EE247 Lecture 12 Administrative issues Midterm exam Oct 20th o You can only bring one 8x11 paper with your own written notes please do not copy o No books class or any other kind of handouts notes calculators computers PDA cell phones o Midterm includes material covered to end of lecture 14 EE247 final exam date has changed to December 13th 12 30 3 30 pm group 2 please check your other class finals to ensure no conflict EECS 247 Lecture 12 Data Converters 2005 H K Page 1 EE247 Lecture 12 Today Summary switched capacitor filters Comparison of various filter topologies Data converters EECS 247 Lecture 12 Data Converters 2005 H K Page 2 SC Filter Summary Pole and zero frequencies proportional to Sampling frequency fs Capacitor ratios High accuracy and stability in response Long time constants realizable without large R C Compatible with transconductance amplifiers Reduced circuit complexity power dissipation Amplifier bandwidth requirements less stringent compared to CT filters low frequencies only L Issue Sampled data filters require anti aliasing prefiltering EECS 247 Lecture 12 Data Converters 2005 H K Page 3 Summary Filter Performance versus Filter Topology Max Usable SNDR Bandwidth Freq tolerance w o tuning Freq tolerance tuning Opamp RC 10MHz 60 90dB 30 50 1 5 OpampMOSFET C 5MHz 40 60dB 30 50 1 5 Opamp 5MHz MOSFET RC 50 90dB 30 50 1 5 Gm C 100MHz 40 70dB 40 60 1 5 Switched Capacitor 10MHz 40 90dB 1 EECS 247 Lecture 12 Data Converters 2005 H K Page 4 Data Converters EECS 247 Lecture 12 Data Converters 2005 H K Page 5 Material Covered in EE247 Filters Continuous time filters Biquads ladder type filters Opamp RC Opamp MOSFET C gm C filters Automatic frequency tuning Switched capacitor SC filters Data Converters D A converter architectures A D converter Nyquist rate ADC Flash Pipeline ADCs Oversampled converters Self calibration techniques Systems utilizing analog digital interfaces Wireline communication systems ISDN XDSL Wireless communication systems Wireless LAN Cellular telephone Disk drive electronics Fiber optics systems EECS 247 Lecture 12 Data Converters 2005 H K Page 6 Data Converter Topics Basic Operation of Data Converters Uniform sampling and reconstruction Uniform amplitude quantization Characterization and Testing Common ADC DAC Architectures Selected Topics in Converter Design Practical Implementations Desensitization to Analog Circuit Non Idealities Figures of Merit and Performance Trends EECS 247 Lecture 12 Data Converters 2005 H K Page 7 Suggested Reference Texts R v d Plassche CMOS Integrated Analog to Digital and Digital to Analog Converters 2nd ed Kluwer 2003 B Razavi Data Conversion System Design IEEE Press 1995 S Norsworthy et al eds Delta Sigma Data Converters IEEE Press 1997 Extensive treatment of oversampled converters including stability tones bandpass converters J G Proakis D G Manolakis Digital Signal Processing Prentice Hall 1995 EECS 247 Lecture 12 Data Converters 2005 H K Page 8 Converter Applications EECS 247 Lecture 12 Data Converters 2005 H K Page 9 Example Typical Cell Phone Contains in integrated form 4 Rx filters 4 Tx filters 4 Rx ADCs 4 Tx DACs 3 Auxiliary ADCs 8 Auxiliary DACs Dual Standard I Q Audio Tx Rx power control Battery charge control display Total Filters 8 ADCs 7 DACs 12 EECS 247 Lecture 12 Data Converters 2005 H K Page 10 Data Converter Basics Analog Input DSP is wonderful but Real world signals are analog Continuous time Continuous amplitude DSP can only process Discrete time Discrete amplitude Need for data conversion from analog to digital and digital to analog EECS 247 Lecture 12 Data Converters Analog Preprocessing Filters A D Conversion DSP 000 001 110 D A Conversion Analog Postprocessing Filters Analog Output 2005 H K Page 11 A D D A Conversion A D Conversion D A Conversion EECS 247 Lecture 12 Data Converters 2005 H K Page 12 Data Converters Stand alone data converters Used in variety of systems Example Analog Devices AD9235 12bit 65Ms s ADC Applications Ultrasound equipment IF sampling in wireless receivers Hand held scopemeters Low cost digital oscilloscopes EECS 247 Lecture 12 Data Converters 2005 H K Page 13 Data Converters Embedded data converters Cost reliability and performance integration of data conversion interfaces along with DSPs Main challenges Feasibility of integrating sensitive analog functions in technologies optimized for digital performance Down scaling of supply voltage Interference spurious signal pick up from on chip digital circuitry Portable applications dictate low power consumption EECS 247 Lecture 12 Data Converters 2005 H K Page 14 D A Converter Transfer Characteristics N V0 VF S i 1 bi i 2 LSB MSB b1 b2 b3 For an ideal digital to analog converter with uniform binary digital encoding a unipolar output range from 0 to VFS bn V0 D A N bi 2 N i bi 0 o r 1 i 1 where N of bits VF S full s c a l e output LSB s t e p size V FS 2N Example N 3 V0 b1 22 b2 21 b3 20 N o t e V0 b i 1 a l l i VF S 1 VFS 1 2N EECS 247 Lecture 12 Data Converters 2005 H K Page 15 Ideal D A Transfer Characteristic Ideal DAC introduces no error One to one mapping from input to output VFS Analog Output Ideal Response VFS 2 Step Height 1LSB VFS 8 001 EECS 247 Lecture 12 Data Converters 010 011 100 101 110 111 Digital Input Code 2005 H K Page 16 A D Converter Transfer Characteristic For an ideal analog to digital converter with uniform binary digital encoding a unipolar input range for 0 to VFS LSB MSB b1 b2 b3 bm Vin A D where m of bits VFS full scale output s t e p size V FS 2m N o t e D bi 1 a l l i VF S 1 VF S 1 2m EECS 247 Lecture 12 Data Converters 2005 H K Page 17 Ideal A D Transfer Characteristic Ideal ADC introduces error max error 1 2 VFS 2m Digital Output 111 110 101 m of bits 100 This error is called quantization error 011 010 001 1LSB Analog input 000 EECS 247 Lecture 12 Data Converters 2 3 4 5 6 7 2005 H K Page 18 Data Converter Performance Metrics Data Converters are typically characterized by static time domain frequency domain performance metrics Static Monotonicity Offset Full scale error Differential nonlinearity DNL Integral nonlinearity INL Dynamic Delay settling time Aperture uncertainty Distortion harmonic content Signal to noise ratio SNR Signal to noise distortion ratio SNDR Idle channel noise Dynamic range spurious free dynamic range SFDR EECS 247 Lecture 12 Data Converters 2005 H K Page 19 What is a discrete time signal qA signal that changes only at discrete time instances qA continous time signal
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