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Original question:

DAC3174: How to exatly set the registers for the application of Single Bus Single Clock Mode?

DAC3174: DAC3174 has no output

Danny R.
Prodigy 75 points
Part Number: DAC3174
Other Parts Discussed in Thread: TRF3705,

Hello,

I tried the setup as suggested here (previous question), but I'm not getting no signal at the Output for I/Q at all. I'm measuring only 50mV, which is almost zero, ,but no signal at all so something isn't working right..

I checked all voltages and Data Lines, DACCLK and DATACLK, all there, fine, getting to the chip's pins.

I also turned the 4-Wire interface and got to read config0 and it was just like I wrote it the first time again on the SDO line. So I know at least the DAC chip is working and responding, nothing is shorted. TXENABLE and RESETB are both high and Sleep is low..

Am I missing something here? I'm toggeling SYNC to high exactly with the first line of DATA, so it should work just fine.

Just for test purposes: I generated [-1,1] data as sine/cosine wave, then mapped these to [0,4095] for 12-bit output. These data are then converted to binary and fed to each of the Data Lines, so I should measure a sine/cosine wave at I/Q output.

Do you know what I can do more? Maybe I'm missing some registers? These are the one I'm writing just as before:

% CONFIG0: (0x00)
0x00: '0x52EC'; % 0101 0010 1110 1100
% CONFIG1: (0x01)
0x01: '0x600E'; % 0110 0000 0000 1110

Any help would be greatly appricated!! DACCLK and DATACLK are running at 50kHz, same as the update of the Data Lines. I also tried to turn up the DACCLK to 1MHz, 10MHz and 100MHz but vainly. I'm almost out of options at this point, since everything else checks out and all LVDS are arriving to the chip reasonably correct.

Thanks!!

  • 0
    Prodigy 75 points

    Hey,

    so I tried running my DACCLK much faster than DATACLK (DACCLK at 100MHz and DATACLK 50kHz) and this didn't solve the issue.

    I also tried to send only 1's at all time, just to check if my setup is faulty in anyway, that the amplitude is too low. This also didn't solve the issue.

    I would appreciate it very much, if you have any suggestion for this problem.

  • 0 in reply to Danny R.
    TI__Expert 3550 points

    Hey Danny, 

    Could you send a schematic of the DAC output stage? 

    Thanks!

    Matt

  • 0 in reply to Matthew Kramer
    Prodigy 75 points

    Hey Matt,

    thank you for answering!

    I actually already asked about this in the forum before (here) and I got the schematic for the EVM board with the TRF3705. I oriented myself with my design on your design as well.

    I have two stages. 50Ohm resistor at the DAC output and again 50Ohm resistor at the modulator input, since the modulator common-mode voltage is at 0.25V (DAC is at 1V with full-scale 20mA output current source).

    Left side is the DAC3174 (output) and right side is the modulator TRF3705:

    Layout of the DAC output to the TRF3705:

    Here the lines are highlighted:

    I'm actually measuring already at the first pad coming from the IOUTA_P & _N and I couldn't see any voltage there.

    If you need more documentation about the schematic, please let me know :)

  • 0 in reply to Danny R.
    TI__Mastermind 41330 points

    Hi Danny,

    I apologize for the delay, if you still need help, please send over the entire schematic.

    This would be helpful, you may have the DAC setup incorrectly.

    It would be helpful, to send over the entire spi write list as well for the DAC so we can see how it is being configured.

    Regards,

    Rob