Datasheet ADT7470 (Analog Devices)

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Temperature Sensor Hub and Fan Controller Data Sheet ADT7470 FEATURES GENERAL DESCRIPTION Monitors up to 10 remote temperature sensors
The ADT74701 controller is a multichannel temperature sensor
Monitors and controls speed of up to 4 fans independently
and PWM fan control er and fan speed monitor for systems
PWM outputs drive each fan under software control
requiring active cooling. It is designed to interface directly to
FULL_SPEED input allows fans to be blasted to maximum
an I2C® bus. The ADT7470 can monitor up to 10 daisy-chained
speed by external hardware
TMP05 temperature sensors. It can also monitor and control
SMBALERT interrupt signals failures to system controller
the speed of four fans, in automatic or in manual control loops.
Three-state ADDR pin allows up to 3 devices on a single bus Temperature decoder interprets TMP05 temperature sensors
A FULL_SPEED input is provided to al ow the fans to be
and communicates values over I2C bus
blasted to maximum speed, via external hardware control,
Limit comparison of all monitored values
under extreme thermal conditions or on system startup. An
Supports fast I2C standard (400 kHz max)
SMBALERT interrupt communicates error conditions such as
Meets SMBus 2.0 electrical specifications
fan under speed and over temperature measurements to the
(fully SMBus 1.1-compliant)
system service processor. Individual error conditions can then
APPLICATIONS
be read from status registers over the I2C bus.
Servers Networking and telecommunications equipment Desktops FUNCTIONAL BLOCK DIAGRAM ADDR SDA SCL SMBALERT ADT7470 SMBus SERIAL BUS FULL_SPEED ADDRESS INTERFACE SELECTION ADDRESS POINTER REGISTER PWM1 PWM AUTOMATIC PWM2 PWM REGISTERS FAN SPEED CONFIG AND CONTROL PWM3 REGISTERS CONTROLLERS PWM4 INTERRUPT TACH1 MASKING TACH2 FAN SPEED TACH3 COUNTERS INTERRUPT TACH4 STATUS REGISTERS TMP_START LIMIT TEMPERATURE COMPARATORS DECODER TMP_IN VALUE AND LIMIT REGISTERS
04684-0-001 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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Document Outline Features Applications General Description Functional Block Diagram Revision History Specifications Serial Bus Timing Specifications Absolute Maximum Ratings Thermal Characteristics ESD Caution Pin Configuration and Function Descriptions Functional Description General Description ADT7470 Monitoring Cycle Configuration Register 1 (Address 0x40) Configuration Register 2 (Address 0x74) ID Registers General-Purpose I/O Pins (Open Drain) SMBus/I2C Serial Interface Address Selection Serial Bus Protocol Write Operations Send Byte Write Byte Read Operations Receive Byte Alert Response Address SMBus Timeout Temperature Measurement Using TMP05/TMP06 Measuring Temperature TMP05/TMP06 Decoder Temperature ReadBack By the Host Temperature Data Format Temperature Measurement Limits Thermal Zones for Automatic Fan Control Thermal Zone TMIN Limit and Status Registers Limit Values Temperature Limits Fan Speed Limits Out-of-Limit Comparisons Status Registers SMBALERT Interrupt Handling SMBALERT Interrupts Masking Interrupt Sources Enabling the SMBALERT Interrupt Output Fan Drive Using PWM Control High Frequency Fan Drive Low Frequency Fan Drive Setting the Fan Drive Frequency Inverted PWM Output Fan Full Speed Function Fan Speed Measurement Tach Inputs Pulse Stretching Disabling Tach measurement Fan Speed Measurement Fan Speed Measurement Registers Reading Fan Speed from the ADT7470 Fan Tach Limit Registers Fan Speed Measurement Rate Calculating Fan Speed and Tachometer Limits Fan Pulses per Revolution Manual Fan Speed Control Setting the PWM Duty Cycle Example 1: For a PWM Duty Cycle of 50% Example 2: For a PWM Duty Cycle of 33% Automatic Fan Speed Control PWM Min Duty Cycle Example: For a PWM Min Duty Cycle of 30% PWN Max Duty Cycle PWM Current Duty Cycle Register Map Detailed Register Descriptions Outline Dimensions Ordering Guide