ADT7460 Analog Devices, Inc., ADT7460 Datasheet - Page 9

• Manufacturer Part Number: ADT7460
• Description: Dbcool? Remote Thermal Controller And Fan Controller
• Manufacturer: Analog Devices, Inc.

PRODUCT DESCRIPTION
The ADT7460 is a thermal monitor and multiple fan controller
for any system requiring monitoring and cooling. The device
communicates with the system via a serial System Management
Bus (SMBus). The serial bus controller has an optional address
line for device selection (Pin 9), a serial data line for reading
and writing addresses and data (Pin 16), and an input line for
the serial clock (Pin 1). All control and programming functions
of the ADT7460 are performed over the serial bus. In addition,
two of the pins can be reconfigured as an SMBALERT output to
indicate out-of-limit conditions.
MEASUREMENT INPUTS
The device has three measurement inputs, one for voltage and
two for temperature. It can also measure its own supply voltage
and can measure ambient temperature with its on-chip
temperature sensor.
Pin 14 is an analog input with an on-chip attenuator and is
configured to monitor 2.5 V.
Power is supplied to the chip via Pin 3, and the system also
monitors V
connected to a 3.3 V standby supply. This pin can, however, be
connected to a 5 V supply and monitor it without overranging.
Remote temperature sensing is provided by the D1± and D2±
inputs, to which diode-connected, external temperature-sensing
transistors, such as a 2N3904 or CPU thermal diode, may be
connected.
The ADC also accepts input from an on-chip band gap
temperature sensor, which monitors system ambient
temperature.
CC
through this pin. In PCs, this pin is normally
FRONT
CHASSIS
FAN
REAR
CHASSIS
FAN
AMBIENT
TEMPERATURE
Figure 13. Recommended Implementation
TACH2
PWM3
TACH3
D1+
D1–
Rev. C | Page 9 of 52
ADT7460
GND
SMBALERT
THERM
TACH1
P
WM1
SEQUENTIAL MEASUREMENT
When the ADT7460 monitoring sequence is started, it cycles
sequentially through the measurement of 2.5 V input and the
temperature sensors. Measured values from these inputs are
stored in value registers. These can be read out over the serial
bus or can be compared with programmed limits stored in the
limit registers. The results of out-of-limit comparisons are
stored in the status registers, which can be read over the serial
bus to flag out-of-limit conditions.
RECOMMENDED IMPLEMENTATION
Configuring the ADT7460 as in Figure 13 allows the systems
designer the following features:
•
•
•
•
•
•
•
SDA
SCL
D2+
D2–
front and rear chassis fans are connected in parallel).
Three TACH fan speed measurement inputs.
V
CPU temperature measured using Remote 1 temperature
channel.
Ambient temperature measured through Remote 2
temperature channel.
Bidirectional THERM pin. Allows Intel Pentium 4
PROCHOT monitoring and can function as an
overtemperature THERM output.
SMBALERT system interrupt output.
Two PWM outputs for fan control of up to three fans (the
CC
PROCHOT
measured internally through Pin 3.
ICH
ADT7460