AD7682 datasheet(13/28 Pages) AD

13 / 28 page

AD7949

Rev. A | Page 13 of 28

TERMINOLOGY

Least Significant Bit (LSB)

The LSB is the smallest increment that can be represented by a

converter. For an analog-to-digital converter with N bits of

resolution, the LSB expressed in volts is

REF

LSB

(V)

Integral Nonlinearity Error (INL)

INL 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 (see Figure 24).

Differential Nonlinearity Error (DNL)

In an ideal ADC, code transitions are 1 LSB apart. DNL is the

maximum deviation from this ideal value. It is often specified in

terms of resolution for which no missing codes are guaranteed.

Offset Error

The first transition should occur at a level ½ LSB above analog

ground. The unipolar offset error is the deviation of the actual

transition from that point.

Gain Error

The last transition (from 111 … 10 to 111 … 11) should occur

for an analog voltage 1½ LSB below the nominal full scale. The

gain error is the deviation in LSB (or percentage of full-scale

range) of the actual level of the last transition from the ideal

level after the offset error is adjusted out. Closely related is the

full-scale error (also in LSB or percentage of full-scale range),

which includes the effects of the offset error.

Aperture Delay

Aperture delay is the measure of the acquisition performance. It

is the time between the rising edge of the CNV input and the

point at which the input signal is held for a conversion.

Transient Response

Transient response is the time required for the ADC to accurately

acquire its input after a full-scale step function is applied.

Dynamic Range

Dynamic range is the ratio of the rms value of the full scale to

the total rms noise measured with the inputs shorted together.

The value for dynamic range is expressed in decibels.

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.

Signal-to-(Noise + 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.

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.

Spurious-Free Dynamic Range (SFDR)

SFDR is 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 by the formula

ENOB = (SINADdB − 1.76)/6.02

and is expressed in bits.

Channel-to-Channel Crosstalk

Channel-to-channel crosstalk is a measure of the level of

crosstalk between any two adjacent channels. It is measured by

applying a dc to the channel under test and applying a full-scale,

100 kHz sine wave signal to the adjacent channel(s). The

crosstalk is the amount of signal that leaks into the test channel

and is expressed in decibels.

Reference Voltage Temperature Coefficient

Reference voltage temperature coefficient is derived from the

typical shift of output voltage at 25°C on a sample of parts at the

maximum and minimum reference output voltage (V

) meas-

ured at T

, T (25°C), and T

. It is expressed in ppm/°C as

REF

MIN

MAX

)

–

(

)

(

)

(

–

)

(

)

ppm/

(

MIN

MAX

REF

Min

Max

TCV

where:

VREF (Max) = maximum VREF at TMIN, T (25°C), or TMAX.

VREF (Min) = minimum VREF at TMIN, T (25°C), or TMAX.

VREF (25°C) = VREF at 25°C.

TMAX = +85°C.

TMIN = –40°C.

AD7682 Datasheet(PDF) 13 Page - Analog Devices

AD7682 Datasheet(HTML) 13 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL