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 - - PowerPoint PPT Presentation

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Mixed-Signal VLSI Design Course Code: EE719 Department: Electrical Engineering Lecture 18: February 13, 2018 Instructor Name: M. Shojaei Baghini E-Mail ID: mshojaei@ee.iitb.ac.in 1 2 2 Module 23 Performance Parameters of Data Converters

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Mixed-Signal VLSI Design Course Code: EE719 Department: Electrical Engineering Lecture 18: February 13, 2018

Instructor Name: M. Shojaei Baghini E-Mail ID: mshojaei@ee.iitb.ac.in

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IIT-Bombay Lecture 18 M. Shojaei Baghini

Module 23 Performance Parameters of Data Converters – Part I Reference

  • Understanding Data Converters, TI, 1995.
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IIT-Bombay Lecture 18 M. Shojaei Baghini

Bridge Between Analog and Digital Domains

Analog Domain Digital Domain Conditioning A/D Conversion D/A Conversion Smoothing and Equalization

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IIT-Bombay Lecture 18 M. Shojaei Baghini

Basic Metrics to Start with

l Full Scale Range l Resolution: Effective Number of Bits (ENOB) l Introduced Noise and Distortion: Signal to

Noise and Distortion Ratio

l Signal Bandwidth l Sampling Frequency

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IIT-Bombay Lecture 18 M. Shojaei Baghini

Assume N-point FFT of a sine wave test. If the fundamental frequency is in bin m and has amplitude Am then SNDR is given by the following relation.

Signal-to-Noise and Distortion Ratio (SNDR)

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IIT-Bombay Lecture 18 M. Shojaei Baghini

SFDR - Example

Source: Nicolas Gray, National Semiconductor, 2006 Noise floor

Note: The average value of the noise contained in each frequency bin of M-point FFT is 10 Β΄ log (M/2) dB below the total noise power.

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IIT-Bombay Lecture 18 M. Shojaei Baghini

Spurious-Free Dynamic Range (SFDR)

l In general dynamic range is the ratio of

largest absolute value of the signal to the smallest absolute value of the signal.

l Spurious-free dynamic range (SFDR) is

ratio of the input signal to the peak harmonic (or spurious) component.

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IIT-Bombay Lecture 18 M. Shojaei Baghini

Intermodulation Distortion (IMD)

l Most of signals contain many frequency components. l Non-linearity causes two or more signal frequencies to

produce intermodulation products.

Source: Analog Devices tutorial MT-053, 2009

Single tone SFDR Multi tone SFDR

Frequency Frequency

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IIT-Bombay Lecture 18 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

Type equation here.

π‘Š

123_567 = βˆ† : 𝑐<Γ—2< ?@A <BC

bi: bit # i

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IIT-Bombay Lecture 18 M. Shojaei Baghini

Quantization Error in Ideal ADC

D 𝑓Fπ‘ž 𝑓, 𝑒 𝑒𝑓 =

K @K

D 𝑓F 1 βˆ† 𝑒𝑓 = βˆ†F 12

βˆ†/F @βˆ†/F

( )

dB N q x SQNR V x V q

e rms FS rms N FS e

76 . 1 02 . 6 log 10 2 2 12 2 12

2 2 2 2 2 2

+ = Γ· Γ· ΓΈ ΓΆ Γ§ Γ§ Γ¨ Γ¦ = = Β΄ = D =

For a sinusoidal signal x(t) and approximate uniform distribution of qe.

Example: N=6 bits Þ SNR=37.9dB N=10 bits Þ SNR=62.0dB

… …

t qe(t)

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End of Lecture 18