AD9240EB 查看數據表（PDF） - Analog Devices
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AD9240EB Datasheet PDF : 24 Pages
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AD9240
PIN FUNCTION DESCRIPTIONS
Pin
Number Name
Description
1
2, 29
3
4, 28
5
6
7
8–10
11
12–23
24
25
26, 27, 30
31
32
33
34, 38, 40,
43, 44
35
36
37
39
41
42
DVSS
AVSS
DVDD
AVDD
DRVSS
DRVDD
CLK
NC
BIT 14
BIT 13–BIT 2
BIT 1
OTR
NC
SENSE
VREF
REFCOM
NC
BIAS*
CAPB
CAPT
CML
VINA
VINB
Digital Ground
Analog Ground
+5 V Digital Supply
+5 V Analog Supply
Digital Output Driver Ground
Digital Output Driver Supply
Clock Input Pin
No Connect
Least Significant Data Bit (LSB)
Data Output Bits
Most Significant Data Bit (MSB)
Out of Range
No Connect
Reference Select
Reference I/O
Reference Common
No Connect
Power/Speed Programming
Noise Reduction Pin
Noise Reduction Pin
Common-Mode Level (Midsupply)
Analog Input Pin (+)
Analog Input Pin (–)
*See Speed/Power Programmability section.
DEFINITIONS OF SPECIFICATION
INTEGRAL NONLINEARITY (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 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 NONLINEARITY (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 14-bit resolution indicates that all 16384
codes, respectively, must be present over all operating ranges.
ZERO ERROR
The major carry transition should occur for an analog value
1/2 LSB below VINA = VINB. Zero error is defined as the
deviation of the actual transition from that point.
GAIN ERROR
The first code transition should occur at an analog value 1/2 LSB
above negative full scale. The last transition should occur at an
analog value 1 1/2 LSB below the nominal full scale. Gain error
is the deviation of the actual difference between first and last
code transitions and the ideal difference between first and last
code transitions.
OVERVOLTAGE RECOVERY TIME
Overvoltage recovery time is defined as that amount of time
required 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.
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 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.
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.
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, an 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
components 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.
SPURIOUS FREE DYNAMIC RANGE (SFDR)
SFDR is the difference in dB between the rms amplitude of the
input signal and the peak spurious signal.
TWO-TONE SFDR
The ratio of the rms value of either input tone to the rms value
of the peak spurious component. The peak spurious component
may or may not be an IMD product. Two-tone SFDR may be
reported in dBc (i.e., degrades as signal level is lowered), or in
dBFS (always related back to converter full scale).
REV. A
–5–
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