AD5273

–15–

CONTROLLING TWO DEVICES ON ONE BUS

Figure 12 shows two AD5273 devices on the same serial bus.

Each has a different slave address since the state of each AD0

pin is different. This allows each device to operate independently.

The master device output bus line drivers are open-drain pull

downs in a fully I

MASTER

SDA SCL

AD0

AD5273

SDA SCL

AD0

AD5273

SDA

SCL

5V

Rp

Rp

5V

Figure 12. Two AD5273 Devices on One Bus

APPLICATIONS

Programmable Voltage Reference

For Voltage Divider mode operation, as shown in Figure 13, it is

common to buffer the output of the digital potentiometer unless

the purpose of impedance conversion, it also allows a heavier

load to be driven.

I

Write Bit Pattern Illustrations

SDA

FRAME 1

SLAVE ADDRESS BYTE

FRAME 2

INSTRUCTION BYTE

FRAME 1

DATA BYTE

SCL

ACK. BY

AD5273

ACK. BY

AD5273

ACK. BY

AD5273

STOP BY

MASTER

START BY

MASTER

0

0

1

0

11

0

AD0 R/W

0

X

X

X

X

X

X

X

X

X

D5

D4

D3

D2

D1

D0

8

0

8

0

8

Figure 10a. Writing to the RDAC Register

SDA

FRAME 1

SLAVE ADDRESS BYTE

FRAME 2

INSTRUCTION BYTE

FRAME 1

DATA BYTE

SCL

ACK. BY

AD5273

ACK. BY

AD5273

ACK. BY

AD5273

STOP BY

MASTER

START BY

MASTER

0

0

1

0

11

0

1

X

X

X

X

X

X

X

X

X

D5

D4

D3

D2

D1

D0

8

0

8

0

8

Figure 10b. Activating One Time Programming

Read Bit Pattern Illustration

SDA

FRAME 1

SLAVE ADDRESS BYTE

FRAME 2

DATA BYTE FROM SELECTED

RDAC REGISTER

SCL

ACK. BY

AD5273

NO ACK. BY

MASTER

STOP BY

MASTER

START BY

MASTER

0

0

1

0

11

0

AD0

E1

E0

D5

D4

D3

D2

D1

D0

8

0

8

R/

W

Figure 11. Reading Data From the RDAC Register

GND

1U1

5V

2

3

AD8601

5V

A

W

B

ADR03

U3

AD5273

U2

Figure 13. Programmable Voltage Reference

Programmable Voltage Source with Boosted Output

For applications that require high current adjustment such as a

laser diode driver or tunable laser, a boosted voltage source can

be considered. See Figure 14.

+V

W

SIGNAL

LD

A

B

U1

AD5273

U3 2N7002

AD8601

U2

–V

Figure 14. Programmable Booster Voltage Source

to be equal to the wiper voltage set by the digital potentiometer.

The load current is then delivered by the supply via the N-Ch

REV. 0