DAC8801IDGK BURR-BROWN [Burr-Brown Corporation], DAC8801IDGK Datasheet - Page 11

• Manufacturer Part Number: DAC8801IDGK
• Description: 14-Bit, Serial Input Multiplying Digital-to-Analog Converter
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

Bipolar Output Circuit
The DAC8801, as a 2-quadrant multiplying DAC, can be used to generate a unipolar output. The polarity of the
full-scale output I
Some applications require full 4-quadrant multiplying capabilities or bipolar output swing. As shown in Figure 22,
external op amp U4 is added as a summing amp and has a gain of 2X that widens the output span to 5 V. A
4-quadrant multiplying circuit is implemented by using a 2.5-V offset of the reference voltage to bias U4.
According to the circuit transfer equation given in Equation 2, input data (D) from code 0 to full scale produces
output voltages of V
Programmable Current Source Circuit
A DAC8801 can be integrated into the circuit in Figure 23 to implement an improved Howland current pump for
precise voltage to current conversions. Bidirectional current flow and high voltage compliance are two features of
the circuit. A application of this circuit includes a 4-mA to 20-mA current transmitter with up to a 500-
a matched resistor network, the load current of the circuit is shown in Equation 3:
I
V
L
OUT
+
www.ti.com
(R2 ) R3)
+
16, 384
R3
D
* 1
OUT
R1
V
REF
OUT
is the inverse of the input reference voltage at V
(+10 V)
+2.5 V
Figure 23. Programmable Bidirectional Current Source Circuit
= -2.5 V to V
V
V
REF
REF
V
REF
D
V
V
REF
DD
V
DAC8801
OUT
V
DD
DD
Figure 22. Bipolar Output Circuit
U1
V
GND
DAC8801
R
DD
= +2.5 V.
FB
GND
R
FB
I
OUT
I
OUT
OPA277
U2
−
+
C1
+
−
OPA277
10 kW
U2
150 kW
150 kW
R14
R1
5 kW
REF
SLAS403A – NOVEMBER 2004 – REVISED DECEMBER 2004
.
−2.5 V 3 V
(−10 V 3 V
+
−
15 kW
15 kW
OPA277
10 pF
10 kW
R24
−
+
C1
R2
U2
C2
OPA277
OUT
U4
OUT
LOAD
3 +2.5 V
3 +10 V)
R34
50 W
R3
50 W
V
I
L
OUT
V
OUT
DAC8801
load. With
(2)
(3)
11