regards,
j-breeze

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

Table 5-53 from the AM437X Datasheet Rev. B specifies a typical value of 50 Ohm for Zo, and a tolerance of +/- 10%. 47 Ohm value for Vtt terminations falls within the specified tolerance. Impedance control in the GEL file is set according to the recommended value in: processors.wiki.ti.com/.../AM437x_DDR_Configuration_and_Programming_Guide

0 j-breeze over 9 years ago in reply to Biser Gatchev-XID

Mastermind 7560 points

Hi Biser,

Thank you for your prompt reply.

So, is it not necessary that the impedance control value(Ron) is set within Zo +/- 10%?
Could you please let me make sure of it?

Best regards,
j-breeze

0 Biser Gatchev-XID over 9 years ago in reply to j-breeze

TI__Guru**** 393215 points

The values given in the wiki are the recommended values.

0 j-breeze over 9 years ago in reply to Biser Gatchev-XID

Mastermind 7560 points

Hi Biser,

I misunderstood.
I appreciate your support and help so much.

Best regards,
j-breeze

Processors

Processors forum

AM437x GP EVM Vtt termination resistor value and IO impedance control settings