I am using AD9467-FMC-250EBZ with ZedBoard. The reference design works with 250 MHz external clock.
I studied on the schematic the PCB of AD9467-FMC-250EBZ. I found out that
c300, c301, (which are related with AD9517 ref input)
c302, c303, (which are related with AD9517 clk input)
c304, c305, (which are related with AD9517 out3 output)
c306, c307, (which are related with AD9517 out5 output)
c205, c206, (which are related with optional oscillator)
r208 (which is related with CLK_IN)
are not connected on the PCB of AD9467-FMC-250EBZ.
These connections show that clock source of the AD9467(ADC chip) is external clock.
As I understand, AD9517 is totally isolated from the AD9467; because of that the reference design, which is in SDK, is only working with external clock. I cannot use AD9517 with this PCB configuration. To change the clock source of AD9467, I should make modifications on the PCB.
Firstly, I want to make minimum modification on the PCB. If it is possible, I do not want to remove anything from the PCB.
My questions are;
Thanks in advance,
Thank you for contacting EngineerZone regarding the AD9467-FMC-250EBZ.
The on-board osc can be enabled by doing the following:
- P200 to enable the osc
- remove R209 R210
- place C205, C206 as 0ohm resistors
- remove CR200
The performance of this oscillator is rather bad. This is because of the bad jitter performance of the on-board oscillator.
To enable the AD9517, the hardware changes shown below need to be made. Then the AD9517 needs to be configured to operate in the correct mode. Also make sure that the appropriate filter R-C components are selected and populated. The best way to get the AD9517 setup is to use the AD9516/17/18 Evaluation software.
Thank you for your reply. As I mentioned before, I want to make minimum modification on PCB. I will use 10MHz reference input from CLK_IN. So, is it possible to use differential reference input to the AD9517 without removing T200 and C204.
I will just populate C300, C301, C304, C305 and remove C209, C210.
Your approach will work as well. If you choose to keep the T200 and C204, the REFIN to AD9517 will act as differential, but you can instruct the AD9517 to use just the REFIN_REF1. Populating C304, C305 and removing C209, C210 will make sure that the LVPECL outputs are fed to the ADC.
To set the desired frequency, you can use a 150x multiplier on the 10MHz reference. Then use a div by 3 and div by 2 to get the 250MHz out to the LVPECL outputs. Let me know if you have any further questions.
I also use the AD9467-FMC-250EBZ board, and have faced a problem about the clock.I want to instruct the AD9517
to use the REFIN_REF1, and the needed modification has been done. But, what should be changed in the SDK software, in the "ad9517_cfg.h ad9517.c or ad9517.h"?