Datasheet ADT7470 (Analog Devices) - 6

ADT7470 Data Sheet PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SCL 1 16 SDA GND 2 15 PWM1 V 3 ADT7470 14 CC SMBALERT TOP VIEW TACH3 4 (Not to Scale) 13 FULL_SPEED/TMP_START PWM2 5 12 TMP_IN TACH1 6 11 ADDR TACH2 7 10 PWM4 8 9 PWM3 TACH4
04684-0-003 Figure 3. Pin Configuration
Table 4. Pin Function Descriptions Pin No. Mnemonic Description
1 SCL Digital Input (Open Drain). SMBus serial clock input. Requires SMBus pull-up, typically 2k2Ω. 2 GND Ground Pin. 3 VCC Power Supply Pin. 4 TACH3 Digital Input (Open Drain). Fan tachometer input to measure the speed of Fan 3. 5 PWM2 Digital I/O (Open Drain). Requires 10 kΩ typical pull-up. Pulse-width modulated output to control the speed of Fan 2. Can be configured as GPIO by setting Bit 0x7F[2] = 1. 6 TACH1 Digital Input (Open Drain). Fan tachometer input to measure the speed of Fan 1. 7 TACH2 Digital Input (Open Drain). Fan tachometer input to measure the speed of Fan 2. 8 PWM3 Digital I/O (Open Drain). Pulse-width modulated output to control the speed of Fan 3. Requires 10 kΩ typical pull-up. Can be configured as GPIO by setting Bit 0x7F[1] = 1. 9 TACH4 Digital Input (Open Drain). Fan tachometer input to measure the speed of Fan 4. 10 PWM4 Digital I/O (Open Drain). Pulse-width modulated output to control the speed of Fan 4. Requires 10 kΩ typical pull-up. Can be configured as GPIO by setting Bit 0x7F[0] = 1. 11 ADDR Three-state Input. Used to set the SMBus device address. 12 TMP_IN Digital Input (Open Drain). PWM input to PWM processing engine that interprets daisy-chained output from multiple TMP05 temperature sensors. Readings from individual TMP05 temperature sensors are available by reading the temperature reading registers over the SMBus. 13 FULL_SPEED Digital Input Active Low (Open Drain). This input blasts the fans to maximum speed when the pin is pulled low externally. Do not leave pin 13 open when not I use, tie to VCC. 13 TMP_START Digital Output (Open Drain). This pin can be used as an output to start daisy-chained temperature measurements from TMP05 or TMP06 temperature sensors. Requires 10 kΩ typical pull-up. 14 SMBALERT Digital Output Active Low (Open Drain). This pin can be reconfigured as an SMBALERT interrupt output to signal out-of-limit conditions such as fan failures. 15 PWM1 Digital I/O (Open Drain). Pulse-width modulated output to control the speed of Fan 1. Requires 10 kΩ typical pull-up. Can be configured as GPIO by setting Bit 0x7F[3] = 1. 16 SDA Digital I/O (Open Drain). SMBus bidirectional serial data. Requires SMBus pull-up, typically 2k2Ω. Rev. E | Page 6 of 40 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