THS6043EVM

THS6043EVM User’s Guide August 2002 High Performance Linear Products SLOU139 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third−party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. 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. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright  2002, Texas Instruments Incorporated EVM IMPORTANT NOTICE Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being provided may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety measures typically found in the end product incorporating the goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may not meet the technical requirements of the directive. Should this evaluation kit not meet the specifications indicated in the EVM User’s Guide, the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user indemnifies TI from all claims arising from the handling or use of the goods. Please be aware that the products received may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. TI currently deals with a variety of customers for products, and therefore our arrangement with the user is not exclusive. TI assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or services described herein. Please read the EVM User’s Guide and, specifically, the EVM Warnings and Restrictions notice in the EVM User’s Guide prior to handling the product. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact the TI application engineer. Persons handling the product must have electronics training and observe good laboratory practice standards. No license is granted under any patent right or other intellectual property right of TI covering or relating to any machine, process, or combination in which such TI products or services might be or are used. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright  2002, Texas Instruments Incorporated EVM WARNINGS AND RESTRICTIONS It is important to operate this EVM within the input voltage ranges described in the EVM User’s Guide. Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM. If there are questions concerning the input range, please contact a TI field representative prior to connecting the input power. Applying loads outside of the specified output range may result in unintended operation and/or possible permanent damage to the EVM. Please consult the EVM User’s Guide prior to connecting any load to the EVM output. If there is uncertainty as to the load specification, please contact a TI field representative. During normal operation, some circuit components may have case temperatures greater than 60°C. The EVM is designed to operate properly with certain components above 60°C as long as the input and output ranges are maintained. These components include but are not limited to linear regulators, switching transistors, pass transistors, and current sense resistors. These types of devices can be identified using the EVM schematic located in the EVM User’s Guide. When placing measurement probes near these devices during operation, please be aware that these devices may be very warm to the touch. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright  2002, Texas Instruments Incorporated Information About Cautions and Warnings Preface
    About This Manual This manual provides information about the EVM used to evaluate the THS6043 high-speed amplifier. Additionally, this document provides a good example of PCB design for high-speed applications. The user should keep in mind the following points. It is recommended that the user initially review the data sheet of the device under test. - It is helpful to review the schematic and layout of the THS6043EVM to determine the design techniques used in the evaluation board. - The design of the high-speed amplifier PCB is a sensitive process. The user must approach high speed PCB design with care and awareness. How to Use This Manual This document contains the following chapters: - Chapter 1: Introduction and Description - Chapter 2: Using the THS6043EVM - Chapter 3: THS6043EVM Applications - Chapter 4: High-Speed Amplifier PCB Layout Tips - Chapter 5: EVM Hardware Description 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. iii Related Documentation From Texas Instruments 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. 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. Electrostatic Sensitive Components This EVM contains components that can potentially be damaged by electrostatic discharge. Always transport and store the EVM in its supplied ESD bag when not in use. Handle using an antistatic wristband. Operate on an antistatic work surface. For more information on poroper handling, refere to SSYA008. Related Documentation From Texas Instruments The URLs below are correct as of the date of publication of this manual. Texas Instruments applications apologizes if they change over time. - THS6043 data sheet (literature number SLOS264) - Application report (literature number SLMA002), Power Pad Thermally Enhanced Package, http://www−s.ti.com/sc/psheets/slma004/slma002.pdf - Application report (literature number SLMA004), Power Pad Made Easy, http://www−s.ti.com/sc/psheets/slma004/slma004.pdf - Application report (literature number SSYA008), Electrostatic Discharge (ESD), http://www−s.ti.com/sc/psheets/ssya008/ssya008.pdf iv Trademarks - Application report (literature number SLOA100), Active Output Imped- ance for ADSL Line Drivers, http://www−s.ti.com/sc/psheets/sloa100/sloa100.pdf Trademarks PowerPAD is a trademark of Texas Instruments. v vi Contents  1 Introduction and Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Evaluation Module Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 THS6043EVM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 EVM Default Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1-2 1-2 1-2 1-2 2 Using the THS6043EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Test Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Power Supply Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Input and Output Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2-2 2-2 2-3 3 THS6043EVM Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 3.1 Standard Gain Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3.2 Single Supply Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 3.3 Active Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 3.4 Snubber Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 3.5 Receive Path Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 3.6 High-Pass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 3.7 Noninverting Single-Ended Gain Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9 3.8 Independent Single-Ended Inverting Gain Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10 3.9 Independent Single-Supply Single-Ended Inverting Gain Stages . . . . . . . . . . . . . . . . . 3-11 3.10 Shutdown Operation (Channels 1 and 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11 4 High-Speed Amplifier PCB Layout Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 5 EVM Hardware Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 vii Contents  1−1 2−1 2−2 3−1 3−2 3−3 3−4 3−5 3−6 3−7 3−8 3−9 3−10 5−1 5−2 5−3 5−4 5−5 Schematic of the Populated Circuit on the EVM (Default Configuration) . . . . . . . . . . . . . . 1-3 Power Supply Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 Signal Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 Default Configuration Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 Single-Supply Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 Differential Positive Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Addition of Snubber Circuit to Active Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 Implementation of the Receive Signal Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 ADSL Spectrum and High-Pass Filter Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 Independent Single-Ended Noninverting Gain Configuration . . . . . . . . . . . . . . . . . . . . . . . . 3-9 Independent Single-Ended Inverting Gain Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10 Independent Single-Ended Single-Supply Inverting Gain Configuration . . . . . . . . . . . . . . 3-11 Shutdown Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12 Top Layer 1 of THS6043EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 Internal Plane (Layer 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 Internal Plane (Layer 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 Bottom (Layer 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 Full Schematic of the THS6043EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6  5−1 viii THS6043EVM Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 Chapter 1     The Texas Instruments THS6043 evaluation module (EVM) helps designers evaluate the performance of the THS6043 operational amplifier. Also, this EVM is a good example of high-speed PCB design. This document details the THS6043EVM. 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 of high-speed amplifier design considerations. This EVM enables the user to implement various circuits to clarify the available configurations presented by the schematic of the EVM. The user is not limited to the circuit configurations presented here. The EVM provides enough hardware hooks that the only limitation should be the creativity of the user. Topic Page 1.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1.2 Evaluation Module Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1.3 THS6043EVM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1.4 EVM Default Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Introduction and Description 1-1 Description 1.1 Description The THS6043EVM provides a platform for developing high-speed op amp application circuits. It contains the THS6043 high-speed dual op amp, 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 PC board measures 4.21 by 2.88 inches. 1.2 Evaluation Module Features THS6043 high-speed operational amplifier EVM features include: - Differential noninverting gain configuration for DSL - Active termination capability (R6 and R11) - Snubber circuit (R19 and C5), for use with active termination - HPF function (C3 and R7) - Hooks for a receive path signal (TP1 through TP4) - Virtual ground capability (JP1, R20, R21) - Power down capability (R25, R26, R27, JP2) - Single supply capability (R4, R14, R20, R21, C9, JP1, Z1, Z2) - Single-ended noninverting gain stage capability (R8, R9, R23, R24, Z3) - Single-ended inverting gain stage capability (R3, R4, R14, R15) - Power supply decoupling components (C6−C15, FB1, FB2) - Short-loop length for the power supply differential high-frequency path (C8) 1.3 THS6043EVM Operating Conditions Supply voltage range, ±VCC ±5 V to ±15 V (see the device data sheet) Supply current, ICC (see the device data sheet) For complete THS6043 amplifier IC specifications, parameter measurement information, and additional application information, see the THS6043 data sheet, TI literature number SLOS264. 1.4 EVM Default Configuration The EVM has a fully functional example circuit; just add power supplies, a signal source, and monitoring instrument. See Figure 1−1 for the default schematic diagram. The complete EVM schematic in Chapter 5 shows all component locations. The default configuration assumes a differential gain, as determined by R5, R16, and R7 in combination with series matching resistors R17 and R18, and assumes a 50-Ω load on the outputs at J6 and J7. Some components such as R10, R25 through R27, C6 through C15, FB1, FB2, JP1, J3, J4, and J5 are omitted on the application schematics of Chapter 3 for clarity. 1-2 EVM Default Configuration Figure 1−1. Schematic of the Populated Circuit on the EVM (Default Configuration) +V J1 IN1 Z1 R23 0 0 14 U1A 3 + THS6043 1 2 − R1 49.9 W 4 TP2 OUT1 TP1 R17 R29 49.9 W 49.9 W R5 750 W −V R25 100 W U1C THS6043 9 5 7 NC SD 15 PWP 8 10 GND R7 210 W J2 IN2 Z2 C3 1 mF U1B R16 THS6043 750 W 12 − R18 13 11 + 49.9 W R24 0 0 R12 49.9 W C10 6 J4 − VCC 0.1 mF +V TP6 C14 JP1 0.1 mF C7 ** C8 ** 0.1 mF 1 mF + C9 1 mF 1 +V 49.9 W C1 + 10 mF C12 R27 4.99 kW J7 OUT2 R28 J5 TP7 TP8 TP9 GND FB1 JP2 R26 4.99 kW TP4 OUT2 TP3 J3 +VCC TP5 SD J6 OUT1 0.1 mF C15 0.1 mF FB2 −V C11 + 10 mF C13 0.1 mF C6** 0.1 mF * Not installed ** Install near U1 Introduction and Description 1-3 1-4 Chapter 2    !" This section describes how to connect the THS6043EVM to test equipment. It is recommended that the user connect the EVM as described in this section to avoid damage to the EVM or the THS6043 installed on the board. Topic Page 2.1 Test Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.2 Power Supply Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.3 Input and Output Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 Using the THS6043EVM 2-1 Test Equipment Required 2.1 Test Equipment Required - Dual dc output power supply (± 15 V, 200 mA output minimum) - Two dc current meters with resolution to 1 mA and capable of the maximum current supplied by the dc power source. Note: Some power supplies incorporate current meters which may be applicable to this test. - 50-Ω source impedance function generator (1 MHz, 10 Vpp sine wave) - Oscilloscope (50 MHz bandwidth minimum, 50-Ω terminated BNC Input) 2.2 Power Supply Setup (See Figure 2−1) - Set the dc power supply to ±15 V. If available, set the current limit on the dc power supply to 200 mA. - Make sure the dc power supply is turned off before proceeding. - Connect the +15 V supply to the + input on current meter 2 (if applicable). - Connect the – input on current meter 2 to J3 (+Vcc) on the EVM. - Connect the –15V supply to the − input on current meter 1 (if applicable). - Connect the + input on current meter 1 to J4 (–Vcc) on the EVM. - Make sure both dc current meters are set to at least 1 mA resolution and can withstand the maximum output current of the power supplies. - Connect the ground(s) of the +15 V and –15 V power supply to J5 (GND) on the EVM. - Verify JP1 is connected to the 1−2 position (lower posts). - Verify JP2 is not shorting the header pins (connect to only one post). Figure 2−1. Power Supply Connection POWER SUPPLY CURRENT METER 1 −15 V + GND CURRENT METER 2 +15 V − + −VCC J4 +VCC GND J5 J3 THS6043 EVM EDGE #6438959 IN1 J6 J1 OUT 1 JP 1 JP 2 IN2 OUT 2 J2 2-2 J7 − Input and Output Test Setup (See Figure 2−2) 2.3 Input and Output Test Setup (See Figure 2−2) - Set the function generator to a 1 MHz, ±2.5 V (5 Vpp) sine wave with no dc offset. - Turn off the function generator before proceeding to the next step. - Using a BNC cable, connect the function generator to J1 (IN1 BNC) on the EVM. - Using a BNC cable, connect the oscilloscope to J6 (OUT1 BNC) on the EVM. Set the oscilloscope to 1 V/Division and a time base of 0.2 µSec/Division. Note : The Oscilloscope must be set to 50-W termination for proper operation. Figure 2−2. Signal Connections −VCC FUNCTION GENERATOR 1 MHz 5 VPP 0 V Offset J4 GND J5 +VCC J3 IN 1 J6 OSCILLOSCOPE THS6043 EVM EDGE #6438959 OUT 50 Ohm Source Impedance J1 JP 1 IN 2 J2 JP 2 OUT 1 CH-1 CH-2 OUT 2 J7 50 Ohm Impedance Using the THS6043EVM 2-3 2-4 Chapter 3 !" # Example applications are presented in this chapter. These applications demonstrate the most popular circuits to the user, but many other circuits can be constructed. The user is encouraged to experiment with different circuits, exploring new and creative design techniques. That, after all, is the function of an evaluation board. Topic Page 3.1 Standard Gain Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3.2 Single Supply Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 3.3 Active Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 3.4 Snubber Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 3.5 Receive Path Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 3.6 High-Pass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 3.7 Noninverting Single-Ended Gain Stages . . . . . . . . . . . . . . . . . . . . . . . . 3-9 3.8 Independent Single-Ended Inverting Gain Stages . . . . . . . . . . . . . . . 3-10 3.9 Independent Single- Supply Single-Ended Inverting Gain Stages 3-11 3.10 Shutdown Operation (Channels 1 and 2) . . . . . . . . . . . . . . . . . . . . . . . 3-11 THS6043EVM Applications 3-1 Standard Gain Configuration 3.1 Standard Gain Configuration The THS6043EVM default configuration is a fully differential input, fully differential output gain stage as shown in Figure 3−1. This gain is calculated according an equation that is similar to the one that describes an instrumentation amplifier: V (diff) + 1 ) 2 R5 Differential gain + O R7 V (diff) I (1) Where: R5 = R16 Series resistors R17 and R18 affect output voltage at J6 and J7. Designers need to take the voltage divider law into account for their load impedance and R17/R18. Figure 3−1. Default Configuration Operation +V J1 IN1 Z1 R23 0 0 R1 49.9 W 14 U1A THS6043 3 + 1 2 − 4 TP2 OUT1 TP1 J6 OUT1 R17 49.9 W R5 750 W −V R7 210 W C3 1 mF J2 IN2 Z2 0 R12 49.9 W 3-2 U1B R16 THS6043 750 W 12 − 13 R24 11 + 0 TP3 J7 OUT2 R18 49.9 W TP4 OUT2 Single Supply Operation 3.2 Single Supply Operation Many designs use single supply voltages, and the THS6043EVM allows single supply operation. The THS6043EVM can be reconfigured for single supply operation as shown in Figure 3−2. To convert to single supply operation: - Connect ground from the power supply to both J5 (GND) and J4 (−VCC). - Jumper pins 2 and 3 of JP1 together with a jumper plug. This enables connection to a half supply voltage divider. - Populate R4, R14, R20, and R21, with 4.99 kΩ 1% resistors. R20 and R21 create the half supply potential (virtual ground for the stage). R4 and R14 sum this potential into the noninverting inputs of the op amps. The half-supply virtual ground potential is also present on the output of the op amps. No provision has been made on the EVM for output dc-blocking capacitors. When the outputs are monitored with equipment that has 50-Ω inputs, 75 mW is dissipated through R17, R18, and the input resistors of the measuring equipment. - Remove the zero Ω jumpers located at Z1 and Z2 and replace them with dc-blocking capacitors. Figure 3−2. Single-Supply Operation +V Z1 J1 IN1 R23 0.1 mF R1 49.9 W 0 R4 4.99 kW 14 U1A 3 + THS6043 1 2 − 4 49.9 W R5 750 W R21 4.99 kW C9 1 mF R14 4.99 kW J2 IN2 J4 −VCC>>> GND FB1 1 + J5 GND J3 +VCC R7 210W JP1 J6 OUT1 R17 +V R20 4.99 kW TP2 OUT1 TP1 Z2 R24 0.1 mF R12 49.9 W 0 C3 1 mF FB2 +V U1B R16 THS6043 750 W 12 − 13 11 + TP3 −V >>> GND J7 OUT2 R18 49.9 W TP4 OUT2 THS6043EVM Applications 3-3 Active Termination 3.3 Active Termination Active termination is a technique that allows the designer to use a small value resistor for the series resistance (R17 or R18). The circuit then uses positive feedback to make the impedance of this resistor appear much larger, when looking from the line side. This accomplishes two things: 1) A very small resistance is evident when the line driver amplifier transmits signals to the line. This lowers the driver stage output voltage swing range requirement. 2) Proper matching impedance when looking from the line to the amplifier Figure 3−3 shows the basic circuit for differential positive feedback. Figure 3−3. Differential Positive Feedback +V 14 J1 IN1 Z1 R23 0 0 R1 49.9 W 3 + 2 − TP1 Vo+ U1A THS6043 1 R17 = RS