Temperature Sensor Hub and Fan Controller ADT7470 Data Sheet FEATURES GENERAL DESCRIPTION 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 communi
ADT7470 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Temperature Data Format ......................................................... 14 Applications ....................................................................................... 1 Temperature Measurement Limits ........................................... 15 General Description .........................................................................
Data Sheet ADT7470 SPECIFICATIONS TA = −40oC to +125oC, VCC = 3.0 V to 5.5 V, unless otherwise noted. Table 1. Parameter 1, 2, 3, 4, 5 POWER SUPPLY1 Supply Voltage Supply Current, ICC Standby Current, ICC FAN RPM-TO-DIGITAL CONVERTER Accuracy Full-Scale Count Nominal Input RPM Min Typ Max Unit 3.0 3.3 0.5 4 5.5 0.
ADT7470 Data Sheet SERIAL BUS TIMING SPECIFICATIONS Table 2.
Data Sheet ADT7470 ABSOLUTE MAXIMUM RATINGS Table 3. Parameter Positive Supply Voltage (VCC) Voltage on Any TACH or PWM Pin Voltage on Any Input or Output Pin Maximum Junction Temperature (TJ max) Storage Temperature Range Lead Temperature, Soldering Vapor Phase, 60 sec Infrared, 15 sec ESD Rating (HBM) Rating 6.5 V –0.3 V to +6.5 V –0.3 V to VCC + 0.3 V 150°C –65°C to +150°C 215°C 200°C 3000 V Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device.
ADT7470 Data Sheet PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SCL 1 16 SDA GND 2 15 PWM1 SMBALERT 3 ADT7470 TACH3 4 TOP VIEW (Not to Scale) 13 FULL_SPEED/TMP_START PWM2 5 12 TMP_IN TACH1 6 11 ADDR TACH2 7 10 PWM4 PWM3 8 9 TACH4 04684-0-003 VCC 14 Figure 3. Pin Configuration Table 4. Pin Function Descriptions Pin No.
Data Sheet ADT7470 FUNCTIONAL DESCRIPTION GENERAL DESCRIPTION The ADT7470 is a multichannel, pulse-width modulation (PWM) fan controller and monitor for any system requiring monitoring and cooling. The device communicates with the system via a serial system management bus. The device has a single address line for address selection (Pin 11), a serial data line for reading and writing addresses and data (Pin 16), and an input line for the serial clock (Pin 1).
ADT7470 Data Sheet GENERAL-PURPOSE I/O PINS (OPEN DRAIN) The ADT7470 has four pins that can be configured as either general-purpose logic pins or as PWM outputs. Each GPIO pin has a corresponding enable, direction, polarity and status bit.
Data Sheet ADT7470 Control of the ADT7470 is carried out using the serial system management bus (SMBus). This interface is fully compatible with SMBus 2.0 electrical specifications and meets 400 pF bus capacitance requirements. The device also supports fast I2C (400 kHz max). The ADT7470 is connected to the bus as a slave device under the control of a master controller or service processor.
ADT7470 Data Sheet To write data to one of the device data registers or read data from it, the address pointer register must be set so that the correct data register is addressed. Then data can be written into that register or read from it. The first byte of a write operation always contains an address that is stored in the address pointer register.
Data Sheet ADT7470 If the ADT7470 address pointer register value is unknown or not the desired value, it is first necessary to set it to the correct value before data can be read from the desired data register. This is done by performing a write to the ADT7470 as before, but only the data byte containing the register address is sent, because data cannot be written to the register. This is shown in Figure 8.
ADT7470 Data Sheet READ OPERATIONS 2. The master initiates a read operation and sends the alert response address (ARA = 000 1100). This is a general call address that must not be used as a specific device address. 3. The device whose SMBALERT output is low responds to the alert response address, and the master reads its device address. The address of the device is now known, and it can be interrogated in the usual way. 4.
Data Sheet ADT7470 TEMPERATURE MEASUREMENT USING TMP05/TMP06 MEASURING TEMPERATURE Table 7. Temperature Reading Registers The ADT7470 can be connected with up to 10 daisy-chained TMP05/TMP06 devices for temperature measurement. Each TMP05/TMP06 performs an ambient temperature measurement, and outputs a PWM signal. The ADT7470 decodes the PWM into a temperature measurement, and stores the result in the temperature reading registers, listed in Table 7.
ADT7470 Data Sheet TEMPERATURE READBACK BY THE HOST Example: The user cannot read the ADT7470 temperature register values if the ADT7470 is in the process of a temperature measurement. The user must wait until the data from all the TMP05s and TMP06s in the chain are received by the ADT7470 before reading these values. Otherwise, the temperature registers may store an incorrect value. It is recommended to wait at least 200 ms for each TMP05 and TMP06 in the chain.
Data Sheet ADT7470 TEMPERATURE MEASUREMENT LIMITS THERMAL ZONES FOR AUTOMATIC FAN CONTROL High and low temperature limits can be individually set for each of the TMP05/06s that the ADT7470 is monitoring. The temperature limit registers are at address 0x44 to 0x57. The power-on default value for all TMP05/06 lower limits is −127°C (0x81). The power –on default value for all TMP05/06 upper limits is +127°C (0x7F). See Table 9 for details on the temperature limit registers.
ADT7470 Data Sheet LIMIT AND STATUS REGISTERS LIMIT VALUES Table 10. Fan Underspeed Limit Registers Associated with each measurement channel on the ADT7470 are high and low limits. These can form the basis of system status monitoring; a status bit can be set for any out-of-limit condition and be detected by polling the device. Alternatively, SMBALERT interrupts can be generated to automatically flag a service processor or microcontroller for out-of-limit conditions as they occur.
Data Sheet ADT7470 STATUS REGISTERS The results of limit comparisons are stored in Status Register 1 and Status Register 2. The status register bit for each channel reflects the status of the last measurement and limit comparison on that channel. If a measurement is within limits, the corresponding status register bit is cleared to 0. If the measurement is out of limit, the corresponding status register bit is set to 1.
ADT7470 Data Sheet SMBALERT INTERRUPT Handling SMBALERT Interrupts The ADT7470 can be polled for status, or an SMBALERT interrupt can be generated for out-of-limit conditions. Note how the SMBALERT output and status bits behave when writing interrupt handler software. To prevent the system from being tied up servicing interrupts, handle the SMBALERT interrupt as follows: Figure 15 shows how the SMBALERT output and sticky status bits behave.
Data Sheet ADT7470 Masking Interrupt Sources Enabling the SMBALERT Interrupt Output Interrupt Mask Register 1 and Interrupt Mask Register 2 are located at Address 0x72 and Address 0x73. These allow individual interrupt sources to be masked out to prevent unwanted SMBALERT interrupts. Masking an interrupt source prevents only the SMBALERT output from being asserted; the appropriate status bit is still set as usual.
ADT7470 Data Sheet FAN DRIVE USING PWM CONTROL The ADT7470 uses pulse-width modulation (PWM) to control fan speed. This relies on varying the duty cycle (or on/off ratio) of a square wave applied to the fan to vary the fan speed. Two main control schemes are used: low frequency and high frequency PWM. Configuration Register 1 Bit[6], at address 0x40, configures the fan drive for high or low frequency operation. If this bit is set to 0, which is the default, high frequency fan drive is selected.
Data Sheet ADT7470 Figure 19 shows a fan drive circuit using an NPN transistor such as a general-purpose MMBT2222. While these devices are inexpensive, they tend to have much lower current handling capabilities and higher on resistance than MOSFETs. When choosing a transistor, care should be taken to ensure that it meets the fan’s current requirements. This is the only major difference between a MOSFET and NPN transistor fan driver circuit.
ADT7470 Data Sheet FAN SPEED MEASUREMENT R1 and R2 should be chosen such that TACH INPUTS 2 V < VPULL-UP × R2/(RPULL-UP + R1 + R2) < 5 V Signal conditioning in the ADT7470 accommodates the slow rise and fall times typical of fan tachometer outputs. The maximum input signal range is 0 V to 5 V, even where VCC is less than 5 V.
Data Sheet ADT7470 FAN SPEED MEASUREMENT The fan counter does not count the fan tach output pulses directly, because the fan speed may be less than 1000 RPM, and it would take several seconds to accumulate a reasonably large and accurate count.
ADT7470 Data Sheet Fan Pulses per Revolution Calculating Fan Speed and Tachometer Limits Assuming that the measured number of tach pulses per rotation corresponds to the number of pulses counted as set in register 0x43, fan speed is calculated by Fan Speed (RPM) = (90,000 × 60)/Fan Tach Reading where Fan Tach Reading is the 16-bit fan tachometer reading.
Data Sheet ADT7470 MANUAL FAN SPEED CONTROL Manual fan speed control on the ADT7470 allows the user to control the PWM duty cycle for each fan via the registers. The ADT7470 powers-up in manual fan control mode, with all PWM duty cycles set to maximum. The PWM Configuration registers determine whether the fans are in manual or automatic fan control mode. SETTING THE PWM DUTY CYCLE The ADT7470 allows the duty cycle of any PWM output to be manually adjusted.
ADT7470 Data Sheet AUTOMATIC FAN SPEED CONTROL In automatic fan speed control mode, fan speed automatically varies with temperature and without CPU intervention, once initial parameters are set up. The advantage is that when a system hangs, the user is guaranteed that the system is protected from overheating. Automatic fan speed control mode is recommended for use only when temperatures > 8°C. In automatic fan control mode, if the temperature drops below 0°C, the fans automatically turn on.
Data Sheet ADT7470 REGISTER MAP Table 23.
ADT7470 Address 0x54 0x55 0x56 0x57 0x58 0x59 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 0x6E 0x6F 0x70 0x71 0x72 0x73 0x74 0x75 0x76 0x77 0x78 0x79 0x7A 0x7B 0x7C 0x7D 0x7E 0x7F 0x80 0x81 Data Sheet R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R R/W R/W R/W R/W R/W R/W R/W R/W R Description Temperature 9 Low Limit Temperature 9 High Limit Temperat
Data Sheet ADT7470 DETAILED REGISTER DESCRIPTIONS Table 24. Register 0x20 to Register 0x29. Temperature Reading Registers (Power-On Default = 0x00). Register Address 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 Read/Write Read-only Read-only Read-only Read-only Read-only Read-only Read-only Read-only Read-only Read-only Description 8-bit Temperature 1 reading (from TMP05 sensor). 8-bit Temperature 2 reading (from TMP05 sensor). 8-bit Temperature 3 reading (from TMP05 sensor).
ADT7470 Data Sheet Table 27. Register 0x38 to Register 0x3B. PWM Max Duty Cycle Registers (Power-On Default = 0xFF). Register Address 0x38 0x39 0x3A 0x3B Read/Write Read/Write Read/Write Read/Write Read/Write Description PWM1 max duty cycle: PWM1 Min duty cycle value (register 0x6A) to 100% duty cycle. PWM2 max duty cycle: PWM2 Min duty cycle value (register 0x6B) to 100% duty cycle. PWM3 max duty cycle: PWM3 Min duty cycle value (register 0x6C) to 100% duty cycle.
Data Sheet ADT7470 Table 32. Register 0x41. Interrupt Status Register 1 (Power-On Default = 0x00). Bit Name [0] R1T Read/Write Read-only [1] R2T Read-only [2] R3T Read-only [3] R4T Read-only [4] R5T Read-only [5] R6T Read-only [6] R7T Read-only [7] OOL Read-only Description A 1 indicates that the Remote 1 temperature high or low limit has been exceeded. This bit is cleared on a read of the status register only if the error condition has subsided.
ADT7470 Data Sheet Table 34. Register 0x43. Fan Pulses per Revolution Register (Power-On Default = 0x55). Bit Name [1:0] Fan 1 Read/Write Read/Write [3:2] Fan 2 Read/Write [5:4] Fan 3 Read/Write [7:6] Fan 4 Read/Write Description Sets the number of pulses to be counted when measuring Fan 1 speed. Can be used to determine fan’s pulses per revolution number for unknown fan type. Pulses Counted 00 = 1 01 = 2 (default) 10 = 3 11 = 4 Sets the number of pulses to be counted when measuring Fan 2 speed.
Data Sheet ADT7470 Table 36. Register 0x58 to Register 0x67. Fan Tachometer Limit Registers.
ADT7470 Data Sheet Table 38. Register 0x69. PWM3/PWM4 Configuration Register (Power-On Default = 0x00). Bit Name [0] [1] [2] [3] [4] INV4 [5] INV3 [6] BHVR4 Read/Write N/A N/A N/A N/A Read/Write Read/Write Read/Write [7] BHVR3 Read/Write Description Set to 0 (default). Set to 0 (default). Set to 0 (default). Set to 0 (default). Setting this bit to 1 inverts the PWM4 output. Default = 0 Setting this bit to 1 inverts the PWM3 output. Default = 0 This bit assigns fan behavior for PWM4 output.
Data Sheet ADT7470 Table 42. Register 0x72. Interrupt Mask Register 1 (Power-On Default = 0x00). Bit Name [7] Not in use [6] R7T Read/Write Read/Write Read/Write [5] R6T Read/Write [4] R5T Read/Write [3] R4T Read/Write [2] R3T Read/Write [1] R2T Read/Write [0] R1T Read/Write Description Not in use. Write 0 to this bit. A 1 masks the Temperature 7 value from generating an interrupt on the SMBALERT output. The R1T bit is set as normal in the status register for out-of-limit conditions.
ADT7470 Data Sheet Table 44. Register 0x74. Configuration Register 2 (Power-On Default = 0x00). Bit Name [7] SHDN [6:4] FREQ Read/Write Read/Write Read/Write [3] T4_dis [2] T3_dis [1] T2_dis [0] T1_dis Read/Write Read/Write Read/Write Read/Write Description Shutdown/low current mode. These bits control PWM1–PWM4 frequency when the fan drive is configured as a low frequency drive. Register 0x74[6:4] Register 0x40[6] = 1 Register 0x40[6] = 0 000 11.0 Hz 1.4 kHz 001 14.7 Hz 22.5 kHz 010 22.1 Hz 22.
Data Sheet ADT7470 Table 47. Register 0x7D. TMP05 Zone Select 2 (Power-On Default = 0x00). Bit Name Read/Write Description [7:4] zone_fan3[3:0] Read/Write [3:0] zone_fan4[3:0] Read/Write These bits determine which temperature zone controls Fan 3. zone_fan3[3:0] Description 0000 max_temperature from Register 0x78 controls Fan 3. 0001 Temperature 1 from Register 0x20 controls Fan 3. 0010 Temperature 2 from Register 0x21 controls Fan 3. 0011 Temperature 3 from Register 0x22 controls Fan 3.
ADT7470 Data Sheet Table 49. Register 0x80. GPIO CONFIG (Power-On Default = 0x00). Bit Name [7] GPIO1_d Read/Write Read/Write [6] GPIO1_p Read/Write [5] GPIO2_d Read/Write [4] GPIO2_p Read/Write [3] GPIO3_d Read/Write [2] GPIO3_p Read/Write [1] GPIO4_d Read/Write [0] GPIO4_p Read/Write Description This bit sets the direction of GPIO 1 when the PWM1 pin is configured as GPIO. 1 = output; 0 = input. Data for GPIO 1 is set by the LSB of the PWM1 min duty cycle register.
Data Sheet ADT7470 OUTLINE DIMENSIONS 0.197 (5.00) 0.193 (4.90) 0.189 (4.80) 9 1 8 0.244 (6.20) 0.236 (5.99) 0.228 (5.79) 0.010 (0.25) 0.006 (0.15) 0.069 (1.75) 0.053 (1.35) 0.065 (1.65) 0.049 (1.25) 0.010 (0.25) 0.004 (0.10) COPLANARITY 0.004 (0.10) 0.158 (4.01) 0.154 (3.91) 0.150 (3.81) 0.025 (0.64) BSC SEATING PLANE 0.012 (0.30) 0.008 (0.20) 8° 0° 0.050 (1.27) 0.016 (0.
ADT7470 Data Sheet NOTES Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. ©2004–2013 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04684-0-4/13(E) Rev.
