REV. 0

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AD5425

TERMINOLOGY

Relative Accuracy

Relative accuracy or endpoint nonlinearity is a measure of the

maximum deviation from a straight line passing through the end-

points of the DAC transfer function. It is measured after adjusting

for zero and full scale and is normally expressed in LSBs or as a

percentage of full-scale reading.

Differential Nonlinearity

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 max over

the operating temperature range ensures monotonicity.

Gain Error

Gain error or full-scale error is a measure of the output error

between an ideal DAC and the actual device output. For these

the DACs is adjustable to 0 with external resistance.

Output Leakage Current

Output leakage current is current that flows in the DAC ladder

can be measured by loading all 0s to the DAC and measuring

when the DAC is loaded with all 1s.

Output Capacitance

Output Current Settling Time

This is the amount of time it takes for the output to settle to a

specified level for a full-scale input change. For these devices, it

is specified with a 100

Ω resistor to ground. The settling time

specification includes the digital delay from

SYNC rising edge

of the full scale output charge.

Digital-to-Analog Glitch lmpulse

The amount of charge injected from the digital inputs to the

analog output when the inputs change state. This is normally

specified as the area of the glitch in either pA-secs or nV-secs

depending upon whether the glitch is measured as a current or

voltage signal.

Digital Feedthrough

When the device is not selected, high frequency logic activity on

the device digital inputs is capacitively coupled through the

into the following circuitry. This noise is digital feedthrough.

Multiplying Feedthrough Error

This is the error due to capacitive feedthrough from the DAC

loaded to the DAC.

Total Harmonic Distortion (THD)

The DAC is driven by an ac reference. The ratio of the rms sum

of the harmonics of the DAC output to the fundamental value is

the THD. Usually only the lower order harmonices are included,

such as second to fifth.

Spurious-Free Dynamic Range (SFDR)

It is the usable dynamic range of a DAC before spurious noise

interferes or distorts the fundamental signal. SFDR is the

measure of difference in amplitude between the fundamental

and the largest harmonically or nonharmonically related spur

from dc to full Nyquist bandwidth (half the DAC sampling rate,

or fs/2). Narrow band SFDR is a measure of SFDR over an

arbitrary window size, in this case 50% of the fundamental.

Digital SFDR is a measure of the usable dynamic range of the

DAC when the signal is digitally generated sine wave.

THD

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