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AD9776A/AD9778A/AD9779A

Rev. B | Page 24 of 56

TERMINOLOGY

Integral Nonlinearity (INL)

INL is defined as the maximum deviation of the actual analog

output from the ideal output, determined by a straight line

drawn from zero scale to full scale.

Differential Nonlinearity (DNL)

DNL is the measure of the variation in analog value, normalized

to full scale, associated with a 1 LSB change in digital input code.

Monotonicity

A DAC is monotonic if the output either increases or remains

constant as the digital input increases.

Offset Error

The deviation of the output current at Code 0 from the ideal

of zero is called offset error. For IOUTA, 0 mA output is expected

when the inputs are all 0s. For IOUTB, 0 mA output is expected

when all inputs are set to 1s.

Gain Error

Gain error is the difference between the actual and the ideal

output spans. The actual span is determined by the difference

between the full-scale output and the bottom-scale output.

Output Compliance Range

Output compliance range is the range of allowable voltage at

the output of a current-output DAC. Operation beyond the

maximum compliance limits may cause either output stage

saturation or breakdown, resulting in nonlinear performance.

Temperature Drift

Temperature drift is specified as the maximum change from

the ambient (25°C) value to the value at either TMIN or TMAX.

For offset and gain drift, the drift is reported in ppm of full-

scale range (FSR) per degree Celsius. For reference drift, the

drift is reported in ppm per degree Celsius.

Power Supply Rejection (PSR)

PSR is the maximum change in the full-scale output as the

supplies are varied from minimum to maximum specified

voltages.

Settling Time

Settling time is the time required for the output to reach and

remain within a specified error band around its final value,

measured from the start of the output transition.

In-Band Spurious-Free Dynamic Range (SFDR)

In-band SFDR is the difference, in decibels, between the peak

amplitude of the output signal and the peak spurious signal

between dc and the frequency equal to half the input data rate.

Out-of-Band Spurious-Free Dynamic Range (SFDR)

Out-of-band SFDR is the difference, in decibels, between the

peak amplitude of the output signal and the peak spurious signal

within the band that starts at the frequency of the input data

rate and ends at the Nyquist frequency of the DAC output sample

rate. Normally, energy in this band is rejected by the interpolation

filters. This specification, therefore, defines how well the inter-

polation filters work and the effect of other parasitic coupling

paths to the DAC output.

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 fundamental. It is

expressed as a percentage or in decibels.

Signal-to-Noise Ratio (SNR)

SNR is the ratio of the rms value of the measured output 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.

Interpolation Filter

If the digital inputs to the DAC are sampled at a multiple rate of

fDATA (interpolation rate), a digital filter can be constructed that

has a sharp transition band near fDATA/2. Images that typically

appear around fDAC (output data rate) can be greatly suppressed.

Adjacent Channel Leakage Ratio (ACLR)

ACLR is the ratio in dBc of the measured power within a

channel relative to its adjacent channel.

Complex Image Rejection

In a traditional two-part upconversion, two images are created

around the second IF frequency. These images have the effect of

wasting transmitter power and system bandwidth. By placing

the real part of a second complex modulator in series with the

first complex modulator, either the upper or lower frequency

image near the second IF can be rejected.

AD9779A-EBZ Datasheet(PDF) 24 Page - Analog Devices

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