AD9861 datasheet(21/52 Pages) AD

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AD9861

Rev. 0 | Page 21 of 52

TERMINOLOGY

Input 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

CLKIN signal and the instant at which the analog input is

actually sampled.

Aperture Uncertainty (Jitter)

The sample-to-sample variation in aperture delay.

Crosstalk

Coupling onto one channel being driven by a –0.5 dBFS signal

when the adjacent interfering channel is driven by a full-scale

signal.

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 input phase 180° and taking the peak measurement again.

Then the difference is computed between both peak

measurements.

Differential Nonlinearity

The deviation of any code width from an ideal 1 LSB step.

Effective Number of Bits (ENOB)

The effective number of bits is calculated from the measured

SNR based on the following equation:

SNR

ENOB

MEASURED −

Pulse Width/Duty Cycle

Pulse width high is the minimum amount of time that a signal

should be left in the logic high state to achieve rated perform-

ance; pulse width low is the minimum time a signal should be

left in the low state, logic low.

Full-Scale Input Power

Expressed in dBm, full-scale input power is computed using the

following equation:

⎟

⎠

⎞

⎜

⎝

⎛

−

001

log

INPUT

RMS

FULLSCALE

Power

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 an 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.

Power Supply Rejection Ratio

The ratio of a change in input offset voltage to a change in

power supply voltage.

Signal-to-Noise and Distortion (SINAD)

The ratio of the rms signal amplitude (set 1 dB below full-scale)

to the rms value of the sum of all other spectral components,

including harmonics, but excluding dc.

Signal-to-Noise Ratio (without Harmonics)

The ratio of the rms signal amplitude (set at 1 dB below full

scale) to the rms value of the sum of all other spectral

components, excluding the first five harmonics and dc.

Spurious-Free Dynamic Range (SFDR)

The ratio of the rms signal amplitude to the rms value of the

peak spurious spectral component. The peak spurious

component may or may not be a harmonic. It also may be

reported in dBc (i.e., degrades as signal level is lowered) or

dBFS (i.e., always related back to converter full scale). SFDR

does not include harmonic distortion components.

Worst Other Spur

The ratio of the rms signal amplitude to the rms value of the

worst spurious component (excluding the second and third

harmonics) reported in dBc.

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