DAC3484evm with TSW1400 setup 2MHz output

Kamal Mokhtar

Other Parts Discussed in Thread: DAC3484, CDCE62005

Dear Sir/Madam

The setup is the DAC3484evm with the TSW1400evm. We would like to set it up, using only the internal 19.2MHz with CDC62005 excluding the primary clock input, so no need for an external clock. The goal is to reach low frequency, 2MHz. If you could show us any example in this range by showing the right calculation and configuration in both GUI’s, it is desirable. From there, we can change it to our exact wished frequency, once it is clear to us!

Briefly, what we have done so far,

Hardware,

Placed jumper4 on pin 2-3

Jumper5 on pin 1-2 (those jumpers, We have put them at all possible combinations)

Software,

installed all needed drivers for both as indicated in the guides, no problems at all.

DAC3484evm

loaded from the Example folder, PLL configuration (DAC3484_FDAC614p4MHz_4xint_NCO_30MHz_QMCon_CDCE62005VCO)

from there I made some modification to the CDCE62005 (indicated in the picture in the attachment)

TSW1400

Loaded basic square wave. It showed in the GUI with no problems (see attachment).

From 20MHZ data rate (HSDC pro), the boards LEDs are not showing me that there is a problem with the clocking (LED1 from DAC3484evm and LED4 from TSW1400 )

The problem we don’t see the wished signal but rather random signal (see attachment) on the oscilloscope, which is directly connected from the DAC board channel 1 to the oscilloscope.

If any point is not clear regarding our question or an ambiguous setup, please contact us.

Kind regards,

Kamal

over 8 years ago

0 jim s over 7 years ago

TI__Guru* 91947 points

Kamal,

We are looking into this.

Regards,

Jim

0 Kamal Mokhtar over 7 years ago in reply to jim s

Intellectual 420 points

Jim,

I wouldn't ask this, if I am not really stuck and in a hurry. But do you have any expectations about how long it might take before I get a reply for my question.

Regards,

Kamal

0 jim s over 7 years ago in reply to Kamal Mokhtar

TI__Guru* 91947 points

Kamal,

I am working on this as we speak. A few questions for you.

1. Do you plan on using any interpolation?

2. Do plan on using the NCO?

3. What rate do you want the DAC to sample at?

4. Are you using your own custom test pattern? If so, have you tried using the multi-tone generator in the bottom left of HSDC Pro GUI instead?

5. What revision is your DAC EVM?

Your setup is confusing as you mention 2MHz, you are interpolating by 4, using the NCO, and sending data from the TSW1400 at 20MHz.

Regards,

Jim

0 Kamal Mokhtar over 7 years ago in reply to jim s

Intellectual 420 points

Hello Jim,

1. Do you plan on using any interpolation?
Yes, I have had it at 4x
2. Do plan on using the NCO?
Yes, if it is needed to reach my aimed signal.
3. What rate do you want the DAC to sample at?
I have had it at 290MHz, but not sure what proper value should be.
4. Are you using your own custom test pattern? If so, have you tried using the multi-tone generator in the bottom left of HSDC Pro GUI instead?
Yes, for now I would like to see simple signal block or sawtooth wave. But in the final product for controlling the Laser is going to be different. Yes, I have tried the multi-tone generator. I am not really getting my results though.
5. What revision is your DAC EVM?
0033317
Your setup is confusing as you mention 2MHz, you are interpolating by 4, using the NCO, and sending data from the TSW1400 at 20MHz.
This is a mistake, as I miss understood the relation of those. My goal is to reach 2MHz output.

Regards,

Kamal

0 jim s over 7 years ago in reply to Kamal Mokhtar

TI__Guru* 91947 points

Kamal,

The revision of the board is labeled in silkscreen and should be a letter. It should be something like "REV G". Please follow the attached document as I was able to get an adjustable output based on the NCO frequency and using the same default config file you used. You should not have to make any changes to the CDC PLL settings.

Regards,

Jim

DAC3484_PLL_DAC_CLK_614p4.pptx

0 Kamal Mokhtar over 7 years ago in reply to jim s

Intellectual 420 points

Hello Jim,

Thanks a lot, really appriciated. I will try it tomorrow. So far it looks raelly clear.

Thanks again,

Regards,

Kamal

0 Kamal Mokhtar over 7 years ago in reply to Kamal Mokhtar

Intellectual 420 points

Hello Jim,

Thanks for the descriptive slides, it works but not my final aim. I have one question, as you see from the attached oscilloscope picture, the output in not clean but rather modulated based on the signal that I am giving. I get the impression there is an intermediate frequency and the signal that I am providing is modulating the IF.

I have attached the file that I am using as a sawtooth signal, screen shots of the sawtooth in the HSDC

Kind Regards,

Kamal

sawtooth.txt

0 Ken C over 7 years ago in reply to Kamal Mokhtar

TI__Genius 12965 points

Kamal,

Have you tried using the signal generator on the lower left to generate a tone?

Tone BW = 0

# = 1

Tone Center = 10M

Click Create tones and then Send.

Does this work? Do you get a 10M output tone?

Based on the time waveform the ramp, you have has a fundamental less than 1MHz. If you are using the default DAC EVM with the transformer output, you may get some signal distortion caused by the high pass response of the transformer.

Ken.

0 Kamal Mokhtar over 7 years ago in reply to Ken C

Intellectual 420 points

Hello Ken,

yes I have tried it now, which gives me a sine wave. but that is not my aim. I want to have a clean sawtooth wave output. if I am not mistaking from the slides that Jim has provided, the DAC output is 30MHz. if you could help me to achieve a sawtooth, that is what I I would like to achive.

Kind Regards,

Kamal

0 Ken C over 7 years ago in reply to Kamal Mokhtar

TI__Genius 12965 points

Kamal,

As you have shown by generating a 10M sinewave, the system is fine. The issue is that you are trying to generate a signal that will not work on the system as it is currently setup.

The ramp you want has a fundamental frequency less than 1MHz (based on the time plot in HSDC Pro, looks closer to 75kHz). You can either increase the ramp fundamental frequency to above the lower frequency response of the transformer or change to a transformer that has the correct frequency response. If you choose a different transformer, ensure that the impedance ratio is the same and the foot print is compatible. Here is a list of transformers from mini circuits. The default transformer on the DAC3484 EVM is the ADT4-1T.

www.minicircuits.com/.../transformers_sm_a.shtml

Ken

0 Kamal Mokhtar over 7 years ago in reply to Ken C

Intellectual 420 points

Hello Ken,

I have changed the ramp (around 4.7MHz) of the signal in the loaded file you can see below both the GUI and what I get on the oscilloscope. I get originally a sine wave that is shaped to something different. I wish to see the same as in the GUI.

sawtoothe with faster ramp.txt

Kind Regards,

Kamal

0 Ken C over 7 years ago in reply to Kamal Mokhtar

TI__Genius 12965 points

Kamal,

Do you have the NCO or coarse mixer enabled in the DAC settings? You can check this by setting the channel pattern to a constant value such as 32767 (full scale) and seeing what the output frequency is.

Ken

0 Kamal Mokhtar over 7 years ago in reply to Ken C

Intellectual 420 points

Hello,

Thank you very, much It works.
appreciate all the support.

Kind Regards,

Kamal

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DAC3484evm with TSW1400 setup 2MHz output