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EVAL-ADAU1772 50kHz sine wave input 3 and 4 Output has a modulated waveform that has a 2kHz message signal is it normal?

Processors & DSP Poster May 8, 2026 00:00 3 replies Original on forum ↗
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Poster Question
May 8, 2026 00:00

Using EVAL-ADAU1772 and following the example in UG-477

When I insert a 50kHz sine wave at the input of 3 and 4 I get a frequency modulated output with 50kHz as my carrier frequency, and there is a 2kHz message frequency,

Was wondering where the 2kHz message frequency came from, which parameter in the register decided this.

I'm happy that the IC is responding to my configuration but wanting to learn more about the IC,

Thanks

hardware

software

adau1772

sigma studio 4.7

processors and dsp

Processors and Microcontrollers

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DaveThib Reply
May 8, 2026 00:00

Hello Poster,

My first guess is that you have the part setup to operate at 48kHz sampling rate. So by putting in a 50kHz signal it will give you the difference out which is 50-48 = 2 kHz.

Detail what functionally you need to do with this part?

Then what clocks are you supplying?

Send your SigmaStudio project with the register settings?

Are you using SigmaStudio?

Dave T

Poster Reply
May 8, 2026 00:00

Hello Dave,

Thanks for the response, please find the file here, I am using SigmaStudio 4.7 I did not have an external clock, I used what was on the EVAL board.

Currently I'm just testing a simple signal in and signal out, we were expecting the output signal to follow the input signal since in the schematic, we route it that way

Is there always going to be the input frequency - the FS frequency where can I find this information in the datasheet?

Thanks,

Po

TestRevC.zip

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Poster Reply
May 13, 2026 00:00

Hello Dave,

Where can I find linkage that the message frequency will be in the input frequency subtracted by the Serial Port FS Frequency?

Thanks