REV. 0

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 two’s

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

below the nominal +full scale (+2.499886 V for the

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 two’s

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

above the nominal –full scale (–2.499962 V for the

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

S

N

D

dB

=+

[]

()

/– .

/ .

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.

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.

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

48-Lead LQFP

(ST-48)

36

35

34

33

32

31

30

29

28

27

26

25

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

1

2

3

4

5

6

7

8

9

10

11

12

48 47 46 45 44

39 38 37

43 42 41 40

PIN 1

IDENTIFIER

TOP VIEW

(Not to Scale)

AD7676

AGND

CNVST

PD

RESET

CS

RD

DGND

AGND

AVDD

NC

BYTESWAP

OB/

2C

NC

NC

NC = NO CONNECT

SEP/

PAR

D0

D1

D2/DIVSCLK[0]

BUSY

D15

D14

D13

D3/DIVSCLK[1]

D12