AD9481 Analog Devices, AD9481 Datasheet - Page 10

• Manufacturer Part Number: AD9481
• Description: 8-Bit, 250 MSPS, 3.3 V A/D Converter
• Manufacturer: Analog Devices

Specifications of AD9481

• Resolution (bits): 8bit
• # Chan: 1
• Sample Rate: 250MSPS
• Interface: Par
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,1 V p-p
• Adc Architecture: Pipelined
• Pkg Type: QFP

AD9481
TERMINOLOGY
Analog Bandwidth
The analog input frequency at which the spectral power of the
fundamental frequency (as determined by the FFT analysis) is
reduced by 3 dB.
Aperture Delay
The delay between the 50% point of the rising edge of the
encode command and the instant the analog input is sampled.
Aperture Uncertainty (Jitter)
The sample-to-sample variation in aperture delay.
Clock Pulse-Width/Duty Cycle
Pulse-width high is the minimum amount of time that the clock
pulse should be left in a Logic 1 state to achieve rated
performance; pulse-width low is the minimum time clock pulse
should be left in a low state. See timing implications of changing
t
these specifications define an acceptable clock duty cycle.
Crosstalk
Coupling onto one channel being driven by a low level
(−40 dBFS) signal when the adjacent interfering channel is
driven by a full-scale signal.
Differential Analog Input Resistance, Differential Analog
Input Capacitance, and Differential Analog Input Impedance
The real and complex impedances measured at each analog
input port. The resistance is measured statically and the
capacitance and differential input impedances are measured
with a network analyzer.
Differential Analog Input Voltage Range
The peak-to-peak differential voltage that must be applied to
the converter to generate a full-scale response. Peak differential
voltage is computed by observing the voltage on a single pin
and subtracting the voltage from the other pin, which is 180°
out of phase. Peak-to-peak differential is computed by rotating
the inputs phase 180° and taking the peak measurement again.
The difference is then computed between both peak
measurements.
Differential Nonlinearity
The deviation of any code width from an ideal 1 LSB step.
Effective Number of Bits (ENOB)
ENOB is calculated from the measured SINAD based on the
equation (assuming full-scale input)
EH
in the Clocking the AD9481 section. At a given clock rate,
ENOB
=
SINAD
MEASURED
6.02
−
1.76
dB
Rev. 0 | Page 10 of 28
Full-Scale Input Power
Expressed in dBm. Computed using the following equation
Gain Error
Gain error is the difference between the measured and ideal
full-scale input voltage range of the ADC.
Harmonic Distortion, Second
The ratio of the rms signal amplitude to the rms value of the
second harmonic component, reported in dBc.
Harmonic Distortion, Third
The ratio of the rms signal amplitude to the rms value of the
third harmonic component, reported in dBc.
Integral Nonlinearity
The deviation of the transfer function from a reference line
measured in fractions of 1 LSB using a best straight line
determined by a least square curve fit.
Minimum Conversion Rate
The encode rate at which the SNR of the lowest analog signal
frequency drops by no more than 3 dB below the guaranteed
limit.
Maximum Conversion Rate
The encode rate at which parametric testing is performed.
Output Propagation Delay
The delay between a differential crossing of CLK+ and CLK−
and the time when all output data bits are within valid logic
levels.
Noise (for Any Range within the ADC)
This value includes both thermal and quantization noise.
where:
Z is the input impedance.
FS is the full scale of the device for the frequency in question.
SNR is the value for the particular input level.
Signal is the signal level within the ADC reported in dB below
full scale.
V
Power
noise
FULLSCALE
=
Z
×
0
.001
=
10
×
10
log
⎛
⎜ ⎜
⎝
⎛
⎜
⎜
⎜
⎜
⎜
⎝
FS
V
dBm
2
FULLSCALE
Z
−
0.001
INPUT
SNR
dBc
10
rms
−
Signal
⎞
⎟
⎟
⎟
⎟
⎟
⎠
dBFS
⎞
⎟ ⎟
⎠