DAC37J82: As the single tone signal frequency increases, the output power decreases

Amy Luo

Part Number: DAC37J82

Hi team,

A question from one of our customers, could you make any troubleshooting suggestions?

In the same configuration, the output power of a 5M 50M 100M single tone on the spectrometer decreases with frequency, but peak detection with the oscilloscope is not much different.

When using the oscilloscope to probe a waveform, the peak of a 5M frequency signal (approximately 970mV) is about 20-30mV higher than the peak of a 50M frequency signal, whereas later I measured the peak of a 100M frequency signal at about 1V.

Output power is approximately 2.6dBm for 5MHz sine signal and 0dBm for 50MHz sine signal.

Also attached is the circuit diagram for the DAC, where T9 is not soldered and R18 is not soldered.

Best Regards,

Amy

over 1 year ago

0 jim s over 1 year ago

TI__Guru* 91947 points

Amy,

This could be related to the transformer. What DAC sampling rate are they using? Are the using any interpolation? Have they tried using only the NCO to see if this issue could be related to the input data?

Regards,

Jim

0 Amy Luo over 1 year ago in reply to jim s

TI__Expert 6890 points

The sampling rate is 625M. They do not use interpolation. They have not yet tried to use only the NCO to check.

0 jim s over 1 year ago in reply to Amy Luo

TI__Guru* 91947 points

Amy,

Attached are power measurements with tones at 5MHz, 50MHz and 100MHz with the DAC sampling at 625MHz. This is using the TI DAC38JxxEVM.

Regards,

Jim

5MHz.WMF 50MHz.WMF 100MHz.WMF

0 Amy Luo over 1 year ago in reply to jim s

TI__Expert 6890 points

Hi Jim,

The customer feedback that they may have some problems with their configuration, ask if you can provide the register configuration you are testing?

0 jim s over 1 year ago in reply to Amy Luo

TI__Guru* 91947 points

Amy,

File attached.

Regards,

Jim

625MHz_Fs_1x_Int.cfg

0 Amy Luo over 1 year ago in reply to jim s

TI__Expert 6890 points

Hi Jim,

Thank you very much for your support. This customer has configured the DAC according to the profile you have given, but found that there is still power attenuation, but the attenuation value is much smaller than before, he is not sure if there is an error with the instrument or his waveform file is not correct, so he asks if you can provide the waveform file you used for the test

Thanks,

Amy

0 jim s over 1 year ago in reply to Amy Luo

TI__Guru* 91947 points

Amy,

The waveform files attached. Each file has two columns of data. The first column is sent to DAC A and the second column is sent to DAC B.

Regards,

Jim

test tones.zip

0 Amy Luo over 1 year ago in reply to jim s

TI__Expert 6890 points

Hi Jim,

Thank you for your supports, the customer's question has been resolved.

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DAC37J82: As the single tone signal frequency increases, the output power decreases