AD5378ABC datasheet(17/28 Pages) AD

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Preliminary Technical Data

AD5378

Rev. PrA | Page 17 of 28

TERMINOLOGY

Relative Accuracy

Relative accuracy or endpoint linearity is a measurement of the

maximum deviation from a straight line passing through the

endpoints of the DAC transfer function. It is measured after

adjusting for zero-scale error and full-scale error and is

expressed in least significant bits (LSB).

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 maximum

ensures monotonicity.

Zero-Scale Error

Zero-scale error is the error in the DAC output voltage when all

0s are loaded into the DAC register.

Ideally, with all 0s loaded to the DAC and m is all 1s,

c is 10 0000 0000 0000:

VOUT(zero-scale) = 2.5 × VREF(−) − AGND) + REFGND

Zero-scale error is a measurement of the difference between

VOUT (actual) and VOUT (ideal) expressed in mV. Zero-scale

error is mainly due to offsets in the output amplifier.

Full-Scale Error

Full-scale error is the error in DAC output voltage when all 1s

are loaded into the DAC register.

Ideally, with all 1s loaded to the DAC and m is all 1s,

c is 10 0000 0000 0000:

VOUT(full-scale) = 3.5 × (VREF(+) − AGND) + 2.5 ×

(VREF(−)− AGND) + REFGND

Full-scale error is a measurement of the difference between

VOUT (actual) and VOUT (ideal) expressed in mV. It does not

include zero-scale error.

Gain Error

Gain error is the difference between full-scale error and zero-

scale error. It is expressed in mV.

Gain Error = Full-Scale Error − Zero-Scale Error

VOUT Temperature Coefficient

This includes output error contributions from linearity, offset,

and gain drift.

DC Output Impedance

DC output impedance is the effective output source resistance.

It is dominated by package lead resistance.

DC Crosstalk

The 32 DAC outputs are buffered by op amps that share

common VDD and VSS power supplies. If the dc load current

changes in one channel (due to an update), this can result in a

further dc change in one or more channel outputs. This effect is

more significant at high load currents and reduces as the load

currents are reduced. With high impedance loads, the effect is

virtually unmeasurable. Multiple VDD and VSS terminals are

provided to minimize dc crosstalk.

Output Voltage Settling Time

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

settle to a specified level for a full-scale input change.

Digital-to-Analog Glitch Energy

This is the amount of energy injected into the analog output at

the major code transition. It is specified as the area of the glitch

in nV-s. It is measured by toggling the DAC register data

between 0x1FFF and 0x2000.

Channel-to-Channel Isolation

Channel-to-channel isolation refers to the proportion of input

signal from one DAC’s reference input that appears at the

output of another DAC operating from another reference. It is

expressed in dB and measured at midscale.

DAC-to-DAC Crosstalk

DAC-to-DAC crosstalk is the glitch impulse that appears at the

output of one converter due to both the digital change and

subsequent analog output change at another converter. It is

specified in nV-s.

Digital Crosstalk

The glitch impulse transferred to the output of one converter

due to a change in the DAC register code of another converter is

defined as the digital crosstalk and is specified in nV-s.

Digital Feedthrough

When the device is not selected, high frequency logic activity

on the device’s digital inputs can be capacitively coupled both

across and through the device to show up as noise on the

VOUT pins. It can also be coupled along the supply and ground

lines. This noise is digital feedthrough.

Output Noise Spectral Density

This is a measurement of internally generated random noise.

Random noise is characterized as a spectral density (voltage per

√Hz). It is measured by loading all DACs to midscale and

measuring noise at the output. It is measurement in nV/(Hz)1/2.

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