Texas Instruments PGA309EVM-USB User Manual
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User's Guide

SBOU084 – February 2010

PGA309EVM-USB

This user’s guide describes the characteristics, operation, and use of the PGA309EVM-USBevaluation module (EVM). This EVM is designed to evaluate the performance of thePGA309, a voltage output, programmable sensor conditioner. This document covers all pertinent areas involved to properly use this EVM board, allowing for user evaluation suitable to a variety of applications. This document also includes the physical printed circuit board (PCB) layout and circuit descriptions. Aschematic of the PGA309EVM-USB is available as a separate download from the TI web site.

 

Contents

 

 

1

Introduction and Overview .................................................................................................

 

2

2

System Setup ................................................................................................................

 

5

3

PGA309EVM-USB Hardware Setup ....................................................................................

 

16

4

PGA309EVM-USB Software Overview .................................................................................

 

25

 

List of Figures

 

 

1

Hardware Included with the INA282-286EVM...........................................................................

 

3

2

PGA309EVM-USB Hardware Setup......................................................................................

 

5

3

PGA309_Test_Board Block Diagram ....................................................................................

 

5

4

PGA309_Test_Board Schematic: Input Circuitry .......................................................................

 

7

5

PGA309_Test_Board Schematic: Power, Reference, and Digital Connections ....................................

 

8

6

PGA309_Test_Board Schematic: Output Circuitry .....................................................................

 

9

7

PGA309_Test_Board Schematic: Sensor Emulator Circuitry........................................................

 

10

8

PGA309_Test_Board Connections to USB-DAQ-Platformand EEPROM.........................................

 

11

9

Theory of Operation For USB-DAQ-Platform ..........................................................................

 

16

10

PGA309EVM-USB Typical Hardware Connections ...................................................................

 

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11

Connecting the Two EVM PCBs ........................................................................................

 

18

12

Connecting Power to the EVM...........................................................................................

 

19

13

Connecting the USB Cable...............................................................................................

 

20

14

Default Jumper Settings (PGA309_Test_Board)......................................................................

 

21

15

Default Jumper Settings (USB-DAQ-Platform) ........................................................................

 

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16

PGA309EVM-USB Software: Registers Tab...........................................................................

 

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17

PGA309EVM-USB Software: EEPROM Tab ..........................................................................

 

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18

PGA309EVM-USB Software: Block Diagram ..........................................................................

 

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19

PGA309EVM-USBSoftware: Auto Calibrate Tab— Sensor Definition..............................................

 

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20

PGA309EVM-USBSoftware: Sensor Emulator Control Panel Tool................................................

 

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21

PGA309EVM-USBSoftware: Auto Calibrate Tab— PGA Setup.....................................................

 

31

22

PGA309EVM-USBSoftware: Auto Calibrate Tab—Two-PointCalibration and Linearization...................

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23

PGA309EVM-USBSoftware: Auto Calibrate Tab— Temperature Error Compensation..........................

 

33

24

PGA309EVM-USBSoftware: Auto Calibrate Tab— Post Cal Error Check.........................................

 

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25

PGA309EVM-USBSoftware: Auto Calibrate Tab— DMM Options..................................................

 

35

Microsoft, Windows are registered trademarks of Microsoft Corporation.

 

 

I2C is a trademark of NXP Semiconductors.

 

 

All other trademarks are the property of their respective owners.

 

 

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Introduction and Overview

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List of Tables

 

1

PGA309 Test Board Parts List...........................................................................................

12

2

J1

Pinout (25-Pin Male DSUB) ..........................................................................................

14

3

J2

Pinout (25-Pin Female DSUB) ......................................................................................

15

4

PGA309_Test_Board Jumper Functions: General ....................................................................

22

5

PGA309_Test_Board Jumper Functions: Miscellaneous Connections.............................................

23

6

PGA309_Test_Board Jumper Functions: Sensor Emulator Section ...............................................

23

7

USB-DAQ-Platform Jumper Settings ...................................................................................

24

1Introduction and Overview

This document provides the information needed to set up and operate the PGA309EVM-USBevaluation module, a test platform for thePGA309 programmable sensor conditioner. For a more detailed description of the PGA309, refer to the product data sheet (SBOS292) available from the Texas Instruments web site athttp://www.ti.com. Additional support documents are listed in the section of this guide entitledRelated Documentation from Texas Instruments.

The PGA309EVM-USBis an evaluation module that is used to fully evaluate the PGA309. The PGA309 is an integrated circuit that provides temperature compensation and linearization for bridge sensors. ThePGA309EVM-USBconsists of two PCBs. One board (theUSB-DAQ-Platform)generates the digital signals required to communicate with the PGA309. The other board (the PGA309_Test_Board) contains the PGA309 device, as well as support and configuration circuitry.

Throughout this document, the abbreviation EVM and the termevaluation module are synonymous with thePGA309EVM-USB.

2

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Introduction and Overview

1.1PGA309EVM-USBHardware

Figure 1 shows the hardware included with thePGA309EVM-USBkit. Contact the factory if any component is missing. It is highly recommended that you check the TI web site (athttp://www.ti.com) to verify that you have the latest software. It is also recommended that you refer to thePGA309 User's Guide if you have questions about the PGA309 device itself.

The complete kit includes the following items:

PGA309_Test_Board

USB DAQ Platform Board

USB cable

6V wall power-supplyunit

CD-ROMcontaining this user'sguide and product software

Figure 1. Hardware Included with the INA282-286EVM

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1.2Related Documentation from Texas Instruments

The following documents provides information regarding Texas Instruments integrated circuits used in the assembly of the PGA309EVM-USB.This user'sguide is available from the TI web site under literature numberSBOU084. Any letter appended to the literature number corresponds to the document revision that is current at the time of the writing of this document. Newer revisions may be available from the TI web site athttp://www.ti.com, or call the Texas Instruments Literature Response Center at (800)477-8924or the Product Information Center at (972)644-5580.When ordering, identify the document by both title and literature number.

Document

Literature Number

 

 

PGA309

SBOS292

 

 

USB DAQ Platform Users Guide

SBOU056

 

 

PGA309 Users Guide

SBOU024

 

 

OPA333 Product Data Sheet

SBOS351

 

 

DAC8555 Product Data Sheet

SLAS475

 

 

XTR117 Product Data Sheet

SBOS344

 

 

PGA309EVM-USBSchematic

SBOR010

 

 

Sensor-EmulatorEVM Reference Guide

SBOA102

 

 

1.3If You Need Assistance

If you have questions about the PGA309EVM-USBevaluation module, send ane-mailto the Linear Application Team atprecisionamps@list.ti.com. IncludePGA309EVM-USB as the subject heading.

1.4Information About Cautions and Warnings

This document contains caution statements.

CAUTION

This is an example of a caution statement. A caution statement describes a situation that could potentially damage your software or equipment.

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System Setup

2System Setup

Figure 2 shows the system setup for the PGA309EVM. The PC runs software that communicates with theUSB-DAQ-Platform.TheUSB-DAQ-Platformgenerates the digital signals used to communicate with the PGA309_Test_Board. Connectors on the PGA309_Test_Board allow for connection to the bridge sensor.

EVM

POWER

USB DAQ

PLATFORM

PGA309

TESTBOARD

Figure 2. PGA309EVM-USBHardware Setup

2.1Theory of Operation for PGA309_Test_Board Hardware

Figure 3 shows the block diagram of the PGA309_Test_Board. The PGA309_Test_Board provides connections to the I2C™ ,one-wire,analog-to-digitalconverters (ADCs) anddigital-to-analogconverters (DACs) on theUSB-DAQ-Platform.It also provides connection points for external connection of the bridge sensor. The PGA309_Test_Board has circuitry to convert the PGA309 voltage output to 4mA to 20mA current.

25-PinMale DSUB Signals From USB DAQ Platform

VDUT Supply

 

Switched 5.0V Power

I2C

 

Interface

 

One-WireInterface

PGA309

4mA to 20mA I/V Converter

Sensor

Emulator

25-PinFemale DSUB Signals From USB DAQ Platform

Sensor

Connection

Figure 3. PGA309_Test_Board Block Diagram

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System Setup

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The PGA309_Test_Board also has an onboard sensor emulator. The sensor emulator is a circuit that generates the same type of signals generated by a bridge sensor. The sensor emulator circuit is controlled by the PGA309EVM-USBsoftware. Using the sensor emulator allows you to get a deeper understanding of thePGA309EVM-USBsoftware and hardware more quickly. When the capabilities and functions of thePGA309EVM-USBare fully understood, you can connect thereal-worldsensor to the EVM and perform a full calibration.

Note that calibrations with real-worldsensors aretime-consumingbecause devices such as these are normally calibrated at multiple temperatures in an environmental chamber. It is not unusual for temperature calibration to require 12 hours.

2.2PGA309_Test_Board Connections

See Figure 4 for the input connections on the PGA309_Test_Board schematic. T1 provides the power connection for an external bridge sensor. T4 allows connections to each input of the external bridge sensor. T5 allows connection of the external temperature sensor. JMP7, JMP4, JMP5, and JMP6 allow users to select either the onboard sensor emulator or an external sensor. JMP12 allows users to choose between VS or VEXC for the sensor power.

The input is filtered with R3, R4, C14, C15, and C16. Note that C14 is ten times larger then C15, and C16 is used for good ac common-moderejection. The cutoff frequency of this filter is 40.6Hz (f = 1/(2 p R3 C14)). This input filter is recommended in your final design if you have available board space.

VEXC has a 100pF capacitor and TEMPin has a 1nF capacitor. These components are also recommended in your final design.

Refer to Figure 5 to see the power, reference, and digital connections on the PGA309_Test_Board schematic. T2 provides a connection for an external reference voltage. JMP1 and JMP2 allow users to select between the internal reference, an external reference, orpower-supplyreference. JMP7 and JMP8 allows users to connect theOne-Wiresignal to the PRG pin directly or through VOUT.

D2 is a transient voltage suppressor. It is useful in helping to prevent damage in an electrical overstress (EOS) condition. R5 is useful in preventing EOS damage to the output. C6 filters noise at the output. C5 filters the reference output. These components are recommended for your design if PCB space permits. C4 is a decoupling capacitor; it is required in the final design.

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System Setup

Figure 4. PGA309_Test_Board Schematic: Input Circuitry

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Figure 5. PGA309_Test_Board Schematic: Power, Reference, and Digital Connections

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System Setup

Figure 6 shows the output section of the PGA309EVM_Test_Board. There are two output options: voltage output and current output. The voltage output option is selected by placing JMP9 in theNC position. The current output option is selected by moving JMP9 to theVOUT to XTR position.

Figure 6. PGA309_Test_Board Schematic: Output Circuitry

In voltage output mode, C10 = 10nF is connected to the PGA309 output. This capacitor is used for radio frequency interference (RFI) and electromagnetic interference (EMI) immunity. This component should be included in your design, if possible.

In current output mode, the PGA309 output is connected to a voltage-to-current(V-I)converter (XTR117). The sum of R6 and R8 convert the output voltage from the PGA309 to an input current for the XTR117. R7 can be used to create an input offset current using the reference. The total input current is IIN = VOUT / (R6 + R8) + VREF/R7. The output current is equal to the input current times the current gain (x 100).

D4 is used for reverse polarity protection. D3 is used for over-voltagetransient protection. D3 was selected for low leakage. Leakage on D3 directly contributes to error. C11 is a decoupling capacitor and is required for proper operation. The external transistor, Q1, conducts the majority of thefull-scaleoutput current. Power dissipation in this transistor can approach 0.8W with high loop voltage (40V) and 20mA output current.

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System Setup

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Figure 7 shows the sensor emulator circuit. The sensor emulator generates signals to help users evaluate the PGA309. No part of this circuit is required in your final design. The sensor emulator uses aDAC8555 (U8) to generate an emulated temperature signal,common-modesignal, and differential signal. These signals can be controlled using software to produce levels that closely matchreal-worldsensors.

Figure 7. PGA309_Test_Board Schematic: Sensor Emulator Circuitry

The operational amplifier U4 and associated resistors is a differential amplifier with jumper selectable attenuation. The possible attenuations are 0.12 and 0.012. The attenuation produces a more accurate and stable emulated sensor output. For example, when the DAC outputs 3V, the sensor emulator outputs 3V × 0.012 = 36mV (assuming that attenuation is set in the 0.012 position). Thus, the maximum output of the sensor emulator is 120mV/V and 12mV/V.

The op amp U6 buffers the emulated temperature signal. Resistors R16, R17, R18, and R19 are used to attenuate the DAC output for temperature emulation and to reference the temperature signal to supply or ground. JMP13 allows the resistor network to be bypassed for direct connection to the DAC (diode temperature sensor mode).

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