Using an AC Reference

the MAX500 has multiplying capability within the limits

a technique for applying a sine-wave signal to the refer-

ence input, where the AC signal is biased up before

than 0.1% with input frequencies up to 50kHz, and the

never be more negative than AGND.

The performance of the MAX500 is specified for both

improved performance of dual-supply operation is

supply can be generated using an ICL7660 in one of

the circuits of Figure 12.

Digital Interface Applications

Figures 13 through 16 show examples of interfacing the

MAX500 to most popular microprocessors.

CMOS, Quad, Serial-Interface

8-Bit DAC

______________________________________________________________________________________

11

DAC B

MAX500

4

14

DGND

36

-5V (OR GND)

DIGITAL INPUTS NOT SHOWN

AGND

+4V

-4V

AC

REFERENCE

INPUT

+15V

15k

10k

5

ICL7660

CAP+

CAP-

V+

GND

ICL7660

CAP+

CAP-

V+

GND

6V

ZENER

12V to 15V

10k

2N2222

10k

10

µF

8

3

2

10

µF

4

5

-5V

10

µF

+5V

LOGIC

SUPPLY

-5V

10

µF

8

3

4

5

10

µF

2

SCL

SDA

LDAC

LOAD*

80C51

P1.0

P1.1

P1.2

P1.3

CONNECT LOAD TO P1.3 FOR 3-WIRE MODE OR

. . . . . . .

SRO

MAX500

*

ADDRESS BUS

EN ADDRESS

CODE

B/A

DATA BUS

CONNECT LOAD TO P1.3 FOR 3-WIRE MODE OR

C/D

CE

RD

INT

D7

D0

Z8420

B0

B1

B2

B3

A15

A0

Z80

I/O REQ

WR

INT

D7

D0

A1

A0

SCL

SDA

LDAC

LOAD*

. .

MAX500

*

Figure 11. AC Reference Input Circuit

Figure 14. Z-80 with Z8420 PIO Interface

Figure 13. 80C51 Interface