DAC38J82EVM: wrong output signal.

Dimitrius

Intellectual 1315 points

Part Number: DAC38J82EVM

Dear All,

My customer has bought 2 EVMs: DAC38J82EVM and TSW38J84EVM.

The customer set up initial parameters as at picture below

and provide QPSK signal to DAC input.

At the output the customer has picture below instead of square form signal.

It looks like DAC is switch on for very short time and falls to hi-impedance state after. The same test on TSW38J84EVM works pretty well.

For DAC38J82EVM: Alarm and Errors GUI page shows information below

What is wrong here?

Best regards,

Dmitry

over 5 years ago

0 dBrock over 5 years ago

TI__Genius 12780 points

Hi Dimitry,

We are taking a closer look into this issue, and will be back with you soon.

Best Regards,

Dan

0 jim s over 5 years ago

TI__Guru* 91947 points

Dmitry,

Is the customer using a TSW14J56EVM to provide the test pattern? If so, are the outputs bad on all channels? Can they send a tone using the Multitone generator in HSDC Pro and see how this looks? The DAC38J82EVM does not have a quadrature modulator like the TSW board does. Could this be there issue? The alarms like fine as shown above.

Can they send us the test pattern they are trying to use?

Regards,

Jim

0 Dimitrius over 5 years ago in reply to jim s

TI__Intellectual 1315 points

Jim,

The customer uses Xilinx KCU105. QPSK pattern is attached. Below you can find initial EVM conditions and output signal

QPSK.zip

Best regards,

Dmitry

0 jim s over 5 years ago in reply to Dimitrius

TI__Guru* 91947 points

Dmitry,

This output does not match what you sent before. What has changed? Can they try a sinewave instead of the QPSK to see how the output looks?

Regards,

Jim

0 Dimitrius over 5 years ago in reply to jim s

TI__Intellectual 1315 points

Jim,

Sorry. You are right. The customer made step back and trying very simple sinewave signal.

Best regards,

Dmitry

0 jim s over 5 years ago in reply to Dimitrius

TI__Guru* 91947 points

Dmitry,

If they no longer need any help I am going to close this ticket.

Regards,

Jim

0 Evgeniy Fedosov over 5 years ago in reply to jim s

Intellectual 510 points

Jim,

No, we still need help with smooth falling of the signal level instead of square form signal:

Yes the DAC38J82EVM does not have a quadrature modulator but we use it on baseband.

We try a sinewave instead of the QPSK and output looks so:

measure

Regards, Evgeniy.

0 jim s over 5 years ago in reply to Evgeniy Fedosov

TI__Guru* 91947 points

Evgeniy,

I setup a DAC38J82EVM and captured data from a tone and the QSPK data file you sent. When you send a sine wave, please use the I/Q Multitone Generator tool in the lower left of the GUI to create the tone. Please see attached file. I have also attached the QSPK file I used for this test. Not sure why you are having this issue. What is the power supply current limit on your power supply?

Regards,

Jim

QDSPK1_Ela.zip

0 Evgeniy Fedosov over 5 years ago in reply to jim s

Intellectual 510 points

Jim,

as external power supply we use wall adapter Mean Well GS18E05-P1J with output 5V@3A.

Regards, Evgeniy

0 Evgeniy Fedosov over 5 years ago in reply to jim s

Intellectual 510 points

Jim,

we use your QPSK file and result is the same:

We also have TSW38J84EVM evaluation board and it works fine.

I have tested DAC supply voltage 0.9 V/1.8 V/3.3 V and its normal but noisy.

0 jim s over 5 years ago in reply to Evgeniy Fedosov

TI__Guru* 91947 points

Evgeniy,

This looks like an expected result due to the transformer on the board. The TSW does not have a transformer and this is why the outputs look different.

Regards,

Jim

0 Evgeniy Fedosov over 5 years ago in reply to jim s

Intellectual 510 points

Jim,

many thanks! This is a true. We removed R33 & R38 0 Ohm resistors at channel C and signal looks normal.

Ticket can be closed.

Regards, Evgeniy

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DAC38J82EVM: wrong output signal.