Datasheet

AD5378
Rev. A | 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 × V
REF
(−) − 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 × (V
REF
(+) − AGND) + 2.5 ×
(V
REF
(−)− 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 V
DD
and V
SS
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 V
DD
and V
SS
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
.