AD5593R datasheet(17/34 Pages) AD

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AD5593R

Data Sheet

Rev. B | Page 16 of 33

TERMINOLOGY

ADC Integral Nonlinearity (INL)

For the ADC, INL is the maximum deviation from a straight

line passing through the endpoints of the ADC transfer function.

The end points of the transfer function are zero scale, a point

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

point that is 1 LSB above the last code transition.

ADC Differential Nonlinearity (DNL)

For the ADC, DNL is the difference between the measured and the

ideal 1 LSB change between any two adjacent codes in the ADC.

Offset Error

Offset error is the deviation of the first code transition (00 …

000) to (00 … 001) from the ideal, that is, AGND + 1 LSB.

Gain Error

Gain error is the deviation of the last code transition (111 …

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

the offset error has been adjusted out.

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 5 kHz sine wave signal to all nonselected ADC input

channels and determining how much that signal is attenuated in

the selected channel. This specification is the worst case across

all ADC channels for the AD5593R.

ADC Power Supply Rejection Ratio (PSRR)

For the ADC, variations in power supply affect the full-scale

transition, but not the converter linearity. Power supply rejection is

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

change in power supply voltage from the nominal value.

Track-and-Hold Acquisition Time

The track-and-hold amplifier goes into track mode when the

ADC sequence register has been written to. The track and hold

amplifier goes into hold mode when the conversion starts (see

Figure 37). 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.

Signal-to-(Noise + Distortion) Ratio (SINAD)

SINAD 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 non-

fundamental 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

quantization noise. The theoretical SINAD for an ideal N-bit

converter with a sine wave input is given by

Signal-to-(Noise + Distortion) (dB) = 6.02N + 1.76

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

ADC Total Harmonic Distortion (THD)

THD is the ratio of the rms sum of harmonics to the

fundamental. For the AD5593R, it is defined as



THD

log







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

V4, V5, and V6 are the rms amplitudes of the second through the

sixth harmonics.

Peak Harmonic or Spurious Noise

Peak harmonic or spurious noise is defined as the ratio of the

rms value of the next largest component in the ADC output

spectrum (up to fS/2 and excluding dc) to the rms value of the

fundamental. Normally, the value of this specification is

determined by the largest harmonic in the spectrum, but for

ADCs where the harmonics are buried in the noise floor, it is a

noise peak.

DAC Relative Accuracy or Integral Nonlinearity (INL)

For the DAC, relative accuracy or integral nonlinearity is a

measurement of the maximum deviation, in LSBs, from a

straight line passing through the endpoints of the DAC transfer

function. A typical INL vs. code plot is shown in Figure 13.

DAC Differential Nonlinearity (DNL)

For the DAC, differential nonlinearity is the difference between

the measured change and the ideal 1 LSB change between any

two adjacent codes. A specified differential nonlinearity of ±1

LSB maximum ensures monotonicity. This DAC is guaranteed

monotonic by design. A typical DNL vs. code plot can be seen

in Figure 14.

Zero Code Error

Zero code error is a measurement of the output error when zero

code (0x000) is loaded to the DAC register. Ideally, the output is

0 V. The zero code error is always positive in the AD5593R

because the output of the DAC cannot go below 0 V due to a

combination of the offset errors in the DAC and the output

amplifier. Zero code error is expressed in mV.

Gain Error

Gain error is a measure of the span error of the DAC. It is the

deviation in slope of the DAC transfer characteristic from the

ideal expressed as % of FSR.

Offset Error

Offset error is a measure of the difference between VOUT (actual)

and VOUT (ideal) expressed in mV in the linear region of the

transfer function. Offset error can be negative or positive.

Offset Error Drift

Offset error drift is a measurement of the change in offset error

with a change in temperature. It is expressed in μV/°C.

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