Mixed-Signal VLSI Design Course Code: EE719 Department: Electrical Engineering Lecture 19: February 15, 2018 Instructor Name: M. Shojaei Baghini E-Mail ID: mshojaei@ee.iitb.ac.in 1
2 2 Module 24 Performance Parameters of Data Converters - Part II β’ Chapter 5, the Data Conversion Handbook, Analog Devices, 2005. IIT-Bombay Lecture 19 M. Shojaei Baghini
3 3 Ideal Characteristics of DAC/ADC D : LSB size Starting from DAC 012 "#$_&'( = β + π - Γ2 - π DAC (I) -34 b i : bit # i Center point β’ Analog input range 1 LSB May be [-V FS /2,V FS /2]. ADC (II) Signed output code β’ may be used. IIT-Bombay Lecture 19 M. Shojaei Baghini
4 4 Classification Based on Sampling Rate β’ fs > 2f max (Nyquist rate sampling) β "Nyquist Convertersβ (fs /f max > 2 but not much higher than 2) β It requires high-performance anti-aliasing filtering. β’ fs >> 2f max Oversampling (Oversampled converters) β Simple anti-aliasing filter and smoothing filter is often enough. β Oversampling reduces quantization noise. β’ fs < 2f max (Undersampling or sub-sampling) Useful for signals of which power is concentrated in a narrow band around a frequency. IIT-Bombay Lecture 19 M. Shojaei Baghini
5 5 Common Performance Measures Static Measures β’ Monotonicity β’ Offset β’ Full-scale gain error and gain error β’ Diff. nonlinearity (DNL) (mainly for Nyquist converters) β’ Integral nonlinearity (INL) (mainly for Nyquist converters) Dynamic Measures β’ Delay, settling time β’ Aperture uncertainty β’ Distortion- harmonic content β’ Signal-to-(noise and distortion) ratio (SNDR) β’ Idle channel noise β’ Spurious-free dynamic range (SFDR) IIT-Bombay Lecture 19 M. Shojaei Baghini
6 6 Module 25 Offset and Gain Error in Data Converters β’ Chapter 5, the Data Conversion Handbook, Analog Devices, 2005. β’ Full speed testing of A/D Converters, J. Doernberg, et al. , IEEE JSSC , December 1984. IIT-Bombay Lecture 19 M. Shojaei Baghini
7 7 Static Specifications Offset Error (Zero Scale Error) Center point 1 LSB Offset error is the shift of the first transition point. Similar notion for full scale error β’ IIT-Bombay Lecture 19 M. Shojaei Baghini
8 8 Static Specifications - Concept of Gain Connecting center of segments will not results in a line. IIT-Bombay Lecture 19 M. Shojaei Baghini
9 9 Static Specifications β Simple Definition of Gain Error for DAC Gain error (in units of LSB) = V 111 / (V FS β 1 LSB) - 1 Source: The data conversion handbook, Analog Devcies, 2005 IIT-Bombay Lecture 19 M. Shojaei Baghini
10 10 Module 26 DNL and INL in Data Converters β’ Chapter 5, the Data Conversion Handbook, Analog Devices, 2005. β’ Full speed testing of A/D Converters, J. Doernberg, et al. , IEEE JSSC , December 1984. IIT-Bombay Lecture 19 M. Shojaei Baghini
11 11 Static Specifications Differential Nonlinearity (DNL) of DAC Variation of LSB with the code results in nonlinearity: SQNR degradation β’ Source: The data conversion handbook, Analog Devices, 2005 IIT-Bombay Lecture 19 M. Shojaei Baghini
12 12 Static Specifications Differential Nonlinearity (DNL) of ADC DNL min : -1 LSB. Source: The data conversion handbook, Analog Devices, 2005 IIT-Bombay Lecture 19 M. Shojaei Baghini
13 13 Static Specifications Integrated Nonlinearity (INL) of DAC 7 5 3 1 Source: The data conversion handbook, Analog Devices, 2005 IIT-Bombay Lecture 19 M. Shojaei Baghini
14 14 Static Specifications Integrated Nonlinearity (INL) of ADC Variation of transition points Understanding Data Converters, TI, 1995 IIT-Bombay Lecture 19 M. Shojaei Baghini
15 15 End of Lecture 19 IIT-Bombay Lecture 19 M. Shojaei Baghini
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