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

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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

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Module 24 Performance Parameters of Data Converters - Part II

• Chapter 5, the Data Conversion Handbook,

Analog Devices, 2005.

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Ideal Characteristics of DAC/ADC

1 LSB Center point ADC (II) DAC (I)

D: LSB size

• Analog input range

May be [-VFS/2,VFS/2].

• Signed output code

may be used. Starting from DAC 𝑊

"#$_&'( = ∆ + 𝑐-×2- 012

• 34

bi: bit # i

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Classification Based on Sampling Rate

• fs > 2fmax (Nyquist rate sampling)

– "Nyquist Converters“ (fs /fmax > 2 but not much higher than 2) – It requires high-performance anti-aliasing filtering.

• fs >> 2fmax Oversampling (Oversampled converters)

– Simple anti-aliasing filter and smoothing filter is often enough. – Oversampling reduces quantization noise.

• fs < 2fmax (Undersampling or sub-sampling)

Useful for signals of which power is concentrated in a narrow band around a frequency.

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IIT-Bombay Lecture 19 M. Shojaei Baghini

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)

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IIT-Bombay Lecture 19 M. Shojaei Baghini

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.

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications Offset Error (Zero Scale Error)

1 LSB Center point

Offset error is the shift of the first transition point.

• Similar notion for full scale error

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications - Concept of Gain Connecting center of segments will not results in a line.

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications – Simple Definition of Gain Error for DAC Gain error (in units of LSB) = V111 / (VFS – 1 LSB) - 1

Source: The data conversion handbook, Analog Devcies, 2005

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IIT-Bombay Lecture 19 M. Shojaei Baghini

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.

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications Differential Nonlinearity (DNL) of DAC

Source: The data conversion handbook, Analog Devices, 2005

• Variation of LSB with the code results in nonlinearity: SQNR degradation

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications Differential Nonlinearity (DNL) of ADC

Source: The data conversion handbook, Analog Devices, 2005

DNLmin: -1 LSB.

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications Integrated Nonlinearity (INL) of DAC

Source: The data conversion handbook, Analog Devices, 2005

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IIT-Bombay Lecture 19 M. Shojaei Baghini

Static Specifications Integrated Nonlinearity (INL) of ADC

Understanding Data Converters, TI, 1995

Variation of transition points

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IIT-Bombay Lecture 19 M. Shojaei Baghini

End of Lecture 19