REV. C

OP490

–11–

10

21

12

27

5

8

1/4

OP490E

A

+5V

R1

100k

11

4

2

1

DAC A

1/4

DAC8408

1/4

OP490E

B

R2

100k

6

7

DAC B

1/4

DAC8408

1/4

OP490E

C

R3

100k

13

14

DAC C

1/4

DAC8408

1/4

OP490E

D

R4

100k

9

8

DAC D

1/4

DAC8408

DAC DATA BUS

PIN9(LSB) – 16(MSB)

2

2

REFERENCE

VOLTAGE

1.5V

21

25

5

4

6

24

23

OP490EY

DAC8408ET

A/B

17

R/W

18

DS1

19

20

DS2

DIGITAL

CONTROL

SIGNALS

28

DGND

Figure 6. Micropower Single-Supply Quad Voltage Output 8-Bit DAC

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 k

W

resistors ensure that the OP490 outputs will swing below 0.8 V

when required.