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Data Sheet

AD9174

Rev. A | Page 27 of 164

TERMINOLOGY

Integral Nonlinearity (INL)

INL is 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.

Offset Error

Offset error is the deviation of the output current from the ideal

value of 0 mA. For DACx+, a 0 mA output is expected when all

inputs are set to 0. For DACx−, a 0 mA output is expected when

all inputs are set to 1.

Gain Error

Gain error is the difference between the actual and ideal output

span. The actual span is determined by the difference between

the output when the input is at its minimum code and the

output when the input is at its maximum code.

Output Compliance Range

The output compliance range is the range of allowable voltages

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

maximum compliance limits can 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.

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.

Spurious-Free Dynamic Range (SFDR)

SFDR is the difference, in decibels, between the peak amplitude

of the output signal and the peak spurious signal within the dc

to Nyquist frequency of the DAC. Typically, energy in this band

is rejected by the interpolation filters. This specification, therefore,

defines how well the interpolation filters work and the effect of

other parasitic coupling paths on the DAC output.

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

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

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

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

Channel Datapath

The channel datapath, sometimes referred to as a channelizer, is

a complex (IQ) datapath. There are six channelizers within the

chip, with three channelizers summed in each main datapath.

The channelizers can be bypassed if unused, depending on the

mode of operation. When the channelizers are in use, a complex

(I/Q) input data stream is required. Each channel datapath

includes an independently controlled gain stage and a channel

NCO. A selectable channel interpolation block is configurable

according to the mode of operation. All channels must be set to

the same interpolation rate.

Main Datapath

The main datapath refers to the portion of the digital datapath after

the summing node in the chip, up to each of the main DAC analog

cores. Each of these main datapaths includes an optional PA

protection block with a feed forward to the ramp up/down gain

stage block for muting the DAC outputs before damaging a power

amplifier in the transmit path. There is a selectable main

interpolation block that is configurable (same setting for both main

interpolation blocks) depending on the mode of operation chosen.

Each main datapath also contains an individually programmable

main NCO per main DAC datapath that can be optionally used

depending on the mode of operation.

Adjacent Channel Leakage Ratio (ACLR)

ACLR is the ratio in decibels relative to the carrier (dBc)

between the measured power within a channel relative to its

adjacent channel.

Adjusted DAC Update Rate

The adjusted DAC update rate is the DAC update rate divided

by the smallest interpolating factor. For clarity on DACs with

multiple interpolating factors, the adjusted DAC update rate for

each interpolating factor may be given.

Physical (PHY) Lane

Physical Lane x refers to SERDINx±.

Logical Lane

Logical Lane x refers to physical lanes after optionally being

remapped by the crossbar block (Register 0x308 to Register 0x30B).

Link Lane

Link Lane x refers to logical lanes considered per link. When

paging Link 0 (Register 0x300[2] = 0), Link Lane x = Logical

Lane x. When paging Link 1 (Register 0x300[2] = 1, dual link

only), Link Lane x = Logical Lane x + 4.

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