DAC38RF82EVM: Continuing to have issues with unreliable DAC synchronization

Matt Ligon

Part Number: DAC38RF82EVM

Earlier this year I received help in the following thread where I needed help with synchronizing dac A and B on the DAC38RF82EVM.

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/962806/dac38rf82evm-dual-dac-real-mode-4x-interpolation-lmf-821-synchronization-between-dacs

I'm now returning to the project after some time and am finding the synchronization problem to be still present. I'm confused because I recall things working reliably last time and I am using the same provided configuration files and working with the same hardware.

Setup Description

TI Hardware

TSW14J56

DAC38RF82EVM

Configuration Files:

Config file provided by David C:

/cfs-file/__key/communityserver-discussions-components-files/73/DAC38RF82_5F00_LMF_5F00_821_5F00_Fs_5F00_6144M.cfg

Initialization config file provided by Jim S:

/cfs-file/__key/communityserver-discussions-components-files/73/GUI-reset-no-LMK.cfg

Behavior:

The two DAC outputs will be synchronized about half of the time. Other times the outputs will be off by one or two samples typically.

There are errors that are reported whether or not the outputs are synchronized correctly

"DAC A, Lane 0 multiframe alignment error"

"DAC A, Lane 1 multiframe alignment error"

"DAC A, Lane 2 multiframe alignment error"

"DAC A, Lane 3 multiframe alignment error"

"DAC B, Lane 4 multiframe alignment error"

"DAC B, Lane 5 multiframe alignment error"

"DAC B, Lane 6 multiframe alignment error"

"DAC B, Lane 7 multiframe alignment error"

Questions:

I would appreciate some insight into how to debug this problem. Or please let me know if there are alternative register settings that would provide reliable synchronization.

Also I would appreciate some insight into the process of synchronizing the multi-DACs. Is it the same as multi-device synchronization between different discrete devices, with the use of SYSREF?

over 4 years ago

0 jim s over 4 years ago

TI__Guru* 91947 points

Matt,

Please send screen shots of the DAC GUI settings so I can see how you have everything configured. If you just send the register settings, it will take several hours to gather the same info.

Regards,

Jim

0 Matt Ligon over 4 years ago in reply to jim s

Prodigy 150 points

Sure I can get to that today.

For clarification, I did not make any modifications to the config files that you and David C sent me in case that was unclear.

0 Matt Ligon over 4 years ago in reply to jim s

Prodigy 150 points

Here are the screenshots

Process to gather:

1. power up DAC38RF82EVM and hook up usb to PC

2. Open DAC38RFXX software, set # of dacs to Dual DAC (to enable Digital(DAC B) tab)

3. Load config file: /cfs-file/__key/communityserver-discussions-components-files/73/DAC38RF82_5F00_LMF_5F00_821_5F00_Fs_5F00_6144M.cfg

4. Take screenshots

DAC_config_ss.zip

+1 jim s over 4 years ago in reply to Matt Ligon

TI__Guru* 91947 points

Matt,

You must use "Skip one SYSREF pulse then use the next" for both links in the JESD Block tab. Your screen shots are showing two different settings.

Both Digital (DAC A) and (DAC B) tabs should be using "Use only the next SYSREF Pulse". You have two different settings.

Use the attached file to reset the DAC JESD Core, not the button on the GUI.

Regards,

Jim

2376.GUI reset no LMK.cfg

0 Matt Ligon over 4 years ago in reply to jim s

Prodigy 150 points

It wasn't clear to me at which stage you wanted the DAC setting screenshots. I had taken them after loading the intial config file:

e2e.ti.com/.../DAC38RF82_5F00_LMF_5F00_821_5F00_Fs_5F00_6144M.cfg

But I have been loading the 'GUI-reset-no-LMK.cfg file which you previously sent me (in the thread earlier this year) and have the synchronization issue.

/cfs-file/__key/communityserver-discussions-components-files/73/GUI-reset-no-LMK.cfg

DAC A and B screenshots after loading GUI-reset-no-LMK.cfg

I checked the CFG file you sent yesterday '2376.GUI-reset-no-LMK.cfg', and the only difference is that it does not include the LMK settings which enables SDCLK.

0 Matt Ligon over 4 years ago in reply to Matt Ligon

Prodigy 150 points

So in summary, the 'CDRV sysref mode' settings are both 'use only the next' and the channels do not reliably synchronize.

0 jim s over 4 years ago in reply to Matt Ligon

TI__Guru* 91947 points

What about the Digital (DAC A) and (DAC B) tab settings? There was an issue here as well.

0 Matt Ligon over 4 years ago in reply to jim s

Prodigy 150 points

I posted screenshots of the Digital (DAC A) and (DAC B) tabs after loading the GUI-reset-no-LMK.cfg file in my earlier comment.

/cfs-file/__key/communityserver-discussions-components-files/73/dac_5F00_a_5F00_postreset.PNG

e2e.ti.com/.../dac_5F00_b_5F00_postreset.PNG

0 jim s over 4 years ago in reply to Matt Ligon

TI__Guru* 91947 points

Matt,

Loading an external config file does not update the GUI settings. The screen shots will not be correct. Can you please manually make all your settings and send new updated screen shots based on this. The key ones I want to see are the quick start tab, the clocking tab, JESD Block tab, and both digital DAC tabs.

Are you doing a software reset and load defaults before loading your config file? If not, try this.

Regards,

Jim

+1 jim s over 4 years ago in reply to jim s

TI__Guru* 91947 points

Matt,

I was able to reproduce your issue. It appears the setting for RBD is not optimized with this GUI setting. By changing the value from 19 to 17, I was able to consistently get both DAC outputs locked at the same phase after every reset cycle.

Regards,

Jim

0 Matt Ligon over 4 years ago in reply to jim s

Prodigy 150 points

Jim, I'm getting reliable phase synchronization now, thank you.

Separate from the RDB setting, I found that I needed to set the 'CDRV sysref mode' settings to 'use only the next' PRIOR To loading GUI-reset-no-LMK.cfg. I was confused because the GUI-reset-no-LMK.cfg config does appear to set this correctly and I figured this was sufficient.

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DAC38RF82EVM: Continuing to have issues with unreliable DAC synchronization