ADT7473-1 View Datasheet(PDF) - ON Semiconductor
Part Name
Description
Manufacturer
ADT7473-1 Datasheet PDF : 74 Pages
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FRONT
CHASSIS
FAN
ADT7473
ADT7473
TACH2
PWM1
TACH1
CPU FAN
REAR
CHASSIS
FAN
AMBIENT
TEMPERATURE
PWM3
TACH3
D2+
D2–
THERM
D1+
SDA
D1–
SCL
SMBALERT
GND
PROCHOT
ICH
CPU
Figure 12. ADT7473 Configuration
Serial Bus Interface
On PCs and servers, control of the ADT7473/ADT7473−1
is carried out using the SMBus. The ADT7473/ADT7473−1
is connected to this bus as a slave device, under the control of
a master controller, which is usually (but not necessarily) the
ICH.
The ADT7473 has a fixed 7−bit serial bus address of
0101110 or 0x2E. The read/write bit must be added to get the
8−bit address (01011100 or 0x5C). When the ADT7473−1
is powered up with Pin 8 (PWM3/ADDREN) high, the
ADT7473−1 has a default SMBus address of 0101110 or
0x2E. If more than one ADT7473−1 is used in a system,
each ADT7473−1 is placed in ADDR SELECT mode by
strapping Pin 8 low on powerup. The logic state of Pin 4 then
determines the device’s SMBus address. The logic of these
pins is sampled on powerup.
The device address is sampled on powerup and latched on
the first valid SMBus transaction, more precisely on the
low−to−high transition at the beginning of the eighth SCL
pulse, when the serial bus address byte matches the selected
slave address. The selected slave address is chosen using the
ADDREN pin/ADDR SELECT pin. Any attempted change
in the address has no effect after this.
Table 3. Hardwiring the ADT7473−1 SMBus Device
Address
Pin 13 State
0
0
1
Pin 14 State
Low (10 kW to GND)
High (10 kW pullup)
Don’t care
Address
0101100 (0x2C)
0101101 (0x2D)
0101110 (0x2E)
ADT7473−1
ADDR SELECT
PWM3/ADDREN
VCC
4
10kΩ
8
ADDRESS = 0x2E
Figure 13. Default SMBus Address = 0x2E
ADT7473−1
ADDR SELECT
4 10kΩ
PWM3/ADDREN
8
ADDRESS = 0x2C
Figure 14. SMBus Address = 0x2C (Pin4 = 0)
ADT7473−1
ADDR SELECT
VCC
10kΩ
4
PWM3/ADDREN 8
ADDRESS = 0x2D
Figure 15. SMBus Address = 0x2D (Pin 4 = 1)
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