AD5821

Rev. 0 | Page 12 of 16

PD

X

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

X

X

X

X

00

SCL

SDA

START BY

MASTER

ACK BY

AD5821

11

91

ACK BY

AD5821

ACK BY

AD5821

STOP BY

MASTER

FRAME 3

LEAST SIGNIFICANT

DATA BYTE

FRAME 2

MOST SIGNIFICANT

DATA BYTE

FRAME 1

SERIAL BUS

ADDRESS BYTE

01

1

1

1

R/W

9

Figure 22. Write Operation

PD

X

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

X

X

X

X

00

SCL

SDA

START BY

MASTER

ACK BY

AD5821

11

91

ACK BY

AD5821

ACK BY

AD5821

STOP BY

MASTER

FRAME 3

LEAST SIGNIFICANT

DATA BYTE

FRAME 2

MOST SIGNIFICANT

DATA BYTE

FRAME 1

SERIAL BUS

ADDRESS BYTE

01

1

1

1

R/W

9

Figure 23. Read Operation

Table 6. Data Format1

Serial Data-Words

High Byte

Low Byte

Serial Data Bits

SD7

SD6

SD5

SD4

SD3

SD2

SD1

SD0

SD7

SD6

SD5

SD4

SD3

SD2

SD1

SD0

Input Register

R15

R14

R13

R12

R11

R10

R9

R8

R7

R6

R5

R4

R3

R2

R1

R0

Function

XSHUTDOWN

X

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

X

X

X

X

POWER SUPPLY BYPASSING AND GROUNDING

When accuracy is important in an application, it is beneficial to

consider power supply and ground return layout on the PCB.

The PCB for the AD5821 should have separate analog and digital

power supply sections. Where shared AGND and DGND is

necessary, the connection of grounds should be made at only

one point, as close as possible to the AD5821.

Special attention should be paid to the layout of the AGND return

path and, and it should be tracked between the voice coil motor

output current sink of the AD5821 and illustrates the importance

of reducing the effective series impedance of AGND and the track

the AD5821 is sinking current. The effect of any series inductance

is minimal.

AGND

AD5821

Q1

GROUND

RETURN

R

TRACE

RESISTANCE

VOICE

COIL

SDA

SCL

XSHUTDOWN

DGND

DGND

Figure 24. Effect of PCB Trace Resistance and Inductance