Datasheet

Data Sheet AD5172/AD5173
Rev. I | Page 23 of 28
Multiple Devices on One Bus (AD5173 Only)
Figure 52 shows four AD5173 devices on the same serial bus.
Each has a different slave address because the states of the AD0
and AD1 pins are different. This allows each device on the bus to
be written to or read from independently. The master device
output bus line drivers are open-drain pull-downs in a fully
I
2
C-compatible interface.
SDA
SDA
AD1
AD0
MASTER
SCL
SCL
AD5173
SDA
AD1
AD0
SCL
AD5173
SDA
AD1
AD0
SCL
AD5173
SDA
5V
R
P
R
P
5V
5V
5V
AD1
AD0
SCL
AD5173
04103-044
Figure 52. Multiple AD5173 Devices on One I
2
C Bus
LEVEL SHIFTING FOR DIFFERENT VOLTAGE
OPERATION
If the SCL and SDA signals come from a low voltage logic
controller and are below the minimum V
IH
level (0.7 V × V
DD
),
level shift the signals for read/write communications between
the AD5172/AD5173 and the controller. Figure 53 shows one
of the implementations. For example, when SDA1 is at 2.5 V,
M1 turns off, and SDA2 becomes 5 V. When SDA1 is at 0 V,
M1 turns on, and SDA2 approaches 0 V. As a result, proper
level shifting is established. It is best practice for M1 and M2
to be low threshold N-channel power MOSFETs, such as the
FDV301N from Fairchild Semiconductor.
2.5V
CONTROLLER
2.7V TO 5.5V
AD5172/
AD5173
R
P
R
P
R
P
R
P
V
DD1
= 2.5V
V
DD2
= 5V
G
G
S
D
M1
S
D
M2
SDA1
SCL1
SDA2
SCL2
04103-061
Figure 53. Level Shifting for Different Voltage Operation