Datasheet

SR=max
DV (t)
OUT
Dt
DAC7568
DAC8168
DAC8568
SBAS430D –JANUARY 2009–REVISED MAY 2012 www.ti.com
Power-Supply Rejection Ratio (PSRR) Channel-to-Channel DC Crosstalk
Power-supply rejection ratio (PSRR) is defined as the Channel-to-channel dc crosstalk is defined as the dc
ratio of change in output voltage to a change in change in the output level of one DAC channel in
supply voltage for a full-scale output of the DAC. The response to a change in the output of another DAC
PSRR of a device indicates how the output of the channel. It is measured with a full-scale output
DAC is affected by changes in the supply voltage. change on one DAC channel while monitoring
PSRR is measured in decibels (dB). another DAC channel remains at midscale. It is
expressed in LSB.
Monotonicity
Channel-to-Channel AC Crosstalk
Monotonicity is defined as a slope whose sign does
not change. If a DAC is monotonic, the output AC crosstalk in a multi-channel DAC is defined as the
changes in the same direction or remains at least amount of ac interference experienced on the output
constant for each step increase (or decrease) in the of a channel at a frequency (f) (and its harmonics),
input code. when the output of an adjacent channel changes its
value at the rate of frequency (f). It is measured with
one channel output oscillating with a sine wave of
DYNAMIC PERFORMANCE
1kHz frequency, while monitoring the amplitude of
Dynamic performance parameters are specifications
1kHz harmonics on an adjacent DAC channel output
such as settling time or slew rate, which are important
(kept at zero scale). It is expressed in dB.
in applications where the signal rapidly changes
and/or high frequency signals are present.
Signal-to-Noise Ratio (SNR)
Signal-to-noise ratio (SNR) is defined as the ratio of
Slew Rate
the root mean-squared (RMS) value of the output
The output slew rate (SR) of an amplifier or other
signal divided by the RMS values of the sum of all
electronic circuit is defined as the maximum rate of
other spectral components below one-half the output
change of the output voltage for all possible input
frequency, not including harmonics or dc. SNR is
signals.
measured in dB.
Total Harmonic Distortion (THD)
Total harmonic distortion + noise is defined as the
Where ΔV
OUT
(t) is the output produced by the
ratio of the RMS values of the harmonics and noise
amplifier as a function of time t.
to the value of the fundamental frequency. It is
expressed in a percentage of the fundamental
Output Voltage Settling Time
frequency amplitude at sampling rate f
S
.
Settling time is the total time (including slew time) for
Spurious-Free Dynamic Range (SFDR)
the DAC output to settle within an error band around
its final value after a change in input. Settling times
Spurious-free dynamic range (SFDR) is the usable
are specified to within ±0.003% (or whatever value is
dynamic range of a DAC before spurious noise
specified) of full-scale range (FSR).
interferes or distorts the fundamental signal. SFDR is
the measure of the difference in amplitude between
Code Change/Digital-to-Analog Glitch Energy
the fundamental and the largest harmonically or non-
harmonically related spur from dc to the full Nyquist
Digital-to-analog glitch impulse is the impulse injected
bandwidth (half the DAC sampling rate, or f
S
/2). A
into the analog output when the input code in the
spur is any frequency bin on a spectrum analyzer, or
DAC register changes state. It is normally specified
from a Fourier transform, of the analog output of the
as the area of the glitch in nanovolt-seconds (nV-s),
DAC. SFDR is specified in decibels relative to the
and is measured when the digital input code is
carrier (dBc).
changed by 1LSB at the major carry transition.
Signal-to-Noise plus Distortion (SINAD)
Digital Feedthrough
SINAD includes all the harmonic and outstanding
Digital feedthrough is defined as impulse seen at the
spurious components in the definition of output noise
output of the DAC from the digital inputs of the DAC.
power in addition to quantizing any internal random
It is measured when the DAC output is not updated. It
noise power. SINAD is expressed in dB at a specified
is specified in nV-s, and measured with a full-scale
input frequency and sampling rate, f
S
.
code change on the data bus; that is, from all '0's to
all '1's and vice versa.
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