Datasheet

AD5686/AD5684 Data Sheet
Rev. A | Page 16 of 28
TERMINOLOGY
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 8.
Differential Nonlinearity (DNL)
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. These DACs are guaranteed monotonic
by design. A typical DNL vs. code plot can be seen in Figure 10.
Zero-Code Error
Zero-code error is a measurement of the output error when
zero code (0x0000) is loaded to the DAC register. Ideally, the
output should be 0 V. The zero-code error is always positive in
the AD5686/AD5684 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. A
plot of zero-code error vs. temperature can be seen in Figure 16.
Full-Scale Error
Full-scale error is a measurement of the output error when full-
scale code (0xFFFF) is loaded to the DAC register. Ideally, the
output should be V
DD
− 1 LSB. Full-scale error is expressed in
percent of full-scale range (% of FSR). A plot of full-scale error
vs. temperature can be seen in Figure 15.
Gain Error
Gain error is a measurement 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 Drift
Offset error drift is a measurement of the change in offset error
with a change in temperature. It is expressed in µV/°C.
Gain Temperature Coefficient
Gain temperature coefficient is a measurement of the change in
gain error with changes in temperature. It is expressed in ppm
of FSR/°C.
Offset Error
Offset error is a measurement of the difference between V
OUT
(actual) and V
OUT
(ideal) expressed in mV in the linear region of
the transfer function. It can be negative or positive.
DC Power Supply Rejection Ratio (PSRR)
DC PSRR indicates how the output of the DAC is affected by
changes in the supply voltage. PSRR is the ratio of the change in
V
OUT
to a change in V
DD
for full-scale output of the DAC. It is
measured in mV/V. V
REF
is held at 2.5 V, a n d V
DD
is varied by
±10%.
Output Voltage Settling Time
The output voltage setting time is the amount of time it takes
for the output of a DAC to settle to a specified level for a ¼ to ¾
full-scale input change and is measured from the rising edge
of
SYNC
.
Digital-to-Analog Glitch Impulse
Digital-to-analog glitch impulse is the impulse injected into the
analog output when the input code in the DAC register changes
state. It is normally specified as the area of the glitch in nV-sec,
and is measured when the digital input code is changed by
1 LSB at the major carry transition (0x7FFF to 0x8000) (see
Figure 30).
Digital Feedthrough
Digital feedthrough is a measure of the impulse injected into the
analog output of the DAC from the digital inputs of the DAC,
but is measured when the DAC output is not updated. It is
specified in nV-sec and measured with a full-scale code change
on the data bus, that is, from all 0s to all 1s and vice versa.
Noise Spectral Density
Noise spectral density is a measurement of the internally
generated random noise. Random noise is characterized as a
spectral density (nV/√Hz). It is measured by loading the DAC
to midscale and measuring noise at the output. It is measured in
nV/√Hz.
DC Crosstalk
DC crosstalk is the dc change in the output level of one DAC
in response to a change in the output of another DAC. It is
measured with a full-scale output change on one DAC (or soft
power-down and power-up) while monitoring another DAC
kept at midscale. It is expressed in μV.
DC crosstalk due to load current change is a measurment of
the impact that a change in load current on one DAC has to
another DAC kept at midscale. It is expressed in μV/mA.
Digital Crosstalk
Digital crosstalk is the glitch impulse transferred to the output
of one DAC at midscale in response to a full-scale code change
(all 0s to all 1s and vice versa) in the input register of another
DAC. It is measured in standalone mode and is expressed in
nV-sec.