关于AD的一些术语

 

 

TERMINOLOGY<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

Integral Nonlinearity Error (INL)

Linearity error refers to the deviation of each individual code from a line drawn from negative full scale through positive full scale. The point used as negative full scale occurs ? LSB before the first code transition. Positive full scale is defined as a level 1? LSB beyond the last code transition. The deviation is measured from the middle of each code to the true straight line.

 

Differential Nonlinearity Error (DNL)

In an ideal ADC, code transitions are 1 LSB apart. Differential nonlinearity is the maximum deviation from this ideal value. It is often specified in terms of resolution for which no missing codes are guaranteed.

 

Full-Scale Error

The last transition (from 111. . .10 to 111. . .11) should occur  for an analog voltage 1? LSB below the nominal full scale (4.999886 V for the 0 V to 5 V range). The full-scale error is the deviation of the actual level of the last transition from the ideal level.

 

Unipolar Zero Error

The first transition should occur at a level ? LSB above analog ground (76.29 μV for the 0 V to 5 V range). The unipolar zero error is the deviation of the actual transition from that point.

 

Signal-to-Noise Ratio (SNR)

SNR is the ratio of the rms value of the actual input signal to the rms sum of all other spectral components below the Nyquist frequency, excluding harmonics and dc. The value for SNR is expressed in decibels.

 

Total Harmonic Distortion (THD)

THD is the ratio of the rms sum of the first five harmonic components to the rms value of a full-scale input signal and is expressed in decibels.

 

Signal-to-Noise and Distortion Ratio (SINAD)

SINAD is the ratio of the rms value of the actual input signal to the rms sum of all other spectral components below the Nyquist frequency, including harmonics but excluding dc. The value for SINAD is expressed in decibels.

 

<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Spurious-Free DynamicRange (SFDR)

The difference, in decibels, between the rms amplitude of the input signal and the peak spurious signal.

 

Effective Number of Bits (ENOB)

ENOB is a measurement of the resolution with a sine wave input. It is related to SINAD and expressed in bits by

ENOB = ((SINADdB ? 1.76)/6.02)

and is expressed in bits.

 

Aperture Delay

Aperture delay is a measure of acquisition performance and is measured from the falling edge of the CNVST input to when the input signals are held for a conversion.

 

Transient Response

The time required for the AD to achieve its rated accuracy after a full-scale step function is applied to its input.
 
 
P.S.: Quote from Analog Devices' datasheet.  引自AD公司的数据手册