THS6212EVM

User's Guide SBOU171 – May 2016 THS6212 Evaluation Module This manual provides information about the evaluation module of the 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: • 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 THS6212 EVM 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 highspeed PCB design with care and awareness. 1 2 3 4 5 Contents Introduction ................................................................................................................... Using the THS6212 EVM ................................................................................................... THS6212 EVM Applications ................................................................................................ High-Speed Amplifier PCB Layout Tips................................................................................... EVM Hardware Description ................................................................................................. 2 3 5 7 8 List of Figures 1 THS6212 EVM Default Configuration Setup Block Diagram ........................................................... 3 2 Default Configuration Operation ........................................................................................... 5 3 Differential Positive Feedback 4 5 6 7 8 ............................................................................................. 6 Top Components and Silk Screen ......................................................................................... 9 Ground Layer ............................................................................................................... 10 Power Layer................................................................................................................. 11 Bottom Components and Silk Screen ................................................................................... 12 Full Schematic of the THS6212 EVM.................................................................................... 13 List of Tables 1 Typical Power Supply Current Reading for Different Bias Modes ..................................................... 4 2 THS6212 EVM Bill of Materials ............................................................................................ 8 PowerPAD is a trademark of Texas Instruments. SBOU171 – May 2016 Submit Documentation Feedback THS6212 Evaluation Module Copyright © 2016, Texas Instruments Incorporated 1 Introduction 1 www.ti.com Introduction The Texas Instruments THS6212 evaluation module (EVM) helps designers evaluate the performance of the THS6212 single-port current feedback architecture, differential line driver amplifier system in a 24-pin QFN package. This EVM is a good example of high-speed PCB design. This document details the THS6212 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 of high-speed amplifier design considerations. 1.1 Description The THS6212 evaluation module (EVM) is used to evaluate the THS6212, which is a single-port currentfeedback architecture, differential line driver amplifier system in a 24-pin QFN package. The EVM is designed to quickly and easily demonstrate the functionality and performance of THS6212 in a gain of 10 V/V, driving an RLOAD = 100 Ω. The EVM is ready to connect to power supplies, signal source, and test instruments through the use of onboard connectors. The board is setup for single-ended input and output operation for interfacing with 50-Ω test equipment. By default, the THS6212EVM comes with the bias setting in Full Bias mode and can be configured in Mid Bias and Low Bias modes using jumper connectors. 1.2 Evaluation Module Features The THS6212 high-speed operational amplifier EVM features include: • Configured for split-supply operation and easily modified for single supply • Designed for single-ended input and output connection facilitated by the onboard balun • Simple interface to the inputs and outputs through the SMA connectors • Bias mode settings changed using jumper connectors • Active termination capability (R12 and R13) • Non-inverting gain configuration for DSL 1.3 THS6212 Operating Conditions Supply voltage range, ±VCC = ±5 to ±13 Vdc (see the device data sheet). Supply current, IQ (see the device data sheet). For complete THS6212 amplifier IC specifications, parameter measurement information, and additional application information, see the THS6212 data sheet (SBOS758). 1.4 EVM Default Configuration As delivered, the EVM has a fully functional example circuit; just add power supplies, a signal source, and a monitoring instrument. See Figure 8 for the default schematic diagram of the THS6212 EVM. The default configuration assumes a differential gain of 10, as determined by R7, R8, and R9 in combination with series-matching resistors R10 and R11, and assuming a 50-Ω load on the output at J2. Some components, such as supply bypass capacitors, JP1 and JP2, are omitted on the application schematics of Section 3 for clarity. 2 THS6212 Evaluation Module SBOU171 – May 2016 Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated Using the THS6212 EVM www.ti.com ±12-V Split Bench Power Supply Signal Generator Oscilloscope (VS+) +12 V (VS>• GND >12 V 25 Q + - TT1-6-KK81+ 1.24 kQ TT1-6-KK81+ 25 Q J1 THS6212 25 Q + J2 274 Q 1.24 kQ 25 Q THS6212 EVM Copyright © 2016, Texas Instruments Incorporated Figure 1. THS6212 EVM Default Configuration Setup Block Diagram 2 Using the THS6212 EVM This section describes how to connect the THS6212 EVM 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 THS6212 installed on the board. 2.1 Required Equipment A list of the required equipment appears in the following: • Dual dc output power supply (± 12 V, 200-mA output minimum). • Two dc current meters with resolution to 1 mA and capable of a maximum current which the dc power supply can supply. If available, set the current limit on the dc power supply to 200 mA. NOTE: Some power supplies incorporate current meters which may be applicable to this test. • • 2.2 50-Ω source impedance function generator (1 MHz, 1 VPP sine wave). Oscilloscope (50-MHz bandwidth minimum, 50-Ω terminated BNC input). Power Supply Setup (Reference Figure 1) Follow the below procedure for power supply setup: • Before connecting the power supply cables to the EVM, set the dual dc output power supply to ±12 V. • Make sure the dc power supply is turned off before proceeding to the next step. • Connect the +12 V power supply to the +Vs of the power supply port (P1) on the EVM. • Connect the –12 V power supply to the -Vs of the power supply port (P1) on the EVM. • Connect the ground(s) of the +12 V and –12 V power supply to the middle port of P1 (GND) on the EVM. • Make sure the dc current meters on the dual dc output power supply are set to at least 1-mA resolution and are set to 200-mA minimum output current capability. • Turn-on the dual dc power supply to ±12 V SBOU171 – May 2016 Submit Documentation Feedback THS6212 Evaluation Module Copyright © 2016, Texas Instruments Incorporated 3 Using the THS6212 EVM www.ti.com The following table provides the typical supply current read on the current meter for the different plug-in jumper (JP1 and JP2) connections. Table 1. Typical Power Supply Current Reading for Different Bias Modes Bias Mode 2.3 JP1 position JP2 position IQ(typ) Full Open Open 21 mA Mid Closed Open 16 mA Low Open Closed 11 mA Shut-down Closed Closed < 1mA Input and Output Test Setup (Reference Figure 1) Follow the below procedure for input and output test setup: • Set the function generator to a 1 MHz, ±0.24 V (0.42 VPP) sine wave with no dc offset. The function generator output should be set in 50-Ω termination mode. • Turn off the function generator before proceeding to the next step. • Connect the function generator output to SMA connector J1 on the EVM. • Scope channel 1 should be connected to SMA connector J2 on the EVM. Set the oscilloscope to 500 mV/division and a time-base of 1 μs / division. NOTE: The oscilloscope must be set in a 50-Ω termination for proper operation. • 4 Turn on the function generator. The measured output on the scope channel 1 at SMA connector J2 should approximately be ±1 V (2 VPP). THS6212 Evaluation Module SBOU171 – May 2016 Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated THS6212 EVM Applications www.ti.com 3 THS6212 EVM Applications Couple of example applications are presented in this section. 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. 3.1 Standard Gain Configuration The THS6212 EVM default configuration is a fully differential input, fully differential output gain of 10 (at the THS6212 device output pins) as shown in Figure 2. This gain is calculated according an equation that is similar to the one that describes an instrumentation amplifier: V (di ff ) 2 ´ RF = 1+ Differential Gain = O V I (di ff ) RG where • • RF = 1.24 kΩ RG = 274 Ω (1) The two series resistors RS= 25 Ω affect the differential output voltage at J2. The designer needs to take the voltage divider law into account for their load impedance and RS. In-addition to the two series resistors RS, the insertion loss in the input and output baluns affects the measured gain and bandwidth of the EVM. As a result, it is required to remove the input and output balun insertion loss from the EVM measurement to determine the true THS6212 device performance. +12V Rs = 25Q + - TT1-6-KK81+ -12V 25Q J1 THS6212 25Q - +12V Rf = 1.24kQ TT1-6-KK81+ J2 Rg = 274 Q Rf = 1.24kQ + Rs = 25Q -12V THS6212 EVM Figure 2. Default Configuration Operation 3.2 Active Termination Active termination is a technique that allows the designer to use a small value resistor for the series resistance (RS). The circuit then utilizes positive feedback to make the impedance of this resistor, when looking from the line-side, appear much larger. This accomplishes two things: • A very small resistance when the line-driver amplifier transmits signals to the line. This lowers the output voltage swing range required from the driver stage. • Proper matching impedance when looking from the line to the amplifier. Figure 3 shows the basic circuit for differential positive feedback. SBOU171 – May 2016 Submit Documentation Feedback THS6212 Evaluation Module Copyright © 2016, Texas Instruments Incorporated 5 THS6212 EVM Applications www.ti.com +12V Rs = 50Q + - TT1-6-KK81+ -12V 25Q J1 THS6212 25Q - +12V Rf