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This version (08 Dec 2014 16:30) was approved by RobK.

Evaluating the AD7175-2 24-Bit, 250 kSPS, Sigma-Delta ADC

Features

  • Full featured evaluation board for the AD7175-2
  • PC control in conjunction with the Analog Devices, Inc., EVAL-SDP-CB1Z system demonstration platform (SDP)
  • PC software for control and data analysis (time domain)
  • Standalone capability

Evaluation Kit Contents

  • EVAL-AD7175-2SDZ evaluation board
  • Evaluation software CD
  • 7 V to 9 V ac-to-dc adapter

Equipment Needed

  • DC signal source
  • PC running Windows XP to Windows 7

General Description

The EVAL-AD7175-2SDZ evaluation kit features the AD7175-2, a 24-bit, 250 kSPS analog-to-digital converter (ADC) with integrated rail-to rail-analog input buffers, on-board power supply regulation, and an external amplifier section for amplifier evaluation. A 7 V to 9 V ac-to-dc adapter is regulated to 5 V and 3.3 V, which supply the AD7175-2 and support components. The EVAL-AD7175-2SDZ evaluation board connects to the USB port of a PC via the EVAL-SDP-CB1Z SDP controller board.

The AD7175-2 Eval+ software fully configures the AD7175-2 device functionality via an interactive block diagram and a user accessible register interface and provides dc time domain analysis in the form of waveform graphs, histograms, and associated noise analysis for ADC performance evaluation. Full specifications for the AD7175-2 are available in the product data sheet, which should be consulted in conjunction with this user guide when using the evaluation board.

Functional Block Diagram

Figure 1. Functional Block Diagram

EVAL-AD7175-2SDZ Quick Start Guide

Follow these steps to set up the evaluation board:

  1. Disconnect the SDP-B board from the USB port of the PC. Install the AD7175-2 Eval+ software from the enclosed CD. Restart the PC after installation.
  2. Connect the SDP-B board to the evaluation board, as shown in Figure 2.
  3. Fasten the two boards together with the enclosed plastic screw washer set.
  4. Connect the external 9 V power supply to Connector J5 of the evaluation board as shown in Figure 2. Set Link LK2 to Position B.
  5. Connect the SDP-B board to the PC via the USB cable. For Windows® XP, you may need to search for the SDP-B drivers. Choose to automatically search for the drivers for the SDP-B board if prompted by the operating system.
  6. Launch the AD7175-2 Eval+ software from the Analog Devices subfolder in the Programs menu.

Quick Start Noise Test

  1. Insert Link LK8 to Link LK12 to initiate the noise performance test mode. In this mode, analog input channels short to the REFOUT pin.
  2. Click Start Sampling to acquire samples from the ADC (see Figure 7).

The Samples numeric control in the top right corner of the main window sets the number of samples collected in each batch (see Figure 7).

Figure 2. Hardware Configuration, Setting Up the EVAL-AD7175-2SDZ Evaluation Board

Evaluation Board Hardware

Device Description

The AD7175-2 is a highly accurate, high resolution, multiplexed, 2-/4-channel (fully differential/single-ended) Σ-Δ ADC. The AD7175-2 has a maximum channel-to-channel scan rate of 50 kSPS (20 µs) for fully settled data The output data rates range from 5 SPS to 250 kSPS. The device includes integrated rail-to-rail analog input and reference input buffers, an integrated precision 2.5 V reference, and an integrated oscillator. See the AD7175-2 data sheet for complete specifications. Consult the data sheet in conjunction with this user guide when using the evaluation board. Full details for the EVAL-SDP-CB1Z are available at the SDP-B product page on the Analog Devices website.

See Table 1 for default link options. By default, the evaluation board is configured to operate from the supplied 9 V ac-to-dc adapter connected to connector J5. The 5 V supply required for the AD7175-2 comes from the ADP7118 on-board low dropout regulator (LDO). The ADP7118, with a 5 V output voltage, receives its input voltage from J3 or J5 (depending on the position of LK2) and generates a 5 V output.

Table 1. Default Link and Solder Link Options

Link Default Option Description
LK1 A Selects the voltage applied to the power supply sequencer circuit (U3); dependent on AVDD1. Place in Position A if using 5 V AVDD1, or Position B if using 2.5 V AVDD1.
LK2 B Selects the external power supply from Connector J3 (Position A) or Connector J5 (Position B).
LK3 to LK7 Not Inserted Inserting these links sets up the on-board noise test prior to SL8 to SL11 to allow the inputs to the on board amplifiers, U8 and U9, to be shorted. In this mode, all inputs short to REFOUT.
LK8 to LK12 Inserted Inserting these links sets up the on-board noise test close to the ADC analog inputs. In this mode, all inputs short to REFOUT.
SL1 A Sets the voltage applied to the AVDD2 pin. Operates using the AVDD1 supply (default). Position B sets the AVDD2 voltage to 3.3 V supply from the ADP7118 (3.3 V) (U10) regulator.
SL2 A Selects between an external or on-board AVDD1 source. Supplies AVDD1 from the ADP7118 (5 V) (U7) (default).
SL3 A Selects between an external or on-board AVSS source. Supplies AVSS from the ADP7182 (−2.5 V) (U4) (default).
SL4 A Connects AIN4 to: A4/J6 (Position A), REFOUT pin on the AD7175-2 (Position B), or AVSS (Position C). Position B and Position C are used to simplify using a single-ended input source.
SL5 B Selects between an external or on-board IOVDD source. Supplies IOVDD from theADP7118 (3.3 V) (U10) (default). The evaluation board operates with a 3.3 V logic.
SL8 A Routes A0 to: AIN0 pin on the AD7175-2 (Position A), Buffer/In-amp U8 (Position B), Funnel Amp U9 with gain of 0.8× (Position C), or J10-1 (Position D).
SL9 A Routes A2 to: AIN2 pin on the AD7175-2 (Position A), Buffer U12 (Position B), or Funnel Amp U9 gain of 0.4× (Position C).
SL10 A Routes A3 to: AIN3 pin on the AD7175-2 (Position A), Buffer U12 (Position B), or Funnel Amp U9 gain of 0.4× (Position C).
SL11 A Routes A1 to: AIN1 pin on the AD7175-2 (Position A), Buffer/In-amp U8 (Position B), Funnel Amp U9 with gain of 0.8× (Position C), or J10-7 (Position D).
G16 Inserted Sets the on board In-amp U8 to a gain of 16. Only one of G16, G32, G64 and G128 should be inserted at a time.
G32 Not Inserted Sets the on board In-amp U8 to a gain of 32. Only one of G16, G32, G64 and G128 should be inserted at a time.
G64 Not Inserted Sets the on board In-amp U8 to a gain of 64. Only one of G16, G32, G64 and G128 should be inserted at a time.
G128 Not Inserted Sets the on board In-amp U8 to a gain of 128. Only one of G16, G32, G64 and G128 should be inserted at a time.
R49 to R51 Inserted Connects AVSS and AGND for single-supply operation. To operate in split supply mode, remove these links.

Sockets And Connectors

Table 2. Connector Details

Connector Function Connector Type Manufacturer Manufacturer Number Order Code
J1 Connector to the EVAL-SDP-CB1Z 120-way connector, 0.6 mm pitch Hirose FX8-120S-SV(21) FEC13246601)
J2 External MCLK Input Straight PCB mount SMB/SMA jack Tyco 1-1337482-0 Not applicable
J3 External bench top voltage supply for the EVAL-AD7175-2SDZ Power socket block, 3-pin, 3.81 mm pitch Phoenix Contact MC 1,5/ 3-G-3,81 FEC3704737
J5 External ac-to-dc adapter input for the EVAL-AD7175-2SDZ, 7 V to 9 V DC power connectors, 2 mm SMT power jack Kycon KLDX-SMT2-0202-A MOUSER 806-KLDX-SMT20202A
J6 Analog input terminal block; wired connection to external source or sensor Power socket block, 8-pin, 3.81 mm pitch Phoenix Contact MC 1,5/ 8-G-3,81 FEC3704774
J9 External bench top voltage supply option for AVDD1/AVDD2, IOVDD, and AVSS inputs on the AD7175-2 Screw terminal block, 3.81 mm pitch Phoenix Contact MKDS 1/4-3.81 FEC3704592
J10 Optional header 7-way, 2.54 mm pin header Samtec SSW-107-01-T-S FEC1803478
J13 Optional header 7-way, 2.54 mm socket Samtec TLW-107-05-G-S FEC1668499
A0 to A4 Analog inputs to ADC Straight PCB mount SMB/SMA jack Tyco 1-1337482-0 Not applicable
A7 PMOD-compatible header 6-Pin SIL header (0.1“ pitch) Harwin 20-9990646 FEC 1022255

Serial Interface

The EVAL-AD7175-2SDZ evaluation board connects via the serial peripheral interface (SPI) to the Blackfin® ADSP-BF527 on the EVAL-SDP-CB1Z. There are four primary signals: CS, SCLK, and DIN (all inputs), and one output from the ADC, DOUT/RDY. To operate the evaluation board in standalone mode, disconnect the evaluation board from the SDP-B controller board. Use the test points to connect the signals to an alternative digital capture setup or the PMOD-compatible header (A7).

Power Supplies

Power the evaluation board from the ac-to-dc adapter connected to J5, or from an external bench top supply applied to J3 or J9. Linear LDOs generate the required voltages from the applied input voltage (VIN) rail when using J3 or J5. Use J9 to bypass the on-board regulators. An ADP7118 regulator generates the 5 V (single supply) and 2.5 V (split supply) supplies for the AVDD1 and AVDD2 rails to the ADC; a second ADP7118 generates 3.3 V for the IOVDD rail. The ADP7104 supplies 5 V for the SDP-B controller board as well as 5 V for the ADM660 voltage converter to generate −5 V to supply the ADP7182. The ADP7182 generates the −2.5 V supply for AVSS when operating in split supply mode. Each supply is decoupled where it enters the board and again at each device in accordance with the schematic. Table 3 shows the various power supply configurations available, including split supply operation.

Table 3. Power Supply Configurations 2)

Configuration Input Voltage Range Description
Single Supply (Regulated) 7 V to 9 V The 7 V to 9 V input is regulated to 5 V for AVDD1/AVDD2 and 3.3 V for IOVDD. This also powers the external 5 V reference. See the Single Supply (Regulated) section in the Power Supply Configurations section.
Single Supply (Unregulated) 7 V to 9 V, 5 V, and 3.3 V The input is unregulated and connects directly to AVDD1/AVDD2 and IOVDD from J5. The 7 V to 9 V input powers the external 5 V reference. See the Single Supply (Unregulated) section in the Power Supply Configurations section.
Split Supply (Regulated) 7 V to 9 V The 7 V to 9 V input is regulated to 2.5 V for AVDD1/AVDD2, -2.5 V for AVSS and 3.3 V for IOVDD. The 7 V to 9 V input powers the external 5 V reference, See the Split Supply (Regulated) section in the Power Supply Configurations section.
Split Supply (Unregulated) 7 V to 9 V, ±2.5 V, and 3.3 V The input is unregulated and connects directly to AVDD1/AVDD2 and IOVDD from J5. The 7 V to 9 V input powers the external 5 V reference. See the Split Supply (Unregulated) section in the Power Supply Configurations section.

Power Supply Configurations

Single Supply (Regulated)

There are two available power supply options for the single supply (regulated) configuration.

  • An ac-to-dc adapter (included) connected to J5. Set LK2 to Position B.
  • A bench top power supply connected to J3. Set LK2 to Position A, and ensure that AVSS = AGND = 0 V.

Set all other links and solder links to the default settings as outlined in Table 1.

Single Supply (Unregulated)

To set up the evaluation board, use the following procedure:

  1. Move SL2 to position B and SL5 to position A.
  2. Connect the two terminals of J9 labeled AGND and AVSS.
  3. Connect 0 V (GND) to J9 at the terminal labeled AGND.
  4. Connect 5 V to J9 at the terminal labeled AVDD.
  5. Connect 3.3 V to J9 at the terminal labeled IOVDD.
  6. Connect the 7 V to 9 V input to J5.

Set all other links and solder links to the default settings as outlined in Table 1.

Split Supply (Regulated)

To set up the evaluation board, use the following procedure:

  1. Remove R49 to R51. These links connect AVSS to AGND.
  2. Insert a 0 Ω resistor for R85.
  3. Set LK1 to Position B, which sets the input to the power monitor circuitry to work with the lower AVDD1 supply of 2.5 V.
  4. Connect a bench top power supply to J5 and set LK2 to Position B.

Set all other links and solder links to the default settings as outlined in Table 1.

Split Supply (Unregulated)

To set up the evaluation board, use the following procedure:

  1. Move SL2, SL3 to position B and SL5 to position A.
  2. Remove R49 to R51.
  3. Connect 0 V (GND) to J9 at the terminal labeled AGND.
  4. Connect 2.5 V to J9 at the terminal labeled AVDD.
  5. Connect −2.5 V to J9 at the terminal labeled AVSS.
  6. Connect 3.3 V to J9 at the terminal labeled IOVDD.
  7. Connect 7 V to 9 V to J5.
  8. Set LK1 to Position B. This sets the input to the power monitor circuitry to work with the lower AVDD1 supply of 2.5 V.

Set all other links and solder links set to the default settings as outlined in Table 1.

Analog Inputs

The primary analog inputs of the EVAL-AD7175-2SDZ evaluation board can be applied in two separate ways.

  • J6 connector on the left side of the board
  • A0 to A4 SMB/SMA footprints on the evaluation board

The analog inputs route directly to the associated analog input pins on the AD7175-2, provided that the LK5 to LK9 links (on-board noise test) are removed. The AD7175-2 Eval+ software is set up to analyze dc inputs to the ADC. The AD7175-2 input buffers work for dc input signals.

Reference Options

The EVAL-AD7175-2SDZ evaluation board includes an external 5 V reference, the ADR445. The AD7175-2 includes an internal 2.5 V reference. The default operation is to use the external reference input, which is set to accept the 5 V ADR445 on the evaluation board.

Evaluation Board Software

software Installation

The EVAL-AD7175-2SDZ evaluation kit includes software on a CD. Double-click the setup.exe file from the CD to run the installer. The default installation location for the software is C:\Program Files\Analog Devices\AD7175-2 Eval+\.

Install the Eval+ software before connecting the evaluation board and EVAL-SDP-CB1Z board to the USB port of the PC to ensure that the evaluation system is correctly recognized when connected to the PC.

There are two parts to the installation.

  • AD7175-2 Eval+ software installation
  • EVAL-SDP-CB1Z system demonstration platform board drivers and Ssrc SVG Plugin installation

Place the software and drivers in the appropriate locations by proceeding through all of the installation steps. Connect the EVAL-SDP-CB1Z board to the PC only after the software and drivers install. The installer may prompt you to allow the program to make changes to the computer. Click Yes to proceed (see Figure 3).

Figure 3. AD7175-2 User Account Control Permission Dialog Box

You may receive a security warning as part of the SDP-B controller board driver installation. Click Install to proceed with the installation of the driver (see Figure 4). Without this confirmation, the software cannot operate correctly.

Figure 4. EVAL-SDP-CB1Z Drivers Installation Confirmation Dialog Box

After installation is complete, connect the evaluation board to the SDP-B board as shown in Figure 2. Connect the evaluation board via the USB cable to the computer. Follow these steps to verify that the SDP-B controller board driver is installed and working correctly:

  1. Allow the Found New Hardware Wizard to run.
  2. When the drivers are installed, check that the board has connected correctly by looking at the Device Manager of the PC. The Device Manager can be found by right clicking My Computer, selecting Manage, then Device Manager from the list of System Tools (see Figure 5).
  3. The EVAL-SDP-CB1Z SDP-B board appears under ADI Development Tools as Analog Devices System Development Platform or similar. The installation is complete.

Figure 5. Device Manager

Launching the Software

The Eval+ software can be launched when the evaluation board and SDP-B board are correctly connected to the PC. The Eval+ software can also be operated without hardware.

To launch the software, complete the following steps:

  1. From the Start menu, click Programs, Analog Devices, then AD7175-2 Eval+. The main window of the Eval+ software displays (see Figure 7).
  2. If the AD7175-2 evaluation system is not connected to the USB port via the EVAL-SDP-CB1Z when the software is launched the Select Interface… dialog box appears. Connect the evaluation board to the USB port of the PC, wait a few seconds, click the green arrows to rescan the USB ports. When connected, click Work Online to proceed. Click Work Offline to use the software without the hardware.

Figure 6. Select Interface Dialog Box

Software Operation

Overview of the Main Window

The main window of the evaluation software displays the significant control buttons and analysis indicators of the AD7175-2 Eval+ software. Figure 7 shows the main window when Hardware evaluation mode is enabled and Figure 8 shows the main window when Functional Model evaluation mode is enabled. The main window is divided into five tabs.

Configuration Tab (1)

Evaluation Mode(2)

Click here to select the evaluation mode. Selecting Hardware evaluation mode uses the EVAL-AD7175-2SDZ board to evaluate the ADC. Selecting Functional Model evaluation mode uses a model of the ADC for evaluation.

ADC Reset (3)

Click ADC Reset to perform a software reset of the AD7175-2. There is no hardware reset pin. Perform a hard reset by removing power to the board. The software reset has the same effect as a hard reset.

Ext. REF (4)

The Ext. REF field sets the external reference voltage used for calculating the results on the waveform and histogram tabs. The evaluation board has an external 5 V ADR445 reference, which can be bypassed; change the external reference voltage value in Ext. REF to ensure correct calculation of results in the Waveform and Histogram tabs.

Functional Block Diagram (5)

The functional block diagram of the ADC shows each of the separate functional blocks within the ADC. Clicking a configuration button on this graph opens the configuration popup window for that block. Not all blocks have a configuration button.

Configuration Popup Button (6)

Each configuration popup button opens a different window allowing for configuration of the relevant functional block.

Channel Configuration Overview (7)

This section shows the channel configuration, including setup and analog inputs. The channel configuration section allows a quick check of how the ADC is set up.

Status Bar (8)

The status bar displays status updates such as Analysis Completed and Reset Completed during software use, as well as the software version and busy indicator.

Analog Supply Voltage (9 & 13)

Sets the analog supply voltages used in the functional model for checking power supply limits and calculating the power dissipation figures. These controls are only visible when Functional Model evaluation mode is enabled.

Digital Supply Voltage (10)

Sets the digital supply voltage used in the functional model for checking power supply limits and calculating the power dissipation figures. This control is only visible when Functional Model evaluation mode is enabled.

Analog Input Voltage (11)

Sets the analog input voltages used in the functional model for calculating the ADC output codes. Note: The voltages set on these controls are DC only voltage with no noise. These controls are only visible when Functional Model evaluation mode is enabled.

External SCLK Frequency (12)

Sets the external SCLK frequency for the SPI interface. This value is used in the functional model to determine if they SCLK frequency is within the permitted range. This control is only visible when Functional Model evaluation mode is enabled.

External MCLK Frequency (14)

Set the external MCLK frequency to be used when an external clock source is selected by the ADC when using the functional model. This control is only visible when Functional Model evaluation mode is enabled.

Figure 7. Configuration Tab of the AD7175-2 Eval+ software in Hardware Evaluation Mode

Figure 8. Configuration Tab of the AD7175-2 Eval+ Software in Functional Model Evaluation Mode

Waveform Tab (15)

Analysis Channel (16)

The Noise Analysis section and histogram graph show the analysis of the channel selected via the Analysis Channel control.

Samples (17 and 18)

The Samples (17) numeric control and batch control (18) set the number of samples gathered per batch and whether a single batch or multiple batches of samples are gathered. This control is unrelated to the ADC mode. You can capture a defined sample set or continuously gather batches of samples. In both cases, the number of samples set in the Samples (17) numeric input dictates the number of samples.

Sample (19)

Click the Sample button to start gathering ADC results. Results appear in the waveform graph (20).

Waveform Graph and Controls (20 and 21)

The data waveform shows each successive sample of the ADC output. Zoom in on the data using the control toolbar (21) in the graph. Change the scales on the graph by typing values into the x-axis and y-axis.

Channel Selection (22)

This control chooses which channels display on the data waveform, and also shows the analog inputs for the channel labeled next to the on and off controls. These controls only affect the display of the channels and have no effect on the channel settings in the ADC register map.

Display Units and Axis Controls (23)

Click Display Units to select whether the data graph displays in units of voltages or codes. This control affects both the waveform graph and the histogram graph. The axis controls can be switched between dynamic and fixed. When dynamic is selected, the axis automatically adjusts to show the entire range of the ADC results after each batch of sample. When fixed is selected, the user can program the axis ranges; the axis ranges do not automatically adjust after each batch of sample.

CRC Error (24)

This LED indicator illuminates when a cyclic redundancy check (CRC) error is detected in the communications between the software and the AD7175-2. The CRC functionality on the AD7175-2 is disabled by default and must be enabled for this indicator to work.

Noise Analysis (25)

The Noise Analysis section displays the results of the noise analysis for the selected analysis channel, which includes both noise and resolution measurements.

Figure 9. Waveform Tab of the AD7175-2 Eval+ Software

Histogram Tab (26)

Histogram Graph and Controls (27 and 28)

The data histogram shows the number of times each sample of the ADC output occurs. Zoom in on the data using the control toolbar (28) in the graph. Change the scales on the graph by typing values into the x-axis and y-axis.

Figure 10. Histogram Tab of the AD7175-2 Eval+ Software

Calculated Performance Tab (29)

The Calculated Performance tab shows a number of ADC performance parameters which are calculated using the ADC functional model. All results in the tab are for the current analysis channel (16).

Filter Profile & Response (30 & 31)

Shows a frequency response graph for the selected digital filter the rejection / attenuation of the digital filter over the Rej BW for f1 and f2 in dB.

Performance Summary (32)

Shows the total power consumption of the part in the current configuration as well as the current consumption on each of the power supply rails. Also shows timing information about the currently selected output data rate (Tsettle, Fnotch, fADC).

Timing Diagram (33)

This graph shows the digital interface timing diagram for the current configuration. It shows the timing for both the configuration of the ADC and the subsequent data reads from the ADC.

Figure 11. Calculated Performance Tab of the AD7175-2 Eval+ Software

Register Map Tab (34)

Register Tree (35)

This control shows the full register map in a tree control. Each register is shown; clicking on the expand button next to each register shows all the bit fields contained within that register.

Register Control (36)

This control allows the user to change the individual bit of the register selected in the register tree (35) by clicking on the bits or by programming the register value directly into the number control field on the right.

Bit Field List (37)

This list shown all the bit fields of the register selected in the register tree (35). Change the values by using the drop-down box or by directly entering a value into the number control field on the right.

Documentation (38)

This field contains the documentation for the register of the bit field selected in the register tree (35).

Save and Load (39 and 41)

The Save and Load buttons allow the user to save the current register map setting to a file and to load the setting from the same file.

Exiting the Software

To exit the software, click the close button at the top right corner of the main window (see Figure 7).

Figure 12. Register Map Tab of the AD7175-2 Eval+ Software

1)
Order codes starting with FEC are for Farnell
2)
Only one configuration can be used at a time
resources/eval/eval-ad7175-2sdz.txt · Last modified: 08 Dec 2014 16:20 by RobK