AD872A Просмотр технического описания (PDF) - Analog Devices

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AD872A

Complete 12-Bit 10 MSPS Monolithic A/D Converter

Analog Devices 

AD872A

DEFINITIONS OF SPECIFICATIONS

LINEARITY 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

1/2 LSB before the first code transition. “Positive full scale” is

defined as a level 1 1/2 LSB beyond the last code transition.

The deviation is measured from the middle of each particular

code to the true straight line.

DIFFERENTIAL LINEARITY ERROR (DNL, NO MISSING

CODES)

An ideal ADC exhibits code transitions that are exactly 1 LSB

apart. DNL is the deviation from this ideal value. Guaranteed

no missing codes to 12-bit resolution indicates that all 4096

codes must be present over all operating ranges.

ZERO ERROR

The major carry transition should occur for an analog value

1/2 LSB below analog common. Zero error is defined as the

deviation of the actual transition from that point. The zero error

and temperature drift specify the initial deviation and maximum

change in the zero error over temperature.

GAIN ERROR

The first code transition should occur for an analog value

1/2 LSB above nominal negative full scale. The last transition

should occur for an analog value 1 1/2 LSB below the nominal

positive full scale. Gain error is the deviation of the actual differ-

ence between first and last code transitions and the ideal differ-

ence between first and last code transitions.

TEMPERATURE DRIFT

The temperature drift for zero error and gain error specifies the

maximum change from the initial (+25°C) value to the value at

TMIN or TMAX.

POWER SUPPLY REJECTION

The specifications show the maximum change in the converter’s

full scale as the supplies are varied from nominal to min/max

values.

APERTURE JITTER

Aperture jitter is the variation in aperture delay for successive

samples and is manifested as noise on the input to the A/D.

APERTURE DELAY

Aperture delay is a measure of the Track-and-Hold Amplifier

(THA) performance and is measured from the rising edge of the

clock input to when the input signal is held for conversion.

OVERVOLTAGE RECOVERY TIME

Overvoltage recovery time is defined as that amount of time re-

quired for the ADC to achieve a specified accuracy after an

overvoltage (50% greater than full-scale range), measured from

the time the overvoltage signal reenters the converter’s range.

DYNAMIC SPECIFICATIONS

SIGNAL-TO-NOISE AND DISTORTION (S/N+D) RATIO

S/N+D is the ratio of the rms value of the measured 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.

TOTAL HARMONIC DISTORTION (THD)

THD is the ratio of the rms sum of the first six harmonic com-

ponents to the rms value of the measured input signal and is ex-

pressed as a percentage or in decibels.

INTERMODULATION DISTORTION (IMD)

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

fb, any device with nonlinearities will create distortion products,

of order (m + n), at sum and difference frequencies of mfa ±

nfb, where m, n = 0, 1, 2, 3 . . . . Intermodulation terms are

those for which m or n is not equal to zero. For example, the

second order terms are (fa + fb) and (fa – fb), and the third or-

der terms are (2 fa + fb), (2 fa – fb), (fa + 2 fb) and (2 fb – fa).

The IMD products are expressed as the decibel ratio of the rms

sum of the measured input signals to the rms sum of the distor-

tion terms. The two signals are of equal amplitude and the peak

value of their sums is –0.5 dB from full scale. The IMD prod-

ucts are normalized to a 0 dB input signal.

FULL-POWER BANDWIDTH

The full-power bandwidth is that input frequency at which the

amplitude of the reconstructed fundamental is reduced by 3 dB

for a full-scale input.

SPURIOUS FREE DYNAMIC RANGE

The difference, in dB, between the rms amplitude of the input

signal and the peak spurious signal.

ORDERING GUIDE

Model

Temperature Range Package Option1

AD872AJD

AD872AJE

AD872ASD2

AD872ASE2

0°C to +70°C

0°C to +70°C

–55°C to +125°C

–55°C to +125°C

D-28

E-44A

D-28

E-44A

NOTES

1D = Ceramic DIP, E = Leadless Ceramic Chip Carrier.

2MIL-STD-883 version will be available; contact factory.

–6–

REV. A

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