ADM1031

ADM1031 Intelligent Temperature Monitor and Dual PWM Fan Controller The ADM1031 is an ACPI−compliant, three−channel digital thermometer and under/overtemperature alarm for use in personal computers and thermal management systems. Optimized for the PentiumRIII, the part offers a 1°C higher accuracy, which allows system designers to safely reduce temperature guard−banding and increase system performance. Two PWM fan control outputs control the speed of two cooling fans by varying output duty cycle. Duty cycle values between 33% and 100% allow smooth control of the fans. The speed of each fan can be monitored via TACH inputs, which can be reprogrammed as analog inputs to allow speeds for 2−wire fans to be measured via sense resistors. The device also detects a stalled fan. A dedicated fan speed control loop provides control without the intervention of CPU software. It also ensures that if the CPU or system locks up, each fan can still be controlled based on temperature measurements, and the fan speed is adjusted to correct any changes in system temperature. Fan speed can also be controlled using existing ACPI software. Two inputs (4 pins) are dedicated to remote temperature−sensing diodes with an accuracy of ±1°C, and an on−chip temperature sensor allows ambient temperature to be monitored. The device has a programmable INT output to indicate error conditions, and a dedicated FAN_FAULT output to signal fan failure. The THERM pin is a fail−safe output for overtemperature conditions that can be used to throttle a CPU clock. Features ♦ http://onsemi.com QSOP−16 CASE 492 MARKING DIAGRAM 1 1031A RQZ #YYWW xxx # YY WW = Specific Device Code = Pb−Free Package = Date Code = Work Week PIN ASSIGNMENT PWM_OUT1 TACH1/AIN1 PWM_OUT2 TACH2/AIN2 GND VCC THERM FAN_FAULT 1 2 3 4 5 6 7 8 16 15 • Optimized for Pentium III SCL SDA INT(SMBALERT) ADD D2+ D2– D1+ D1– • • • • • • • • • Reduced Guard−banding Software ♦ Automatic Fan Speed Control, Independent of CPU Intervention After Initial Setup 0.125°C Resolution on External Temperature Channels Control Loop to Minimal Acoustic Noise and Battery Consumption Remote Temperature Measurement Accurate to 1°C Using Remote Diode (Two Channels) Local Sensor with 0.25°C Resolution Pulse Width Modulation (PWM) Fan Control for 2 Fans Programmable PWM Frequency and PWM Duty Cycle Tach Fan Speed Measurement (Two Channels) Analog Input to Measure Fan Speed of 2−Wire Fans (Using Sense Resistor) 2−Wire System Management Bus (SMBus) with ARA Support ADM1031 14 13 12 11 10 9 • Overtemperature THERM Output Pin for CPU • • • • • Throttling Programmable INT Output Pin Configurable Offsets for Temperature Channels 3.0 V to 5.5 V Supply Range Shutdown Mode to Minimize Power Consumption Limit Comparison of All Monitored Values This is a Pb−Free Device Applications • Notebook PCs, Network Servers, and Personal Computers • Telecommunications Equipment ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 29 of this data sheet. © Semiconductor Components Industries, LLC, 2010 May, 2010 − Rev. 4 1 Publication Order Number: ADM1031/D ADM1031 VCC 6 13 ADM1031 SLAVE ADDRESS REGISTER FAN FILTER REGISTER FAN CHARACTERISTICS REGISTER SERIAL BUS INTERFACE ADDRESS POINTER REGISTER ADD SDA SCL 15 16 14 INT (SMBALERT) THERM PWM_OUT1 PWM_OUT2 1 3 PWM CONTROLLERS TACH SIGNAL CONDITIONING FAN SPEED CONFIG REGISTER FAN SPEED COUNTER INTERRUPT STATUS REGISTERS LIMIT COMPARATOR 7 TACH2/AIN2 4 TACH1/AIN1 2 D1+ 10 D1– 9 8 FAN_FAULT VALUE AND LIMIT REGISTERS OFFSET REGISTERS CONFIGURATION REGISTERS D2+ 12 D2– 11 BANDGAP TEMPERATURE SENSOR ANALOG MULTIPLEXER ADC 2.5V BANDGAP REFERENCE 5 GND Figure 1. Functional Block Diagram ABSOLUTE MAXIMUM RATINGS Parameter Positive Supply Voltage (VCC) Voltage on Any Input or Output Pin Input Current at Any Pin Package Input Current Maximum Junction Temperature (TJ max) Storage Temperature Range Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) Rating 6.5 −0.3 to +6.5 ±5 ±20 150 −65 to +150 215 200 Unit V V mA mA °C °C °C ESD Rating − All Pins 2000 V Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. NOTE: This device is ESD sensitive. Use standard ESD precautions when handling. THERMAL CHARACTERISTICS Package Type 16−lead QSOP NOTE: qJA 105 qJC 39 Unit °C/W qJA is specified for the worst−case conditions, that is, a device soldered in a circuit board for surface−mount packages. http://onsemi.com 2 ADM1031 PIN ASSIGNMENT Pin No. 1 2 3 4 5 6 7 Mnemonic PWM_OUT1 TACH1/AIN1 PWM_OUT2 TACH2/AIN2 GND VCC THERM Description Digital Output, Open−Drain. Pulse width modulated output to control fan speed. Requires pullup resistor (10 kW typical). Digital/Analog Input. Fan tachometer input to measure FAN1 fan speed. Can be reprogrammed as an analog input to measure speed of a 2−wire fan via a sense resistor (2 W typical). Digital Output, Open−Drain. Pulse width modulated output to control FAN2 fan speed. Requires pullup resistor (10 kW typical). Digital/Analog Input. Fan tachometer input to measure FAN2 fan speed. Can be reprogrammed as an analog input to measure speed of a 2−wire fan via a sense resistor (2 W typical). System Ground. Power. Can be powered by 3.3 V standby power if monitoring in low power states is required. Digital I/O, Open−Drain. An active low thermal overload output that indicates a violation of a temperature set point (overtemperature). Also acts as an input to provide external fan control. When this pin is pulled low by an external signal, a status bit is set, and the fan speed is set to full−on. Requires pullup resistor (10 kW). Digital Output, Open−Drain. Can be used to signal a fan fault. Drives second fan to full speed if one fan fails. Requires pullup resistor (typically 10 kW). Analog Input. Connected to cathode of first remote temperature−sensing diode. The temperature−sensing element is either a Pentium III substrate transistor or a general−purpose 2N3904. Analog Input. Connected to anode of first remote temperature−sensing diode. Analog Input. Connected to cathode of second remote temperature−sensing diode. Analog Input. Connected to anode of second remote temperature−sensing diode. Three−State Logic Input. Sets two lower bits of device SMBus address. Digital Output, Open−Drain. Can be programmed as an interrupt (SMBus ALERT) output for temperature/fan speed interrupts. Requires pullup resistor (10 kW typical). Digital I/O, Serial Bus Bidirectional Data. Open−drain output. Requires pullup resistor (2.2 kW typical). Digital Input, Serial Bus Clock. Requires pullup resistor (2.2 kW typical). 8 9 FAN_FAULT D1– 10 11 12 13 14 15 16 D1+ D2– D2+ ADD INT(SMBALERT) SDA SCL ELECTRICAL CHARACTERISTICS TA = TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted. (Note 1) Parameter POWER SUPPLY Supply Voltage, VCC Supply Current, ICC TEMPERATURE−TO−DIGITAL CONVERTER Local Sensor Accuracy Resolution Remote Diode1 Sensor Accuracy Remote Diode2 Sensor Accuracy Resolution Remote Sensor Source Current High level Low level IOUT = –6.0 mA; VCC = 3.0 V VOUT = VCC; VCC = 3.0 V 0.1 60°C ≤ TD ≤ 100°C 60°C ≤ TD ≤ 100°C ±1.0 0.25 ±0.5 ±0.5 0.125 180 11 0.4 1.0 ±1.0 ±1.75 ±3.0 °C °C °C °C °C mA Interface inactive, ADC active Standby mode 3.0 3.3 1.4 32 3.6 3.0 50 V mA mA Test Conditions/Comments Min Typ Max Unit OPEN−DRAIN DIGITAL OUTPUTS (THERM, INT, FAN_FAULT, PWM_OUT) Output Low Voltage, VOL High−Level Output Leakage Current, IOH V mA http://onsemi.com 3 ADM1031 ELECTRICAL CHARACTERISTICS TA = TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted. (Note 1) Parameter OPEN−DRAIN SERIAL DATA BUS OUTPUT (SDA) Output Low Voltage, VOL High−Level Output Leakage Current, IOH SERIAL BUS DIGITAL INPUTS (SCL, SDA) Input High Voltage, VIH Input Low Voltage, VIL Hysteresis DIGITAL INPUT LOGIC LEVELS (Note 2) (ADD, THERM, TACH1/2) Input High Voltage, VIH Input Low Voltage, VIL DIGITAL INPUT LEAKAGE CURRENT Input High Current, IIH Input Low Current, IIL Input Capacitance, CIN FAN RPM−TO−DIGITAL CONVERTER Accuracy Full−Scale Count TACH Nominal Input RPM Divisor N = 1, Fan Count = 153 Divisor N = 2, Fan Count = 153 Divisor N = 4, Fan Count = 153 Divisor N = 8, Fan Count = 153 4400 2200 1100 550 637 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2 250 300 4.7 4.7 4.0 4.0 1.3 4.0 50 1000 300 10 50 100 60°C ≤ TA ≤ 100°C ±6.0 255 RPM % VIN = VCC VIN = 0 5.0 –1.0 1.0 mA mA pF 2.1 0.8 V V 500 2.1 0.8 V V mV IOUT = –6.0 mA; VCC = 3.0 V VOUT = VCC 0.1 0.4 1.0 V mA Test Conditions/Comments Min Typ Max Unit Conversion Cycle Time SERIAL BUS TIMING (Note 3) Clock Frequency, fSCLK Glitch Immunity, tSW Bus Free Time, tBUF Start Setup Time, tSU;STA Start Hold Time, tHD;STA Stop Condition Setup Time, tSU;STO SCL Low Time, tLOW SCL High Time, tHIGH SCL, SDA Rise Time, tR SCL, SDA Fall Time, tF Data Setup Time, tSU;DAT Data Hold Time, tHD;DAT ms kHz ns ms ms ms ms ms ms ns ns ns ns 1. Typicals are at TA = 25°C and represent most likely parametric norm. Shutdown current typ is measured with VCC = 3.3 V. 2. ADD is a three−state input that can be pulled high, low, or left open−circuit. 3. Timing specifications are tested at logic levels of VIL = 0.8 V for a falling edge and VIH = 2.2 V for a rising edge. tLOW SCL tR tF tHD:STA tHD:STA SDA tHD:DAT tHIGH tSU:DAT tSU:STA tSU:STO tBUF P S S P Figure 2. Diagram for Serial Bus Timing http://onsemi.com 4 ADM1031 TYPICAL CHARACTERISTICS 15 REMOTE TEMPERATURE ERROR (°C) 10 5 DXP TO GND 0 –5 –10 –15 –20 DXP TO VCC (3.3 V) REMOTE TEMPERATURE ERROR (°C) 17 15 13 11 9 7 5 3 1 –1 1 3.3 10 30 100 LEAKAGE RESISTANCE (MW) VIN = 100mV p−p VIN = 200mV p−p 0 500k 2M 4M 6M 10M 100M 400M FREQUENCY (Hz) Figure 3. Temperature Error vs. PCB Track Resistance 7 REMOTE TEMPERATURE ERROR (°C) 6 5 READING (°C) 300M 400M 500M 4 3 VIN = 40mV p−p 2 1 0 VIN = 20mV p−p –1 0 100k 1M 100M 200M Figure 4. Temperature Error vs. Power Supply Noise Frequency 110 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 90 100 110 FREQUENCY (Hz) PIII TEMPERATURE (°C) Figure 5. Temperature Error vs. Common−Mode Noise Frequency Figure 6. Pentium III Temperature Measurement vs. ADM1031 Reading REMOTE TEMPERATURE ERROR (°C) SUPPLY CURRENT (mA) 1 0 –1 –2 –3 –4 –5 –6 –7 –8 –9 –10 –11 –12 –13 –14 –15 –16 110 100 90 80 70 60 50 40 30 20 10 1 2.2 3.3 4.7 10 22 47 0 0 1 5 10 25 50 75 100 250 500 750 1000 VCC = 3.3 V VCC = 5.0 V DXP, DXN CAPACITANCE (nF) SCLK FREQUENCY (kHz) Figure 7. Temperature Error vs. Capacitance Between D+ and D– Figure 8. Standby Current vs. Clock Frequency http://onsemi.com 5 ADM1031 TYPICAL CHARACTERISTICS 7 VIN = 30mV p−p REMOTE TEMPERATURE ERROR (°C) 6 5 4 3 2 1 0 –1 VIN = 20mV p−p 200 180 160 SUPPLY CURRENT (mA) 140 120 100 80 60 40 20 0 300M 400M 500M –20 0 1.1 1.3 1.5 1.7 1.9 2.1 2.5 2.9 4.5 ADD = GND ADD = VCC ADD = Hi−Z 0 100k 1M 100M 200M FREQUENCY (Hz) SUPPLY VOLTAGE (V) Figure 9. Temperature Error vs. Differential−Mode Noise Frequency Figure 10. Standby Supply Current vs. Supply Voltage 0.08 0 –0.08 –0.16 –0.24 ERROR (°C) –0.32 –0.40 –0.48 –0.56 –0.64 –0.72 ––0.80 0 20 40 60 80 85 100 105 120 ERROR (°C) 0.08 0 –0.08 –0.16 –0.24 –0.32 –0.40 –0.48 –0.56 –0.64 –0.72 ––0.80 0 20 40 60 80 85 100 105 120 TEMPERATURE (°C) TEMPERATURE (°C) Figure 11. Local Sensor Temperature Error Figure 12. Remote Temperature Sensor Error 1.30 1.25 1.20 SUPPLY CURRENT (mA) TEMPERATURE (°C) 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 SUPPLY VOLTAGE (V) 120 110 100 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 TIME (Sec) 6 7 8 9 10 Figure 13. Supply Current vs. Supply Voltage Figure 14. Response to Thermal Shock http://onsemi.com 6 ADM1031 Functional Description The ADM1031 is a temperature monitor and dual PWM fan controller for microprocessor−based systems. The device communicates with the system via a serial System Management Bus (SMBus). The serial bus controller has a hardwired address pin for device selection (Pin 13), a serial data line for reading and writing addresses and data (Pin 15), and an input line for the serial clock (Pin 16). All control and programming functions of the ADM1031 are performed over the serial bus. The device also supports Alert Response Address (ARA). Internal Registers defines the range over which auto fan control is provided, and hence determines the temperature at which the fan is run at full speed. Serial Bus Interface Brief descriptions of the ADM1031’s principal internal registers are given below. For more detailed information on the function of each register, see Table 14 through Table 29. Configuration Register This register controls and configures various functions on the device. Address Pointer Register Control of the ADM1031 is carried out via the SMBus. The ADM1031 is connected to this bus as a slave device, under the control of a master device, for example, the 810 chipset. The ADM1031 has a 7−bit serial bus address. When the device is powered up, it does so with a default serial bus address. The five MSBs of the address are set to 01011; the two LSBs are determined by the logical state of Pin 13 (ADD). This is a three−state input that can be grounded, connected to VCC, or left open−circuit to give three different addresses. The state of the ADD pin is only sampled at powerup, so changing ADD with power on has no effect until the device is powered off, then on again. Table 1. ADD Pin Truth Table ADD Pin GND No Connect VCC A1 0 1 0 A0 0 0 1 This register contains the address that selects one of the other internal registers. When writing to the ADM1031, the first byte of data is always a register address, which is written to the address pointer register. Status Registers These registers provide status of each limit comparison. Value and Limit Registers If ADD is left open−circuit, then the default address is 0101110. The facility to make hardwired changes at the ADD pin allows the user to avoid conflicts with other devices sharing the same serial bus; for example, if more than one ADM1031 is used in a system. Serial Bus Protocol Theses registers store the results of temperature and fan speed measurements, along with their limit values. Fan Speed Configuration Register This register is used to program the PWM duty cycle for each fan. Offset Registers These registers allow the temperature channel readings to be offset by a 5−bit twos complement value written to these registers. These values are automatically added to the temperature values (or subtracted from if negative). This allows the systems designer to optimize the system if required, by adding or subtracting up to 15°C from a temperature reading. Fan Characteristics Registers These registers are used to select the spin−up time, PWM frequency, and speed range for the fans used. THERM Limit Registers These registers contain the temperature values at which THERM is asserted. TMIN/TRANGE Registers These registers are read/write registers that hold the minimum temperature value below which the fan does not run when the device is in automatic fan speed control mode. These registers also hold the temperature range value that 1. The master initiates data transfer by establishing a START condition, defined as a high−to−low transition on the serial data line SDA while the serial clock line SCL remains high. This indicates that an address/data stream follows. All slave peripherals connected to the serial bus respond to the START condition, and shift in the next eight bits, consisting of a 7−bit address (MSB first) plus an R/W bit that determines the direction of the data transfer, that is, whether data is written to or read from the slave device. The peripheral whose address corresponds to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the Acknowledge Bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a 0, then the master writes to the slave device. If the R/W bit is a 1, then the master reads from the slave device. 2. Data is sent over the serial bus in sequences of nine clock pulses, eight bits of data, followed by an acknowledge bit from the slave device. Transitions on the data line must occur during the low period of the clock signal and remain stable http://onsemi.com 7 ADM1031 during the high period, as a low−to−high transition when the clock is high can be interpreted as a stop signal. The number of data bytes that can be transmitted over the serial bus in a single read or write operation is limited only by what the master and slave devices can handle. 3. When all data bytes have been read or written, stop conditions are established. In write mode, the master pulls the data line high during the tenth clock pulse to assert a stop condition. In read mode, the master device overrides the acknowledge bit by pulling the data line high during the low period before the ninth clock pulse. This is known as No Acknowledge. The master then takes the data line low during the low period before the tenth clock pulse, then high during the tenth clock pulse to assert a stop condition. Any number of bytes of data can be transferred over the serial bus in one operation, but it is not possible to mix read and write in one operation, because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation. In the case of the ADM1031, write operations contain either one byte or two bytes, and read operations contain one byte, and perform the functions described next. Writing Data to a Register internal data register to be written to, which is stored in the address pointer register. The second data byte is the data to be written to the internal data register. Reading Data from a Register When reading data from a register there are two possibilities: 1. If the ADM1031’s 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 ADM1031 as before, but only the data byte containing the register address is sent, as data is not to be written to the register. This is shown in Figure 16. A read operation is then performed consisting of the serial bus address, R/W bit set to 1, followed by the data byte read from the data register. This is shown in Figure 17. 2. If the address pointer register is known to be already at the desired address, data can be read from the corresponding data register without first writing to the address pointer register, so Figure 16 can be omitted. Notes • Although it is possible to read a data byte from a data 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; data can then be written to 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. If data is to be written to the device, the write operation contains a second data byte that is written to the register selected by the address pointer register. This is illustrated in Figure 15. The device address is sent over the bus followed by R/W set to 0. This is followed by two data bytes. The first data byte is the address of the • • register without first writing to the address pointer register, if the address pointer register is already at the correct value, it is not possible to write data to a register without writing to the address pointer register. This is because the first data byte of a write is always written to the address pointer register. In Figure 15, Figure 16, and Figure 17, the serial bus address is shown as the default value 01011(A1)(A0), where A1 and A0 are set by the three−state ADD pin. The ADM1031 also supports the Read Byte protocol, as described in the system management bus specification. 1 SCL 9 1 9 SDA START BY MASTER 0 1 0 1 1 A1 A0 R/W ACK. BY ADM1031 D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADM1031 FRAME 1 SERIAL BUS ADDRESS BYTE 1 SCL (CONTINUED) FRAME 2 ADDRESS POINTER REGISTER BYTE 9 SDA (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADM1031 STOP BY MASTER FRAME 3 DATA BYTE Figure 15. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register http://onsemi.com 8 ADM1031 1 SCL 9 1 9 SDA START BY MASTER 0 1 0 1 1 A1 A0 R/W ACK. BY ADM1031 D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADM1031 STOP BY MASTER FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE Figure 16. Writing to the Address Pointer Register Only 1 SCL 9 1 9 SDA START BY MASTER 0 1 0 1 1 A1 A0 R/W ACK. BY ADM1031 D7 D6 D5 D4 D3 D2 D1 D0 STOP BY NO ACK. BY MASTER MASTER FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 DATA BYTE FROM ADM1031 Figure 17. Reading Data from a Previously Selected Register Alert Response Address External Measurement Alert Response Address (ARA) is a feature of SMBus devices that allows an interrupting device to identify itself to the host when multiple devices exist on the same bus. The INT output can be used as an interrupt output or can be used as an SMBALERT. One or more INT outputs can be connected to a common SMBALERT line connected to the master. If a device’s INT line goes low, the following procedure occurs: 1. SMBALERT is pulled low. 2. Master initiates a read operation and sends the Alert Response Address (ARA = 0001 100). This is a general call address that must not be used as a specific device address. 3. The device whose INT 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 can be interrogated in the usual way. 4. If more than one device’s INT output is low, the one with the lowest device address has priority, in accordance with normal SMBus arbitration. 5. Once the ADM1031 has responded to the alert response address, it resets its INT output. However, if the error condition that caused the interrupt persists, then INT is reasserted on the next monitoring cycle. Temperature Measurement System Internal Measurement The ADM1031 can measure the temperatures of two external diode sensors or diode−connected transistors, connected to Pins 9 and 10, and Pins 11 and 12. These pins are dedicated temperature input channels. The function of Pin 7 is as a THERM input/output and is used to flag overtemperature conditions. The forward voltage of a diode or diode−connected transistor, operated at a constant current, exhibits a negative temperature coefficient of about –2 mV/°C. Unfortunately, the absolute value of VBE, varies from device to device, and individual calibration is required to null this out. As a result, the technique is unsuitable for mass production. The technique used in the ADM1031 is to measure the change in VBE when the device is operated at two different currents. This is given by: DVBE = KT/q × In (N) where: K is Boltzmann’s constant. q is charge on the carrier. T is absolute temperature in Kelvins. N is ratio of the two currents. Figure 18 shows the input signal conditioning used to measure the output of an external temperature sensor. This figure shows the external sensor as a substrate transistor, provided for temperature monitoring on some microprocessors, but it could equally well be a discrete transistor. The ADM1031 contains an on−chip bandgap temperature sensor. The on−chip ADC performs conversions on the output of this sensor and outputs the temperature data in 10−bit twos complement format. The resolution of the local temperature sensor is 0.25°C. The format of the temperature data is shown in Table 2. http://onsemi.com 9 ADM1031 VDD I N× I IBIAS The extended temperature resolution for the local and remote channels is stored in the extended temperature resolution register (Register 0×06), and is outlined in Table 27. VOUT+ TO ADC D+ REMOTE SENSING TRANSISTOR Table 4. Local Sensor Extended Temperature Resolution Extended Resolution 0.00°C 0.25°C 0.50°C 0.75°C Local Temperature Low Bits 00 01 10 11 D– BIAS DIODE LOW−PASS FILTER fC = 65kHz VOUT– Figure 18. Signal Conditioning If a discrete transistor is used, then the collector is not grounded, and is linked to the base. If a PNP transistor is used, the base is connected to the D– input and the emitter to the D+ input. If an NPN transistor is used, the emitter is connected to the D– input and the base to the D+ input. One LSB of the ADC corresponds to 0.125°C, so the ADM1031 can theoretically measure temperatures from –127°C to +127.75°C, although –127°C is outside the operating range for the device. The extended temperature resolution data format is shown in Table 3 and Table 4. Table 2. Temperature Data Format − (Local Temperature and Remote Temperature High Bytes) Temperature (5C) −128°C −125°C −100°C −75°C −50°C −25°C −1°C 0°C +1°C +10°C +25°C +50°C +75°C +100°C +125°C +127°C Digital Output 1000 0000 1000 0011 1001 1100 1011 0101 1100 1110 1110 0111 1111 1111 0000 0000 0000 0001 0000 1010 0001 1001 0011 0010 0100 1011 0110 0100 0111 1101 0111 1111 To prevent ground noise interfering with the measurement, the more negative terminal of the sensor is not referenced to ground, but biased above ground by an internal diode at the D– input. If the sensor is used in a very noisy environment, a capacitor of value up to 1000 pF can be placed between the D+ and D– inputs to filter the noise. To measure DVBE, the sensor is switched between operating currents of I and N × I. The resulting waveform is passed through a 65 kHz low−pass filter to remove noise, then to a chopper−stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage proportional to DVBE. This voltage is measured by the ADC to give a temperature output in 11−bit twos complement format. To further reduce the effects of noise, digital filtering is performed by averaging the results of 16 measurement cycles. An external temperature measurement nominally takes 9.6 ms. Layout Considerations Table 3. Remote Sensor Extended Temperature Resolution Extended Resolution 0.000°C 0.125°C 0.250°C 0.375°C 0.500°C 0.625°C 0.750°C 0.875°C Remote Temperature Low Bits 000 001 010 011 100 101 110 111 Digital boards can be electrically noisy environments and care must be taken to protect the analog inputs from noise, particularly when measuring the very small voltages from a remote diode sensor. The following precautions should be taken: 1. Place the ADM1031 as close as possible to the remote sensing diode. Provided that the worst noise sources such as clock generators, data/address buses, and CRTs are avoided, this distance can be 4 to 8 inches. 2. Route the D+ and D– tracks close together, in parallel, with grounded guard tracks on each side. Provide a ground plane under the tracks if possible. 3. Use wide tracks to minimize inductance and reduce noise pickup. Ten mil track minimum width and spacing is recommended. GND 10MIL 10MIL D+ 10MIL 10MIL D– 10MIL 10MIL GND 10MIL Figure 19. Arrangement of Signal Tracks http://onsemi.com 10 ADM1031 4. Try to minimize the number of copper/solder joints, which can cause thermocouple effects. Where copper/solder joints are used, make sure that they are in both the D+ and D– path and at the same temperature. Thermocouple effects should not be a major problem as 1°C corresponds to about 200 mV, and thermocouple voltages are about 3 mV/°C of temperature difference. Unless there are two thermocouples with a big temperature differential between them, thermocouple voltages should be much less than 200 mV. 5. Place a 0.1 mF bypass capacitor close to the ADM1031. 6. If the distance to the remote sensor is more than 8 inches, the use of twisted pair cable is recommended. This works up to about 6 to 12 feet. 7. For extra long distances (up to 100 feet), use a shielded twisted pair cable, such as the Belden #8451 microphone cable. Connect the twisted pair to D+ and D– and the shield to GND close to the ADM1031. Leave the remote end of the shield unconnected to avoid ground loops. Because the measurement technique uses switched current sources, excessive cable and/or filter capacitance can affect the measurement. When using long cables, the filter capacitor C1 can be reduced or removed. In any case the total shunt capacitance should not exceed 1000 pF. Cable resistance can also introduce errors. One ohm series resistance introduces about 0.5°C error. Addressing the Device ADD (Pin 13) is a three−state input. It is sampled, on powerup to set the lowest two bits of the serial bus address. Up to three addresses are available to the systems designer via this address pin. This reduces the likelihood of conflicts with other devices attached to the system management bus. The Interrupt System register) is cleared to 0, then the fans do not run full−speed. The THERM limit can be programmed at a lower temperature than the high temperature limit. This allows the system to run in silent mode, where the CPU can be throttled while the cooling fan is off. If the temperature continues to increase, and exceeds the high temperature limit, an INT is generated. Software can then decide whether the fan should run to cool the CPU. This allows the system to run in silent mode. 3. If the THERM−to−Fan Enable bit is set to 1, then the fan runs full−speed whenever THERM is asserted low. In this case, both throttling and active cooling take place. If the high temperature limit is programmed to a lower value than the THERM limit, exceeding the high temperature limit asserts INT low. Software could change the speed of the fan depending on temperature readings. If the temperature continues to increase and exceeds the THERM limit, THERM asserts low to throttle the CPU and the fan runs full−speed. This allows the system to run in performance mode, where active cooling takes place and the CPU is only throttled at high temperature. Using the high temperature limit and the THERM limit in this way allows the user to gain maximum performance from the system by only slowing it down, should it be at a critical temperature. Although the ADM1031 does not have a dedicated interrupt mask register, clearing the appropriate enable bits in Configuration Register 2 clears the appropriate interrupts and masks out future interrupts on that channel. Disabling interrupt bits prevents out−of−limit conditions from generating an interrupt or setting a bit in the status registers. Using THERM as an Input The ADM1031 has two interrupt outputs, INT and THERM. These have different functions. INT responds to violations of software programmed temperature limits and is maskable. THERM is intended as a “fail−safe” interrupt output that cannot be masked. If the temperature is below the low temperature limit, the INT pin is asserted low to indicate an out−of−limit condition. If the temperature exceeds the high temperature limit, the INT pin is also asserted low. A third limit, THERM limit, can be programmed into the device to set the temperature limit above which the overtemperature THERM pin is asserted low. The behavior of the high limit and THERM limit is as follows: 1. Whenever the temperature measured exceeds the high temperature limit, the INT pin is asserted low. 2. If the temperature exceeds the THERM limit, the THERM output asserts low. This can be used to throttle the CPU clock. If the THERM−to−Fan Enable bit (Bit 7 of THERM behavior/revision The THERM pin is an open−drain input/output pin. When used as an output, it signals overtemperature conditions. When asserted low as an output, the fan is driven full−speed if the THERM−to−Fan Enable bit is set to 1 (Bit 7 of Register 0×3F). When THERM is pulled low as an input, the THERM bit (Bit 7) of Status Register 2 is set to 1, and the fans are driven full−speed. Note that the THERM−to−Fan Enable bit has no effect whenever THERM is used as an input. If THERM is pulled low as an input, and the THERM−to−Fan Enable bit = 0, then the fans are still driven full−speed. The THERM−to−Fan Enable bit only affects the behavior of THERM when used as an output. Status Registers All out−of−limit conditions are flagged by status bits in Status Register 1 (0×02) and Status Register 2 (0×03). Bit 0 (Alarm Speed) and Bit 1 (Fan Fault) of Status Register 1, once set, can be cleared by reading Status Register 1. Once the alarm speed bit is cleared, this bit is not reasserted on the next monitoring cycle even if the condition still persists. This bit can be reasserted only if the fan is no longer at alarm http://onsemi.com 11 ADM1031 speed. Bit 1 (Fan Fault) is set whenever a fan tach failure is detected. Once cleared, it reasserts on subsequent fan tach failures. Bit 2 and Bit 3 of Status Register 1 and Status Register 2 are the Remote 1 and Remote 2 Temperature High and Low status bits. Exceeding the high or low temperature limits for the external channel sets these status bits. Reading the status register clears these bits. However, these bits are reasserted if the out−of−limit condition still exists on the next monitoring cycle. Bit 6 and Bit 7 are the Local Temperature High and Low status bits. These behave exactly the same as the Remote Temperature High and Low status bits. Bit 4 of Status Register 1 indicates that the Remote Temperature THERM limit has been exceeded. This bit gets cleared on a read of Status Register 1 (see Figure 20). Bit 5 indicates a remote diode error. This bit is a 1 if a short or open is detected on the remote temperature channel on powerup. If this bit is set to 1 on powerup, it cannot be cleared. Bit 6 of Status Register 2 (0×03) indicates that the Local THERM limit has been exceeded. This bit is cleared on a read of Status Register 2. Bit 7 indicates that THERM has been pulled low as an input. This bit can also be cleared on a read of Status Register 2. THERM LIMIT Automatic Fan Speed Control The ADM1031 has a local temperature channel and two remote temperature channels, which can be connected to an on−chip diode−connected transistor on a CPU. These three temperature channels can be used as the basis for an automatic fan speed control loop to drive fans using pulse width modulation (PWM). How Does the Control Loop Work? The automatic fan speed control loop is shown in Figure 21. MAX SPIN−UP FOR SECONDS FAN SPEED MIN TMIN TEMPERATURE TMAX = TMIN + TRANGE Figure 21. Automatic Fan Speed Control Loop 5° TEMP THERM INT REARMED INT STATUS REG. READ Figure 20. Operation of THERM and INT Signals Figure 20 shows the interaction between INT and THERM. Once a critical temperature THERM limit is exceeded, both INT and THERM assert low. Reading the status registers clears the interrupt and the INT pin goes high. However, the THERM pin remains asserted until the measured temperature falls 5°C below the exceeded THERM limit. This feature can be used to CPU throttle or drive a fan full speed for maximum cooling. Note that the INT pin for that interrupt source is not rearmed until the temperature has fallen below the THERM limit –5°C. This prevents unnecessary interrupts from tying up valuable CPU resources. Fan Control Modes of Operation The ADM1031 has four different modes of operation. These modes determine the behavior of the system. 1. Automatic Fan Speed Control Mode. 2. Filtered Automatic Fan Speed Control Mode. 3. PWM Duty Cycle Select Mode (directly sets fan speed under software control). 4. RPM Feedback Mode. TMIN is the temperature at which the fan should switch on and run at minimum speed. The fan only turns on once the temperature being measured rises above the TMIN value programmed. The fan spins up for a predetermined time (default = 2 seconds). See the Fan Spin−Up section for more details. TRANGE is the temperature range over which the ADM1031 automatically adjusts the fan speed. As the temperature increases beyond TMIN, the PWM_OUT duty cycle increases accordingly. The TRANGE parameter actually defines the fan speed vs. temperature slope of the control loop. TMAX is the temperature at which the fan is at its maximum speed. At this temperature, the PWM duty cycle driving the fan is 100%. TMAX is given by TMIN + TRANGE. Since this parameter is the sum of the TMIN and TRANGE parameters, it does not need to be programmed into a register on−chip. A hysteresis value of 5°C is included in the control loop to prevent the fan continuously switching on and off if the temperature is close to TMIN. The fan continues to run until the temperature drops 5°C below TMIN. Figure 22 shows the different control slopes determined by the TRANGE value chosen, and programmed into the ADM1031. TMIN is set to 0°C to start all slopes from the same point. The figure shows how changing the TRANGE value affects the PWM duty cycle vs. temperature slope. http://onsemi.com 12 ADM1031 100 93 PWM DUTY CYCLE (%) 87 80 73 66 60 53 47 40 33 0 5 10 TMIN 20 40 TRANGE = 5°C TRANGE = 10°C TRANGE = 20°C TRANGE = 40°C TRANGE = 80°C 60 80 TMAX = TMIN + TRANGE Table 5. Fan Spin−Up Times Bits 2:0 000 001 010 011 100 101 110 111 Spin−Up Time (Fan Characteristics Registers 1, 2) 200 ms 400 ms 600 ms 800 ms 1 sec 2 sec (Default) 4 sec 8 sec TEMPERATURE ( °C) Figure 22. PWM Duty Cycle vs. Temperature Slope (TRANGE) Figure 23 shows how, for a given TRANGE, changing the TMIN value affects the loop. Increasing the TMIN value increases the TMAX (temperature at which the fan runs full speed) value, since TMAX = TMIN + TRANGE. Note, however, that the PWM duty cycle vs. temperature slope remains exactly the same. Changing the TMIN value merely shifts the control slope. The TMIN can be changed in increments of 4°C. 100 93 PWM DUTY CYCLE (%) 87 80 73 66 60 53 47 40 33 0 TMIN 20 40 TEMPERATURE ( °C) TRANGE = 40°C 60 80 TMAX = TMIN + TRANGE Once the automatic fan speed control loop parameters have been chosen, the ADM1031 device can be programmed. The ADM1031 is placed into automatic fan speed control mode by setting Bit 7 of Configuration Register 1 (Register 0×00). The device powers up in automatic fan speed control mode by default. The control mode offers further flexibility in that the user can decide which temperature channel/channels control each fan. Table 6. Auto Mode Fan Behavior Bits 6, 5 00 01 10 11 Control Operation (Configuration Register 1) Remote Temperature 1 Controls Fan 1 Remote Temperature 2 Controls Fan 2 Remote Temperature 1 Controls Fan 1 and 2 Remote Temperature 2 Controls Fan 1 and 2 Maximum Speed Calculated by Local and Remote Temperature Channels Controls Fans 1 and 2 Figure 23. Effect of Increasing TMIN Value on Control Loop Fan Spin−Up As mentioned in the How Does the Control Loop Work? section, once the temperature being measured exceeds the TMIN value programmed, the fan turns on at minimum speed (default = 33% duty cycle). However, the problem with fans being driven by PWM is that 33% duty cycle is not enough to reliably start the fan spinning. The solution is to spin the fan up for a predetermined time, and once the fan has spun up, its running speed can be reduced in line with the temperature being measured. The ADM1031 allows fan spin−up times between 200 ms and 8 seconds. Bits of Fan Characteristics Register 1 (Register 0×20) and Fan Characteristic Register 2 (Register 0×21) program the fan spin−up times. When Bit 5 and Bit 6 of Configuration Register 1 are both set to 1, increased flexibility is offered. The local and remote temperature channels can have independently programmed control loops with different control parameters. Whichever control loop calculates the fastest fan speed based on the temperature being measured, drives the fans. Figure 24 and Figure 25 show how the fan’s PWM duty cycle is determined by two independent control loops. This is the type of auto mode fan behavior seen when Bit 5 and Bit 6 of Configuration Register 1 are set to 11. Figure 24 shows the control loop for the local temperature channel. Its TMIN value has been programmed to 20°C, and its TRANGE value is 40°C. The local temperature’s TMAX is thus 60°C. Figure 25 shows the control loop for the remote temperature channel. Its TMIN value has been set to 0°C, while its TRANGE = 80°C. Therefore, the remote temperature’s TMAX value is 80°C. Consider if both temperature channels measure 40°C. Both control loops calculate a PWM duty cycle of 66%. Therefore, the fan is driven at 66% duty cycle. If both temperature channels measure 20°C, the local channel calculates 33% PWM duty cycle, while the Remote 1 channel calculates 50% PWM duty cycle. Thus, the fans are driven at 50% PWM duty cycle. Consider the local http://onsemi.com 13 ADM1031 temperature measuring 60°C while the Remote 1 temperature is measuring 70°C. The PWM duty cycle calculated by the local temperature control loop is 100% (because the temperature = TMAX). The PWM duty cycle calculated by the Remote 1 temperature control loop at 70°C is approximately 90%. Therefore, the fan runs full−speed (100% duty cycle). Remember, that the fan speed is based on the fastest speed calculated, and is not necessarily based on the highest temperature measured. Depending on the control loop parameters programmed, a lower temperature on one channel, can actually calculate a faster speed than a higher temperature on the other channel. 100 93 PWM DUTY CYCLE (%) 87 80 73 66 60 53 47 40 33 0 20 40 60 TRANGE = 40°C TMIN TMAX = TMIN + TRANGE LOCAL TEMPERATURE ( °C) 100 93 PWM DUTY CYCLE (%) 87 80 73 66 60 53 47 40 33 0 TMIN 16 28 40 TRANGE = 40°C 60 2 3 Programming the Automatic Fan Speed Control Loop 1. Program a value for TMIN. 2. Program a value for the slope TRANGE. 3. TMAX = TMIN + TRANGE. 4. Program a value for fan spin−up time. 5. Program the desired automatic fan speed control mode behavior, that is, which temperature channel controls the fan. 6. Select automatic fan speed control mode by setting Bit 7 of Configuration Register 1. Other Control Loop Parameters It should be noted that changing the minimum PWM duty cycle affects the control loop behavior. Slope 1 of Figure 26 shows TMIN set to 0°C and the TRANGE chosen is 40°C. In this case, the fan’s PWM duty cycle varies over the range 33% to 100%. The fan runs full−speed at 40°C. If the minimum PWM duty cycle at which the fan runs at TMIN is changed, its effect can be seen on Slope 2 and Slope 3. Take Case 2, where the minimum PWM duty cycle is reprogrammed from 33% (default) to 53%. Figure 24. Maximum Speed Calculated by Local Temperature Control Loop Drives Fan 100 93 PWM DUTY CYCLE (%) 87 80 73 66 60 53 47 40 33 0 TMIN 20 TRANGE = 80°C 40 70 80 TMAX = TMIN + TRANGE REMOTE TEMPERATURE ( °C) 1 TEMPERATURE ( °C) Figure 26. Effect of Changing Minimum Duty Cycle on Control Loop with Fixed TMIN and TRANGE Values Figure 25. Maximum Speed Calculated by Local Temperature Control Loop Drives Fan The fan actually reaches full speed at a much lower temperature, 28°C. Case 3 shows that when the minimum PWM duty cycle is increased to 73%, the temperature at which the fan runs full speed is 16°C. Therefore, the effect of increasing the minimum PWM duty cycle, with a fixed TMIN and fixed TRANGE, is that the fan actually reaches full speed (TMAX) at a lower temperature than TMIN + TRANGE. In automatic fan speed control mode, the register that holds the minimum PWM duty cycle at TMIN, is the fan speed configuration register (Register 0×22). Table 7 shows the relationship between the decimal values written to the fan speed configuration register and PWM duty cycle obtained. How can TMAX be calculated? http://onsemi.com 14 ADM1031 Table 7. Programming PWM Duty Cycle Decimal Value 00 01 02 03 04 05 06 07 08 09 10 (0×0A) 11 (0×0B) 12 (0×0C) 13 (0×0D) 14 (0×0E) 15 (0×0F) PWM Duty Cycle 0% 7% 14% 20% 27% 33% (Default) 40% 47% 53% 60% 67% 73% 80% 87% 93% 100% TMAX = 0 + ((100% DC – 33% DC) × 40/10) TMAX = 0 + ((15 – 5) × 4) = 40 TMAX = 40°C (as seen on Slope 1 of Figure 26) In this case, since the minimum duty cycle is the default 33%, the equation for TMAX reduces to: TMAX = TMIN + ((Max DC – Min DC) × TRANGE/10) TMAX = TMIN + ((15 – 5) × TRANGE/10) TMAX = TMIN + (10 × TRANGE/10) TMAX = TMIN + TRANGE Relevant Registers for Automatic Fan Speed Control Mode Register 0y00 Configuration Register 1 Logic 1 selects automatic fan speed control, Logic 0 selects software control (Default = 1). 00 = Remote Temp 1 controls Fan 1, Remote Temp 2 controls Fan 2. 01 = Remote Temp 1 controls Fan 1 and Fan 2 10 = Remote Temp 2 controls Fan 1 and Fan 2 11 = Fastest Calculated Speed controls Fan 1 and 2 Register 0y20, 0y21 Fan Characteristics Registers 1, 2 The temperature at which the fan runs full−speed (100% duty cycle) is given by: TMAX = TMIN + ((Max DC – Min DC) × TRANGE/10) where: TMAX = Temperature at which fan runs full−speed. TMIN = Temperature at which fan turns on. Max DC = Maximum duty cycle (100%) = 15 decimal. Min DC = Duty cycle at TMIN, programmed in to fan speed configuration register (default = 33% = 5 decimal). TRANGE = PWM duty cycle vs. temperature slope. Example 1 TMIN = 0°C, TRANGE = 40°C Min DC = 53% = 8 decimal (Table 7) Calculate TMAX. TMAX = TMIN + ((Max DC − Min DC) × TRANGE/10) TMAX = 0 + ((100% DC − 53% DC) × 40/10) TMAX = 0 + ((15 − 8) × 4) = 28 TMAX = 28°C (as seen on Slope 2 of Figure 26) Example 2 TMIN = 0°C, TRANGE = 40°C Min DC = 73% = 11 decimal (Table 7) Calculate TMAX. TMAX = TMIN + ((Max DC – Min DC) × TRANGE/10) TMAX = 0 + ((100% DC – 73% DC) × 40/10) TMAX = 0 + ((15 – 11) × 4) = 16 TMAX = 16°C (as seen on Slope 3 of Figure 26) TMIN = 0°C, TRANGE = 40°C Min DC = 33% = 5 decimal (Table 7) Calculate TMAX. TMAX = TMIN + ((Max DC – Min DC) × TRANGE/10) Fan X Spin−Up Time. 000 = 200 ms 001 = 400 ms 010 = 600 ms 011 = 800 ms 100 = 1 sec 101 = 2 sec (Default) 110 = 4 sec 111 = 8 sec PWM Frequency Driving the Fan. 000 = 11.7 Hz 001 = 15.6 Hz 010 = 23.4 Hz 011 = 31.25 Hz (Default) 100 = 37.5 Hz 101 = 46.9 Hz 110 = 62.5 Hz 111 = 93.5 Hz Speed Range N; defines the lowest fan speed that can be measured by the device. 00 = 1: Lowest Speed = 2647 RPM 01 = 2: Lowest Speed = 1324 RPM 10 = 4: Lowest Speed = 662 RPM 11 = 8: Lowest Speed = 331 RPM Register 0y22 Fan Speed Configuration Register Example 3 Min Speed: This nibble contains the speed at which the fan runs when the temperature is at TMIN. The default is 0×05, meaning that the fan runs at 33% duty cycle when the temperature is at TMIN. Min Speed: Determines the minimum PWM cycle for Fan 2 in automatic fan speed control mode. http://onsemi.com 15 ADM1031 Register 0y24 Local Temperature TMIN/TRANGE Filtered Control Mode Local Temperature TMIN. These bits set the temperature at which the fan turns on when under auto fan speed control. TMIN can be programmed in 4°C increments. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C | | 01000 = 32°C (Default) | | 11110 = 120°C 11111 = 124°C Local Temperature TRANGE. This nibble sets the temperature range over which automatic fan speed control takes place. 000 = 5°C 001 = 10°C 010 = 20°C 011 = 40°C 100 = 80°C Register 0y25, 0y26 Remote 1, 2 Temperature TMIN/TRANGE Remote Temperature TMIN. Sets the temperature at which the fan switches on based on Remote X Temperature Readings. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C | | 01100 = 48°C | | 11110 = 120°C 11111 = 124°C Remote Temperature TRANGE. This nibble sets the temperature range over which the fan is controlled based on remote temperature readings. 000 = 5°C 001 = 10°C 010 = 20°C 011 = 40°C 100 = 80°C The automatic fan speed control loop reacts instantaneously to changes in temperature, that is, the PWM duty cycle responds immediately to temperature change. In certain circumstances, we do not want the PWM output to react instantaneously to temperature changes. If significant variations in temperature are found in a system, the fan speed changes, which could be obvious to someone in close proximity. One way to improve the system’s acoustics would be to slow down the loop so that the fan ramps slowly to its newly calculated fan speed. This also ensures that temperature transients are effectively ignored, and the fan’s operation is smooth. There are two means by which to apply filtering to the automatic fan speed control loop. The first method is to ramp the fan speed at a predetermined rate, to its newly calculated value instead of jumping directly to the new fan speed. The second approach involves changing the on−chip ADC sample rate, to change the number of temperature readings taken per second. The filtered mode on the ADM1031 is invoked by setting Bit 0 of the fan filter register (Register 0×23) for Fan 1 and Bit 1 for Fan 2. Once the fan filter register has been written to, and all other control loop parameters (such as TMIN, TRANGE) have been programmed, the device can be placed into automatic fan speed control mode by setting Bit 7 of Configuration Register 1 (Register 0×00) to 1. Effect of Ramp Rate on Filtered Mode Bits of the fan filter register determine the ramp rate in filtered mode. The PWM_OUT signal driving the fan has a period, T, given by the PWM_OUT drive frequency, f, since T = 1/f. For a given PWM period, T, the PWM period is subdivided in to 240 equal time slots. One time slot corresponds to the smallest possible increment in PWM duty cycle. A PWM signal of 33% duty cycle is thus high for 1/3 × 240 time slots and low for 2/3 × 240 time slots. Therefore, 33% PWM duty cycle corresponds to a signal that is high for 80 time slots and low for 160 time slots. PWM_OUT 33% DUTY CYCLE 80 TIME SLOTS 160 TIME SLOTS PWM OUTPUT (ONE PERIOD = 240 TIME SLOTS Figure 27. 33% PWM Duty Cycle Presented in Time Slots The ramp rates in filtered mode are selectable between 1, 2, 4, and 8. The ramp rates are actually discrete time slots. For example, if the ramp rate = 8, then eight time slots are added to the PWM_OUT high duty cycle each time the PWM_OUT duty cycle needs to be increased. Figure 28 shows how the filtered mode algorithm operates. http://onsemi.com 16 ADM1031 140 READ TEMPERATURE 120 RTEMP 100 RTEMP (°C) CALCULATE NEW PWM DUTY CYCLE 80 60 60 40 20 0 PWM DUTY CYCLE 40 120 100 PWM DUTY CYCLE (%) PWM DUTY CYCLE (%) PWM DUTY CYCLE (%) 80 IS NEW PWM VALUE > PREVIOUS VALUE? YES NO DECREMENT PREVIOUS PWM VALUE BY RAMP RATE 20 0 TIME (s) 12 0 INCREMENT PREVIOUS PWM VALUE BY RAMP RATE Figure 29. Filtered Mode with Ramp Rate = 8 Figure 28. Filtered Mode Algorithm The filtered mode algorithm calculates a new PWM duty cycle based on the temperature measured. If the new PWM duty cycle value is greater than the previous PWM value, the previous PWM duty cycle value is incremented by either 1, 2, 4, or 8 time slots (depending on the setting of bits of the fan filter register). If the new PWM duty cycle value is less than the previous PWM value, the previous PWM duty cycle is decremented by 1, 2, 4, or 8 time slots. Each time the PWM duty cycle is incremented or decremented, it is stored as the previous PWM duty cycle for the next comparison. What does an increase of 1, 2, 4, or 8 time slots actually mean in terms of PWM duty cycle? Figure 30 shows how changing the ramp rate from 8 to 4 affects the control loop. The overall response of the fan is slower. Because the ramp rate is reduced, it takes longer for the fan to achieve full running speed. In this case, it took approximately 22 seconds for the fan to reach full speed. 120 140 120 RTEMP 100 80 RTEMP (°C) 80 60 PWM DUTY CYCLE 60 40 40 20 0 110 A ramp rate of 1 corresponds to one time slot, which is 1/240 of the PWM period. In filtered auto fan speed control mode, incrementing or decrementing by 1 changes the PWM output duty cycle by 0.416%. Table 8. Effect of Ramp Rates on PWM_OUT Ramp Rate 1 2 4 8 PWM Duty Cycle Change 0.416% 0.833% 1.66% 3.33% 20 0 0 TIME (s) 22 Figure 30. Filtered Mode with Ramp Rate = 4 Figure 31 shows the PWM output response for a ramp rate of 2. In this instance the fan took about 54 seconds to reach full running speed. 140 120 RTEMP 100 RTEMP (°C) 80 60 60 40 20 0 PWM DUTY CYCLE 40 120 100 So programming a ramp rate of 1, 2, 4, or 8 simply increases or decreases the PWM duty cycle by the amounts shown in Table 8, depending on whether the temperature is increasing or decreasing. Figure 29 shows remote temperature plotted against PWM duty cycle for filtered mode. The ADC sample rate is the highest sample rate; 11.25 kHz. The ramp rate is set to 8, which would correspond to the fastest ramp rate. With these settings, it took approximately 12 seconds to go from 0% duty cycle to 100% duty cycle (full−speed). The TMIN value = 32°C and the TRANGE = 80°C. Even though the temperature increased very rapidly, the fan gradually ramps up to full speed. 80 20 0 TIME (s) 54 0 Figure 31. Filtered Mode with Ramp Rate = 2 http://onsemi.com 17 ADM1031 Finally, Figure 32 shows how the control loop reacts to temperature with the slowest ramp rate. The ramp rate is set to 1, while all other control parameters remain the same. With the slowest ramp rate selected, it took 112 seconds for the fan to reach full speed. 120 140 120 RTEMP 100 80 60 PWM DUTY CYCLE 40 60 40 20 0 RTEMP (°C) 110 PWM DUTY CYCLE (%) 80 the ADC sample rate, the more temperature samples are obtained per second. One way to apply filtering to the control loop is to slow down the ADC sampling rate. This means that the number of iterations of the filtered mode algorithm per second is effectively reduced. If the number of temperature measurements per second is reduced, how often the PWM_OUT signal controlling the fan is updated is also reduced. Bits of the fan filter register (Register 0×23) set the ADC sample rate. The default ADC sample rate is 1.4 kHz. The ADC sample rate is selectable from 87.5 Hz to 11.2 kHz. Table 9 shows how many temperature samples are obtained per second, for each of the ADC sample rates. Table 9. Temperature Updates per Second ADC Sample Rate 87.5 Hz 175 Hz 350 Hz 700 kHz 1.4 kHz 2.8 kHz 5.6 kHz 11.2 kHz Temperature Updates/Sec 0.0625 0.125 0.25 0.5 1 (Default) 2 4 8 20 0 0 TIME (s) 112 Figure 32. Filtered Mode with Ramp Rate = 1 As can be seen from Figure 29 through Figure 32, the rate at which the fan reacts to temperature change is dependent on the ramp rate selected in the fan filter register. The higher the ramp rate, the faster the fan reaches the newly calculated fan speed. Figure 33 shows the behavior of the PWM output as temperature varies. As the temperature rises, the fan speed ramps up. Small drops in temperature do not affect the ramp−up function because the newly calculated fan speed is still higher than the previous PWM value. The filtered mode allows the PWM output to be made less sensitive to temperature variations. This is dependent on the ramp rate selected and the ADC sample rate programmed into the fan filter register. 90 80 70 PWM DUTY CYCLE (%) 60 50 40 30 20 10 0 TIME (s) RTEMP PWM DUTY CYCLE 90 80 70 60 50 40 30 20 10 0 RTEMP (°C) Relevant Registers for Filtered Automatic Fan Speed Control Mode In addition to the registers used to program the normal automatic fan speed control mode, the following register needs to be programmed. Register 0y23 Fan Filter Register Figure 33. How Fan Reacts to Temperature Variation in Filtered Mode Effect of ADC Sample Rate on Filtered Mode The second way to change the filtered mode characteristics is to adjust the ADC sample rate. The faster Spin−up Disable: When this bit is set to 1, fan spin−up is disabled. (Default = 0) Ramp Rate: These bits set the ramp rate for filtered mode. 00 = 1 (0.416% Duty Cycle Change) 01 = 2 (0.833% Duty Cycle Change) 10 = 4 (1.66% Duty Cycle Change) 11 = 8 (3.33% Duty Cycle Change) ADC Sample Rate. 000 = 87.5 Hz 001 = 175 Hz 010 = 350 Hz 011 = 700 Hz 100 = 1.4 kHz (Default) 101 = 2.8 kHz 110 = 5.6 kHz 111 = 11.2 kHz Fan 2 Filter Enable: When this bit is set to 1, it enables filtering on Fan 2. Default = 0. Fan 1 Filter Enable: When this bit is set to 1, it enables filtering on Fan 1. Default = 0. http://onsemi.com 18 ADM1031 Programming the Filtered Automatic Fan Speed Control Loop RPM Feedback Mode 1. Program a value for TMIN. 2. Program a value for the slope TRANGE. 3. TMAX = TMIN + TRANGE. 4. Program a value for fan spin−up time. 5. Program the desired automatic fan speed control mode behavior, that is, which temperature channel controls the fan. 6. Program a ramp rate for the filtered mode. 7. Program the ADC sample rate in the fan filter register. 8. Set Bit 0 to enable fan filtered mode for Fan 1. 9. Set Bit 1 to enable the fan filtered mode for Fan 2. 10. Select automatic fan speed control mode by setting Bit 7 of Configuration Register 1. PWM Duty Cycle Select Mode The ADM1031 can operate under software control by clearing Bit 7 of Configuration Register 1 (Register 0×00). This allows the user to directly control PWM duty cycle for each fan. Clearing Bit 5 and Bit 6 of Configuration Register 1 allows fan control by varying PWM duty cycle. Values of duty cycle between 0% and 100% can be written to the fan speed configuration register (0×22) to control the speed of each fan. Table 10 shows the relationship between hex values written to the fan speed configuration register and PWM duty cycle obtained. Table 10. PWM Duty Cycle Select Mode Hex Value 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F PWM Duty Cycle 0% 7% 14% 20% 27% 33% 40% 47% 53% 60% 67% 73% 80% 87% 93% 100% The second method of fan speed control under software is RPM feedback mode. This involves programming the desired fan RPM value to the device to set fan speed. The advantages include a very tightly maintained fan RPM over the fan’s life, and virtually no acoustic pollution due to fan speed variation. Fans typically have manufacturing tolerances of ±20%, meaning a wide variation in speed for a typical batch of identical fan models. If it is required that all fans run at exactly 5000 RPM, it can be necessary to specify fans with a nominal fan speed of 6250 RPM. However, many of these fans run too fast and make excess noise. A fan with nominal speed of 6250 RPM could run as fast as 7000 RPM at 100% PWM duty cycle. RPM mode allows all of these fans to be programmed to run at the desired RPM value. Clearing Bit 7 of Configuration Register 1 (Register 0×00) to 0 places the ADM1031 under software control. Once under software control, the device can be placed into RPM feedback mode by writing to Bit 5 and Bit 6 of Configuration Register 1. Writing a 1 to Bit 5 and Bit 6 selects RPM feedback mode for each fan. Once RPM feedback mode has been selected, the required fan RPM can be written to the fan tach high limit registers (0×10, 0×11). The RPM feedback mode function allows a fan RPM value to be programmed into the device, and the ADM1031 maintains the selected RPM value by monitoring the fan tach and speeding up the fan as necessary, should the fan start to slow down. Conversely, should the fan start to speed up due to aging, the RPM feedback slows the fan down to maintain the correct RPM speed. The value to be programmed into each fan tach high limit register is given by: Count = (f × 60)/R × N where: f = 11.25 kHz R = desired RPM value N = speed range; must be set to 2 The speed range, N, really determines what the slowest fan speed measured can be before generating an interrupt. The slowest fan speed is measured when the count value reaches 255. Since N = 2 Count = (f × 60)/R × N R = (f × 60)/Count × N R = (11250 × 60)/255 × 2 R = (675000)/510 R = 1324 RPM, fan fail detect speed Programming RPM Values in RPM Feedback Mode Bits set the PWM duty cycle for Fan 1; Bits set the PWM duty cycle for Fan 2. Rather than writing a value such as 5000 to a 16−bit register, an 8−bit count value is programmed instead. The count to be programmed is given by: Count = (f × 60)/R × N where: f = 11.25 kHz R = desired RPM value N = speed range 2 http://onsemi.com 19 ADM1031 Example 1: If the desired value for RPM feedback mode is 5000 RPM, the count to be programmed is: Count = (f × 60)/R × N Since the desired RPM value, R, is 5000 RPM, the value for count is: N = 2: Count = (11250 × 60)/5000 × 2 Count = 675000/10000 Count = 67 (assumes 2 tach pulses/rev) Example 2: If the desired value for RPM feedback mode is 3650 RPM, the count to be programmed is: Count = (f × 60)/R × N Since the desired RPM value, R, is 3650 RPM, the value for count is: N = 2: Count = (11250 × 60)/3650 × 2 Count = 675000/7300 Count = 92 (assumes 2 tach pulses/rev) Once the count value has been calculated, it should be written to the fan tach high limit register. It should be noted that in RPM feedback mode, there is no high limit register for underspeed detection that can be programmed as there are in the other fan speed control modes. The only time each fan indicates a fan failure condition is whenever the count reaches 255. Since the speed range N = 2, the fan fails if its speed drops below 1324 RPM. Programming RPM Values To find the lowest RPM value allowed for a given fan, do the following: 1. Run the fan at 53% PWM duty cycle in software mode. Clear Bit 5 and Bit 7 of Configuration Register 1 (Register 0×00) to enter PWM duty cycle mode. Write 0×08 to the fan speed configuration register (Register 0×22) to set the PWM output to 53% duty cycle. 2. Measure the fan RPM. This represents the fan RPM below which the RPM mode fails to operate. Do not program a lower RPM than this value when using RPM feedback mode. 3. Ensure that speed range N = 2 when using RPM feedback mode. Fan Drive and Speed Measurement Fans come in a variety of different options. One distinguishing feature of fans is the number of poles that a fan has internally. The most common fans available have four, six, or eight poles. The number of poles the fan has generally affects the number of pulses per revolution the fan outputs. If the ADM1031 is used to drive fans other than 4−pole fans that output 2 tach pulses/revolution, then the fan speed measurement equation needs to be adjusted to calculate and display the correct fan speed, and also to program the correct count value in RPM feedback mode. Fan Speed Measurement Equations 1. Choose the RPM value to be programmed. 2. Set speed range value N = 2. 3. Calculate count value based on RPM and speed range values chosen. Use the count equation to calculate the count value. 4. Clear Bit 7 of Configuration Register 1 (Register 0×00) to place the ADM1031 under software control. 5. Write a 1 to Bit 5 of Configuration Register 1 to place the device in RPM feedback mode. 6. Write the calculated count value to the fan tach high limit register (Register 0×10). The fan speed now goes to the desired RPM value and maintains that fan speed. RPM Feedback Mode Limitations For a 4−pole fan (2 tach pulses/rev): Fan RPM = (f × 60)/Count × N For a 6−pole fan (3 tach pulses/rev): Fan RPM = (f × 60)/(Count × N × 1.5) For an 8−pole fan (4 tach pulses/rev): Fan RPM = (f × 60)/(Count × N × 2) If in doubt as to the number of poles the fans used have, or the number of tach output pulses/rev, consult the fan manufacturer’s data sheet, or contact the fan vendor for more information. Fan Drive Using PWM Control RPM feedback mode only controls fan RPM over a limited fan speed range of about 75% to 100%. However, this should be enough range to overcome fan−manufacturing tolerance. In practice, however, the program must not function at too low an RPM value for the fan to run at, or the RPM mode does not operate. The external circuitry required to drive a fan using PWM control is extremely simple. A single NMOS FET is the only drive transistor required. The specifications of the MOSFET depend on the maximum current required by the fan being driven. Typical notebook fans draw a nominal 170 mA, and so SOT devices can be used where board space is a constraint. If driving several fans in parallel from a single PWM output, or driving larger server fans, the MOSFET needs to handle the higher current requirements. The only other stipulation is that the MOSFET should have a gate voltage drive, VGS Local Temp TMIN R/W R/W Description Contains the minimum temperature value for automatic fan speed control based on local temperature readings. TMIN can be programmed to positive values only in 4°C increments. Default is 32°C. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C | | 01000 = 32°C (Default) | | | 11110 = 120°C 11111 = 124°C This nibble contains the temperature range value for automatic fan speed control based on the local temperature readings. 000 = 5°C 001 = 10°C (Default) 010 = 20°C 011 = 40°C 100 = 80°C Local Temp TRANGE R/W http://onsemi.com 27 ADM1031 Table 24. Register 0y25 Remote 1 Temp TMIN/TRANGE Power−On Default = 61H Bit Name Remote 1 Temp TMIN R/W R/W Description Contains the minimum temperature value for automatic fan speed control based on local temperature readings. TMIN can be programmed to positive values only in 4°C increments. Default is 32°C. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C | | 01100 = 48°C | | | 11110 = 120°C 11111 = 124°C This nibble contains the temperature range value for automatic fan speed control based on the Remote 1 Temp Readings. 000 = 5°C 001 = 10°C (Default) 010 = 20°C 011 = 40°C 100 = 80°C Remote 1 Temp TRANGE R/W Table 25. Register 0y26 Remote 2 Temp TMIN/TRANGE Power−On Default = 61H Bit Name Remote 2 Temp TMIN R/W R/W Description Contains the minimum temperature value for automatic fan speed control based on Remote 2 Temperature Readings. TMIN can be programmed to positive values only in 4°C increments. Default is 32°C. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C | | 01100 = 48°C (Default) | | 11110 = 120°C 11111 = 124°C This nibble contains the temperature range value for automatic fan speed control based on the Remote 2 Temp Readings. 000 = 5°C 001 = 10°C (Default) 010 = 20°C 011 = 40°C 100 = 80°C Remote 2 Temp TRANGE R/W Table 26. Register 0y3F THERM Behavior/Revision Power−On Default = 80H Bit Name THERM−to−Fan En R/W R/W Description Setting this bit to 1, enables the fan to run full−speed when THERM is asserted low. This allows the system to be run in performance mode. Clearing this bit to 0 disables the fan from running full−speed whenever THERM is asserted low. This allows the system to run in silent mode. (Power−On Default = 1). This nibble contains the revision number for the ADM1031. Revision R http://onsemi.com 28 ADM1031 Table 27. Register 0y0D Local Temperature Offset Power−On Default = 00H Bit Name Sign Local Offset R/W R/W R Description When this bit is 0, the local offset is added to the Local Temperature Reading. When this bit is set to 1, the local offset is subtracted from the Local Temperature Reading. These four bits are used to add an offset to the Local Temperature Reading. These bits allow an offset value of up to ±15°C to be added to or subtracted from the temperature reading. Table 28. Register 0y0E Remote 1 Temperature Offset Power−On Default = 00H Bit Name Sign R/W R/W Description When this bit is 0, the remote offset is added to the Remote 1 Temperature Reading. When this bit is set to 1, the remote offset is subtracted from the Remote 1 Temperature Reading. Unused. Read back 0. These four bits are used to add an offset to the Remote 1 Temperature Reading. These bits allow an offset value of up to ±15°C to be added to or subtracted from the temperature reading, depending on the sign bit. Unused Remote 1 Offset R/W R/W Table 29. Register 0y0F Remote 2 Temperature Offset Power−On Default = 00H Bit Name Sign R/W R/W Description When this bit is 0, the remote offset is added to the Remote 2 Temperature Reading. When this bit is set to 1, the remote offset is subtracted from the Remote 2 Temperature Reading. Unused. Read back 0. These four bits are used to add an offset to the Remote 2 Temperature Reading. These bits allow an offset value of up to ±15°C to be added to or subtracted from the temperature reading, depending on the sign bit. Unused Remote 2 Offset R/W R/W ORDERING INFORMATION Device Order Number* ADM1031ARQZ ADM1031ARQZ−REEL ADM1031ARQZ−R7 16−Lead QSOP RQ−16 Package Type Package Option Shipping† 98 Tube 2500 Tape & Reel 1000 Tape & Reel †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. *These are Pb−Free packages. http://onsemi.com 29 ADM1031 PACKAGE DIMENSIONS QSOP−16 CASE 492−01 ISSUE O −A− R Q H x 45 _ U RAD. 0.013 X 0.005 DP. MAX −B− MOLD PIN MARK NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: INCH. 3. THE BOTTOM PACKAGE SHALL BE BIGGER THAN THE TOP PACKAGE BY 4 MILS (NOTE: LEAD SIDE ONLY). BOTTOM PACKAGE DIMENSION SHALL FOLLOW THE DIMENSION STATED IN THIS DRAWING. 4. PLASTIC DIMENSIONS DOES NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 6 MILS PER SIDE. 5. BOTTOM EJECTOR PIN WILL INCLUDE THE COUNTRY OF ORIGIN (COO) AND MOLD CAVITY I.D. INCHES DIM MIN MAX A 0.189 0.196 B 0.150 0.157 C 0.061 0.068 D 0.008 0.012 F 0.016 0.035 G 0.025 BSC H 0.008 0.018 J 0.0098 0.0075 K 0.004 0.010 L 0.230 0.244 M 0_ 8_ N 0_ 7_ P 0.007 0.011 Q 0.020 DIA R 0.025 0.035 U 0.025 0.035 8_ V 0_ MILLIMETERS MIN MAX 4.80 4.98 3.81 3.99 1.55 1.73 0.20 0.31 0.41 0.89 0.64 BSC 0.20 0.46 0.249 0.191 0.10 0.25 5.84 6.20 0_ 8_ 0_ 7_ 0.18 0.28 0.51 DIA 0.64 0.89 0.64 0.89 0_ 8_ RAD. 0.005−0.010 TYP L 0.25 (0.010) M G T P DETAIL E C K −T− SEATING PLANE M V N 8 PL D 16 PL 0.25 (0.010) TB S A S M J F DETAIL E Pentium is a registered trademark of Intel Corporation. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. PUBLICATION ORDERING INFORMATION LITERATURE FULFILLMENT: Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada Email: orderlit@onsemi.com N. American Technical Support: 800−282−9855 Toll Free USA/Canada Europe, Middle East and Africa Technical Support: Phone: 421 33 790 2910 Japan Customer Focus Center Phone: 81−3−5773−3850 ON Semiconductor Website: www.onsemi.com Order Literature: http://www.onsemi.com/orderlit For additional information, please contact your local Sales Representative http://onsemi.com 30 ADM1031/D