Texas Instruments ADS1675REF Manuale utente

User's Guide

SBAU162A–December 2009–Revised September 2010

ADS1675REF

This user's guide describes the characteristics, operation, and use of the ADS1675REF reference design

board. This reference design board (REF) is an evaluation platform for the ADS1675, a 4MSPS,

high-speed, high-precision, 24-bit analog-to-digital converter (ADC). The ADS1675REF allows evaluation

of all aspects of the ADS1675 device. A complete circuit description as well as schematic diagram and bill

of materials are included.

The following related documents are available through the Texas Instruments web site at

http://www.ti.com except where indicated.

Related Documents

Device Literature Number

ADS1675 SBAS416C

THS4503 SLOS352D

OPA211 SBOS377

REF5025 SBOS410

XEM3010 http://www.opalkelly.com/products/xem3010

ADCPro is a trademark of Texas Instruments.

Microsoft, Windows, WindowsXP, Vista are registered trademarks of Microsoft Corporation.

All other trademarks are the property of their respective owners.

SBAU162A–December 2009–Revised September 2010 ADS1675REF

Preface

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Contents

1 Preface ....................................................................................................................... 2

2 Overview ..................................................................................................................... 3

3 Power-Supply Requirements .............................................................................................. 4

4 Analog Interface ............................................................................................................. 5

5 Digital Interface .............................................................................................................. 6

6 Reference Voltage .......................................................................................................... 6

7 ADS1675REF Plug-in Operation .......................................................................................... 8

8 Schematic and Bill of Materials .......................................................................................... 15

List of Figures

1 ADS1675REF Schematic: Typical Analog Input Section .............................................................. 6

2 ADS1675REF Reference Circuit.......................................................................................... 7

3 ADCPro Software Start-up Display Window............................................................................. 9

4 ADS1675REF Plug-in Display Window................................................................................. 10

5 ADS1675REF Plug-in Status Information Display Window.......................................................... 10

6 XEM3010 Driver Installation (Screen 1)................................................................................ 11

7 XEM3010 Driver Installation (Screen 2)................................................................................ 11

8 XEM3010 Driver Installation (Screen 3)................................................................................ 12

9 XEM3010 Driver Installation (Screen 4)................................................................................ 12

10 LVDS or CMOS Mode Selection ........................................................................................ 13

11 Low-Latency or Wide-Bandwidth Digital Filter......................................................................... 13

12 Six Default Data Rates for LVDS........................................................................................ 14

13 Four Default Data Rates for CMOS..................................................................................... 14

14 MultiFFT Test Plug-In (Example)........................................................................................ 14

15 CMOS Mode with Wide-Bandwidth Filter at 1MSPS Sample Rate................................................. 15

16 ADS1675REF Silkscreen Drawing...................................................................................... 17

List of Tables

1 Recommended Power-Supply Inputs .................................................................................... 4

2 Factory Jumper Defaults................................................................................................... 8

3 ADS1675REF Bill of Materials .......................................................................................... 16

1 Preface

1.1 How to Use This Manual

This document contains the following sections:

• REF Overview (Section 2)

• Introduction (Section 2.2)

• Power-Supply Requirements (Section 3)

• Analog Interface (Section 4)

• Digital Interface (Section 5)

• Reference Voltage (Section 6)

• ADS1675REF Plug-In Operation (Section 7)

• ADS1675REF Schematic and Board Layout (Section 8)

2ADS1675REF SBAU162A–December 2009–Revised September 2010

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Overview

2 Overview

2.1 Features

ADS1675REF Features:

• Full-featured evaluation board for the ADS1675 24-bit, Delta-Sigma (ΔΣ) analog-to-digital converter

• Analog inputs can be applied to the ADC through an analog input driver circuit

• Onboard voltage references

• Clock options: onboard adjustable frequency default setup is 32MHz

• Supports both serial CMOS and low-voltage differential signaling (LVDS) interface modes by two

different versions of software plug-in

ADCPro™ Plug-In Features:

• Easy-to-use evaluation software for Microsoft®Windows®XP

• Data collection to text files

• Built-in analysis tools including scope, FFT, and histogram displays

• Complete control of board settings

• Easily expandable with new analysis plug-in tools from Texas Instruments

This kit combines the ADS1675REF board with the FPGA and SDRAM-based XEM3010 board, and

includes ADCPro™ software for evaluation.

You can connect the ADS1675REF to the XEM3010 board and then to a computer via an available USB

port. This manual shows how to use the XEM3010 as part of the ADS1675REF kit, but does not provide

technical details about the XEM3010 itself. Refer to the Opal Kelly website (at www.opalkelly.com) for

specific details about the XEM3010-1500.

ADCPro is a program for collecting, recording, and analyzing data from ADC evaluation boards. ADCPro

has a number of plug-in programs, so it can be expanded easily with new test and data collection plug-ins.

You control the ADS1675REF with a plug-in that runs in ADCPro. For more information about ADCPro,

see the ADCPro™ Analog-to-Digital Converter Evaluation Software User's Guide (literature number

SBAU128), available for download from the TI web site.

This manual covers the operation of both the ADS1675REF and the ADS1675REF Plug-in for ADCPro.

Throughout this document, the abbreviation REF and the term reference board are synonymous with the

ADS1675REF.

2.2 Introduction

The ADS1675REF is a 24-bit, ΔΣ analog-to-digital converter that operates from independent AVDD (+5V)

and DVDD (+3V) supplies. The analog input pre-amplifier THS4503 can be powered from +9V and -4V

supplies. The XEM3010 FPGA processor board can be supplied either with a +5V external wall adapter

power supply or with +5V (JP4) from the ADS1675REF board itself.

The maximum sample rate of the ADS1675 is 4MSPS. The maximum output clock speed is 96MHz.

The output interface can be configured as either CMOS or LVDS interface; the ADS1675REF works easily

with both interfaces.

There are two digital decimation filters built into the ADS1675 device. The first one is low-latency filter that

can reduce digital processing time, but only provide narrow signal bandwidth; this filter is best used for fast

digital processing applications. The second option is a wide-bandwidth digital filter that can provide a

much wider and flat signal bandwidth, but with slower processing time.

The ADS1675REF hardware platform consists of a two-board solution: one ADS1675REF printed circuit

board (PCB) plus one FPGA processor board (XEM3010). The ADS1675REF hardware uses a very

common FPGA Spartan-3, Micron 16-MByte (16-bit word-wide) synchronous DRAM (SDRAM) chip,

Cypress CY22393 PLL, and USB 2.0 microcontroller.

SBAU162A–December 2009–Revised September 2010 ADS1675REF

Power-Supply Requirements

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The SDRAM controller code is preloaded within the FPGA. The ADCPro software works with the USB 2.0

driver in the ADS1675REF environment, so that 8M, 24-bit sampled ADC data can be captured and saved

in the SDRAM per single acquisition in order to allow the FPGA processor to do post-data processing or

transfer the test data continually through the FPGA, SDRAM, and USB interface into a PC processor for

further data processing.

The Cypress CY22393 PLL can provide up to five clocks. The ADS1675REF platform uses one 48MHz

clock for the USB microcontroller, one 64MHz clock for the SDRAM chip, one 64MHz clock for the FPGA

processor, and one 32MHz clock for the ADS1675 device.

The ADS1675REF supports fast response mode for both the wide-bandwidth and low-latency filter paths,

as well as an internal shift clock (SCLK) mode for LVDS and CMOS digital output interfaces.

3 Power-Supply Requirements

WARNING

The Opal Kelly XEM3010 board can only accept a maximum 5V

power supply. When the 5V external wall adaptor is applied,

remove JP4. (See Table 1 for additional details.)

The factory configuration of the board is for the analog input driver THS4503 with +9V and –4V supplies

and a shared +5V supply for analog and digital REF board circuitry sections as well as the XEM3010

board. For the best total harmonic distortion (THD) performance, the user can provide independent digital

+5V to +5VD, +3.0V to 3.3VD, and wall adaptor +5V to P1 on the XEM3010 board. All power to the board

is recommend to be sourced from a well-regulated linear supply that has current-limiting capabilities; for

example, a 40mA limit for +9V and –4V, and 400mA limit for +VA.

Power must be supplied through jumpers J2, J4, J5, and J9 (top side of the REF board) and port P1 on

the XEM3010 board. Table 1 shows the recommended power-supply input configuration.

Table 1. Recommended Power-Supply Inputs

Signal Name Connector Number Description

+5VA J5-1 J5-2 Analog +5V supply

+VCC J4-1 J4-2 Analog input driver +9V supply

–VCC J4-3 J4-2 Analog input driver –4V supply

+5VD (optional for the best

performance; remove R39 when using J9-1 J9-2 Digital +5V supply

+5VD)

+3.3VD (optional for the best

performance; remove JP2 when J2-1 J2-2 Digital +3.0V supply

applying +3.0V)

+5V (optional for the best performance;

remove JP4 when applying a +5V wall P1-1 P1-2 XEM3010 board +5V wall adaptor supply

adaptor to the XEM3010)

For standalone operation, the power sources can be applied via various test points located on the REF

board. Refer to the schematic (located at the end of this document) for additional details.

3.1 Analog Input Driver +9V and –4V Supplies

The ADS1675REF analog input driver is a THS4503 (U3), a wideband, fully-differential amplifier, to drive

the differential inputs of the ADS1675 (U4) . This device was selected because of its wide bandwidth

(370MHz) and low harmonic distortion. It is pre-configured at the factory for +9V and –4V analog

operation. The THS4503 can tolerate maximum power supplies of ±7.5VDC. Care must be taken to ensure

the user-supplied 15VDC limit is not exceeded, or potential damage to the op amps under the test circuits

can occur. The +9V and –4V voltages are to be applied to J4 pins +VCC and –VCC referenced to GND.

4ADS1675REF SBAU162A–December 2009–Revised September 2010

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Analog Interface

3.2 Analog +5V Supply

The ADS1675REF board requires an independent analog +5V supply to power the analog portion of the

device under test, the external reference, and the external reference buffer, as well as provide the

amplifier common-mode voltage. This voltage is applied to J5 pin 3 and is denoted as +5VA. This supply

can be monitored at TP7.

3.3 Digital +5V Supply

For the best THD performance, the ADS1675 requires an independent digital +5V supply to power the

clock portion of the device under test. This voltage is applied to J9 pin 3 and is denoted as +5VD. This

supply can be monitored at TP3. For a quick function test, the digital +5VD can be shared with the analog

+5VA on this REF board. R39 is a short circuit that supplies both the analog and digital 5V to the ADS1675

device.

3.4 Digital +3.0V Supply

For the best THD performance, the ADS1675 also requires an independent digital +3.0V supply to power

the digital portion of the device under test. This voltage is applied to J2 pin 3 and is denoted as +3.3VD.

This supply can be monitored at TP5. For a quick function test, the digital +3.0V can be fed back from the

3.3V regulator on the XEM3010 board and connected by jumper JP2 on the REF.

For optimal performance, it is recommended to remove the shunt jumpers from JP2 and JP4. This

configuration requires the user to supply an independent 3.0V digital supply to the ADS1675 at J2. The

user must also provide separate power to the XEM3010 at P1; refer to the Opal Kelly website for specific

details about configuring the XEM3010 board.

3.5 XEM3010 Board +5V Supply

To obtain the best THD performance, the ADS1675 requires an independent +5V supply to power the

XEM3010 board. This voltage is applied to P1 on the XEM3010 from an external wall adapter power

supply. For a quick function test, the +5V can be shared with the digital +5VD on the ADS1675REF by

jumper JP4.

4 Analog Interface

The analog circuit of the board is divided into four parts. The first part is the analog input buffer or

front-end circuit of the ADC. Its function is to provide optional gain and impedance matching of the input

signal. The second part of the analog circuit is the analog power supplies for both the high voltage rails on

the ADC and the input buffer. The final sections of the analog input include the basic analog functions of

the ADS1675 and the optional external reference circuit. Each of these sections is described below.

The analog inputs to the ADS1675REF board can be applied to J1 and J3 of the input differential

connectors. The range of the analog input depends on the range setting of the ADS1675 and THS4503.

The analog input to the ADS1675REF board consists of the THS4503 operational amplifier. The THS4503

is powered from a user-provided, 9V and –4V analog supply. The amplifier is used as true differential

driver. When the analog supply is 5V, the ADS1675 analog difference input common-mode voltage is

2.5V. This configuration requires the output of the THS4503 amplifier common-mode voltage to be set as

2.5V. The common-mode voltage to the THS4503 is set by the onboard REF5025 (U1), which sets this

voltage at 2.5V.

SBAU162A–December 2009–Revised September 2010 ADS1675REF

R18

R15

249W

R20

10W

R13

249W

R19

10W

R17

C17

750pF

AINP

AINN

VIN+

VIN-

COM

VOUT-

VOUT+

VS+

VS-

THS4503ID

C40

10 Fm

C39

0.1 Fm

-VCC

C38

10 Fm

C37

0.1 Fm

+VCC

RCM

JP1

C14

Not Installed

C72

C12

Not Installed

Digital Interface

www.ti.com

To maximize the dynamic range of the THS4503 and reduce the THD impact from this amplifier, +9V and

–4V are used for this THS4503. This configuration gives a maximum ±6.5V swing range. Figure 1

illustrates the typical analog input section of the ADS1675REF.

Figure 1. ADS1675REF Schematic: Typical Analog Input Section

5 Digital Interface

The ADS1675REF is designed for easy interfacing with the USB2.0 interface for use with the XEM3010

board. The ADS1675REF kit also provides ADCPro software so that the user can configure the ADS1675

and read out the captured data through the USB interface on the XEM3010 board.

6 Reference Voltage

The ADS1675REF provides a 3.0V reference source via a REF5030 (U2) and OPA211A (U5) to provide a

high-quality reference voltage for ADS1675. The REF5030 (U2) generates the 3.0V reference signal. The

output of the REF5030 is heavily filtered to remove noise. The onboard OPA211 (U5) again filters and

buffers the reference signal so that the reference signal noise to the ADS1675 is less than the noise

generated by the converter itself. The OPA211 is a low-noise, unity-gain stable amplifier that provides a

reliable current source for the ADS1675 reference input. The OPA211 and output decoupling capacitors

work together to settle the VREFP (ADS1675) reference input voltage to within ±1/2 LSB, every 50ns. This

board uses a 10mF ceramic capacitor with a 0.1mF ceramic capacitor directly across the reference inputs,

VREFP and VREFN. Note that the 10mF and 0.1mF capacitors are placed as close to the ADS1675

reference pins as possible. These capacitors further reduce noise that is common to both inputs. The

ADS1675 VREFN pin goes to ground.

6ADS1675REF SBAU162A–December 2009–Revised September 2010

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DNCDNC

VIN

TEMP

GND

N/C

OUT

TRIM

REF5030AID

+5VA

C10

1 Fm

C15

1 Fm

C21

1 Fm

C47

10 Fm

C46

10 Fm

C48

1 Fm

C20

10 Fm

C19

0.1 Fm

R21

1kW

R22

49.9W

R25

100W

OPA211AIDGK

C22

0.15 Fm

C30

0.1 Fm

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Reference Voltage

Figure 2 shows the ADS1675REF reference circuit.

Figure 2. ADS1675REF Reference Circuit

SBAU162A–December 2009–Revised September 2010 ADS1675REF

ADS1675REF Plug-in Operation

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7 ADS1675REF Plug-in Operation

This section provides information on using the ADS1675REF Plug-in, including setup, program installation,

and program usage. The board is factory-configured for the analog input driver THS4503 with +9V and

–4V supplies and the shared analog, digital, and XEM3010 board with a +5VA supply on the ADS1675.

Table 2 lists the default jumper setup.

Table 2. Factory Jumper Defaults

Shunt Jumpers Position Description

ADS1675REF Jumpers

U3 Negative Supply (JP1) 1-2; use 2mm shunt jumper -V is supplied by J4

OK3.3V (JP2) Closed; use 2mm shunt jumper 3.3VDC is supplied to ADS1675REF

from the Opal Kelly Board

OK5V (JP4) Closed; use 2mm shunt jumper 5.0VDC is supplied to the Opal Kelly

board from the user's external 5V

supply

CAPT (JP3) Open Strobe for data capture card used in

debug

XEM3010 Jumpers

J1 Closed

J2 Open

JP1 Open

To prepare to evaluate the ADS1675 with the ADS1675REF Plug-in, complete the following steps:

Step 1. Verify all jumper settings against the settings described in Table 2.

Step 2. Download the latestversion of the ADCPro software from www.ti.com/adcpro.

Step 3. Install the ADCPro application. Once the application is installed, run the

ADS1675REF-plug-in file located on the CD-ROM (included with the ADS1675REF package)

under the Plug-in Installer directory. Please note that while installing the ADS1675 plug-in, a

separate installer for the Opal Kelly board will also be launched. Accept all default settings

and choose the Continue anyway option if you see a warning regarding driver authenticity.

Step 4. Complete the Microsoft Windows USB driver installation process.

Step 5. Ensure the XEM3010 board is firmly seated onto the mating connectors found on the

ADS1675REF board.

Step 6. Apply power to the ADS1675REF board as described in Section 7.2; note that best

performance is achieved by using clean linear supplies. Set the current limits and voltages

first, then connect power leads to the board before enabling the supply outputs.

Step 7. Apply +9V and –4V to the screw terminals marked J4. +VCC, GND, and –VCC are labeled

below the entry point to the screw terminal.

Step 8. Apply +5 VDC to the screw terminal marked J5. +5VA and GND are marked at the terminal

entry points. R39 is a short circuit that supplies both the digital 5V to the ADS1675 and 5V to

the XEM3010 board. The XEM3010 generates a 3.3V supply that is fed back to the

ADS1675.

7.1 Installing the ADCPro Software

The latest version of the ADCPro software is available from Texas Instruments' website at

http://www.ti.com/adcpro. The CD-ROM shipped with the ADS1675REF may not contain the latest

software, but the ADCPro installer will check for updates when executed (if connected to the Internet), and

then give you the option of downloading and installing the latest version. Refer to the ADCPro™

Analog-to-Digital Converter Evaluation Software User's Guide for instructions on installing and using

ADCPro.

To install the ADS1675REF plug-in, run the file: ads1675ref-plug-in-1.0.0.exe (1.0.0 is the version

number, and increments with software version releases; you may have a different version on your CD).

Double-click the file to run it; then follow the instructions shown. After installation, you can use the ADCPro

Update Check feature to check for newer versions of the ADS1675REF plug-in.

8ADS1675REF SBAU162A–December 2009–Revised September 2010

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ADS1675REF Plug-in Operation

The software should now be installed, but the USB drivers may not have been loaded by the PC operating

system. The USB driver upload step completes when the ADCPro software is executed (see Section 7.2,

Running the Software and Completing the Driver Installation).

7.2 Running the Software and Completing the Driver Installation

NOTE: The software is continually under development. These instructions and screen images are

current at the time of this writing, but may not exactly correspond to future releases.

ADCPro uses a series of software plug-ins to communicate with the ADS1675REF. The ADS1675REF

plug-in is included in the ADS1675REF package.

The program currently runs only on Microsoft Windows platforms of WindowsXP®; Windows Vista®is not

supported.

Follow these procedures to run ADCPro and complete the necessary driver installation.

Step 1. Start the software by selecting ADCPro from the Windows Start menu. The screen in Figure 3

appears.

Figure 3. ADCPro Software Start-up Display Window

SBAU162A–December 2009–Revised September 2010 ADS1675REF

ADS1675REF Plug-in Operation

www.ti.com

space

Step 2. Select ADS1675REF from the REF drop-down menu. The ADS1675REF plug-in appears in

the left pane, as shown in Figure 4.

Figure 4. ADS1675REF Plug-in Display Window

Step 3. The ADS1675REF plug-in window has a status area at the top of the screen. When the

plug-in is first loaded, the plug-in searches for the board. You will see a series of messages

in the status area that indicate this action, such as Connected (as Figure 5 illustrates).

Figure 5. ADS1675REF Plug-in Status Information Display Window

Step 4. Apply power to the REF board and connect the board to an available PC USB port.

Step 5. If you have not yet loaded the XEM3010 system drivers, Windows will display the Windows

Found New Hardware Wizard sequence (illustrated in Figure 6 through Figure 9). When

prompted, accept the Continue Anyway option as Figure 8 shows.

10 ADS1675REF SBAU162A–December 2009–Revised September 2010

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