AD4134 datasheet(27/92 Pages) AD

27 / 92 page

Data Sheet

AD4134

TERMINOLOGY

analog.com

Rev. 0 | 27 of 92

AC Common-Mode Rejection Ratio (CMRR)

AC CMRR is defined as the ratio of the power in the ADC output at

frequency, f, to the power of a 100 mV p-p sine wave applied as the

common-mode voltage to the AINx+ pin and AINx− pin at sampling

frequency (fS).

AC CMRR (dB) = 10 log(Pf/PfS)

where:

Pf is the power at frequency, f, in the ADC output.

PfS is the power at frequency, fS, in the ADC output.

Integral Nonlinearity (INL) Error

INL 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 ½ LSB before the first code

transition. Positive full scale is defined as a level 1½ LSB beyond

the last code transition. The deviation is measured from the middle

of each code to the true straight line.

Intermodulation Distortion

With inputs consisting of sine waves at two frequencies, fa and fb,

any active device with nonlinearities creates distortion products at

the sum and difference frequencies of mfa and nfb, where m, n =

0, 1, 2, 3, and so on. Intermodulation distortion terms are those for

which neither m nor n is equal to 0. For example, the second-order

terms include (fa + fb) and (fa − fb), and the third-order terms

include (2fa + fb), (2fa − fb), (fa + 2fb), and (fa − 2fb).

The AD4134 is tested using the International Telephonic Consulta-

tive Committee (CCIF) standard, where two input frequencies near

to each other are used. In this case, the second-order terms are

usually distanced in frequency from the original sine waves, and

the third-order terms are usually at a frequency close to the input

frequencies. As a result, the second-order and third-order terms

are specified separately. The calculation of the intermodulation

distortion is as per the THD specification, where it is the ratio of the

rms sum of the individual distortion products to the rms amplitude of

the sum of the fundamentals expressed in decibels.

Gain Error

The first transition (from 100 … 000 to 100 …001) occurs at a level

½ LSB above nominal negative full scale (−4.095999755859375 V

for the ±4.096 V range). The last transition (from 011 … 110 to

011 … 111) occurs for an analog voltage 1½ LSB below the nominal

full scale (+4.095999755859375 V for the ±4.096 V range). The

gain error is the deviation of the difference between the actual level

of the last transition and the actual level of the first transition from

the difference between the ideal levels.

Gain Drift

Gain drift is the ratio of the gain error change due to a temperature

change of 1°C and the full-scale range (2N). Gain drift is expressed

in parts per million.

Least Significant Bit (LSB)

The least significant bit, or LSB, is the smallest increment that can

be represented by a converter. For a fully differential input ADC with

N bits of resolution, the LSB expressed in volts is

LSB=2×VREFCAP2N

where:

VREFCAP is the voltage measured on the REFCAP pin.

N = 24 for the AD4134.

DC Power Supply Rejection Ratio (DC PSRR)

Variations in power supply affect the full-scale transition but not the

linearity of the converter. DC PSRR is the maximum change in the

full-scale transition point due to a change in power supply voltage

from the nominal value.

AC Power Supply Rejection (AC PSR)

AC PSR is the amplitude of the tone observed when a 100 mV p-p

signal is injected on the supply.

For example, if a 100 mV p-p signal injected on the supply at a

frequency of 1 kHz and a −108 dB tone is observed at 1 kHz in the

FFT output, −108 dB is the ac power supply rejection.

Alias Rejection

Alias rejection is defined as the ratio of the power in the ADC

output at frequency, fIN, to the power of a −6 dBFS input signal at

frequency, MCLK ± fIN.

Alias rejection = 10 log(PfIN/PMCLK ± fIN)

where:

PfIN is the power at frequency, fIN, in the ADC output.

PMCLK ± fIN is the power at frequency, MCLK ± fIN, in the ADC

output.

Group Delay

Group delay is defined as the difference of phase delays measured

at the ADC output and full-scale sine wave ADC input.

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 ODR/2

frequency, excluding harmonics and dc. The value for SNR is

expressed in decibels.

Signal-to-Noise-and-Distortion (SINAD) Ratio

SINAD is the ratio of the rms value of the actual input signal to

the rms sum of all other spectral components below the ODR/2

frequency, including harmonics but excluding dc. The value for

SINAD is expressed in decibels.

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