AD7679 datasheet(7/20 Pages) AD

7 / 20 page

REV. B

AD7676

–7–

DEFINITION OF SPECIFICATIONS

Integral Nonlinearity Error (INL)

Integral nonlinearity is the maximum deviation of a straight line

drawn through the transfer function of the actual ADC. The

deviation is measured from the middle of each code.

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 011 ... 10 to 011 . . . 11 in twos comple-

ment coding) should occur for an analog voltage 1 1/2 LSB below

the nominal +full scale (+2.499886 V for the

±2.5 V range). The

+full-scale error is the deviation of the actual level of the last

transition from the ideal level.

–Full-Scale Error

The first transition (from 100 ... 00 to 100 . . . 01 in twos comple-

ment coding) should occur for an analog voltage 1/2 LSB above

the nominal –full scale (–2.499962 V for the

±2.5 V range). The

–full-scale error is the deviation of the actual level of the last

transition from the ideal level.

Bipolar Zero Error

The bipolar zero error is the difference between the ideal midscale

input voltage (0 V) and the actual voltage producing the midscale

output code.

Spurious-Free Dynamic Range (SFDR)

The difference, in decibels (dB), 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 S/(N+D) by the following formula:

ENOB

[]

()

/– .

/ .

176

6 02

and is expressed in bits.

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 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 (dB).

Signal-to-(Noise + Distortion) Ratio (S/[N+D])

S/(N+D) 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 S/(N+D) is expressed in decibels (dB).

Aperture Delay

Aperture delay is a measure of the acquisition performance and

is measured from the falling edge of the

CNVST input to when

the input signal is held for a conversion.

Transient Response

The time required for the AD7676 to achieve its rated accuracy

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

PIN CONFIGURATION

13 14 15 16 17 18 19 20 21 22 23 24

48 47 46 45 44

39 38 37

43 42 41 40

PIN 1

IDENTIFIER

TOP VIEW

(Not to Scale)

AGND

CNVST

RESET

DGND

AGND

AVDD

BYTESWAP

OB/

NC = NO CONNECT

SER/

PAR

D2/DIVSCLK[0]

BUSY

D15

D14

D13

AD7676

D3/DIVSCLK[1]

D12

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