DAC39J84EVM: Reason for distorted square pulses on oscilloscope

Vaibhav Jain

Part Number: DAC39J84EVM
Other Parts Discussed in Thread: ADC12DJ3200EVM,

Hi All,

Hope you are doing great!!

We are generating constant amplitude square pulses from TSW14J56EVM using a .csv file (attached with the message) and sending it to DAC39J84EVM ( screenshot of the pattern as visible on HSDC Pro software is attached with the message) with 10000 samples in the file, sampling at 20 samples per pulse and duty cycle of 0.5. Two channels of this DAC are connected respectively to an oscilloscope and ADC12DJ3200EVM, to monitor the output generated. However, when oscilloscope and ADC receive these pulses from DAC (screenshot attached of the pattern received on ADC is attached and similar pattern is observed on oscilloscope), there is a ringing effect in the pattern as shown in the attached screenshot. What could be the reason for this ringing and how can this be resolved.

Thanks for your help and looking forward to your response.

Square_pulse.csv Pattern-sent-to-DAC-_2800_Captured-on-HSDC-Pro_2900_.png Pattern Recieved on ADC

over 2 years ago

0 jim s over 2 years ago

TI__Guru* 91947 points

Vaibhav,

This is related to the transformers on the output of the DAC on the EVM. You will have to convert the EVM to output differential data and then probably send this to an external differential to single-ended amplifier. To convert the EVM for this mode for CHA, you would need to do the following:

Remove T1, T2 and R12.

Short pins 3 to 4 and pins 1 to 6 on T1.

Short pins 1 to 6 and 3 to 4 on T2.

Install 0 Ohms for R14.

Install SMA J4.

Regards,

Jim

3582.DAC3XJ8XEVM-SCH_D.pdf

0 Vaibhav Jain over 2 years ago in reply to jim s

Prodigy 180 points

Thanks a lot Jim. Will give this a try and will be back with the results.

0 jim s over 2 years ago in reply to Vaibhav Jain

TI__Guru* 91947 points

I will close this post for now.

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DAC39J84EVM: Reason for distorted square pulses on oscilloscope