This user guide describes the AD9645 and AD9635 evaluation boards, AD9645-125EBZ and AD9635-125EBZ, which provide all of the support circuitry required to operate these parts in their various modes and configurations. The application software used to interface with the devices is also described.
The AD9645 and AD9635 data sheets provide additional information and should be consulted when using the evaluation board. All documents and software tools are available at www.analog.com/hsadcevalboard. For additional information or questions, send an email to email@example.com.
Before using the software for testing, configure the evaluation board as follows:
The evaluation board provides the support circuitry required to operate the AD9645 and AD9635 in their various modes and configurations. Figure 1 shows the typical bench characterization setup used to evaluate AC performance. It is critical that the signal sources used for the analog input and clock have very low phase noise (<1 ps rms jitter) to realize the optimum performance of the signal chain. Proper filtering of the analog input signal to remove harmonics and lower the integrated or broadband noise at the input is necessary to achieve the specified noise performance.
See the Getting Started section to get started, and visit UG-448 Design Support for the complete schematics and layout diagrams. These diagrams demonstrate the routing and grounding techniques that should be applied at the system level when designing application boards using these converters.
This evaluation board comes with a wall-mountable switching power supply that provides a 6V, 2A maximum output. Connect the supply to a 100V ac to 240V ac, 47Hz to 63Hz wall outlet. The output from the supply is provided through a 2.1mm inner diameter jack that connects to the printed circuit board (PCB) at P101. The 6V supply is fused and conditioned on the PCB before connecting to the low dropout linear regulators that supply the proper bias to each of the various sections on the board.
The evaluation board can be powered in a nondefault condition using external bench power supplies. To do this, remove the E101, E102, E103, E104, E105, E106, E108 and E109 ferrite beads to disconnect the outputs from the on-board LDOs. Note that in some board configurations some of these might already be uninstalled. This enables the user to bias each section of the board individually. Use P102 and P103 to connect a different supply for each section. E113, E114, E115 and E116 need to be populated to connect P102 and P103 to the board power domains. A 1.8V, 0.5A supply is needed for 1.8V_AVDD and 1.8V_DRVDD. Although the power supply requirements are the same for AVDD and DRVDD, it is recommended that separate supplies be used for both analog and digital domains. The SPI and its level shifters are powered by 1.8V_DRVDD.
Two additional supplies, AMP_VDD and 3.3V_AVDD, are used to bias the optional input path amplifiers and optional AD9517-4 clock chip, respectively. If used, these supplies should each have 0.5A current capability.
When connecting the ADC clock and analog source, use clean signal generators with low phase noise, such as the Rohde & Schwarz SMA, or HP 8644B signal generators or an equivalent. Use a shielded, RG-58, 50Ω coaxial cable (optimally 1 m or shorter) for connecting to the evaluation board. Enter the desired frequency and amplitude (see the Specifications section in the data sheet of the respective part). When connecting the analog input source, use of a multipole, narrow-band band-pass filter with 50Ω terminations is recommended. Analog Devices uses band-pass filters from TTE and K&L Microwave, Inc. Connect the filters directly to the evaluation board.
If an external clock source is used, it should also be supplied with a clean signal generator as previously specified. Analog Devices evaluation boards typically can accept ~2.8V p-p or 13dBm sine wave input for the clock. If an external off-board clock source is used, remove the jumper on P601 to disable the on-board crystal oscillator.
The default setup uses the Analog Devices high speed converter evaluation platform (HSC-ADC-EVALCZ) for data capture. The serial LVDS outputs from the ADC are routed to Connector P802 using 100Ω differential traces. For more information on the data capture board and its optional settings, visit www.analog.com/hsadcevalboard.
Set the jumper settings/link options on the evaluation board for the required operating modes before powering on the board. The functions of the jumpers are described in Table 1. Figure 2 shows the default jumper settings.
|P401||This jumper enables the optional ADA4930-1 amplifier on Channel A. Connect pin 2 to pin 3 for default (amplifier disabled) operation|
|P501||This jumper enables the optional ADL5565 amplifier on Channel B. Connect pin 2 to pin 3 for default (amplifier disabled) operation|
|J301||This jumper sets the ADC for SPI communications with the HSC-ADC-EVALCZ.
Connect Pin 1 to Pin 2 for SDIO, Pin 4 to Pin 5 for SCLK, and Pin 8 to Pin 9 for CSB.
|P601||This jumper enables the on-board crystal oscillator. Remove this jumper if an external off-board clock source is used.|
Connect the switching power supply that is supplied in the evaluation kit between a rated 100V ac to 240V ac, 47Hz to 63Hz wall outlet and P101.
Both analog inputs on the evaluation board are set up for a double balun-coupled analog input with a 50Ω impedance. The default analog input configuration supports analog input frequencies of up to ~200 MHz.
RBIAS has a default setting of 10 kΩ (R201) to ground and is used to set the ADC core bias current. Note that using a resistor value other than a 10 kΩ, 1% resistor for RBIAS may degrade the performance of the device.
The default clock input circuit is derived from a simple transformer-coupled circuit using a high bandwidth 1:1 impedance ratio transformer (T603) that adds a low amount of jitter to the clock path. The clock input is 50 Ω terminated and ac-coupled to handle single-ended sinusoidal inputs. The transformer converts the single-ended input to a differential signal that is clipped by CR601 before entering the ADC clock inputs. The AD9645 and AD9635 ADCs are equipped with an internal 8:1 clock divider to facilitate usage with higher frequency clocks. When using the internal divider and a higher input clock frequency, remove CR601 to preserve the slew rate of the clock signal.
The AD9645-125EBZ and AD9635-125EBZ boards are set up to be clocked through the transformer-coupled input network from the crystal oscillator, Y602. If a different clock source is desired, remove C610 (optional) and Jumper P601 to disable the oscillator from running and connect the external clock source to the SMA connector, J602 (labeled CLK+).
The AD9645/AD9635 ADCs can operate in pin mode if there is no need to program and change the default modes of operation via the SPI. For applications that do not require SPI mode operation, the CSB pin is tied to DRVDD by removing the J301 jumper that connects Pin 6 to Pin 9. In this configuration the SDIO/PDWN pin controls the power-down function, and the SCLK/DFS pin controls the digital output format. Table 2 and Table 3 specify the settings for pin mode operation.
|SDIO/PDWN (J301 Pin 2) Voltage||Device Mode|
|DRVDD||Power Down Device|
|AGND||Run Device, Normal Operation|
|SCLK/DFS (J301 Pin 5) Voltage||Output Format|
To operate the device under test (DUT) using the SPI, follow the jumper settings for J301 as shown in Table 1.
After configuring the board, set up the ADC data capture using the following steps:
Figure 3. VisualAnalog, New Canvas Window
Figure 5. VisualAnalog Window Toolbar, Collapsed Display
Figure 6. VisualAnalog, Main Window Expanded Display
After the ADC data capture board setup is complete, set up the SPI controller software using the following procedure:
Figure 7. SPI Controller, CHIP ID(1) Box
Figure 8. SPI Controller, New DUT Button
Figure 9. SPI Controller, CLOCK DIVIDE(B) Box
Figure 10. SPI Controller, Example ADC A Page
Figure 11. Run Button (Encircled in Red) in VisualAnalog Toolbar, Collapsed Display
The next step is to adjust the amplitude of the input signal for each channel as follows:
Figure 12. Graph Window of VisualAnalog
Lack of SPI communication will cause difficulty in configuring the ADC.
If the FFT plot appears abnormal, do the following:
If the FFT appears normal but the performance is poor, check the following:
If the FFT window remains blank after Run in VisualAnalog (see Figure 11) is clicked, do the following:
If VisualAnalog indicates that the FIFO Capture timed out, do the following: