OP490
Micropower Single-Supply Quad Voltage-Output 8-Bit DAC
The circuit of Figure 6 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 mA. The DAC8408 is used
in voltage switching mode and each DAC has an output resistance
(ª10 kW) independent of the digital input code. The output
amplifiers act as buffers to avoid loading the DACs. The 100 kW
resistors ensure that the OP490 outputs will swing below 0.8 V
when required.
+5V
4
2
1
REFERENCE
VOLTAGE
1.5V
4
I
OUT1A
V
A
OUT
DAC A
1/4
V
A
2
2
REF
1/4
OP490E
A
R1
DAC8408
100k⍀
11
I
5
6
OUT2A/2B
6
5
7
V
B
OUT
DAC B
1/4
V
B
8
REF
1/4
I
OUT1B
OP490E
B
R2
DAC8408
100k⍀
13
12
14
25
I
OUT1C
V
C
OUT
DAC C
1/4
V
C
27
REF
1/4
R3
OP490E
C
DAC8408
100k⍀
24
23
I
OUT2C/2D
9
8
V
D
OUT
21
DAC D
V
D
21
10
REF
1/4
1/4
I
OUT1D
R4
OP490E
D
DAC8408
100k⍀
OP490EY
DAC DATA BUS
PIN9(LSB) – 16(MSB)
17
A/B
R/W
DS1
DS2
18
19
20
DAC8408ET
DIGITAL
CONTROL
SIGNALS
DGND
28
Figure 6. Micropower Single-Supply Quad Voltage Output 8-Bit DAC
–11–
REV. C
ADI [ ADI ]
