AN67-1 Application Note 67
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Application Note 67 September 1996 Linear Technology Magazine Circuit Collection, Volume III Data Conversion, Interface and Signal Processing Richard Markell, Editor INTRODUCTION Application Note 67 is a collection of circuits from the first differential, 8-channel, 12-bit A/D system. The categories five years of Linear Technology, targeting data conversion, included herein are data conversion, interface, filters, interface and signal processing applications. This instrumentation, video/op amps and miscellaneous Application Note includes circuits such as fast video circuits. Application Note 66, which covers power products multiplexers for high speed video, an ultraselective and circuits from Linear Technology’s first five years, is bandpass filter circuit with adjustable gain and a fully also available from LTC. ARTICLE INDEX Data Conversion ........................................................................................................... 3 Fully Differential, 8-Channel, 12-Bit A/D System Using the LTC®1390 and LTC1410 ......................................... 3 12-Bit DAC Applications ..................................................................................................................................... 5 LTC1329 Micropower, 8-Bit, Current Output DAC Used for Power Supply Adjustment, Trimmer Pot Replacement ................................................................................................................................. 7 12-Bit Cold Junction Compensated, Temperature Control System with Shutdown ............................................ 8 A 12-Bit Micropower Battery Current Monitor .................................................................................................... 9 Interface ................................................................................................................... 10 V.35 Transceivers Allow 3-Chip V.35 Port Solution ......................................................................................... 10 Switching, Active GTL Terminator .................................................................................................................... 12 RS232 Transceivers for DTE/DCE Switching .................................................................................................... 14 Active Negation Bus Terminators ..................................................................................................................... 16 RS485 Repeater Extends System Capability..................................................................................................... 18 An LT®1087-Based 1.2V GTL Terminator ......................................................................................................... 19 LTC1145/LTC1146 Achieve Low Profile Isolation with Capacitive Lead Frame................................................. 19 LTC485 Line Termination ................................................................................................................................. 21 Filters ...................................................................................................................... 22 Sallen and Key Filters Use 5% Values .............................................................................................................. 22 Low Power Signal Detection in a Noisy Environment ....................................................................................... 25 Bandpass Filter Has Adjustable Q ..................................................................................................................... 28 An Ultraselective Bandpass Filter with Adjustable Gain .................................................................................... 30 LT1367 Builds Rail-to-Rail Butterworth Filter ................................................................................................... 32 DC Accurate, Clock Tunable Lowpass Filter with Input Antialiasing Filter......................................................... 33 The LTC1066-1 DC Accurate Elliptic Lowpass Filter ......................................................................................... 35 Clock Tunable Bandpass Filter Operates to 160kHz in Single Supply Systems................................................. 37 A Linear Phase Bandpass Filter for Digital Communications ............................................................................ 39 , LTC and LT are registered trademarks of Linear Technology Corporation. AN67-1 Application Note 67 Instrumentation ........................................................................................................... 41 Wideband RMS Noise Meter ............................................................................................................................ 41 LTC1392 Micropower Temperature and Voltage Measurement Sensor ........................................................... 45 Humidity Sensor to Data Acquisition System Interface .................................................................................... 46 A Single Cell Barometer.................................................................................................................................... 48 Noise Generators for Multiple Uses—A Broadband Random Noise Generator................................................. 49 Noise Generators for Multiple Uses—A Diode Noise Generator for “Eye Diagram” Testing ............................. 52 Video/Op Amps............................................................................................................ 53 LT1251 Circuit Smoothly Fades Video to Black ................................................................................................ 53 Luma Keying with the LT1203 Video Multiplexer ............................................................................................. 54 LT1251/LT1256 Video Fader and DC Gain Controlled Amplifier ....................................................................... 56 Extending Op Amp Supplies to Get More Output Voltage ................................................................................. 58 Using Super Op Amps to Push Technological Frontiers: An Ultrapure Oscillator ............................................. 62 Fast Video MUX Uses LT1203/LT1205 ............................................................................................................. 66 Using a Fast Analog Multiplexer to Switch Video Signals for NTSC “Picture-in-Picture” Displays ................... 67 Applications for the LT1113 Dual JFET Op Amp............................................................................................... 69 LT1206 and LT1115 Make Low Noise Audio Line Driver.................................................................................. 70 Driving Multiple Video Cables with the LT1206 ................................................................................................ 71 Optimizing a Video Gain Control Stage Using the LT1228................................................................................ 72 Differential Gain and Phase .............................................................................................................................. 74 LT1190 Family Ultrahigh Speed Op Amp Circuits............................................................................................. 75 An LT1112 Dual Output Buffered Reference..................................................................................................... 78 Three Op Amp Instrumentation Amp Using the LT1112/LT1114...................................................................... 79 Ultralow Noise Three Op Amp Instrumentation Amplifier ................................................................................. 80 A Temperature Compensated, Voltage Controlled Gain Amplifier Using the LT1228........................................ 80 The LTC1100, LT1101 and LT1102: A Trio of Effective Instrumentation Amplifiers ......................................... 83 Miscellaneous Circuits .................................................................................................. 86 Driving a High Level Diode Ring Mixer with an Operational Amplifier .............................................................. 86 AN67-2 Application Note 67 Data Conversion FULLY DIFFERENTIAL, 8-CHANNEL, 12-BIT A/D combined with the LTC1390 8-channel serial interfaced SYSTEM USING THE LTC1390 AND LTC1410 analog multiplexer to create a differential ADC system with by Kevin R. Hoskins conversion throughput rates up to 625ksps. This rate applies to situations where the selected channel changes The LTC1410’s fast 1.25Msps conversion rate and differ- ± with each conversion. The conversion rate increases to ential 2.5V input range make it ideal for applications that 1.25Msps if the same channel is used for consecutive require multichannel acquisition of fast, wide bandwidth conversions. signals. These applications include multitransducer vibra- tion analysis, race vehicle telemetry data acquisition and Figure 1 shows the complete differential, 8-channel A/D multichannel telecommunications. The LTC1410 can be circuit. Two LTC1390s, U1 and U2, are used as noninvert- +5V –5V 0.1µF +CH0 S0 V+ U1 +CH1 S1 D LTC1390 0.1µF +CH2 S2 V– +AIN AVDD 10µF µ +CH3 S3 DATA2 0.1 F –AIN DVDD + +CH4 S4 DATA1 + VREF VSS µ µ µ µ +CH5 S5 CS 10 F0.1 F 0.1 F + 10 F REFCOMP BUSY +CH6 S6 CLK AGND CS +CH7 S7 GND D11 CONVST µP CONTROL U3 LINES D10 LTC1410 RD SERIAL DATA D9 SHDN CHIP