In order for us to configure a setup file for you as a starting point, we need the following:
1. System clock input frequency
2. Desired input and output frequencies
3. Desired loop bandwidth (if any)
4. Any other special reqirements
Bear in mind that GPS applications require either a TCXO or OCXO for the system clock source. The minimum loop BW for using an xtal for the system clock is about 50 Hz.
1. External clock frecuency at 16 MHz (the most desirable value)
2. System clock freq. 640MHz
3. Reference input 1Hz (GPS 1-pps, the most desirable option)
4. DDS freq. 63MHz (or greater)
5. Output 16MHz (or any)
6. Any bandwidth
Other special requirements isn't important for us.
At the moment we failed to achieve synchronization. We can not set the correct settings for the profile of Reference A.
Could you send the file (*.stp) on my email: ILNUR655@gmail.com
Thanks in advance!
Attached please find a sample setup file and eval board instructions. If you download the evaluation software from www.analog.com<http://www.analog.com>, you’ll be able to load this file.
For best performance, we generally run the DDS between 100 and 250 MHz, and we generally run the system clock close to 1 GHz.
Have a look at these files and let me know if you have questions.
I also downloaded the evaluation software (and bought the evaulation board) to make some experiment about the AD9548 component.
Actually, i'm trying to use the AD9548 to synchronize a device with either a 1Hz reference or a 32 Mhz reference.
I made a priority to prefer the 1 Hz reference when available, or the 32Mhz reference when not.
However i just don't understand how to fill the parameters in "profiles" . I failed to achieve synchronization. I can't set the correct settings for the Reference A and B Profiles.
To resume, i'd like to have :
1Hz and 32 MHz reference inputs
32Mhz output frequency
800MHz primary clock VCO
Could you post the file (*.stp) to have a starting point.
I'm happy to create a setup file for you, but before I do so, I need to ask the following:
In order to lock to a 1 pps signal, some changes are needed for the eval board:
1. You must use a TCXO, OCXO, or other stable source (like a low noise signal generator) for the system clock. How are you planning on doing this and what is the frequency?
2. You must DC couple the 1 pps reference input.
Thank you for you answer.
I will use the AD9548 on a custom card where i 'm already using a 32MHz oscillator (ECS-3525-320-B-TR) but as you said it seems to be not a TCXO.I can add another crystal, my question is, which one (at least which frequency) is the better for the application i'm developping ? ( I may try with this one : FOX924B-19.440. I also have a DG535 generator but i'm not sure it would be enough stable).
In a first time i would like to test it on the evaluation board by using a 1Hz reference signal.
Other question : in the AD9547/AD9548 Evaluation Board, on page 3, do modifications need to be done directly on the board in case of using a 1pps signal that is , i need to unsolder C39 and replace it by a 0 Ohm resistor to have a DC-coupled on ref BB and i need to remove R23 ?(Actually, R23 is already missing on the eval board : is it normal ?)
For the 1pps signal it would be generated on the same custom card (IRIG-B signal).
In general, the part works best when the DPLL output frequency is at least 100 MHz, as it synthesizes at sine wave, and better slew rate results in better performance. Also, the post dividers on the part are very deep can capable of dividing all the way back down to 1pps. It's possible to directly synthesize 1Hz directly, but I can't think of a reason why you'd want to.
For the TCXO, the only recommendation is to avoid a frequency that's integer related to out output frequency. For your application, a TCXO with a 19.44, 19.2, 38.4, or 38.88 MHz is ideal. There's a place for a Vectron TX-700 on the eval board, and we've mounted many devices from Vectron, Connor-Winfield, NDK, Suntsu, Rakon, Epson, and Valpey-Fisher. We don't endorse one vendor over another.
> Do i need to unsolder C39 and replace it by a 0 Ohm resistor to have a
> DC-coupled on ref BB and i need to remove R23 ?
Yes. Although you will probably find that putting a 10ohm series resistor will work better (less ringing).
For the TCXO, there's a good diagram in the "Input/Output Termination Recommendations" section of this datasheet: http://www.analog.com/static/imported-files/data_sheets/AD9557.pdf
This is the best way to hook up a TCXO to the AD9548 as well.
Thank you for your answer, I really appreciate and I'm sorry to disturb you once again.
There is still something I don't understand. I need the AD9548 to synchronize a 32 MHz signal with a 1Hz signal : in other words i need every rising edge from 1Hz clock to be in phase with the 32MHz clock.
So I have to put something like 128 Mhz for DPLL output frequency and then i need to divide by a factor 4 to have the 32 Mhz I need in output clkout. Is it correct ?
Yes. That's correct. Actually, the DPLL output can be any integer multiple of 32 MHz. and it will work fine. The evaluation board has a 240 MHz low pass filter at the DPLL output, so I'd recommend setting the DPLL output frequency to 224MHz and doing a /7. Don't worry. The duty cycle will still be 50%.
One more thing: when setting up the DPLL, be sure to set the threshold priority to a value higher than any of the priority settings in the DPLL profiles. For instance, set the threshold priority to >=2 if you have two profiles where one is priority 0 and the other is priority 1. This will guarantee that you will maintain the same static phase offset (and have output phase slewing) as you switch references.
The other requirement is that the R divider always be one.This may be a problem for you, as you're limited to an input frequency of 10 MHz if the R divider must be one. Can you do a /4 on the 32 MHz input? Keeping the static phase offset constant for the 1 pps is not a problem.
I'm using a 32MHz oscillator on a custom card but i'm using a cyclone III on this card too, so I would be able to do a /4 (alt_pll) on the 32MHz to respect the limited input of 10 MHz frequency in input of AD9548.
I ordered a Connor WinField D75F-019.44M this morning on DigiKey. I wonder if the ppm precision would be enough.
I really appreciate the help you gave to me and I will let you know as soon as I get the TCXO.