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AD9172 mode 21 does not work with DAC1

Category: Software


I'm using a VCU128 FPGA board to push data to a DAC9172 on the HTG board (part number: HTG-FMC-12ADC-16DAC). On FPGA, I use JESD204 IPs from Analog Devices to communicate with AD9172 through multiple gigabit lanes. The DAC9172 was configured to operate at mode 21 with DAC0 successfully. My questions are:

1. Is it possible to configure the DAC9172 at mode 21 with DAC1? If it was possible, which change do I have to make to achieve that? I tried to change the main data page (reg 0x008) but it didn't work.

2. Does the phase "Link 1" represent the link for DAC1? QBD0 and QBD1 are used for DAC0 and DAC1 respectively, is it right?

3. I saw that in your datasheet the QBD1 is enabled only in dual-mode so I thought DAC9172 can only work in two modes: single link (DAC0 only) and dual links (DAC0 and 1), am I right?

Thanks in advance.

  • Hi, please let me know if these notes answer your questions:

    1. Mode 21 can only be used with real input data for a single DAC output, because M=1. In any single DAC mode DAC0 is used as the sole output, thus it is not possible to configure mode 21 to run on DAC1.

    2. Not necessarily. It is possible to run the 9172 as a single link dual DAC. For example, in Modes 10, 11, & 12: L=8 (single link) and M=2. If you are using real data (interpolation set to 1x for channel and main datapaths) then M=2 means both DACs use this same single link (Link 0). However, in any case where you are in dual link mode (and thus Link 1 exists) then Link 1 does correspond to DAC 1. The only exception to this is when using the modulator switch to sum real data from datapath1 into datapath0, as seen in Fig 76 below.

    Additionally, in switch mode 2 (Fig 75) you can route baseband I/Q data from main datapath0 prior to the NCO to send I data to DAC0 and Q data to DAC1.

    3. Similar to your second question: you can run in single link with both DACs as noted above, and you could run in dual link mode with the modulator switch configured to mode 3, where the main datapaths are summed post NCOs and routed to DAC0 only.