DAC5682 - generate single tone output

Valentin Popa

Other Parts Discussed in Thread: DAC5686

In this thread: http://e2e.ti.com/support/data_converters/high_speed_data_converters/f/68/p/374137/1317502#1317502 Ken had a very cool idea about setting up DAC5682 to generate some output by setting it in offset binary mode and using CMI1 to Fs/4 and setting the data input to the DAC to 0.

We have all the data line to the DAC to 0 and SYNC high but our output is not quite sinusoidal and the frequency of the output is ~26MHz like you can see bellow. All the registers are the default values with the exception of register 0x2 which is 0x48.

CLKIN is 40MHz and DCLK is 20MHz. What could be the issue?

Thanks,

Valentin

over 10 years ago

0 Neeraj Gill over 10 years ago

TI__Mastermind 20541 points

Hi Valentin,

I am looking into the issue. I will update you as soon with my progress.

Regards,
Neeraj

0 Neeraj Gill over 10 years ago in reply to Neeraj Gill

TI__Mastermind 20541 points

Hi Valentin,

Can you please read the register configuration data after you set it up and send it to me?
Can you also provide following info:
What is DAC output rate?
What interpolation is used?
What is the input CLOCK rate?
Do you intend to use PLL?
What frequency were you expecting to show up?

Regards,
Neeraj Gill

0 Valentin Popa over 10 years ago in reply to Neeraj Gill

Intellectual 680 points

Hi Neeraj,
Register read back values are as bellow:
STATUS0 0x03
CONFIG1 0x10
CONFIG2 0x48
CONFIG3 0x70
STATUS4 0x00
CONFIG5 0x00
CONFIG6 0x0C
CONFIG7 0xFF
CONFIG8 0x00
CONFIG9 0x00
CONFIG10 0x00
CONFIG11 0x00
CONFIG12 0x00
CONFIG13 0x00
CONFIG14 0x00
CONFIG15 0x00

DAC5686 clocks are: CLKIN is 40MHz and DCLK is 20MHz.
Valentin

0 Valentin Popa over 10 years ago in reply to Valentin Popa

Intellectual 680 points

Hi Neeraj,
I believe we found the issue. Our PLL was enabled - that is why we didn't get the expected output frequency.
Also we expected to get a sine wave output when actually the output is square wave.
Thanks,
Valentin

0 Neeraj Gill over 10 years ago in reply to Valentin Popa

TI__Mastermind 20541 points

Hi Valentin,

You are right, the PLL was enabled but it was not setup for the right frequency that is why you were getting some random frequency at the output. As you mentioned, bypassing the PLL would produce expected output at Fs/4.

Regards,
Neeraj

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DAC5682 - generate single tone output