ADT7460(2013) データシートの表示（PDF） - ON Semiconductor
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ADT7460 Datasheet PDF : 47 Pages
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ADT7460
ADT7460 Address Selection
Pin 8 is the dual-function PWM3/ADDRESS ENABLE
pin. If Pin 8 is pulled low on powerup, the ADT7460 reads
the state of Pin 9 (TACH4/ADDRESS SELECT/THERM)
to determine the ADT7460’s slave address. If Pin 8 is high
on powerup, the ADT7460 defaults to SMBus Slave
Address 0x2E. This function is described in more detail
later.
Internal Registers of the ADT7460
Table 5 summarizes the ADT7460’s principal internal
registers. Table 42 to Table 82 describe the registers in more
detail.
Table 5. SUMMARY INTERNAL REGISTERS
Register
Description
Configuration
These registers provide control and configuration of the ADT7460, including alternate pinout functionality.
Address Pointer
This register contains the address that selects one of the other internal registers. When writing to the
ADT7460, the first byte of data is always a register address, which is written to the address pointer register.
Status Registers
These registers provide the status of each limit comparison and are used to signal out-of-limit conditions on
the temperature, voltage, or fan speed channels. If Pin 14 or Pin 5 is configured as SMBALERT, this pin
asserts low whenever an unmasked status bit is set.
Interrupt Mask
These registers allow each interrupt status event to be masked when Pin 14 or Pin 5 is configured as an
SMBALERT output.
Value and Limit
The results of analog voltage input, temperature, and fan speed measurements are stored in these registers,
along with their limit values.
Offset
These registers allow each temperature channel reading to be offset by a twos complement value written to
these registers.
TMIN
TRANGE
These registers program the starting temperature for each fan under automatic fan speed control.
These registers program the temperature-to-fan speed control slope in automatic fan speed control mode for
each PWM output.
Operating Point
These registers define the target operating temperatures for each thermal zone when running under
dynamic TMIN control. This function allows the cooling solution to adjust dynamically in response to
measured temperature and system performance.
Enhance Acoustics
These registers allow each PWM output controlling fan to be tweaked to enhance the system’s acoustics.
Theory of Operation
Serial Bus Interface
Control of the ADT7460 is carried out using the serial
System Management Bus (SMBus). The ADT7460 is
connected to this bus as a slave device, under the control of
a master controller.
The ADT7460 has a 7-bit serial bus address. When the
device is powered up with Pin 8 (PWM3/ADDRESS
ENABLE) high, the ADT7460 has a default SMBus address
of 0101110 or 0x2E. If more than one ADT7460 is to be used
in a system, each ADT7460 should be placed in address
select mode by strapping Pin 8 low on powerup. The logic
state of Pin 9 then determines the device’s SMBus address.
The logic state of these pins is sampled on powerup.
The device address is sampled 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 address byte matches the selected slave address. The
selected slave address is chosen using the ADDRESS
ENABLE/ADDRESS SELECT pins. Any attempted
changes in the address has no effect after this.
Table 6. ADDRESS SELECT MODE
Pin 8
State
Pin 9 State
Address
0
Low (10 kW to GND) 0101100 (0x2C)
0
High (10 kW Pullup)
0101101 (0x2D)
1
Don’t Care
0101110 (0x2E) (Default)
VCC
ADT7460
ADDR_SEL 9
10 kW
PWM3/ 8
ADDR_EN
ADDRESS = 0x2E
Figure 13. Default SMBus Address 0x2E
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