This user guide describes how to set up and use the AD9914 evaluation board. The AD9914 is a 3.5 GSPS direct digital synthesizer (DDS) with a 12-bit DAC. The evaluation board software provides a graphical user interface (GUI) for easy communication with the device along with many user friendly features, such as the mouse-over effect. This user guide is intended for use in conjunction with the AD9914 data sheet.
The AD9914 evaluation software allows the user to control the full functionality of the AD9914 through SPI communication on the evaluation board. 64-bit versions of Windows® are supported. Use the following instructions to set up the evaluation board software.
Do not connect the evaluation board until the software installation is complete.
After the installation of the evaluation software is complete, follow these steps to install the device driver:
A successful connection of the software to the board is indicated by a green USB icon, which can be found at the bottom right corner of the main GUI window.
An unsuccessful connection is indicated by a flashing red USB icon located at the bottom right corner of the window. Most installation errors can be resolved by checking jumper settings, making sure that the evaluation board is powered up correctly, and inspecting the USB port and cable connections. When all power, USB port/cable connections, and jumper settings are correct, an error may still appear if the clock input is not configured properly. Check to make sure that the clock input source is connected and configured properly. Another reason an error may appear is due to the presence of a conflicting device driver. To resolve this issue, update the driver by plugging the USB connector into another USB port. When the Found New Hardware Wizard appears, install a device driver as follows:
The evaluation board provides all of the support circuitry required to operate the AD9914 in its various modes and configurations. Figure 1 shows the typical bench characterization connections used to evaluate the ac performance.
The AD9914 evaluation board has one power supply connector labeled P300 to power the USB interface circuitry and the AD9914. This connector has four pins; connect individual wires back to power supplies to power the AD9914 evaluation board. Table 1 shows the necessary connections and the appropriate supply voltage
Table 1. Power Supply Connections
The AD9914 architecture provides the user with two options when providing an input clock signal to the part:
The maximum frequency rate of the PFD of the internal PLL is 125 MHz. The input clock to the DDS is called the REF CLK. The internal system clock runs at the REF CLK rate if the internal REF CLK multiplier (PLL) is disabled. Otherwise, the internal system clock runs at the output frequency rate of the PLL. Note that the input clock path on the AD9914 evaluation board uses an ADCLK925 clock buffer to drive the AD9914 differentially. Therefore, if the input signal into the ADCLK925 has a slow slew rate, the in-close phase noise performance of the AD9914 may be dramatically limited by the ADCLK925.
Refer to the ADCLK925 data sheet for details on the maximum input speeds and input sensitivities. The SYNC_CLK runs at 1/24th the system clock rate and the default state is SYNC_CLK enabled. Thus, if the SYNC_CLK is not running, the device is powered down or the REF CLK is invalid.
The main output signal of the DDS is the DAC output. Note that the output of the DDS may or may not have a DAC reconstruction filter after the balun on the evaluation board depending on the revision of the board.
The jumpers on the AD9914 evaluation board are factory set so that the board is ready to use with PC control. The AD9914 software GUI operates the evaluation board in a serial interface only; however, you can also opt to use an alternative external control. Note that this user guide does not cover all aspects of externally controlling the AD9914 evaluation board.
If you tri-state the USB circuitry to drive the board externally, you must control all tri-stated inputs to the AD9914. Otherwise, the device may not response to the external stimulus. For example, if the master reset input or the EXT_PWR_DWN input are floating, any external programming will have intermittent issues. All AD9914 digital inputs are accessible via the provided header connectors.
For PC control (factory settings)
For external control
The external I/O control headers provide a parallel or serial communication interface for the AD9914 when the part is under the command of an external controller. In addition, the headers provide an interface for modulation data depending on the setting of the function pins. See the AD9914 data sheet for more details on the function pins settings.
Disabling the ICs on the evaluation board allows operation of the board with an external serial or parallel control by configuring each buffer in its high impedance state by its nearby jumper.
When the part is under PC control (default mode), the evaluation board communicates with the AD9914 via the USB port.
In profile mode, the three DDS signal control parameters (frequency, phase offset, and amplitude scaling) are supplied directly from 1 of 8 internal profile registers. A profile is an independent register that contains all three control parameters. You can use a profile register to output a single tone frequency or use multiple preprogram profile registers and the profile pins to hop between frequencies, phase offsets and/or different amplitude settings. The following example are the steps to program a single profile to output a single tone frequency using the AD9914 software GUI.
To select a profile other than Profile 0, use the Selected Profile drop-down menu. Note that, unfortunately, the profile pin signals are sent asynchronously from the buffer ICs on the evaluation board to the AD9914 profile pins. Thus, it is possible that the profile found may not be the profile you selected because the profile signals are not synchronous to the SYNC_CLK. If the selected profile setting does not point to the correct profile settings chosen, send an IO_UPDATE or click Load tocorrect the issue. This would not be an issue if the profile signals were sychrnonously transmitted to the AD9914.
The Frequency box is used to set the frequency generated by the DDS. The input values are in megahertz. Refer to the AD9914 data sheet for the acceptable range of output frequencies.
The Phase Offset box controls the phase of the DDS output. The input is in degrees and can be changed from 0° to 360° with 16-bit resolution.
The Amplitude Scale Factor box digitally controls the amplitude of the carrier from the DDS. This scalar ranges from 0 to 1 and has a 12-bit resolution. Note that this function works only if the OSK enable is selected in the Control tab.
Note that Frequency, Phase Offset, and Amplitude Scale Factor can accept native data that are to be loaded directly to the registers. This data is binary in form, but can also be expressed as hexadecimal or decimal. Change the format by clicking the drop-down button to the right of each box.
The Digital Ramp Generator (DRG) window is accessible via the Sweep Tab directly below the GUI tool bar. The DRG can sweep frequency, phase, or amplitude. The DRG allows independent control of the slope of a rising sweep and the falling sweep along with other features (see Figure 5).
To enable the DRG for configuration,
In the Settings section, the Auto Clear Digital Ramp Accumulator check box allows the DRG to be cleared every time the I/O update signal is applied or when there is a profile pin change. The Clear Digital Ramp Accumulator check box keeps the DRG cleared until the check box is cleared. The Load SRR @ I/O Update check box allows the reload of a new digital ramp rate when an I/O update is issued or when there is a profile change.
If the parameter to be sweeped is Frequency, use the Sweep Frequency 0 and Sweep Frequency 1 boxes to enter the lower frequency limit value and upper frequency limit value, respectively. The units are megahertz for freqency, degrees for phase, and volts for amplitude. Note that the value in the Sweep Frequency 0 box is required to be be less than the value in the Sweep Frequency 1 box regardless of the parameter being swept. The Rising Sweep Ramp Rate and Falling Sweep Ramp Rate boxes are used to set the time between each rising or falling step on the ramp and is in units of microseconds.
The No Dwell High and No Dwell Low check boxes are used to instantaneously return to the lower or upper limit depending of which box is checked. To continously repeat a parameter sweep without clicking the up/down buttons or just enable both No Dwell bits. If not, use the Up, Down, and Pause buttons at the bottom of the window to control the sweep direction or to halt the sweep. The Ramp Finished indicator illuminates when the ramp is complete.
Keep the following points in mind:
Programmable Modulus Window
The chip is in programmable modulus mode when the Enable Programmable Modulus check box is selected. Note that the digital ramp generator mode is automatically disabled.
The Programmable Modulus window is used to alter the frequency equation of the DDS core, making it possible to implement fractions that are not restricted to a power of 2 in the denominator.
When you enter the desired output frequency (in megahertz) in the FOUT box, the values in the Register Values boxes and the Divide Ratio boxes are automatically updated. You can also directly input a divide ratio, which in turn automatically updates the Register Values boxes and the Output Frequency box.
The toolbar near the top of the evaluation software main window includes several buttons, each labeled with an icon, that allow you to easily initiate various actions (refer to Figure 6 for a detailed description of the requirements of each toolbar element).
There are five tabs available in the main window of the evaluation software: Control, Profiles, Sweep, Modulus, and Debug. The following tab descriptions provide a brief overview of each tab; more detailed information can be found in the Evaluation and Test section.
Figure 8. Tabs Available
The Control tab provides control of the internal PLL, parallel port, auxiliary functions, I/O control, power-down functions, output shift keying (OSK), clock calibration, and multichip sync function of the AD9914.
The Profiles tab allows enabling of profile mode, in which the DDS signal control parameters are supplied directly from the profile programming registers. A profile is an independent register that contains the DDS signal control parameters.
Note that, unfortunately, it is not guaranteed that selecting a profile will switch to the correct profile setting. This is because the profile signals are sent asynchronously via the GUI hardware. The reality is that the profile signals need to meet setup and hold times to the SYNC_CLK.
Digital ramp generator (DRG) is synonymous with linear sweep. The ramp generation parameters in the Sweep tab allow you to control both the rising and falling slopes of the ramp, the upper and lower boundaries of the ramp, the step size and step rate of the rising portion of the ramp, and the step size and step rate of the falling portion of the ramp. This is digitally generated with a 32-bit output resolution that can be programmed to represent frequency, phase, or amplitude. Refer to the AD9914 data sheet for more information on DRG.
The Modulus tab allows you to enable programmable modulus mode and to alter the frequency equation of the DDS core, making it possible to implement fractions that are not restricted to a power of 2 in the denominator. See the AD9914data sheet for more details.
The Debug tab provides complete direct access to the register map as well as control of many external pins. The Debug tab is intended for debugging issues with the AD9914. Although this tab can be used for all programming, it is not user friendly for programming purposes and, therefore, using the Debug tab for purposes other than debugging may result in improper programming of reserved bits.