Data Sheet
FEATURES
Temperature Sensor Hub and Fan Controller
GENERAL DESCRIPTION
The ADT7470
controller is a multichannel temperature sensor
and PWM fan controller and fan speed monitor for systems
requiring active cooling. It is designed to interface directly to
an I
2
C® bus. The ADT7470 can monitor up to 10 daisy-chained
TMP05 temperature sensors. It can also monitor and control
the speed of four fans, in automatic or in manual control loops.
A FULL_SPEED input is provided to allow the fans to be
blasted to maximum speed, via external hardware control,
under extreme thermal conditions or on system startup. An
SMBALERT interrupt communicates error conditions such as
fan under speed and over temperature measurements to the
system service processor. Individual error conditions can then
be read from status registers over the I
2
C bus.
Monitors up to 10 remote temperature sensors
Monitors and controls speed of up to 4 fans independently
PWM outputs drive each fan under software control
FULL_SPEED input allows fans to be blasted to maximum
speed by external hardware
SMBALERT interrupt signals failures to system controller
Three-state ADDR pin allows up to 3 devices on a single bus
Temperature decoder interprets TMP05 temperature sensors
and communicates values over I
2
C bus
Limit comparison of all monitored values
Supports fast I
2
C standard (400 kHz max)
Meets SMBus 2.0 electrical specifications
(fully SMBus 1.1-compliant)
APPLICATIONS
Servers
Networking and telecommunications equipment
Desktops
FUNCTIONAL BLOCK DIAGRAM
ADDR
SDA SCL SMBALERT
ADT7470
SMBus
ADDRESS
SELECTION
SERIAL BUS
INTERFACE
FULL_SPEED
ADDRESS
POINTER
REGISTER
PWM1
PWM2
PWM3
PWM4
PWM
REGISTERS
AND
CONTROLLERS
AUTOMATIC
FAN SPEED
CONTROL
PWM
CONFIG
REGISTERS
TACH1
TACH2
TACH3
TACH4
FAN SPEED
COUNTERS
INTERRUPT
MASKING
INTERRUPT
STATUS
REGISTERS
TMP_START
TMP_IN
TEMPERATURE
DECODER
LIMIT
COMPARATORS
Figure 1.
1
Protected by Patent Numbers US6,169,442, US6,097,239, US5,982,221, US5,867,012. Other patents pending.
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Tel: 781.329.4700 ©2004–2013 Analog Devices, Inc. All rights reserved.
Rev. E
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04684-0-001
VALUE AND
LIMIT
REGISTERS
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