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Original question:

Need Help! I can't get DAC34h84evm output based on my configuration.

DAC34H84EVM: Is it possible to generate trapezoidal wave of more than 30 micro second using DAC34H84

AMIT WAGHMARE
Prodigy 200 points
Part Number: DAC34H84EVM
Other Parts Discussed in Thread: DAC34H84

Hello everyone,

 I want to generate trapezoidal wave from DAC34h84evm of 30 microseconds Or the constant dc output voltage for 20 microseconds, is it possible to generate from this DAC EVM?

  • 0
    TI__Guru 66014 points
    Amit,

    The DAC34H84 itself cannot directly generate these types of tones, it relies on the external FPGA/ASIC to provide the data. The FPGA or ASIC interfacing the DAC will need to provide the waveform data necessary to generate these waveforms. The 30s requirement is mainly on the FPGA/ASIC side where the memory store on the FPGA/ASIC has to be large enough.

    The DAC can generate DC assuming DC coupled interface (i.e. 25ohm each positive/negative leg to ground).

    -Kang
  • 0 in reply to Kang Hsia
    Prodigy 200 points

    hello @Kang Hsia , thanks for the reply!

    I am giving samples to the DAC evm through the Xilinx zc706  SOC board, I had generated the Rf wave through this dac now I want to generate trapezoidal it is giving me output like the image below for trapezoidal wave. for trapezoidal wave, my rise time, flat time and fall time is 1 microsecond total 3 microseconds , timing is showing correctly  on CRO. but the shape is not coming as expected. CRO input is on 50-ohm termination.

    my DAC is running at 250MSPS. 

    Regards,

    Amit

  • 0 in reply to AMIT WAGHMARE
    TI__Guru 66014 points
    Hi Amit,

    The DAC34H84 EVM default has transformer/Balun coupled output. There is no DC coupling path and the transformer/balun creates a high pass network and hence your waveform never settled down to DC.

    You will need to modify the EVM accordingly to accommodate resistive termination, along with your scope interface.
    App note below has full explanation:
    www.ti.com/.../slua647a.pdf


    -Kang