Texas Instruments SLOU106 User Manual

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THS4140

EVM User's Guide for High!Speed

Fully!Differential Amplifier

User's Guide

February 2001

Mixed-SignalProducts

SLOU106

IMPORTANT NOTICE

Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability.

TI warrants performance of its products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements.

Customers are responsible for their applications using TI components.

In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards.

TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such products or services might be or are used. TI's publication of information regarding any third party's products or services does not constitute TI's approval, license, warranty or endorsement thereof.

Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations and notices. Representation or reproduction of this information with alteration voids all warranties provided for an associated TI product or service, is an unfair and deceptive business practice, and TI is not responsible nor liable for any such use.

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Also see: Standard Terms and Conditions of Sale for Semiconductor Products. www.ti.com/sc/docs/stdterms.htm

Mailing Address:

Texas Instruments

Post Office Box 655303

Dallas, Texas 75265

Copyright 2001, Texas Instruments Incorporated

Preface

About This Manual

This manual is written to provide information about the evaluation module of the fully differential amplifier under test. Additionally, this document provides a good example of PCB design for high speed applications. The user should keep in mind the following points.

The design of the high-speedamplifier PCB is an elegant and sensitive process. Therefore, the user must approach the PCB design with care and awareness. It is recommend that the user initially review the datasheet of the device under test. It is also helpful to review the schematic and layout of the THS4140 EVM to determine the design techniques used in the evaluation board. In addition, it is recommended that the user review the application noteFully-Differential Amplifiers (literature number SLOA054B) to gain more insight about differential amplifiers. This application note reviews the differential amplifiers and presents calculations for various filters.

How to Use This Manual

-Chapter 1ÐIntroduction and Description

-Chapter 2ÐUsing the THS4140 EVM

-Chapter 3ÐGeneral High-SpeedAmplifier Design Considerations

Read This First

iii

Related Documentation From Texas Instruments

Information About Cautions and Warnings

This book may contain cautions and warnings.

This is an example of a caution statement.

A caution statement describes a situation that could potentially damage your software or equipment.

This is an example of a warning statement.

A warning statement describes a situation that could potentially cause harm to you.

The information in a caution or a warning is provided for your protection. Please read each caution and warning carefully.

Related Documentation From Texas Instruments

-THS4140 data sheet (literature number SLOS320)

-THS4140 application report (literature number SLOA054A),

Fully-DifferentialAmplifiers

FCC Warning

This equipment is intended for use in a laboratory test environment only. It generates, uses, and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to subpart J of part 15 of FCC rules, which are designed to provide reasonable protection against radio frequency interference. Operation of this equipment in other environments may cause interference with radio communications, in which case the user at his own expense will be required to take whatever measures may be required to correct this interference.

Trademarks

PowerPAD is a trademark of Texas Instruments.

iv

Running TitleÐAttribute Reference

Contents

1

Introduction and Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

 

1.1

Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-2

 

1.2

Evaluation Module Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-2

 

1.3

THS4140 EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-3

 

1.4

Schematic of the Populated Circuit (Default Configuration) . . . . . . . . . . . . . . . . . . . . . . .

1-3

 

1.5

THS4140 EVM Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4

 

1.6

Additional Sample Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-5

 

1.7

THS4140 EVM Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-7

2

Using the THS4140 EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-1

2.1 Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22.2 Power Supply Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-22.3 Input and Output Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32.4 Testing the EVM Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-42.5 Power Down Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-52.6 Measuring the Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-52.7 Butterworth Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-62.8 THS4140 EVM Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7

3 General High-SpeedAmplifier Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

Chapter TitleÐAttribute Reference

v

Running TitleÐAttribute Reference

Figures

1±1

Schematic of the Populated Circuit on the EVM (Default Configuration) . . . . . . . . . . . . . .

1-3

1±2

Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4

1±3

Fully-DifferentialIn/Fully-DifferentialOut, Without Transformer . . . . . . . . . . . . . . . . . . . . . .

1-5

1±4

Fully-DifferentialIn/Fully-DifferentialOut, Utilizing Transformer . . . . . . . . . . . . . . . . . . . . . .

1-5

1±5

VICR Level Shifter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-6

1±6

Butterworth Filter With Multiple Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-6

1±7

Top Layer (Silkscreen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-7

1±8

Top (Layer 1) (Signals) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-7

1±9

Internal Plane (Layer 2) (Ground Plane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-8

1±10

Internal Plane (Layer 3) (+ VCC Plane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-8

1±11

Bottom (Layer 4) (Ground and Signal) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-9

2±1

Power Supply Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-2

2±2

Signal Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-3

2±3

Driver 1 Output Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-4

2±4

Multiple Feedback Filter Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-6

2±5

Gain vs Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-7

Tables

2±1

THS4140 EVM Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-7

vi

Chapter 1

Introduction and Description

The Texas Instruments THS4140 evaluation module (EVM) helps designers evaluate the performance of the THS4140 operational amplifier. Also, this EVM is a good example of high-speedPCB design.

This document details the Texas Instruments THS4140 high-speedoperational amplifier evaluation module (EVM). It includes a list of EVM features, a brief description of the module illustrated with a series of schematic diagrams, EVM specifications, details on connecting and using the EVM, and a discussion ofhigh-speedamplifier design considerations.

This EVM enables the user to implement various circuits to clarify the available configurations presented by the schematic of the EVM. In addition, the schematic of the default circuit has been added to depict the components mounted on the EVM when it is received by the customer. This configuration correlates to the single input/differential output signal.

Other sample circuits are presented to show how the user can implement other circuit configurations such as differential input/differential output signal, transformer utilization on the input and output terminals, VICR level shifter, and Butterworth filter with multiple feedback. The user may be able to create and implement circuit configurations in addition to those presented in this document using the THS4140 EVM.

Topic

 

Page

 

 

 

1.1

Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 1-2

1.2

Evaluation Module Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1-2

1.3

THS4140 EVM Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1-3

1.4

Schematic of the Populated Circuit (Default Configuration) . . . . . .

. 1-3

1.5

THS4140 EVM Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1-4

1.6

Additional Sample Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1-5

1.7

THS4140 EVM Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1-7

 

 

 

 

Introduction and Description

1-1

Description

1.1 Description

The THS4140 EVM is a good example of PCB design and layout for high-speedoperational amplifier applications. It is a complete circuit for thehigh-speedoperational amplifier. The EVM is made of the THS4140high-speedoperational amplifier, a number of passive components, and various features and footprints that enable the user to experiment, test, and verify various operational amplifier circuit implementations. The board measures 4.5 inches in length by 2.5 inches in width. Initially, this board is populated for asingle-endedinput amplifier (see Figure1-2for populated circuits). The outputs (VO+ and V) can be tested differentially or single ended. Gain is set to one and can be changed by changing the ratios of the feedback and gain resistors (see the device datasheet for recommended resistor values). The user may populate various footprints on the evaluation module board to verify filter designs or perform other experiments. Each input is terminated with a50-Ωresistor to provide correctline-impedancematching.

1.2 Evaluation Module Features

THS4140 high-speedoperational amplifier EVM features include:

JVoltage supply operation range: 5-Vto±15-Voperation (see the device data sheet)

JSingle and differential input and output capability

JNominal 50-Ωinput and output termination resistors. They can be configured according to the application requirement.

JVOCM direct input control (see schematic and the device data sheet)

JVOCM pin can be controlled via transformercenter-tap(see schematic)

JShutdown pin control, JU1 (if applicable to the device, see the device data sheet)

JInput and output transformer footprints for changing single-endedsignals to differential signals

JFootprint for high-precision,balanced feedback and gain resistors (0.01% or better)

JFootprints for low-passfilter implementation (see application note SLOA054A)

JFootprints for antialiasing filter implementation (see application note SLOA054A)

JDifferential probe terminals on input and output nodes for differential probe insertion

JVarious GND and signal test points on the PCB

JCircuit schematic printed on the back of the EVM

JA good example of high-speedamplifier PCB design and layout

1-2

Introduction and Description

THS4140 EVM Specifications

1.3 THS4140 EVM Specifications

Supply voltage range, ± VCC . . . . 5 V to± 15 V (see the device data sheet)

Supply current, ICC . . . . . . . . . . . . . . . . . . . . . . . . (see the device data sheet) Output drive, IO, VCC =± 15 . . . . . . . . . . . . . . . . . (see the device data sheet)

For complete THS4140 amplifier IC specifications, parameter measurement information, and additional application information, see the THS4140 data sheet, TI literature number SLOS320.

1.4 Schematic of the Populated Circuit (Default Configuration)

For verification of jumper locations and other bypass components, see the complete EVM schematic in Figure 1±2.

Figure 1±1. Schematic of the Populated Circuit on the EVM (Default Configuration)

 

 

 

 

 

 

R6B

 

 

 

 

RX3

 

 

402 Ω

 

 

 

 

 

 

 

C4

 

 

 

 

49.9

Ω

 

 

 

VCC

 

 

 

50 Ω

 

 

 

 

 

 

 

 

RX1

 

R1b

R3b

 

 

R4b

JU4 Rx4

R10

Source

 

 

+

VIN

0 Ω

 

0 Ω

374 Ω

 

±

0 Ω

0 Ω

49.9 Ω

 

 

THS4140

AC

 

 

R1a

R3a

 

R4a

Rx5

Rx6

 

 

 

+

 

 

JU3

0 Ω

374 Ω

 

±

 

 

 

 

 

 

 

0 Ω

0 Ω

49.9 Ω

 

 

 

Rx0

 

C1

VCC±

C6

 

 

 

 

24.9 Ω

 

 

VOCM

 

 

 

 

 

 

 

 

 

R6a

 

 

 

 

 

 

 

 

 

402 Ω

 

 

 

NOTE: Default populated footprints on the EVM from the input nodes to the output terminals Gain = 1

Introduction and Description

1-3

THS4140 EVM Schematic

1.5 THS4140 EVM Schematic

Figure 1±2. Schematic

1-4

Introduction and Description