AD9775EB datasheet(9/48 Pages) AD

9 / 48 page

REV. 0

AD9775

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DEFINITIONS OF SPECIFICATIONS

Adjacent Channel Power Ratio (ACPR)

A ratio in dBc between 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 are redundant

and have the effect of wasting transmitter power and system

bandwidth. By placing the real part of a second complex modu-

lator in series with the first complex modulator, either the upper

or lower frequency image near the second IF can be rejected.

Complex Modulation

The process of passing the real and imaginary components of a

signal through a complex modulator (transfer function = e

j t =

cos t + jsin t) and realizing real and imaginary components on

the modulator output.

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.

Gain Error

The difference between the actual and ideal output span. The

actual span is determined by the output when all inputs are set

to “1,” minus the output when all inputs are set to “0.”

Glitch Impulse

Asymmetrical switching times in a DAC give rise to undesired

output transients that are quantified by a glitch impulse. It is

specified as the net area of the glitch in pV–S.

Group Delay

Number of input clocks between an impulse applied at the

device input and peak DAC output current. A half-band FIR

filter has constant group delay over its entire frequency range.

Impulse Response

Response of the device to an impulse applied to the input.

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

with a sharp transition band near fDATA/2. Images that would

typically appear around fDAC (output data rate) can be greatly

suppressed.

Linearity Error (Also Called Integral Nonlinearity or INL)

Linearity error is defined as the maximum deviation of the actual

analog output from the ideal output, determined by a straight

line drawn from zero to full scale.

Monotonicity

A D/A converter is monotonic if the output either increases

or remains constant as the digital input increases.

Offset Error

The deviation of the output current from the ideal of “0” is

called offset error. For IOUTA, 0 mA output is expected when the

inputs are all “0.” For IOUTB, 0 mA output is expected when all

inputs are set to “1.”

Output Compliance Range

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.

Pass Band

Frequency band in which any input applied therein passes

unattenuated to the DAC output.

Power Supply Rejection

The maximum change in the full-scale output as the supplies

are varied from minimum to maximum specified voltages.

Settling Time

The time required for the output to reach and remain within a

specified error band about its final value, measured from the

start of the output transition.

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.

Spurious-Free Dynamic Range

The difference, in dB, between the rms amplitude of the output

signal and the peak spurious signal over the specified bandwidth.

Stop-Band Rejection

The amount of attenuation of a frequency outside the pass band

applied to the DAC, relative to a full-scale signal applied at the

DAC input within the pass band.

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

°C. For reference drift, the drift is reported in

ppm per

°C.

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 (dB).

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