ADT7475 Analog Devices, Inc., ADT7475 Datasheet - Page 19

• Manufacturer Part Number: ADT7475
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

Single-Channel ADC Conversions
Setting Bit 6 of Configuration Register 2 (0x73) places the
ADT7475 into single-channel ADC conversion mode. In this
mode, the ADT7475 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 (0x55).
Table 11. Programming Single-Channel ADC Mode
for Temperatures
Register 0x55, Bits [7:5]
101
110
111
Configuration Register 2 (0x73)
Bit 4 = 1, averaging off.
Bit 6 = 1, single-channel convert mode.
TACH1 Minimum High Byte Register ( 0x55)
Bits [7:5] select the ADC channel for single-channel convert
mode.
Overtemperature Events
Overtemperature events on any of the temperature channels can
be detected and dealt with automatically in automatic fan speed
control mode. Register 0x6A to Register 0x6C are the THERM
temperature limit registers. When a temperature exceeds its
THERM temperature limit, all PWM outputs run at the
maximum PWM duty cycle (Register 0x38, Register 0x39, and
Register 0x3A). This effectively runs the fans at the fastest
allowed speed.
Channel Selected
Remote 1 temperature
Local temperature
Remote 2 temperature
Rev. B | Page 19 of 68
The fans run at this speed until the temperature drops below
THERM minus hysteresis. This can be disabled by setting the
boost bit in Configuration Register 3 (0x78), Bit 2. The
hysteresis value for the THERM temperature limit is the value
programmed into Register 0x6D and Register 0x6E (hysteresis
registers). The default hysteresis value is 4°C.
THERM can be disabled on specific temperature channels using
Bits [7:5] of Configuration Register 5 (0x7C). THERM can also
be disabled by
•
•
THERM LIMIT
FANS
In Offset 64 mode, writing −64°C to the appropriate THERM
temperature limit.
In twos complement mode, writing −128°C to the
appropriate THERM temperature limit.
TEMPERATURE
Figure 24. THERM Temperature Limit Operation
100%
HYSTERESIS (°C)
ADT7475