• AD9119-CBLTX-EBZ or AD9129-CBLTX-EBZ Evaluation Board
• Mini-USB Cable
• Evaluation Board CD

• +5Vdc, +8 Vdc Power Supply
• Data Pattern Generator Series 2 (DPG2)
• Spectrum Analyzer Ex: Agilent PXA or Rohde Schwarz FSU

The AD9119-CBLTX-EBZ and AD9129-CBLTX-EBZ are built from the same printed circuit board, with the only difference being which DAC device is loaded, the AD9119 or the AD9129. This Quick Start Guide will describe the set-up of the AD9129-CBLTX-EBZ, but the steps apply equally to setting up the AD9119-CBLTX-EBZ. The slight differences in performance between the two boards are documented in the data sheet, and are related to the 11-bit resolution of the AD9119. Thus, noise spectral density and some ACLR measurements are affected, and the AD9119 performance is lower than the corresponding performance of the AD9129. For ease of reading, only the AD9129-CBLTX-EBZ will be mentioned for the rest of the document.

The AD9129-CBLTX-EBZ connects to a DPG2 to allow for quick evaluation of the AD9129, a high-speed, RF Digital to Analog converter (RF DAC). The DPG2 automatically formats the data and sends it to the AD9129-CBLTX-EBZ, simplifying evaluation of the device. The Evaluation Board (EVB) runs from +5 volt and +8 volt supplies. Figure 2 is an image of the top side of the AD9129 EVB. The AD9129-CBLTX-EBZ evaluation board is intended for evaluation purposes only with no implied guarantee of performance or reliability. This evaluation board was solely developed to aid our customers in the development of a cable transmit solution and not intended to be directly leveraged into any final product.

The AD9129 Evaluation Board software has an easy-to-use graphical user interface (GUI). It is included on the Evaluation Board CD, or can be downloaded from the DPG Web site at http://www.analog.com/dpg. This will install DPGDownloader (for loading vectors into the DPG2) and the AD9129 SPI Controller application.

Connect +5V to P3, GND to P4, and +8V to P5. The evaluation board connects to the DPG2 unit through connectors P1 and P2. The spectrum analyzer should connect to the N-connector at J1. Because cable systems are typically 75 Ω systems, the output of the board is also 75 Ω. For best results using a 50 Ω spectrum analyzer, a transformer should be used to transform the output impedance from 75 Ω to 50 Ω. The PC should be connected to the EVB using the mini-USB connector XP2 after installation of the Evaluation Board software.

The PC software comes on the included Evaluation Board CD, but may also be downloaded from the DPG Web site at http://www.analog.com/dpg. The installation will include the DPG Downloader and ADF4350 programming software as well as all the necessary AD9129 files including schematic, board layout, data sheet, SPI GUI, and other files. The following procedure will set up a basic 1-carrier, 256-QAM signal.

1. Install the DPG Downloader, ADF4350, and AD9129 software and support files on your PC
2. Start the AD9129 Control Panel GUI (but don’t hit the run arrow yet)
3. Connect the EVB to your PC and lab equipment as shown in Figure 1 above. Use a USB cable to connect your PC to the EVB, and another USB cable to connect your PC to the DPG2 unit. Note that a DPG3 unit can also be used.
4. Start the ADF4350 SPI for AD9129
It is suggested that the basic set-up is verified before making any modifications to the evaluation board.

To begin, open the AD9129 SPI application (Start > Programs > Analog Devices > AD9129 > AD9129_27 SPI). The screen should look similar to Figure 3 on the Common tab. The AD9129 SPI loads default settings that should be usable for most applications.

Configure the hardware according to the hardware set-up instructions given in the Hardware Setup section above. The spectrum analyzer can be configured with Start Frequency = 20 MHz, Stop Frequency 1 GHz, and Resolution Bandwidth of 100 kHz. Use an Average/RMS detector setting, and choose Input Attenuation to be 10 dB. This can be adjusted later if indications are that the analyzer is causing degradations (warnings on the analyzer itself, or third order products appearing on the output spectrum.). The potentiometer should be tuned so that VAGC, the automatic gain control voltage for the power amplifier, is 1.2 V to replicate the following example measurements.

Open the ADF4350 SPI application (Start>Programs>Analog Devices> AD9129>ADF4350 SPI for AD9129) that programs the external PLL on the board. The screen should look like Figure 4 on the Main Window tab.

The PLL and the chosen reference crystal do not allow for as much frequency precision as the DPG, which specifies its sample frequency down to tens of Hertz. A suggested accuracy for this evaluation board is 100 kHz. To achieve this level of precision, the “Reference Divider” is changed to 250 so that the “PFD Frequency” changes to 0.100 MHz. Then, in the “RF Frequency” section, the “Output Frequency” box should be changed to 2305 MHz to most closely match the DPG sample frequency of 2.30503091 GHz. The discrepancy between the data sample frequency and the programmed clock frequency may create some low level distortion, but the effects have proven negligible in lab. The rest of the settings may be left in their default states. Click the “Write All Reg” button, and the boxes along the bottom of the screen should change from green to grey, indicating that the registers have been programmed.

On the “PLL” tab, the “Controller Ena” button should be green. Click the “Play” button () to program the registers. The Readback light next to the button should change from red to green, and the PLL LOCK light should turn green. Note that in some cases, it may be necessary to click the “Controller Reset” button (it goes to green), click the () button, and then click the “Controller Reset” button (it goes to red) and the () button again to reset the PLL in order for it to lock.

Open DPGDownloader (Start > Programs > Analog Devices > DPG > DPGDownloader). Ensure that the program detects the AD9129, as indicated in the “Evaluation Board” drop-down list, and select it. For this evaluation board, LVDS is the only valid Port Configuration, and it will be selected automatically. The “Data Clock Frequency” window may not yet show a clock frequency, but it normally does.

Click on “Add Generated Waveform”, and then “Cable Infrastructure”, as shown in Figure 6. A Cable Infrastructure panel will be added to the vector list. Enter the sample rate, or DAC clock frequency, in this case 2.305030910 GHz. Next, choose the “Resolution” to be 14 bits. Choose a center frequency of 70 MHz. Keep “Relative Amplitude” as 0 dB, and “Number of Channels” as ‘1’. Then, click the “Add Channels” button. The signal should appear on the list of signals as shown in Figure 7.

Next, in the lower portion of the screen, select “1I: CIFR Vector (I)” as the Data Vector. The other options can be left at their default values. The Data Clock Out (DCO) frequency from the AD9129 should be reported in the Data Clock Frequency window as roughly 576.25 MHz.

Make sure the DPG2 unit is powered up and the AD9129 eval board is plugged into it correctly. Click the “Download” button () to download the pattern from the computer to the DPG2 unit, wait for the Play () button to become active, and then click the Play () button to begin vector playback to the AD9129.

On the AD9129 SPI GUI’s “DLL” tab, the “DUTY Corr Ena” button and the “DLL_ENA” button should be green (selected). Click the () button to program the registers. The Readback light next to both buttons should change from red to green, and the DLL Lock light should change from red to green. It may be necessary to click the () button again to get a full readback status since the controller may take slightly longer to lock than the GUI allowed on the first write and then readback.

In rare cases, the data link may have gotten corrupted and the registers not programmed correctly. In these cases, the output of the DAC will show significantly degraded performance. To remedy this situation, click the “DUTY Corr Ena” button and the “DLL_ENA” buttons, and then click the () button to program the registers. Then, re-click the “DUTY Corr Ena” button and the “DLL_ENA” buttons, and then click the () button to program the registers. This disables and re-enables the Data Interface DLL and allows it to re-lock to the DCI. At this time, it is also possible to click the “Repeat” button () to continuously program the part, making the SPI GUI run in a more interactive mode.

The final result should be a single 256-QAM carrier centered at 70 MHz, as shown in Figure 10. An attenuation of 30 dB was used in this measurement, which raises the noise floor of the measurement, but avoided saturating the input and causing higher-ordered products being created. Selecting appropriate attenuation becomes especially important for the cable transmitter board, since its output power is relatively high. A 6 dB pad was used at the output of the board to add some attenuation before the input of the spectrum analyzer. The output signal in Figure 10 is tuned to a level 2 dB above the DOCSIS requirements for a single channel. This is accomplished by adjusting the Vagc knob until the appropriate level is achieved. The power is best adjusted using a narrow span on the spectrum analyzer. In Figure 11, an adjacent channel power ratio (ACPR) measurement is done and in that measurement the power of the signal is properly measured. The measurement is taken with a 6 dB pad at the input to the spectrum analyzer, so 6 dB must be added to the result seen in the plot.

To check for flatness across the full cable band, the user can create a new vector or load the vector included in the EVB document package. To do this, select “Add Data File” in the DPG Downloader window, as shown in Figure 12.

Then, choose the file called “158Channel2.3GSample0dBbackoff.txt” in the C:/Program Files (x86)/Analog Devices/HSDAC/AD9129 folder. Click the button to download the pattern from the computer to the DPG2 unit, wait for the Play () button to become active, and then click the Play () button to begin vector playback to the AD9129. Then, re-initialize and lock the LVDS interface by clicking the “DUTY Corr Ena” button and the “DLL_ENA” buttons, and then clicking the () button to program the registers. Then, re-click the “DUTY Corr Ena” button and the “DLL_ENA” buttons, and then click the () button to program the registers. This disables and re-enables the Data Interface DLL and allows it to re-lock to the DCI. If the () button has been pressed and the SPI is in continuous programming mode, the () button does not need to be pressed. The registers will be programmed when each of the DUTY Corr Ena and DLL_ENA buttons are pressed. The output spectrum should then appear similar to that in Figure 13. Note that the analyzer settings have been changed to show more detail, with 2 dB/division on the vertical scale. It can be seen that there is about 1.4 dB of variation in output amplitude across the band, meeting DOCSIS 3.0 specifications.

The AD9129 SPI software is conveniently organized in a series of tabs that groups registers according to their functions. In this way, all registers associated with the fDAC PLL, for example, are on the “PLL” tab, all registers associated with the data clock Delay Locked Loop (DLL) are on the “DLL” tab, and so on. A full description of each register and its settings is given in the AD9129 data sheet. Some of the registers and their functions are described here as they pertain to the AD9129 evaluation board. Please note that some of the screen images in this document may not match exactly with the latest revision of the software, due to ongoing improvements and enhancements to the software. The full screen layout is shown in Figure 14. The tabs can be seen across the top of the work area, and a “READBACK” area is below the active tab area. This READBACK section is present on each of the tabs, so that the user can quickly assess status of the PLL and DLL lock, as well as parity and the FIFO phase. Each of the tabs is discussed in its own section below.

The common tab has selections that apply to the general configuration of the DAC. The Reset bit is set or reset here, as well as basic configuration of the serial port: Short vs. Long mode; SDIO pin as an output or bi-directional, MSB or LSB first for the data words, format of the data words (unsigned or two’s complement), and whether the 2x interpolator filter is ENabled (“DDR”) or DISabled (“SDR”). With the 2x interpolator filter enabled, two filter options are available to provide either 25 or 40 dB of out of band rejection. Filter selection is controlled in the common tab. The mode of the Frame/Parity pins is also chosen on this tab, along with MixMode™ or Normal mode for the DAC output. Finally, the SPI_FRM_ACK bit (reg 0x11[6]) is set on this tab. That bit is used to flag an interrupt if the SPIFrmReq bit is set, which indicates that a SPI-based FIFO alignment has been requested.