TI THS7314视频放大器应用方案

       TI 公司THS7314/5/6三路视频放大器采用3V-5V电源,轨到轨输出,可以AC耦合,也可以DC耦合.每一路可驱动两条视频线,或75欧姆负载.它还集成了5阶Butterworth滤波器,可以用作DAC的重建滤波器,或作为ADC的抗混淆滤波器.8.5MHz滤波器非常适合SDTV视频应用.本文介绍了THS7314/5/6三路视频放大器的主要性能,方框图及其评估板THS7315EVM的性能介绍,电路图以及所用的材料清单(BOM).

       The THS7314, THS7315 and THS7316 offer design flexibility as the inputs can be configured for either AC- or DC-coupled applications. In addition, unlike typical solutions, the family can support a single 3-V to 5-V supply, eliminating the need for a separate 5-V supply. The devices rail-to-rail output allows AC- or DC-output coupling so that designers can use 3.3-V supply without headroom issues. The ability for each channel to drive two video lines, or 75-ohms loading, allows for maximum flexibility as a video line driver.

       Fabricated using the revolutionary complementary silicon-sermanium (SiGe) BiCom3 process, the THS7315 is a low-power, single-supply, 3-V to 5-V 3-channel integrated video buffer. It incorporates a 5th-order Butterworth filter that is useful as a digital-to-analog converter (DAC) reconstruction filter or an analog-to-digital converter (ADC) anti-aliasing filter. The 8.5-MHz filter is a perfect choice for SDTV video, including Composite Video Baseband Signals (CVBS), S-Video, Y’U’V’, G’B’R’ (R’G’B’), and Y’P’BP’R 480i/576i.

       The THS7315 inputs can be either ac- or dc-coupled. The 230-mV output level shift allows for a full sync dynamic range at the output with 0 V input. The ac-coupled modes include a transparent sync-tip clamp option for CVBS, Y, and GBR signals with bottom-level sync. AC-coupled biasing for C/PB/PR channels can easily be achieved by adding an external resistor to VS+.

       The THS7315 is the perfect choice for all output buffer applications. Its rail-to-rail output stage with 5.2-V/V gain allows for both ac and dc line driving, making it a perfect choice for DaVinci processors. The ability for each channel to drive two video lines, or 75-ohm loading, allows for maximum flexibility as a video line driver. The 15.6-mA quiescent current at 3.3 V also makes it an excellent choice for USB-powered, portable, or other power-sensitive video applications
The THS7315 is available in a small SOIC-8 package that is lead-free and compliant with green requirements.

       主要特性:

       Three SDTV Video Amplifiers for CVBS, S-Video, YPBPR 480i/576i, YUV, or GBR (RGB)
Integrated Low-Pass Filters:
5th-Order, 8.5-MHz (-3dB) Butterworth
-1dB Passband Bandwidth at 7 MHz
47 dB Attenuation at 27 MHz
Versatile Input Biasing:
DC-Coupled with 230-mV Output Shift
AC-Coupled with Sync-Tip Clamp
Allows AC-Coupled With DC-Biasing
Built-in 5.2 V/V Gain (14.3 dB)
+3-V to +5-V Single Supply Operation
Rail-to-Rail Output:
Output Swings Within 100 mV of the Rails, Allowing AC- or DC-Output Coupling
Supports Driving Two Lines per Channel
Low Total Quiescent Current: 15.6 mA at 3.3 V
Low Differential Gain/Phase of 0.2%/0.3°
Lead-free, Green SOIC-8 Package
APPLICATIONS
Set Top Box Output Video Buffering
PVR/DVDR Output Buffering
USB/Portable Low-Power Video Buffering

       下图为放大器的方框图.

       THS7315EVM评估板性能介绍:
The THS7315EVM is an evaluation module for the THS7315 in the D (8-lead SOIC) package.

The THS7315EVM is designed to demonstrate the functionality and versatility of the THS7315. The EVM is ready for power, signal source, and test instruments. The EVM is configured with 75 ohm input and output termination.

       评估板主要特性:
Configured with 75 ohms input/output impedance
Single Supply: +3 V to +5 V
Connectors: Vs+, GND, INPUT, OUTPUT and test points
Input and Output signals are via RCA and BNC connectors

上图是THS7315D EVM 电路图

       THS7315EVM 材料清单(BOM):

http://focus.ti.com/lit/ds/symlink/ths7315.pdf

本文来源：TI公司    作者：

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