PCIe AC coupling of the MCIMX6DL-SDP

cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

PCIe AC coupling of the MCIMX6DL-SDP

Jump to solution
1,262 Views
torus1000
Contributor V

Hi,

I created this thread for separating new questions from original one. igorpadykov
https://community.nxp.com/message/987667

My questions about PCIe of MCIMX6DL-SDP are as following.
Please refer to the circuit diagram SPF-27417_C4.pdf on page 16.

pcie_ac_couple.png

According to the PCIe standard, All Transmitters shall be AC coupled.

PCIe AC coupling capacitors values
https://community.nxp.com/thread/463277
http://composter.com.ua/documents/PCI_Express_Base_Specification_Revision_3.0.pdf p357

(Q) Why 0 ohm resister placed at C7 and C8 instead of capacitor.

I think REFCLKM/P need no capacitors but there was differntial termination and AC coupled.

(Q) Why reference clocks also AC coupled?

Can anyone help me?

Labels (1)
Tags (2)
0 Kudos
1 Solution
766 Views
igorpadykov
NXP Employee
NXP Employee

Hi torus1000

>(Q) Why 0 ohm resister placed at C7 and C8 instead of capacitor.

C7,8 are i.MX PCIe receiver side, no capacitors are needed as you correctly noted that

according to the PCIe standard,  all transmitters shall be AC coupled.

So capacitors are installed on PCIe card side acting as transmitter.

>(Q) Why reference clocks also AC coupled?

i.MX reference clocks are transmitter side, so as you correctly noted that

according to the PCIe standard,  all transmitters shall be AC coupled.

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

View solution in original post

0 Kudos
1 Reply
767 Views
igorpadykov
NXP Employee
NXP Employee

Hi torus1000

>(Q) Why 0 ohm resister placed at C7 and C8 instead of capacitor.

C7,8 are i.MX PCIe receiver side, no capacitors are needed as you correctly noted that

according to the PCIe standard,  all transmitters shall be AC coupled.

So capacitors are installed on PCIe card side acting as transmitter.

>(Q) Why reference clocks also AC coupled?

i.MX reference clocks are transmitter side, so as you correctly noted that

according to the PCIe standard,  all transmitters shall be AC coupled.

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

0 Kudos