Mixed-Signal VLSI Design Course Code: EE719 Department: Electrical - PowerPoint PPT Presentation

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 • 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 "#$_&'( = ∆ + 𝑐 - ×2 - 𝑊 DAC (I) -34 b i : bit # i Center point • Analog input range 1 LSB May be [-V FS /2,V FS /2]. ADC (II) Signed output code • may be used. IIT-Bombay Lecture 19 M. Shojaei Baghini

4 4 Classification Based on Sampling Rate • fs > 2f max (Nyquist rate sampling) – "Nyquist Converters“ (fs /f max > 2 but not much higher than 2) – It requires high-performance anti-aliasing filtering. • fs >> 2f max Oversampling (Oversampled converters) – Simple anti-aliasing filter and smoothing filter is often enough. – Oversampling reduces quantization noise. • 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 • Monotonicity • Offset • Full-scale gain error and gain error • Diff. nonlinearity (DNL) (mainly for Nyquist converters) • Integral nonlinearity (INL) (mainly for Nyquist converters) Dynamic Measures • Delay, settling time • Aperture uncertainty • Distortion- harmonic content • Signal-to-(noise and distortion) ratio (SNDR) • Idle channel noise • Spurious-free dynamic range (SFDR) IIT-Bombay Lecture 19 M. Shojaei Baghini

6 6 Module 25 Offset and Gain Error in Data Converters • Chapter 5, the Data Conversion Handbook, Analog Devices, 2005. • 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 • 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 – Simple Definition of Gain Error for DAC Gain error (in units of LSB) = V 111 / (V FS – 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 • Chapter 5, the Data Conversion Handbook, Analog Devices, 2005. • 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 • 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