DAC729JH BURR-BROWN [Burr-Brown Corporation], DAC729JH Datasheet - Page 11

• Manufacturer Part Number: DAC729JH
• Description: Ultra-High Resolution 18-BIT DIGITAL-TO-ANALOG CONVERTER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

FIGURE 12. Differential Linearity Adjustment Circuit for the
The DAC729 offers superb dynamic range. Dynamic range
is a measure of the ratio of the smallest signals the converter
can produce to the full-scale range, usually expressed in
decibels (dB). The theoretical dynamic range of a converter
is approximately 6dB per bit. For the DAC729 the theoreti-
cal range is 108dB! The actual dynamic range is limited by
noise (signal-to-noise) and linearity errors. The DAC729’s
6 V typical noise floor, fast settling op amp, and adjustable
18-bit linearity minimize the limitation.
Total harmonic distortion (THD) is the measure of the
magnitude and distribution of the linearity error, differential
linearity error, noise, and quantization error. The THD is
defined as the ratio of the square root of the sum of the
squares of the harmonics to the values of the input funda-
mental frequency. The rms value of a DAC error can be
shown to be
where n is the number of samples in one cycle of any given
sine wave, E
sampling point, and E
sampling point. The THD can then be expressed as
where E rms is the rms signal-voltage level.
This expression indicates that, in general, there is a correla-
tion between the THD and the square root of the sum of the
squares of the linearity errors at each digital word of interest.
However, this expression does not mean that the worst-case
linearity error of the D/A is directly correlated to the THD.
Adjust
Adjust
Adjust
Adjust
Bit 1
Bit 2
Bit 3
Bit 4
–V
V
THD =
POT
CC
40
39
38
37
36
21
RMS
–V
–V
–V
–V
E
L
CC
CC
CC
CC
0.01µF
0.01µF
0.01µF
0.01µF
4MSBs.
(i) is the linearity error of the DAC729 at each
RMS
=
RMS
1.0M
1.0M
1.0M
1.0M
NOTE: (1) Low leakage film type.
=
(1)
(1)
(1)
(1)
1
n
i =1
n
Q
1
n
(i) is the quantization error at each
[E
i =1
n
L
150k
100k
(i) + E
[E
E
L
RMS
(i) + E
Q
(i)]
150k
100k
2
Q
(i)]
2
150k
100k
X x 100%
150k
100k
(2)
11
FIGURE 13. 0 to 10V FSR.
The DAC729 has demonstrated THD of 0.0009% at full
scale (at 1kHz). This is the level of distortion that is desired
to test other professional audio products, making the DAC729
ideal for professional audio test equipment.
The ability to adjust the linearity of the 4MSBs, the 18-bit
resolution, fast settling and low noise give the DAC729
unmatched performance.
AUTOMATIC TEST EQUIPMENT
The pin functions of the DAC729 are convenient for use in
automatic test equipment systems. The ability to use internal
or external reference and internal or external op amp means
versatility for the system designer. For example, in auto-
matic test systems with several DACs and ADCs, it is
desirable to operate all of the high accuracy converters from
the same reference, improving the tracking characteristics of
those components to one another. The reference in the
DAC729 is a very stable precision reference, and is suitable
for use as the system reference.
Test systems, and other large systems are the ideal applica-
tion for a DAC of this accuracy, because the DAC will be
calibrated in the environment in which it will be used. Since
the environment is very stable, the manual calibration (Fig-
ure 12) may be adequate. However, highly automated sys-
tems will go to an automatic calibration routine. Replacing
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1
2
3
4
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9
18-Bit
DAC
40
39
38
37
36
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DAC729
V
OUT