SMP08

–7–

REV. D

SMP08

13

14

15

12

1

2

4

5

3

16

6

7

8

9

10

11

+12V

3

15

1

5

16

17

4

+12V

+5V

REF02

+12V

GND

WR

CS

DAC8228

A

B

C

ADDRESS

DECODE

ADDRESS

BUS

DIGITAL

INPUTS

WR

DGND

INH

0.1µF

PIN 9

C

PIN 10

B

PIN 11

A

PIN 6

INH

CH

PIN

0

0

0

0

1

1

1

1

X

0

0

1

1

0

0

1

1

X

0

1

0

1

0

1

0

1

X

0

0

0

0

0

0

0

0

1

0

1

2

3

4

5

6

7

NONE

13

14

15

12

1

5

2

4

–

CHANNEL DECODING

Figure 18. 8-Channel Multiplexed D/A Converter

Do not apply signals to the SMP08 with power off unless the

input current is limited to less than 10 mA.

TYPICAL APPLICATIONS

AN 8-CHANNEL MULTIPLEXED D/A CONVERTER

Figure 18 illustrates a typical demultiplexing function of the

SMP08. It is used to sample-and-hold eight different output

voltages corresponding to eight different digital codes from a

D/A converter. The SMP08’s droop rate of 20 mV/s requires a

refresh once every 500 ms, before the voltage drifts beyond

1/2 LSB accuracy (1 LSB of an 8-bit DAC is equivalent to

19.5 mV out of a full-scale voltage of 5 V). For a 10-bit DAC

the refresh rate must be less than 120 ms, and, for a 12-bit

system, 31 ms. This implementation is very cost effective com-

pared to using multiple DACs as the number of output channels

increases.