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User's Guide

SLWU058 – August 2008

Voltage-Controlled Amplifier Evaluation Kit

The TSW7001 is an evaluation module that demonstrates an ultra-wideband, high-performance,

voltage-controllable gain stage with 40 dB of voltage-controlled gain (nominal gain of 100). The

demonstration kit includes an optional path for an onboard OPA656 transimpedance input stage, a 16-bit

precision voltage DAC8831 to implement the gain control voltage, and the VCA824 ultra-wideband,

voltage-controlled amplifier. Also onboard are linear regulators to provide the voltages necessary for the

amplifier circuits and a precision 1.2-V reference for the control voltage digital-to-analog converter (DAC).

Control of the board is achieved through a USB interface and GUI software. This allows a personal

computer to control the gain of the VCA824 without the need for extra signal generators. The control

levels can be static voltage levels or dynamically changing waveforms, both selectable from the GUI.

Figure 1. TSW7001EVM

Contents

1 TSW7001EVM Configuration Options .................................................................................... 2

2 Block Diagrams .............................................................................................................. 3

3 Key Texas Instruments Components ..................................................................................... 3

4 Software Installation ......................................................................................................... 4

5 Software ....................................................................................................................... 4

6 TSW7001 EVM Introduction .............................................................................................. 11

7 Demonstration Kit Test Configuration ................................................................................... 12

8 Initial Power Up and Test ................................................................................................. 14

9 Optional Configurations.................................................................................................... 14

10 Bill of Materials and Schematics ......................................................................................... 16

11 References .................................................................................................................. 21

List of Figures

SLWU058 – August 2008 Voltage-Controlled Amplifier Evaluation Kit 1

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Summary of content (23 pages)

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User's Guide SLWU058 – August 2008 Voltage-Controlled Amplifier Evaluation Kit The TSW7001 is an evaluation module that demonstrates an ultra-wideband, high-performance, voltage-controllable gain stage with 40 dB of voltage-controlled gain (nominal gain of 100). The demonstration kit includes an optional path for an onboard OPA656 transimpedance input stage, a 16-bit precision voltage DAC8831 to implement the gain control voltage, and the VCA824 ultra-wideband, voltage-controlled amplifier.
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TSW7001EVM Configuration Options 1 2 3 4 5 6 7 8 9 10 11 12 13 14 www.ti.com TSW7001EVM ............................................................................................................... 1 Optional Onboard OPA656 Transimpedance Input Stage.............................................................. 2 TSW7001EVM Block Diagram ............................................................................................. 3 VCA824 Schematic .......................................................
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Block Diagrams www.ti.com 1.2 Using External Operational Amplifier Supplies By default both amplifiers are set up to operate with a ±5 V. This is adequate in most cases for evaluation purposes; however, both the OPA656 and VCA824 can be operated at a maximum of ±6-V supply. Ferrite beads allow the use of a different ±Vamp supply for both amplifiers, if desired. 2 Block Diagrams 2.1 System Block Diagram Figure 3 shows the functional blocks on the TSW7001 board.
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Software Installation 3.2 www.ti.com OPA656 The OPA656 is a wideband, unity-gain-stable, FET-input, voltage-feedback operational amplifier, allowing exceptional performance in high-speed, low-noise applications. Extremely low dc errors give good precision in optical applications. Typical applications for the OPA656 include wideband photodiode amplifiers, sample and hold buffers, CCD output buffers, ADC input buffers, wideband precision amplifiers, and test and measurement front ends.
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www.ti.com 5.2 Software Software Installation The GUI can be installed via the TSW7001_setup.exe file. Executing this file starts the program and driver installation. Click Next to proceed to the end-user license agreement. Read and accept the end-user license agreement, and click Next.
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Software www.ti.com Set up the User Name and Organization. Click Next. Do a Complete Install. Click Next, then click Install.
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Software www.ti.com Wait a couple of minutes for the installer to complete. Then Click Finish. The new executable can be found under the Programs\Texas Instruments\TSW7001 folder from the Start menu or in the C: drive at C:\Program Files\Texas Instruments\TSW7001\TSW7001_DAC8831_USB_GUI.exe Plug in the USB cable to the PC and the TSW7001. This causes the hardware wizard to detect the TSW7001 and start installing the drivers. Click Continue Anyway when asked about Windows Compatibility.
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Software www.ti.com The hardware is found and is ready to use. 5.3 TSW7001 GUI Software Once the TSW7001 GUI is started, and the EVM has gone through USB enumeration, the CONNECT button must be pressed to establish an open communications channel between the PC and the TSW7001. The GUI responds with a message indicating that communication has been established.
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Software www.ti.com Figure 5. TSW7001 Control Voltage GUI Figure 6.
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Software www.ti.com Figure 7. TSW7001 Ramp Output Figure 8.
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TSW7001 EVM Introduction www.ti.com Figure 9. Output of TSW7001 With Arbitrary Gain Profile 6 TSW7001 EVM Introduction The TSW7001 was designed to provide an easy way to test the VCA824 in a high-performance, voltage-controlled gain application. The EVM includes a16-bit DAC8831 voltage-controlled DAC to precisely control the voltage-controlled gain of the VCA824.
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Demonstration Kit Test Configuration 6.4 www.ti.com Power Management The TSW7001 requires an input of 6 Vdc either from the banana jack connectors or the supplied 6-V wall supply. A current rating of at least 2 A is recommended for the 6-V supply. The rest of the supplies: 3.3, ±5 V are all generated on the board with linear regulators. 7 Demonstration Kit Test Configuration 7.1 Test Setup Block diagram The test setup for the TSW7001 is shown in Figure 10.
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Demonstration Kit Test Configuration www.ti.com The input of the TSW7001 is by default terminated with a 50-Ω to ground to enable a connection to a 50-Ω signal source. Typical IMD3 and harmonic distortion data was obtained for the default case of 40-dB gain (Rf=402, Rg=18) driving 100 Ω at the output of the TSW7001 (50-Ω source into 50-Ω spectrum analyzer). Figure 11. IMD3 Plot for TSW7001 at 10 MHz -50 -52 -54 Gain - dB -56 -58 -60 -62 -64 -66 -68 -70 1 10 f - Frequency - MHz 100 Figure 12.
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Initial Power Up and Test www.ti.com -30 -35 HD2 Gain - dB -40 -45 HD3 -50 -55 -60 -65 1 10 f - Frequency - MHz 100 Figure 13. Harmonic Distortion for TSW7001 in 40-dB Gain Mode 8 Initial Power Up and Test Plug in the 6-V power supply. This lights up the power LED D18. Plug in the USB cable, and connect it to the PC. Allow a few seconds for the USB to register and enumerate. Once the computer has detected the TSW7001 EVM, then start the TSW7001 Control Panel GUI – refer to Section 5.
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Optional Configurations www.ti.com The high unity-gain-stable bandwidth and JFET input allows exceptional performance in high-speed, low-noise integrators. The high-input impedance and low-bias current provided by the FET input is supported by the ultra-low, 7-nV/Hz, input voltage noise to achieve a low integrated noise in wideband photodiode transimpedance applications. Broad transimpedance bandwidths are achievable given the OPA656’s high 230-MHz-gain bandwidth product.
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Bill of Materials and Schematics 10 www.ti.com Bill of Materials and Schematics This section contains the bill of materials and schematics for the TSW7001EVM. Table 2. Bill of Materials QTY 16 Part Reference Value PCB Footprint Mfr_Name Mfr_Part_No. 1 C37 2.2 µF 1206 Murata GRM31MR71C225KA3 5L 2 C38 C39 2.2 µF TANT_A ROHM TCA1C225M8R 3 C56 C79 C124 0.01 µF 0603 Panasonic ECJ-1VB1C103K 10 C57 C61 C65 C66 C69 C100 C131 C149 C168 C352 0.
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Bill of Materials and Schematics www.ti.com Table 2. Bill of Materials (continued) QTY Part Reference Value PCB Footprint Mfr_Name Mfr_Part_No.
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J26 IN SMA END 4 3 2 5 1 0 R119 3 1 TP15 (SHUNT 1-2) 2 SJP5 0 R121 4 C73 1500pF U19 -VS 6 C65 .1uF +5VA VR1 LM285-1.2 + R120 0 R85 250K +5VA OPA656 OUT +VS -V_AMP 3 IN+ 2 IN20pF C72 7 +V_AMP 50K R290 0.6pF C350 2 Voltage-Controlled Amplifier Evaluation Kit 3 1.2V 2 C69 .
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SLWU058 – August 2008 Submit Documentation Feedback GND1 VCC -DATA +DATA GND2 GND 1 2 3 4 USB_B_S_F_B_TH 6 5 J13 USB_CONN C59 47pF FB4 C60 47pF 68 OHM @ 100MHz C56 .01uF C57 .1uF C61 .1uF + C58 4.7uF 20V 25 7 18 21 26 17 28 27 24 19 8 4 15 16 20 FT245RL AGND GND GND GND TEST WR RD TXE RXF D7 D6 D5 D4 D3 D2 D1 D0 PWREN U5 3V3OUT OSCO OSCI NC2 RESET NC1 VCCIO USBDP USBDM VCC 22.1 22.1 22.1 R79 R97 10 12 14 13 22 23 6 2 R89 22.1 9 11 R84 22.
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-5V + C126 10uF 10V C80 10uF 10V +5VA 68 OHM @ 100MHz FB13 68 OHM @ 100MHz FB7 C92 .01uF C37 2.2uF C125 1uF 20% 25V C78 1uF 20% 25V 2 3 5 +V_AMP C124 .01uF TP3 +V_AMP Z_SCREW1 D20 20V, 1A MBR120LSFT1 100uH L9 C62 100uF + 20% 10V LOW ESR + VSENSE 1 2 3 4 5 6 7 8 9 10 Z_STANDOFF2 STANDOFF ALUM HEX 4-40 x .500 STANDOFF ALUM HEX 4-40 x .500 SCREW PANHEAD 4-40 x 3/8 Z_SCREW2 STANDOFF ALUM HEX 4-40 x .
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References www.ti.com U15 C163 10uF 10% 16V LOW ESR + TP14 3.3V 20 19 18 17 16 15 14 13 12 11 21 R83 R118 100K 0 +3.3V_LOGIC FB26 68 OHM @ 100MHz + LOW ESR C164 10uF + 10% 16V TPS76733QPWP C169 47uF 20% 10V + C170 10uF 10% 16V 1 GND/HTSNK1 GND/HTSNK2 GND GND/HTSNK8 NC1 GND/HTSNK7 EN NC4 IN1 NC3 IN2 RESET NC2 FB/NC GND/HTSNK3 OUT2 GND/HTSNK4 OUT1 GND/HTSNK6 GND/HTSNK5 PWRPAD 2 +6.0VDC 1 2 3 4 5 6 7 8 9 10 C168 .1uF 10% 16V +6.0VDC J12 FB16 1 2 3 68 OHM @ 100MHz R117 300 J24 +6.
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EVALUATION BOARD/KIT IMPORTANT NOTICE Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY and is not considered by TI to be a finished end-product fit for general consumer use. Persons handling the product(s) must have electronics training and observe good engineering practice standards.
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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.