AD9281 データシートの表示（PDF） - Analog Devices

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AD9281

Dual Channel 8-Bit Resolution CMOS ADC

Analog Devices 

AVDD

DRVDD

AVDD

AVDD

AD9281

AVDD

AVDD

AVSS

DRVSS

DRVSS

a. D0–D9

AVSS

AVSS

b. Three-State Standby

AVSS

AVSS

c. CLK

IN

AVSS

AVDD

AVDD

AVSS

d. INA, INB

AVDD

AVDD

REFBS

AVSS

AVDD

REFBF

AVSS

AVSS

e. Reference

f. REFSENSE

Figure 2. Equivalent Circuits

AVDD

AVSS

g. VREF

OFFSET ERROR

The first transition should occur at a level 1 LSB above “zero.”

Offset is defined as the deviation of the actual first code transi-

tion from that point.

OFFSET MATCH

The change in offset error between I and Q channels.

EFFECTIVE NUMBER OF BITS (ENOB)

For a sine wave, SINAD can be expressed in terms of the num-

ber of bits. Using the following formula,

N = (SINAD – 1.76)/6.02

It is possible to get a measure of performance expressed as N,

the effective number of bits.

Thus, effective number of bits for a device for sine wave inputs

at a given input frequency can be calculated directly from its

measured SINAD.

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 expressed as a percentage or in decibels.

SIGNAL-TO-NOISE RATIO (SNR)

SNR 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, excluding the first six harmonics and dc.

The value for SNR is expressed in decibels.

scale. Gain error is the deviation of the actual difference be-

tween first and last code transitions and the ideal difference

between the first and last code transitions.

GAIN MATCH

The change in gain error between I and Q channels.

PIPELINE DELAY (LATENCY)

The number of clock cycles between conversion initiation and

the associated output data being made available. New output

data is provided every rising clock edge.

MUX SELECT DELAY

The delay between the change in SELECT pin data level and

valid data on output pins.

POWER SUPPLY REJECTION

The specification shows the maximum change in full scale from

the value with the supply at the minimum limit to the value

with the supply at its maximum limit.

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 Sample-and-Hold Amplifier

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

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

SPURIOUS FREE DYNAMIC RANGE (SFDR)

The difference in dB between the rms amplitude of the input

signal and the peak spurious signal.

GAIN ERROR

The first code transition should occur for an analog value 1 LSB

above nominal negative full scale. The last transition should

occur for an analog value 1 LSB below the nominal positive full

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

RATIO

S/N+D is the ratio of the rms value of the measured input sig-

nal 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.

REV. E

–5–

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