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
Table 16. TEMPERATURE OFFSET REGISTERS
Register
Description
Default
0x70
0x71
0x72
Remote 1 Temperature Offset
Local Temperature Offset
Remote 2 Temperature Offset
0x00 (0°C)
0x00 (0°C)
0x00 (0°C)
Temperature Measurement Limit Registers
Associated with each temperature measurement channel
are high and low limit registers. Exceeding the programmed
high or low limit causes the appropriate status bit to be set.
Exceeding either limit can also generate SMBALERT
interrupts.
Table 17. TEMPERATURE MEASUREMENT LIMIT
REGISTERS
Register
Description
Default
0x4E
0x4F
0x50
0x51
0x52
0x53
Remote 1 Temperature Low Limit
Remote 1 Temperature High Limit
Local Temperature Low Limit
Local Temperature High Limit
Remote 2 Temperature Low Limit
Remote 2 Temperature High Limit
0x81
0x7F
0x81
0x7F
0x81
0x7F
Overtemperature Events
Overtemperature events on any of the temperature
channels can be detected and dealt with automatically in
automatic fan speed control mode. Registers 0x6A to 0x6C
are the THERM limits. When a temperature exceeds its
THERM limit, all fans run at 100% duty cycle. The fans
continue running at 100% until the temperature drops below
THERM – Hysteresis. (This can be disabled by setting the
BOOST bit in Configuration Register 3, Bit 2,
Register 0x78). The hysteresis value for that THERM limit
is the value programmed into Registers 0x6D and 0x6E
(hysteresis registers). The default hysteresis value is 4°C.
THERM LIMIT
TEMPERATURE
HYSTERESIS (°C)
FANS
100%
Figure 27. THERM Limit Operation
Additional ADC Functions for Temperature Measurement
A number of other functions are available on the
ADT7460 to offer the systems designer increased flexibility.
Turn-off Averaging
For each temperature measurement read from a value
register, 16 readings have actually been made internally and
the results averaged before being placed into the value
register. Sometimes it may be necessary to take a very fast
measurement, for example, of CPU temperature. Setting
Bit 4 of Configuration Register 2 (Reg. 0x73) turns
averaging off. This takes a reading every 15.5 ms. Each
remote temperature measurement takes 4 ms and the local
temperature measurement takes 1.4 ms.
Single-channel ADC Conversions
Setting Bit 6 of Configuration Register 2 (Reg. 0x73)
places the ADT7460 into single-channel ADC conversion
mode. In this mode, the ADT7460 can be made to read a
single temperature channel only. The appropriate ADC
channel is selected by writing to Bits <7:5> of the TACH1
minimum high byte register (Reg. 0x55).
Table 18. CONFIGURATION REGISTER 2 (REG. 0X73)
Bit
Description
<4> 1: Averaging Off
<6> 1: Single-channel Convert Mode
Table 19. TACH1 MINIMUM HIGH BYTE (REG. 0X55)
Bit
Description
<7:5>
Selects ADC Channel for
Single-channel Convert Mode
Value
Channel Selected
101
Remote 1 Temp
110
Local Temp
111
Remote 2 Temp
Limits, Status Registers, and Interrupts
Limit Values
Associated with each measurement channel on the
ADT7460 are high and low limits. These can form the basis
of system status monitoring: a status bit can be set for any
out-of-limit condition and detected by polling the device.
Alternatively, SMBALERT interrupts can be generated to
flag a processor or micro controller of out-of-limit
conditions.
8-bit Limits
The following is a list of 8-bit limits on the ADT7460.
Table 20. VOLTAGE LIMIT REGISTERS
Register
Description
0x44
0x45
0x48
0x49
2.5 V Low Limit
2.5 V High Limit
VCC Low Limit
VCC High Limit
Default
0x00
0xFF
0x00
0xFF
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