AD5590BBCZ datasheet(24/44 Pages) AD

24 / 44 page

AD5590

Rev. 0 | Page 24 of 44

Multiplying Bandwidth

The amplifiers within the DAC have a finite bandwidth. The

multiplying bandwidth is a measure of this. A sine wave on the

reference (with full-scale code loaded to the DAC) appears on

the output. The multiplying bandwidth is the frequency at

which the output amplitude falls to 3 dB below the input.

DAC Total Harmonic Distortion (THD)

Total harmonic distortion is the difference between an ideal

sine wave and its attenuated version using the DAC. The sine

wave is used as the reference for the DAC, and the THD is a

measure of the harmonics present on the DAC output. It is

measured in decibels.

ADC Differential Nonlinearity

This is the difference between the measured and the ideal 1 LSB

change between any two adjacent codes in the ADC.

ADC Integral Nonlinearity

This is the maximum deviation from a straight line passing

through the endpoints of the ADC transfer function. The

endpoints of the transfer function are zero scale, a point 1 LSB

below the first code transition, and full scale, a point 1 LSB

above the last code transition.

ADC Offset Error

This is the deviation of the first code transition (00…000 to

00…001) from the ideal, that is, ADCGND + 1 LSB.

ADC Offset Error Match

This is the difference in offset error between any two channels.

ADC Gain Error

This is the deviation of the last code transition (111…110

to 111…111) from the ideal (that is, VREFA − 1 LSB) after the

offset error has been adjusted out.

ADC Gain Error Match

This is the difference in gain error between any two channels.

ADC Zero-Code Error

This applies when using the twos complement output coding

option, in particular to the 2 × VREFA input range with−VREFA

to +VREFA biased about the VREFA point. It is the deviation of the

midscale transition (all 0s to all 1s) from the ideal VIN voltage,

that is, VREFA − 1 LSB.

ADC Zero-Code Error Match

This is the difference in ADC zero-code error between any two

channels.

ADC Positive Gain Error

This applies when using the twos complement output coding

option, in particular to the 2 × VREFA input range with −VREFA

to +VREFA biased about the VREFA point. It is the deviation of the

last code transition (011…110 to 011…111) from the ideal (that

is, +VREFA − 1 LSB) after the zero-code error has been adjusted out.

ADC Positive Gain Error Match

This is the difference in ADC positive gain error between any

two channels.

ADC Negative Gain Error

This applies when using the twos complement output coding

option, in particular to the 2 × VREFA input range with −VREFA

to +VREFA biased about the VREFA point. It is the deviation of

the first code transition (100…000 to 100…001) from the

ideal (that is, −VREFA + 1 LSB) after the ADC zero-code error

has been adjusted out.

ADC Negative Gain Error Match

This is the difference in negative gain error between any two

channels.

ADC Channel-to-Channel Isolation

Channel-to-channel isolation is a measure of the level of

crosstalk between channels. It is measured by applying a full-

scale 400 kHz sine wave signal to all 15 nonselected input

channels and determining how much that signal is attenuated

in the selected channel with a 50 kHz signal. The figure is given

worst case across all 16 channels for the ADC.

ADC PSR (Power Supply Rejection)

Variations in power supply affect the full scale transition, but

not the linearity of the converter. Power supply rejection is the

maximum change in full-scale transition point due to a change

in power supply voltage from the nominal value (see the Typical

Performance Characteristics section).

ADC Track-and-Hold Acquisition Time

The track-and-hold amplifier returns into track on the 14th

ASCLK falling edge. Track-and-hold acquisition time is the

minimum time required for the track-and-hold amplifier to

remain in track mode for its output to reach and settle to within

±1 LSB of the applied input signal, given a step change to the

input signal.

ADC Signal-to-(Noise + Distortion) Ratio

This is the measured ratio of signal to (noise + distortion) at the

output of the analog-to-digital converter. The signal is the rms

amplitude of the fundamental. Noise is the sum of all nonfunda-

mental signals up to half the sampling frequency (fS/2), excluding

dc. The ratio is dependent on the number of quantization levels

in the digitization process; the more levels, the smaller the quanti-

zation noise. The theoretical signal-to-(noise + distortion) ratio

for an ideal N-bit converter with a sine wave input is given by

(

)

[dB]

−

Distortion

Noise

Signal

Thus, for a 12-bit converter, this is 74 dB.

ADC Total Harmonic Distortion

Total harmonic distortion (THD) is the ratio of the rms sum of

harmonics to the fundamental. For the ADC, it is defined as

THD

log

[dB]

where V1 is the rms amplitude of the fundamental and V2, V3,

, V5, and V6 are the rms amplitudes of the second through the

sixth harmonics.

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