ADAQ23875 User Guide

Evaluating Using ZedBoard

Features

• Evaluation board for the ADAQ23875 (16-bit, 15 MSPS) µModule Data Acquisition Solutions

• Integrated fully differential ADC driver with signal scaling

• On-board reference buffer with VCMO generation

• PC software for control and data analysis of time and frequency domain

Evaluation Requirements

Hardware

• EVAL-ADAQ23875FMCZ evaluation board

• ZedBoard

• 12V power supply

• Host PC running Windows 10 or higher

• SD Card (16GB or larger)

• LAN Cable

• SMA Cable

• XLR to SMA adapter cable

• Audio Analyzer (Audio Precision APX525) or other input source

Software

• Analog Devices Kuiper Linux image

General Description

The EVAL-ADAQ23875FMCZ evaluation board enables simplified evaluation of the ADAQ23875 15 MSPS, 16-bit, High Speed, Precision µModule Data Acquisition Solutions. The µModule integrates passive components with superior matching and drift characteristics to minimize temperature-dependent error sources.

Figure 1 EVAL-ADAQ23875FMCZ Evaluation Board

Getting Started

Setting Up the Evaluation Board

The evaluation board consists of:

• U1: ADAQ23875 µModule

• U5: LTC6655 4.096V reference, or U3: ADR4520 2.048V reference

• U6: LTM8049 power µModule

• U4: ADP7118

• U7: ADP7183

• U8: LT3023

• U13: 800 MHz clock distribution IC

• Optional amplifiers: ADA4899-1 (A2, A3)

Power Supplies

Figure 2 On-Board Power Supplies

The EVAL-ADAQ23875FMCZ can be powered from an external 3.3V supply via the JP9 solder link.

The positive supply rails generated are:

• 7V (+VS)

• 5V (VDD)

• 2.5V (VIO)

The negative supply rail generated is:

• −2.0V (−VS)

Components used: LTM8049 (U6), ADP7118 (U4), LT3023 (U8), ADP7183 (U7).

Each supply rail has the necessary decoupling capacitors placed as close as possible to the device. A single ground plane is used to minimize the effect of high-frequency noise interference.

Analog Inputs

Subminiature Version A (SMA) connectors (VIN+ and VIN−) provide analog inputs from a low-noise, audio precision signal source (SYS-2700 or SYS-x555 series).

Three options are available for feeding the input signals:

1. Feed directly to the ADG774 analog switch

2. Feed through the optional ADA4899-1 amplifiers (A2, A3)

3. Feed directly to the ADAQ23875

The optional ADA4899-1 amplifiers (A2, A3) can be configured in unity-gain, driving the ADAQ23875. The default configuration allows the input signal via VIN+ and VIN− to feed directly to the ADAQ23875 by bypassing U2, A2, and A3.

The default board configuration provides 4.096V on the REFBUF pin and a buffered 2.048V (midscale) at the VCMO pin.

Note

For low input frequency testing below 100 kHz, use a low-noise audio precision signal source (SYS-2700 series) with outputs set to balanced floating.

Link Options

Figure 3 Link Options for the EVAL-ADAQ23875FMCZ

Multiple link options must be set correctly before applying power and signal.

Evaluation Board Connector Configuration

Figure 4 On-Board Connectors

Figure 5 160-Pin FMC Connector (P5)

Note

1. User-defined signals: the P suffix denotes the positive pin of a differential pair; the N suffix denotes the negative pin. See the VITA 57 specification.

2. User-defined signals with the CC suffix are preferred for transmitting clock signals from the controller board to the daughter board. These are connected to global clock lines on the FPGA. See the VITA 57 specification.

Loading the Image onto the SD Card

To properly evaluate the EVAL-ADAQ23875FMCZ, the ADI Kuiper Linux must be properly flashed on the SD card. Complete instructions are available at Kuiper Linux.

Follow the directions for preparing the image specifically for the EVAL-ADAQ23875FMCZ.

SD Card Preparation

1. Download the ADI Kuiper Image

   Follow the instructions at Kuiper Linux. The Kuiper Linux image is an open-source embedded Linux operating system based on Raspberry Pi OS, incorporating Linux device drivers for ADI products.

   The ZedBoard can be accessed from a remote PC via LAN cable or Wi-Fi.

2. Format and Flash the SD Card on Windows hosts

   Follow the Windows hosts instructions.

3. Format and Flash the SD Card on Linux hosts

   Follow the Linux hosts instructions.

After flashing, ensure the SD card is configured for the correct FPGA project per the Kuiper Linux documentation.

Copy the following key files to the root folder of the SD card:

1. BOOT.BIN

2. devicetree.dtb

3. uImage (from the zynq-common folder)

Hardware Connection

Figure 6 Signal Chain Connection

Setup steps (using the Audio Precision Audio Analyzer as input source):

1. Download and install the IIO Oscilloscope application on the host PC.

2. Flash the Analog Devices Kuiper Linux image on the SD card.

3. Properly configure the SD card for the EVAL-ADAQ23875FMCZ.

4. Insert the SD card into the ZedBoard.

5. Attach the EVAL-ADAQ23875FMCZ to the ZedBoard through the FMC pin connector.

6. Power up the ZedBoard using the 12V cable.

7. Connect the EVAL-ADAQ23875FMCZ to the Audio Precision Audio Analyzer using the XLR to SMA adapter cable.

8. Connect the Audio Precision Audio Analyzer USB cable to the PC.

After completing these steps, the IIO Oscilloscope software should run smoothly.

Navigating the IIO Oscilloscope

Main Window

Figure 7 Main Window

The main window displays a configuration panel (plugin) for each device recognized by the system. Additional plugins are loaded for device debugging and monitoring (Debug Tab/Plugin and DMM Tab/Plugin).

Each plugin can be detached by clicking the button on the right side of the plugin name. Close a detached window to re-attach it to the main window.

Debug Tab/Plugin

Figure 8 Debug Tab/Plugin

The Debug plugin is a tool for device debugging. Some features may not work unless the oscilloscope application is started as root.

1. Device Selection: Sets the active device.

2. IIO Device Attributes: Allows read/write operations for device attributes.

3. Register: Provides low-level access to device registers.

   1. Enable AutoRead: Allows automatic register reading as the register address changes.

   2. Address: Register address field.

   3. Value: Register value at the given address.

DMM Tab/Plugin

Figure 9 DMM Tab/Plugin

The DMM (Digital Multimeter) plugin displays device-specific data continuously once the start button is activated.

1. Device tab: Lists all available devices.

2. Active channels tab: Lists the channels of enabled devices. The “All Channels” button enables all channels simultaneously.

3. Right side tab: Displays data readings of the enabled channels.

Capture Window

Menu (along top):

• File

  • Save As: Saves data to a file.

  • Quit: Closes the capture/plot window.

• Edit

  • Plot Title: Changes the window name.

• View

  • Show Settings: Shows/hides the settings panel on the left, allowing the plot to fill the entire window.

  • Full Screen: Makes the window full screen.

Plot options/icons (along top):

• Capture/Stop: Start or stop data capture.

• Zoom In: Zoom in on the plot region.

• Zoom Out: Zoom out from the plot region.

• AutoZoom: Automatic zoom to fit the screen.

• Save As: Save data to a file.

• FullScreen: Enter/leave fullscreen mode.

• Auto scale: Automatically re-scale the visible area to fit the entire plot.

• Show grid: Show or hide the grid in the plot window.

• Y Max: Adjust the upper limit of the vertical axis (when Auto scale is disabled).

• Y Min: Adjust the lower limit of the vertical axis (when Auto scale is disabled).

• New Plot: Create a new plot of the same type.

Plot types:

Time Domain

Figure 10 Time Domain Plot

Plots the signal in the time domain. Displays raw samples.

1. Sample Count: Selects the number of samples for time domain, constellation, and cross-correlation plotting.

2. Graph Type: Selects the graph type (lines or dots).

Frequency Domain

Figure 11 Frequency Domain Plot

Plots the signal in the frequency domain. Performs an FFT on the signal.

1. FFT size: Selects the FFT size for frequency domain plotting.

2. Window: Selects the FFT window function. Each window has its own characteristics and suitability; see the window functions page.

3. FFT Average: Selects the average weight applied to FFT samples.

4. PWR Offset: Selects the FFT graph offset.

Constellation Plot

Plots the signal as a constellation plot, with the I-channel on the x-axis and the Q-channel on the y-axis.

1. Sample Count: Selects the number of samples.

2. Graph Type: Selects the graph type (lines or dots).

Cross Correlation Plot

Plots the signal as a cross-correlation plot.

1. Sample Count: Selects the number of samples.

2. Graph Type: Selects the graph type (lines or dots).

Activating Markers

Markers are used for plot data measurement in the frequency domain or during cross correlation. Right-click on the plot and select a marker type to enable.

Available marker types:

• FFT domain (1 channel enabled): Peak, Fixed, Single Tone

• FFT domain (2 channels enabled): Peak, Fixed, Single Tone, Image

• Constellation: Peak Marker

Five markers are displayed by default. Add more via Add Marker or remove via Remove Marker.

Saving Captured Data

Figure 12 Save As Window

Captured data can be saved in the following formats:

• Agilent VSA

• CSV (.csv)

• MATLAB (.mat)

• PNG (.png)

Evaluating the EVAL-ADAQ23875FMCZ Using IIO Oscilloscope

Download the latest release of IIO Oscilloscope.

1. Select the Refresh button to display available IIO devices.

   

   Figure 13 Refreshing the IIO Oscilloscope Connection

2. Once ltc2387 appears in the device list, select Connect.

   

   Figure 14 Connecting the IIO Oscilloscope

IIO Oscilloscope Capture Window

Waveform Plot:

Figure 15 Time Domain Waveform Plot

FFT Plot:

Figure 16 FFT Plot

To obtain the FFT plot:

1. Select Frequency Domain for the plot type.

   

   Figure 17 Selecting the Plot Type

2. Designate the preferred number of samples under FFT size.

   

   Figure 18 Setting the Number of Samples

3. Specify the window type as Blackmann-Harris.

   

   Figure 19 Selecting the Window Type

4. Press Run to view the result.

   

   Figure 20 View the Result

Board Layout Guidelines

PCB layout is critical for preserving signal integrity and achieving the expected performance from the ADAQ23875.

• Use a multilayer board with an internal, clean ground plane in the first layer beneath the ADAQ23875.

• Apply careful placement of individual components and routing of signals.

• Route input and output signals symmetrically.

• Solder the ground pins of the ADAQ23875 directly to the ground plane using multiple vias.

• Remove ground and power planes under the analog input/output and digital input/output pins (including F1 and F2) of the ADAQ23875 to avoid undesired parasitic capacitance. Undesired parasitic capacitance impacts distortion and linearity performance.

Signal routing:

The pinout of the ADAQ23875 eases layout by placing analog signals on the left side and digital signals on the right side.

• Separate sensitive analog and digital sections on the PCB.

• Keep power supply circuitry away from the analog signal path.

• Fast switching signals (CNV±, CLK±) and DA±, DB± digital outputs must not run near or cross analog signal paths.

Decoupling:

• Use good-quality ceramic bypass capacitors of at least 2.2 µF (0402, X5R) at the output of each LDO regulator generating the µModule supply rails (VDD, VIO, VS+, VS−) to GND.

• This minimizes electromagnetic interference (EMI) susceptibility and reduces glitch effects on the power supply lines.

• All other required bypass capacitors are laid out within the ADAQ23875.

• External decoupling capacitors on the REFIN, VDD, and VIO pins near the µModule can be removed with no significant impact on performance.

Mechanical Stress

Mechanical stress from mounting the device to the board can cause subtle changes to SNR and the internal voltage reference.

The recommended soldering method is IR reflow or convection soldering with a controlled temperature profile. Hand soldering with a heat gun or soldering iron is not recommended.

Board Schematic and PCB Layout

The complete design support package — including schematics, PCB layout, and Bill of Materials — is available for download from the EVAL-ADAQ23875FMCZ product page.