DAC8822QB BURR-BROWN [Burr-Brown Corporation], DAC8822QB Datasheet - Page 15

• Manufacturer Part Number: DAC8822QB
• Description: 16-Bit, Dual, Parallel Input, Multiplying Digital-to-Analog Converter
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

The DAC8822 is a multiplying, dual-channel, current output, 16-bit DAC. The architecture, illustrated in
Figure
switched to GND or to the I
use of an external I/V converter op amp. The R-2R ladder is connected to an external reference input (V
determines the DAC full-scale output current. The R-2R ladder presents a code-independent load impedance to
the external reference of 5k
providing bipolar I
DAC8822, an output voltage range of –V
The DAC output voltage is determined by V
Each DAC code determines the 2R-leg switch position to either GND or I
noise gain will also change because the DAC output impedance (as seen looking into the I
versus code. Because of this change in noise gain, the external I/V converter op amp must have a sufficiently
low offset voltage such that the amplifier offset is not modulated by the DAC I
External op amps with large offset voltages can produce INL errors in the transfer function of the DAC8822
because of offset modulation versus DAC code. For best linearity performance of the DAC8822, an op amp
(such as the OPA277) is recommended, as shown in
+10V.
V
OUT
www.ti.com
A B + *V
V
40, is an R-2R ladder configuration with the three MSBs segmented. Each 2R leg of the ladder is either
REF
REF
2R
OUT
2R
current operation. By using an external I/V converter op amp and the R
65536
D
V
2R
REF
OUT
terminal. The I
25%. The external reference voltage can vary in a range of –18V to +18V, thus
2R
U1
Figure 41. Voltage Output Configuration
Figure 40. Equivalent R-2R DAC Circuit
GND
V
V
DD
DD
2R
R
DAC8822
REF
THEORY OF OPERATION
OFS
Submit Documentation Feedback
2R
REF
to +V
R
FB
OUT
and the digital data (D) according to
2R
REF
R
I
terminal of the DAC is held at a virtual GND potential by the
OUT
A/B
can be generated.
Figure
2R
41. This circuit allows V
U2
OPA277
2R
+15V
-15V
R
V+
V-
SBAS390A – DECEMBER 2006 – REVISED MARCH 2007
OUT
2R
. The external I/V converter op amp
R
OUT
V
2R
OUT
Equation
terminal impedance change.
REF
2R
to swing from –10V to
OUT
1:
terminal) changes
FB
R
FB
resistor in the
DAC8822
I
GND
OUT
REF
) that
(1)
15