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## PowerPoint Slideshow about 'Mixed Signal VLSI' - garima

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Presentation Transcript

Outline

Test methods

1. Static test - SIN Histogram

i.e. Gain and Offset

2. Dynamic test –

i.e. ENOB using 16K FFT

SIN fit.

Does this make sense??

- Static Tests
- Number of digitized bits
- Gain
- Offset
- Differential Nonlinearity (DNL)
- Integral Nonlinearity (INL)
- Monotonicity

- Dynamic Tests
- Effective number of bits (ENOB)
- Signal-to-noise ration (SNR)
- Total Harmonic distortion (THD)
- Total spurious distortion (TSD)
- Spurious-free dynamic range (SFDR)

Static Test

- Objective:
- Converter accuracy
- Transfer function of the converter
- Monotonicity of the converter
- Quantify the gain, offset, DNL and INL of the converter

- Disadvantage:
- Nonlinearites which coupled to the input signal bandwidth cannot be revealed
- For high bit converters, measurement is lengthy

Test Setup

Pattern generator -

Period jitter (peak to peak)

less than

Logic Analyzer -

Word length > N

Word depth > > 20π*2N

Clock

Digital

Analog

Source generator-

Resolution N +3 bits

Digital

Digital Control

fB is the input signal frequency

N is the ADC resolution

Ramp???? test setup

- Each voltage step less or equal to 1/8 LSB
- At lest 10 samples sampled at each voltage level

Static Test

Transfer function described as below

Using conventional linear least-squares estimation techniques, get G and Vos as below

G is the Gain

Vos is the offset

T1 is the ideal value corresponding to T[1]

T[k] is the input value

Q is the ideal width of a code bin

ε[k] is the residual error

ADC static test result

Static Test

Illustration of DNL and INL

Static Test The maximum INL is the maximum value of |INL[k]| for all k.

Integral nonlinearity

- Where
- INL(k) is the integral nonlinearity at output code k,
- ε[k] is the difference between ideal output bin T’[k] and T[k] computed from G and Vos,
- that is,

- Q is the ideal code bin width, expressed in input units,
- VFS is the full-scale range of the ADC in input units.

Too many different fonts

Harmonic and spurious distortion information

Input bandwidth

Signal-to-noise ratio

Effective number of bits (ENOB)

Spurious-free dynamic range (SFDR)

Dynamic Test

Think about the consistency with slide 4

Cannot test for monotonicity of the ADC

Input signal must be sampled using an integer number of cycles

Histogram test measure the noise of the ADC

Test methods

Histogram test

FFT test

Dynamic TestWhat is the recommended method for measuring the noise of an ADC?

Dynamic Test

Pattern generator -

Period jitter (peak to peak)

less than

Logic Analyzer -

Word length > N

Word depth > 2π*2N ???

Clock

Digital

Analog

Source generator-

Resolution N +3 bits

Digital

fB is the input signal frequency

N is the ADC resolution

Test setup for histogram and FFT test

Histogram Test

- Record length selection
There must be an exact integer number of cycles in a record, and the number of cycles in a record must be relatively prime to the number of samples in the record.

fi is the input signal frequency

fs is the sampling signal frequency

J is the number of cycles per record

M is a record length

Histogram Test cont’

The procedure to find the near-optimum input signal frequency

- Find an integer, r, such that the desired frequency is approximately fs/r.
- Let J equal the number of full cycles that can be recorded at the frequency in step a)
J=int(M/r)

- Let fi equal

a) b) etc are NOT consistent with the rest of the ppt slides

Histogram Test cont’

Review SIN reconstruction after this slide

Illustration of histogram test results

FFT Test

Too Many Fonts

- Total harmonic distortion

The THD is also often expressed as a dB ratio with respect to rms amplitude of the fundamental component of the output,

FFT Test

Too Many Fonts

- Total spurious distortion
Each of the spurious frequencies in fsp is the frequency of a persistent spectral output component that is neither the fundamental nor a harmonic distortion component.

FFT Test

- Spurious-free dynamic range (SFDR)
- The ratio of the amplitude of the ADC output averaged spectral component at the input frequency, fi, to the amplitude of the largest harmonic or spurious spectral component observed over the full Nyquist band:

- Where
- Xavg is the averaged spectrum of the ADC output,
- fi is the input signal frequency,
- fs and fh are the frequencies of the set of harmonic and spurious spectral components

FFT Test

Spectrum of a sine wave and its harmonics

FFT Test

Fundamental

frequency

Harmonics

Spurious frequency

SFDR

Spectrum of a real ADC FFT test result

SINAD is the ration of the signal to the total noise

Time domain calculation

Signal-to-noise and distortion ratio (SINAD)Signal-to-noise and distortion ratio (SINAD) cont’

- Effective number of bits (ENOB)

Where

A is the amplitude of the sine wave fitted to the output

V is the full-scale range of the ADC under test

Summary Must follow

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