Datasheet

OP490
Rev. E | Page 11 of 16
MICROPOWER SINGLE-SUPPLY QUAD VOLTAGE-
OUTPUT 8-BIT DAC
The circuit shown in Figure 23 uses the DAC8408 CMOS quad
8-bit DAC, and the OP490 to form a single-supply quad voltage
output DAC with a supply drain of only 140 μA. The DAC8408
is used in voltage switching mode and each DAC has an output
resistance (≈10 kΩ) independent of the digital input code. The
output amplifiers act as buffers to avoid loading the DACs. The
100 kΩ resistors ensure that the OP490 outputs swing below 0.8 V
when required.
00308-023
DGND
A/B
28
V
REF
A
REFERENCE
VOLTAGE
1.5V
V
REF
B
V
REF
C
V
REF
D
I
OUT1D
DAC DATA BUS
PIN 9 (LSB) TO PIN 16 (MSB)
DAC A
1/4
DAC8408
OP490
DAC8408
DAC B
1/4
DAC8408
DAC C
1/4
DAC8408
DAC D
1/4
DAC8408
R4
100k
V
OUT
D
R3
100k
V
OUT
C
R2
100k
V
OUT
B
R1
100k
V
OUT
A
1
4
11
7
14
8
+5
V
2
3
6
5
13
12
9
1021
23
I
OUT2C/2D
24
I
OUT1C
25
I
OUT1B
6
I
OUT2A/2B
5
I
OUT1A
4
27
8
2
19
18
DIGITAL
CONTROL
SIGNALS
20
17
DS2
DS1
R/W
+
–
1/4
OP490
A
+
–
1/4
OP490
B
+
–
1/4
OP490
C
+
–
1/4
OP490
D
Figure 23. Micropower Single-Supply Quad Voltage Output 8-Bit DAC