ADM1031

ADM1031 AD | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 32

Technical content

REV.0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. a ADM1031 Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 2001 Intelligent Temperature Monitor and Dual PWM Fan Controller FUNCTIONAL BLOCK DIAGRAM SERIAL BUS INTERFACE INTERRUPT ST A TUS REGISTERS VALUE AND LIMIT REGISTERS OFFSET REGISTERS CONFIGURA TION REGISTERS LIMIT COMP ARA TOR 2.5V BANDGAP REFERENCE ANALOG MUL TIPLEXER BANDGAP TEMPERA TURE SENSOR SLAVE ADDRESS REGISTER ADD SDA SCL GND ADM1031 FAN FIL TER REGISTER FAN CHARACTERISTICS REGISTERS FAN SPEED COUNTER ADDRESS POINTER REGISTER PWM CONTROLLERS T ACH SIGNAL CONDITIONING INT (SMBALERT) THERM FAN_FAULT PWM_OUT1 T ACH1 / AIN1 D1+ D1– VCC ADC FAN SPEED CONFIG REGISTER T ACH2 / AIN2 PWM_OUT2 D2+ D2–

FEATURES

Optimized for Pentium® III: Allows Reduced Guardbanding Software and Automatic Fan Speed Control Automatic Fan Speed Control Allows Control Indepen- dent of CPU Intervention after Initial Setup Control Loop Minimizes Acoustic Noise and Battery Consumption Remote Temperature Measurement Accurate to 1 /H11543C Using Remote Diode (Two Channels) 0.125/H11543C Resolution on External Temperature Channels Local Temperature Sensor with 0.25 /H11543C Resolution Pulsewidth Modulation Fan Control (PWM) for Two Fans Programmable PWM Frequency Programmable 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 Overtemperature THERM Output Pin for CPU Throttling Programmable INT Output Pin Configurable Offsets for Temperature Channels 3 V to 5.5 V Supply Range Shutdown Mode to Minimize Power Consumption Limit Comparison of All Monitored Values

APPLICATIONS

Notebook PCs, Network Servers and Personal Computers Telecommunications Equipment PRODUCT DESCRIPTION The ADM1031 is an ACPI-compliant three-channel digital thermometer and under/over temperature alarm, for use in personal computers and thermal management systems. Opti- mized for the Pentium III, the higher 1 °C accuracy offered allows systems designers to safely reduce temperature guard- banding and increase system performance. Two Pulsewidth Modulated (PWM) Fan Control outputs control the speed of two cooling fans by varying output duty cycle. Duty cycle values between 33%–100% allow smooth control of the fans. The speed of each fan can be monitored via TACH inputs. The TACH inputs may be reprogrammed as analog inputs, allowing fan speeds for 2-wire fans to be measured via sense resistors. The device will also detect a stalled fan. A dedicated Fan Speed Control Loop provides control even 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 mea sure- ments, and the fan speed adjusted to correct any changes in system temperature. Fan speed may also be controlled using existing ACPI software. Two inputs (four pins) are dedicated to remote temperature-sensing diodes with an accuracy of ±1°C, and an on-chip temperature sensor allows ambient temp erature to be monitored. The device has a programmable INT output to indicate error conditions. There is 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. *Patents pending. Pentium is a registered trademark of Intel Corporation.

REV. 0–2– ADM1031–SPECIFICATIONS1 (TA = TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted.) Parameter Min Typ Max Unit Test Conditions/Comments POWER SUPPLY Supply Voltage, V CC 3.0 3.30 5.5 V Supply Current, I CC 1.4 3 mA Interface Inactive, ADC Active 32 50 µA Standby Mode TEMPERATURE-TO-DIGITAL CONVERTER Local Sensor Accuracy ± 1 ± 3 °C Resolution 0.25 °C Remote Diode1 Sensor Accuracy ±0.5 ±1 °C6 0 °C ≤ TD ≤ 100°C Remote Diode2 Sensor Accuracy ±0.5 ±1.75 °C6 0 °C ≤ TD ≤ 100°C Resolution 0.125 °C Remote Sensor Source Current 180 µA High Level 11 µA Low Level OPEN-DRAIN DIGITAL OUTPUTS (THERM, INT, FAN_FAULT, PWM_OUT) Output Low Voltage, V OL 0.4 V I OUT = –6.0 mA; V CC = 3 V High-Level Output Leakage Current, I OH 0.1 1 µAV OUT = VCC; VCC = 3 V OPEN-DRAIN SERIAL DATA BUS OUTPUT (SDA) Output Low Voltage, V OL 0.4 V I OUT = –6.0 mA; V CC = 3 V High-Level Output Leakage Current, I OH 0.1 1 µAV OUT = VCC SERIAL BUS DIGITAL INPUTS (SCL, SDA) Input High Voltage, V IH 2.1 V Input Low Voltage, V IL 0.8 V Hysteresis 500 mV DIGITAL INPUT LOGIC LEVELS 2 (ADD, THERM, TACH1/2) Input High Voltage, V IH 2.1 V Input Low Voltage, V IL 0.8 V DIGITAL INPUT LEAKAGE CURRENT Input High Current, I IH –1 µAV IN = VCC Input Low Current, I IL 1 µAV IN = 0 Input Capacitance, C IN 5p F FAN RPM-TO-DIGITAL CONVERTER Accuracy ±6% 6 0 °C ≤ TA ≤ 100°C Full-Scale Count 255 TACH Nominal Input RPM 4400 RPM Divisor N = 1, Fan Count = 153

2200 RPM Divisor N = 2, Fan Count = 153

1100 RPM Divisor N = 4, Fan Count = 153

550 RPM Divisor N = 8, Fan Count = 153

Conversion Cycle Time 637 ms SERIAL BUS TIMING 3 Clock Frequency, f SCLK 10 100 kHz See Figure 1 Glitch Immunity, t SW 50 ns See Figure 1 Bus Free Time, t BUF 4.7 µs See Figure 1 Start Setup Time, t SU;STA 4.7 µs See Figure 1 Start Hold Time, t HD;STA 4 µs See Figure 1 Stop Condition Setup Time t SU;STO 4 µs See Figure 1 SCL Low Time, t LOW 1.3 µs See Figure 1 SCL High Time, t HIGH 45 0 µs See Figure 1 SCL, SDA Rise Time, t R 1000 ns See Figure 1 SCL, SDA Fall Time, t F 300 ns See Figure 1 Data Setup Time, t SU;DAT 250 ns See Figure 1 Data Hold Time, t HD;DAT 300 ns See Figure 1 NOTES 1Typicals are at T A = 25°C and represent most likely parametric norm. Shutdown current typ is measured with V CC = 3.3 V. 2ADD is a three-state input that may be pulled high, low or left open-circuit. 3Timing specifications are tested at logic levels of V IL = 0.8 V for a falling edge and V IH = 2.2 V for a rising edge. Specifications subject to change without notice.

conditions for extended periods may affect device reliability. Figure 1. Diagram for Serial Bus Timing

REV. 0 ADM1031 –4– PIN FUNCTION DESCRIPTIONS Pin No. Mnemonic Description 1 PWM_OUT1 Digital Output (Open-Drain). Pulsewidth modulated output to control fan speed. Requires pull- up resistor (10 kΩ typical). 2 TACH1/AIN1 D igital/Analog Input. Fan tachometer input to measure FAN1 fan speed. May be reprogrammed as an analog input to measure speed of a 2-wire fan via a sense resistor (2 Ω typical). 3 PWM_OUT2 Digital Output (Open-Drain). Pulsewidth Modulated output to control FAN2 fan speed. Requires pull-up resistor (10 k Ω typical). 4 TACH2/AIN2 D igital/Analog Input. Fan tachometer input to measure FAN2 fan speed. May be repro- grammed as an analog input to measure speed of a 2-wire fan via a sense resistor (2 Ω typical). 5 GND System Ground. CC Power. Can be powered by 3.3 V Standby power if monitoring in low power states is required. 7 THERM 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 pull-up resistor (10 k Ω). 8 FAN_FAULT Digital Output (Open-Drain). Can be used to signal a fan fault. Drives second fan to full speed if one fan fails. Requires pull-up resistor (typically 10 k Ω). 9 D1– Analog Input. Connected to c athode of first remote temperature-sensing diode. The temperature- sensing element is either a Pentium III substrate transistor or a general-purpose 2N3904. 10 D1+ Analog Input. Connected to anode of first remote temperature-sensing diode. 11 D2– Analog Input. Connected to cathode of second remote temperature-sensing diode. 12 D2+ Analog Input. Connected to anode of second remote temperature-sensing diode. 13 ADD Three-State Logic Input. Sets two lower bits of device SMBus address. 14 INT (SMBALERT) Digital Output (Open-Drain). Can be programmed as an interrupt (SMBus ALERT) output for temperature/fan speed interrupts. Requires pull-up resistor (10 k Ω typical). 15 SDA Digital I/O. Serial Bus Bidirectional Data. Open-drain output. Requires pull-up resistor (2.2 k Ω typical). 16 SCL Digital Input. Serial Bus Clock. Requires pull-up resistor (2.2 k Ω typical). PIN CONFIGURATION TACH2/AIN2 TOP VIEW (Not to Scale) PWM_OUT1 SCL ADM1031 SDA PWM_OUT2 INT (SMBALERT) ADD GND D2+ VCC D2– THERM D1+ FAN_FAULT D1– TACH1/AIN1

REV. 0 –5– Typical Performance Characteristics–ADM1031 LEAKAGE RESIST ANCE – M/H9024 1 1003.3 REMOTE TEMPERA TURE ERROR – /H11543C 10 30 –20 –10 –15 DXP TO GND DXP TO VCC (3.3V) TPC 1. Temperature Error vs. PCB Track Resistance FREQUENCY – Hz REMOTE TEMPERA TURE ERROR – /H11543C15 500k 2M 4M 6M 10M 100M 400M VIN = 100mV p-p VIN = 200mV p-p TPC 2. Temperature Error vs. Power Supply Noise Frequency FREQUENCY – Hz 0 400M100k 1M 100M 200M 300M 500M REMOTE TEMPERA TURE ERROR – /H11543C VIN = 40mV p-p VIN = 20mV p-p TPC 3. Temperature Error vs. Common-Mode Noise Frequency PIII TEMPERA TURE – /H11543C 06 0 10 READING – /H11543C 20 30 40 50 70 80 90 100 110 110 100 TPC 4. Pentium III Temperature Measurement vs. ADM1031 Reading DXP – DXN CAP ACIT ANCE – nF –10 14 7 2.2 REMOTE TEMPERA TURE ERROR – /H11543C 3.3 4.7 10 22 –11 –12 –13 –14 –15 –16 TPC 5. Temperature Error vs. Capacitance between D+ and D– SCLK FREQUENCY – kHz 0 751 SUPPL Y CURRENT – /H9262A 5 10 25 50 100 250 500 750 1000 100 110 VCC = 5V VCC = 3.3V TPC 6. Standby Current vs. Clock Frequency

REV. 0 ADM1031 –6– FREQUENCY – Hz 0 400M100k REMOTE TEMPERA TURE ERROR – /H11543C 1M 100M 200M 300M 500M VIN = 30mV p-p VIN = 20mV p-p TPC 7. Temperature Error vs. Differential-Mode Noise Frequency SUPPL Y VOL T AGE – V 200SUPPL Y CURRENT – /H9262A 180 160 140 120 100 –20 ADD = Hi-Z ADD = GND ADD = VCC TPC 8. Standby Supply Current vs. Supply Voltage TEMPERA TURE – /H11543C 0.08 ERROR – /H11543C –0.08 –0.16 –0.24 –0.32 –0.40 –0.48 –0.56 –0.64 –0.72 –0.80 20 40 60 80 85 100 105 120 TPC 9. Local Sensor Temperature Error TEMPERA TURE – /H11543C 0.08 ERROR – /H11543C –0.08 –0.16 –0.24 –0.32 –0.40 –0.48 –0.56 –0.64 –0.72 –0.80 20 40 60 80 85 100 105 120 TPC 10. Remote Temperature Sensor Error SUPPL Y VOL T AGE – V 1.30 0.80 2.0 SUPPL Y CURRENT – mA 2.4 1.25 1.20 1.15 1.05 0.95 1.10 1.00 0.90 0.85 TPC 11. Supply Current vs. Supply Voltage TIME – Sec 120 TEMPERA TURE – /H11543C 110 100 468 1 013579 TPC 12. Response to Thermal Shock

REV. 0 ADM1031 –7– GENERAL DESCRIPTION The ADM1031 is a temperature monitor and dual PWM fan controller for microprocessor-based systems. The device com- municates with the system via a serial System Management Bus. 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 OF THE ADM1031 A brief description of the ADM1031’s principal internal regis- ters is given below. More detailed information on the function of each register is given in Table XII to Table XXIX. Configuration Register Provides control and configuration of various functions on the device. Address Pointer Register 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 The results of temperature and fan speed measurements are stored in these registers, along with their limit values. Fan Speed Config Register This register is used to program the PWM duty cycle for each fan. Offset Registers Allows the temperature channel readings to be offset by a 5-bit two’s complement value written to these registers. These values will automatically be added to the temperature values (or sub- tracted 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 fre- quency, and speed range for the fans used. THERM Limit Registers These registers contain the temperature values at which THERM will be asserted. TMIN/TRANGE Registers These registers are read/write registers that hold the minimum temperature value below wh ich the fan will not run when the device is in Automatic Fan Speed Control Mode. These registers also hold the temperature range value that defines the range over which auto fan control will be provided, and hence deter- mines the temperature at which the fan will run at full speed. SERIAL BUS INTERFACE 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, e.g., the 810 chipset. The ADM1031 has a 7-bit serial bus address. When the device is powered up, it will do 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 V CC, or left open-circuit to give three different addresses. The state of the ADD pin is only sampled at power-up, so changing ADD with power on will have no effect until the device is powered off, then on again. Table I. ADD Pin Truth Table ADD Pin A1 A0 GND 0 0 No Connect 1 0 VCC 01 If ADD is left open-circuit, the default address will be 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. The serial bus protocol operates as follows: 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 will follow. All slave peripherals connected to the serial bus respond to the START condition, and shift in the next 8 bits, consisting of a 7-bit address (MSB first) plus an R/ W bit that deter- mines the direction of the data transfer, i.e., whether data will be w ritten 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 Acknowl- edge 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, the master w ill write to the slave device. If the R/W bit is a 1, the master will read from the slave device. 2. Data is sent over the serial bus in sequen ces 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 during the high period, as a low-to-high transition when the clock is high may 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 condi- tions are established. In WRITE mode, the master will pull the data line high during the tenth clock pulse to assert a STOP condition. In READ mode, the master device will override 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 will then take 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 may 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.

Register (Register 0x06), and is outlined in Table XVIII. temperature measurement nominally takes 9.6 ms.

1. Place the ADM1031 as close as possible to the remote sens-

distance can be 4 to 8 inches.

1. Route the D+ and D– tracks close together, in parallel, with

under the tracks if possible.

1. Use wide tracks to minimize inductance and reduce noise pick-

up. 10 mil track minimum width and spacing is recommended. Figure 4. Arrangement of Signal Tracks

1. Try to minimize the number of copper/solder joints, which

path and at the same temperature. them, thermocouple voltages should be much less than 200 µV.

1. Place a 0.1 µF bypass capacitor close to the ADM1031.
2. If the distance to the remote sensor is more than 8 inches, the
3. For really long distances (up to 100 feet) use shielded twisted

nected to avoid ground loops. tance should not exceed 1000 pF. introduces about 0.5°C error. attached to the System Management Bus. The ADM1031 has two interrupt outputs, INT and THERM. (described in more detail later).

temperature channel/channels control each fan. 01 Remote Temp 1 Controls Fans 1 and 2. 10 Remote Temp 2 Controls Fans 1 and 2.

11 Maximum Speed Calculated by Local and Remote

Temperature Channels Controls Fans 1 and 2. speed based on the temperature being measured, drives the fans. Behavior seen when Bits 5 and 6 of Config Register 1 are set to 11. value is 40°C. The local temperature’s TMAX will thus be 60°C. nel. Its TMIN value has been set to 0°C, while its TRANGE = 80°C. Therefore, the Remote Temperature’s TMAX value will be 80 °C. will be driven at 66% duty cycle. Figure 9. Max Speed Calculated by Local and Remote

1. Program a value for T MIN.
2. Program a value for the slope T RANGE.
3. Program a value for Fan Spin-up Time.
4. Program the desired Automatic Fan Speed Control Mode

Behavior, i.e., which temperature channel controls the fan.

1. Select Automatic Fan Speed Control Mode by setting Bit 7

of Configuration Register 1. to 33%, the fan control loops will operate as previously described.

duty cycle affects the control loop behavior. Figure 10. Effect of Changing Minimum Duty Cycle on reach full speed (TMAX) at a lower temperature than TMIN + TRANGE. MAX = Temperature at which fan runs full-speed. TMIN = Temperature at which fan will turn on. Max DC = Maximum Duty Cycle (100%) = 15 decimal. Config Register (default = 33% = 5 decimal). TRANGE = PWM Duty Cycle versus Temperature Slope.

REV. 0 ADM1031 –15– RELEVANT REGISTERS FOR AUTOMATIC FAN SPEED CONTROL MODE Register 0x00 Configuration Register 1 <7> Logic 1 selects Automatic Fan Speed Control, Logic 0 selects software control (Default = 1). <6:5> 00 = Remote Temp 1 controls Fan 1, Remote Temp 2 controls Fan 2. 01 = Remote Temp 1 controls Fans 1 and 2 10 = Remote Temp 2 controls Fans 1 and 2 11 = Fastest Calculated Speed controls Fans 1 and 2 Register 0x20, 0x21 Fan Characteristics Registers 1, 2 <2:0> Fan X Spin-Up Time 000 = 200 ms 001 = 400 ms 010 = 600 ms 011 = 800 ms 100 = 1 sec 101 = 2 secs (Default) 110 = 4 secs 111 = 8 secs <5:3> 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 <7:6> 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 0x22 Fan Speed Configuration Register <3:0> Min Speed: This nibble contains the speed at which the fan will run when the temperature is at TMIN. The default is 0x05, meaning that the fan will run at 33% duty cycle when the temperature is at T MIN. <7:4> Min Speed: Determines the minimum PWM cycle for Fan 2 in Automatic Fan Speed Control Mode. Register 0x24 Local Temperature T MIN/TRANGE <7:3> Local Temperature T MIN. These bits set the temperature at which the fan will turn 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 <2:0> Local Temperature T RANGE. This nibble sets the tem- perature 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 0x25, 0x26 Remote 1, 2 Temperature T MIN/TRANGE <7:3> Remote Temperature T MIN. Sets the temperature at which the fan will switch on based on Remote X Tem- perature Readings. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C 01100 = 48°C 11110 = 120 11111 = 124°C <2:0> Remote Temperature T RANGE. This nibble sets the tem- perature range over which the fan will be controlled based on Remote Temperature readings. 000 = 5°C 001 = 10°C 010 = 20°C 011 = 40°C 100 = 80°C

will effectively be ignored, and the fan’s operation will be smooth. change the number of temperature readings taken per second. Register 1 (Register 0x00) to 1.

160 TIME

80 TIME

240 TIME SLOTS

Figure 11. 33% PWM Duty Cycle Represented in Time Figure 12. Filtered Mode Algorithm previous PWM duty cycle for the next comparison. very rapidly, the fan gradually ramps up to full speed.

100 RTEMP

Figure 13. Filtered Mode with Ramp Rate = 8 the fan to reach full speed. Figure 14. Filtered Mode with Ramp Rate = 4

1. In this instance the fan took about 54 seconds to reach full

Figure 15. Filtered Mode with Ramp Rate = 2 Figure 16. Filtered Mode with Ramp Rate = 1 the ADC sample rate programmed into the Fan Filter Register. Figure 17. How Fan Reacts to Temperature Variation in

REV. 0 ADM1031 –18– Effect of ADC Sample Rate on Filtered Mode The second means by which to change the Filtered Mode charac- teristics is to adjust the ADC sample rate. The faster the ADC sample rate, the more temperature samples are obtained per sec- ond. 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 <4:2> of the Fan Filter Register (Reg 0x23) 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 IX shows how many temperature samples are obtained per second, for each of the ADC sample rates. Table IX. Temperature Updates per Second ADC Sample Rate Temperature Updates/Sec 87.5 Hz 0.0625 175 Hz 0.125 350 Hz 0.25 700 Hz 0.5 1.4 kHz 1 (Default) 2.8 kHz 2 5.6 kHz 4 11.2 kHz 8 RELEVANT REGISTERS FOR FILTERED AUTOMATIC FAN SPEED CONTROL MODE In addition to the registers used to program the normal Auto- matic Fan Speed Control Mode, the following register needs to be programmed. Register 0x23 Fan Filter Register <7> Spin-up Disable :- when this bit is set to 1, fan spin-up is disabled. (Default = 0) <6:5> 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) <4:2> 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 <1> Fan 2 Filter Enable: when this bit is set to 1, it enables filtering on Fan 2. Default = 0. <0> Fan 1 Filter Enable: when this bit is set to 1, it enables filtering on Fan 1. Default = 0. PROGRAMMING THE FILTERED AUTOMATIC FAN SPEED CONTROL LOOP 1. Program a value for T MIN. 2. Program a value for the slope T RANGE. 3. T MAX = TMIN + TRANGE. 4. Program a value for Fan Spin-up Time. 5. Program the desired Automatic Fan Speed Control Mode Behavior, i.e., 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 may be operated under software control by clearing Bit 7 of Configuration Register 1 (Register 0x00). This allows the user to directly control PWM duty cycle for each fan. Clearing Bits 5, 6 of Configuration Register 1 allows fan control by varying PWM duty cycle. Values of duty cycle between 0% to 100% may be written to the Fan Speed Config Register (0x22) to control the speed of each fan. Table X shows the relationship between hex values written to the Fan Speed Configuration Register and PWM duty cycle obtained. Table X. PWM Duty Cycle Select Mode Hex Value PWM Duty Cycle 00 0% 01 7% 02 14% 03 20% 04 27% 05 33% 06 40% 07 47% 08 53% 09 60% 0A 67% 0B 73% 0C 80% 0D 87% 0E 93% 0F 100% Bits <3:0> set the PWM duty cycle for Fan 1; Bits <7:4> set the PWM duty cycle for Fan 2.

REV. 0 ADM1031 –19– RPM FEEDBACK MODE 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 virtu- ally 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 may be necessary to specify fans with a nominal fan speed of 6250 RPM. However, many of these fans will 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 will allow all of these fans to be programmed to run at the desired RPM value. Clearing Bit 7 of Configuration Register 1 (Reg 0x00) to 0 places the ADM1031 under software control. Once under soft- ware control, the device may be placed in to RPM Feedback Mode by writing to Bits 5, 6 of Configuration Register 1. Writing a 1 to Bits 5, 6 selects RPM Feedback Mode for each fan. Once RPM Feedback Mode has been selected, the required fan RPM may be written to the Fan Tach High Limit Registers (0x10, 0x11). The RPM Feedback Mode function allows a fan RPM value to be programmed into the device, and the ADM1031 will maintain 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 will slow 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 will be measured when the Count value reaches 255. Since speed range, 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 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 pro- grammed is given by: Count = (f × 60)/R × N where: f = 11.25 kHz R = desired RPM value N = Speed Range = 2 Example 1: If the desired value for RPM Feedback Mode is 5000 RPM, what value needs to be programmed for Count? 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, what value needs to be programmed for Count? 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 under- speed detection that can be programmed as there are in the other fan speed control modes. The only time each fan will indicate a fan failure condition is whenever the count reaches 255. Since the speed range, N, = 2, the fan will fail if its speed drops below 1324 RPM. Programming RPM Values 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 Count Equation to calculate Count Value. 4. Clear Bit 7 of Configuration Register 1 (Reg. 0x00) 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 (Reg. 0x10). The fan speed will now go to the desired RPM value and maintain that fan speed. RPM Feedback Mode Limitations 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 prac- tice, however, the program must not function at too low an RPM value for the fan to run at, or the RPM Mode will not operate. To find the lowest RPM value allowed for a given fan, do the following:

REV. 0 ADM1031 –23– Table XII. Registers Address A7–A0 Register Name in Hex Comments Value Registers 0x08–0x1E See Table XIII. Device ID Register 0x3D This location contains the device identification number. Since this device is the ADM1031, this register contains 0x31. This register is read only. Company ID 0x3E This location contains the company identification number (0x41). This register is read only. THERM Behavior/Revision 0x3F This location contains the revision number of the device. The lower four bits reflect device revisions [3:0]. Bit 7 of this register is the THERM-to-fan enable bit. See Table XXII. Configuration Register 1 0x00 See Table XIV. Power-on value = 1001 0000. Configuration Register 2 0x01 See Table XV. Power-on value = 0111 1111. Status Register 1 0x02 See Table XVI. Power-on value = 0000 0000. Status Register 2 0x03 See Table XVII. Power-on value = 0000 0000. Manufacturer’s Test Register 0x07 This register is used by the manufacturer for test purposes only. This register should not be read from or written to in normal operation. Fan Characteristics Register 1 0x20 See Table XIX. Power-on value = 0101 1101. Fan Characteristics Register 2 0x21 See Table XX. Power-on value = 0101 1101. Fan Speed Configuration Register 0x22 See Table XXI. Power-on value = 0101 0101. Fan Filter Register 0x23 See Table XXII. Power-on value = 0101 0000. Local Temperature T MIN/TRANGE 0x24 See Table XXIII. Power-on value = 0100 0001. Remote 1 Temperature T MIN/TRANGE 0x25 See Table XXIV. Power-on value = 0110 0001. Remote 2 Temperature T MIN/TRANGE 0x26 See Table XXV. Power-on value = 0110 0001. Table XIII. Value Registers Address Read/Write Description 0x06 Read/Only Extended Temperature Resolution (see Table XVIII). 0x08 Read/Write Fan 1 Speed—this register contains the value of the Fan 1 tach measurement. 0x09 Read/Write Fan 2 Speed—this register contains the value of the Fan 2 tach measurement. 0x0A Read/Only Local Temperature Value—this register contains the 8 MSBs of the local temperature measurement. 0x0B Read/Only Re mote 1 Temperature Value—this register contains the 8 MSBs of the Remote 1 temperature reading. 0x0C Read/Only Remote 2 Temperature Value—this register contains the 8 MSBs of the Remote 2 temperature reading. 0x0D Read/Write Local Temperature Offset—See Table XXVII. (Power-On Default = 00h.) 0x0E Read/Write Remote 1 Temperature Offset—See Table XXVIII. (Power-On Default = 00h.) 0x0F Read/Write Remote 2 Temperature Offset—See Table XXIX. (Power-On Default = 00h.) 0x10 Read/Write Fan 1 Tach High Limit—this register contains the limit for the Fan 1 tach measurement. Since the tach circuit counts between pulses, a slow fan will result in a large measured value, so exceeding the limit is the way to detect a slow or stalled fan. (Power-On Default = FFh.) 0x11 Read/Write Fan 2 Tach High Limit—this register contains the limit for the Fan 2 tach measurement. Since the tach circuit counts between pulses, a slow fan will result in a large measured value, so exceeding the limit is the way to detect a slow or stalled fan. (Power-On Default = FFh.) 0x14 Read/Write Local Temperature High Limit (Power-On Default 60 °C). 0x15 Read/Write Local Temperature Low Limit (Power-On Default 0 °C). 0x16 Read/Write Local Temperature Therm Limit (Power-On Default 70 °C). 0x18 Read/Write Remote 1 Temperature High Limit (Power-On Default 80 °C). 0x19 Read/Write Remote 1 Temperature Low Limit (Power-On Default 0 °C). 0x1A Read/Write Remote 1 Temperature Therm Limit (Power-On Default 100 °C). 0x1C Read/Write Remote 2 Temperature High Limit (Power-On Default 80 °C). 0x1D Read/Write Remote 2 Temperature Low Limit (Power-On Default 0 °C). 0x1E Read/Write Remote 2 Temperature Therm Limit (Power-On Default 100 °C).

REV. 0 ADM1031 –24– Table XIV. Register 0x00 Configuration Register 1 Power-On Default 90h Bit Name R/ W Description 0 MONITOR Read/Write Setting this bit to a “1” enables monitoring of temperature and enables measurement of the fan tach signals. (Power-Up Default = 0.) 1 INT Enable Read/Write Setting this bit to a “1” enables the INT output. 1 = Enabled 0 = Disabled (Power-Up Default = 0.) 2 TACH/AIN Read/Write Clearing this bit to “0” selects digital fan speed measurement via the TACH pins. Setting this bit to “1” configures the TACH pins as analog inputs that can measure the speed of 2-wire fans via a sense resistor. (Power-Up Default = 0.) 3 PWM Invert Read/Write Setting this bit to “1” inverts the PWM signal on the output pins. (Power-Up Default = 0.) 4 Fan Fault Enable Read/Write Logic 1 enables FAN_FAULT pin; Logic 0 disables FAN_FAULT output. (Power-Up Default = 1.) 6–5 PWM Mode Read/Write These two bits control the behavior of the fans in Auto Fan Speed Control Mode. 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 = Max of Local Temp and Remote Temp 1 and 2 drives Fans 1 and 2. These two bits have the following effect in Software Control Mode. 00 = Program PWM duty cycles for Fans 1 and 2. 11 = Program RPM Speeds for Fans 1 and 2. 7 Auto/SW Ctrl Read/Write Logic 1 selects Automatic Fan Speed Control; Logic 0 selects SW control. (Power-Up Default = 1) When under software control, PWM duty cycle or RPM values may be programmed for each fan. Table XV. Register 0x01 Configuration 2 Power-On Default = 7FH Bit Name R/ W Description 0 PWM 1 En Read/Write Enables Fan 1 PWM output when this bit is a “1.” 1 PWM 2 En Read/Write Enables Fan 2 PWM output when this bit is a “1.” 2 TACH 1 En Read/Write Enables Tach 1 input when set to “1.” 3 TACH 2 En Read/Write Enables Tach 2 input when set to “1.” 4 Loc Temp En Read/Write Enables Interrupts on Local Temperature Channel when set to “1.” 5 Remote 1 Temp En Read/Write Enables Interrupts on Remote 1 Channel when set to “1.” Default is normally enabled, except when a diode fault is detected on power-up. 6 Remote 2 Temp En Read/Write Enables Interrupts on Remote 2 Channel when set to “1.” Default is normally enabled, except when a diode fault is detected on power-up. 7 SW Reset Read/Write When set to “1,” resets the device. Self-clears. Power-Up Default = 0.

REV. 0 ADM1031 –25– Table XVI. Register 0x02 Status Register 1 Power-On Default = 00H Bit Name R/ W Description 0 Alarm 1 Speed Read Only This bit is set to “1” when fan is running at alarm speed. Once read, this bit will not reassert on next monitoring cycle, even if the fan is still running at alarm speed. 1 Fan 1 Fault Read Only This bit is set to “1” if Fan 1 becomes stuck or is running under speed. 2 Remote 1 High Read Only “1” indicates Remote 1 high temperature limit has been exceeded. If the temperature is still outside the Remote 1 Temp High Limit, this bit will reas- sert on next monitoring cycle. 3 Remote 1 Low Read Only “1” indicates Remote 1 low temperature limit exceeded (below). If the tem- perature is still outside the Remote 1 Temp Low Limit, this bit will reassert on next monitoring cycle. 4 Remote 1 Therm Read Only “1” indicates Remote 1 temperature Therm limit has been exceeded. This bit is cleared on a read of Status Register 1. 5 Remote Diode 1 Error Read Only This bit is set to “1” if a short or open is detected on the Remote 1 tempera- ture channel. This test is only done on power-up, and if set to 1 cannot be cleared by reading the Status Register 1. 6 Local Temp High Read Only “1” indicates Local Temp High Limit has been exceeded. If the temperature is still outside the Local Temp High Limit, this bit will reassert on next monitoring cycle. 7 Local Temp Low Read Only “1” indicates Local Temp Low Limit has been exceeded (below). If the tem- perature is still outside the Local Temp Low Limit, this bit will reassert on next monitoring cycle. Table XVII. Register 0x03 Status Register 2 Power-Up Default = 00H Bit Name R/ W Description 0 Alarm 2 Speed Read Only This bit is set to “1” when Fan 2 is running at alarm speed. Once read, this bit will not reassert on next monitoring cycle, even if the fan is still running at alarm speed. 1 Fan 2 Fault Read Only This bit is set to “1” if Fan 2 becomes stuck or is running under speed. 2 Remote 2 High Read Only “1” indicates Remote 2 high temperature limit has been exceeded. If the temperature is still outside the Remote 2 Temp High Limit, this bit will reas- sert on the next monitoring cycle. 3 Remote 2 Low Read Only “1” indicates Remote 2 low temperature limit exceeded (below). If the tem- perature is still outside the Remote 2 Temp Low Limit, this bit will reassert on the next monitoring cycle. 4 Remote 2 Therm Read Only “1” indicates Remote 2 temperature Therm limit has been exceeded. This bit is cleared on reading Status Register 2. 5 Remote Diode 2 Error Read Only This bit is set to “1” if a short or open is detected on the Remote 2 tempera- ture channel. This test is only done on power-up, and if set to 1 ca nnot be cleared by reading Status Register 2. 6 Local Therm Read Only “1” indicates Local temperature Therm limit has been exceeded. This bit clears on a read of Status Register 2. 7 THERM Read Only Set to “1” when THERM is pulled low as an input. This bit clears on a read of Status Register 2. Table XVIII. Register 0x06 Extended Temperature Resolution Power-On Default = 00H Bit Name R/ W Description <2:0> Remote Temp 1 Read Only Holds extended temperature resolution bits for Remote 1 channel. <5:3> Remote Temp 2 Read Only Holds extended temperature resolution bits for Remote 2 channel. <7:6> Local Temp Read Only Holds extended temperature resolution bits for Local Temperature channel.

REV. 0 ADM1031 –26– Table XIX. Register 0x20 Fan Characteristics Register 1 Power-On Default = 5DH Bit Name R/ W Description <2:0> Fan 1 Spin-up Read/Write These bits contain the Fan Spin-up time to allow Fan 1 to overcome its own inertia. 000 = 200 ms 001 = 400 ms 010 = 600 ms 011 = 800 ms 100 = 1 sec 101 = 2 secs (Default) 110 = 4 secs 111 = 8 secs <5:3> PWM 1 Frequency Read/Write These bits allow programmability of the nominal PWM 1 output frequency driving Fan 1. (Default = 31 Hz.) 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 <7:6> Speed Range, N Read/Write Speed Range 00 = 1 01 = 2 10 = 4 11 = 8 Table XX. Register 0x21 Fan Characteristics Register 2 Power-On Default = 5DH Bit Name R/ W Description <2:0> Fan 2 Spin-up Read/Write These bits contain the Fan Spin-up time to allow Fan 2 to overcome its own inertia. 000 = 200 ms 001 = 400 ms 010 = 600 ms 011 = 800 ms 100 = 1 sec 101 = 2 secs (Default) 110 = 4 secs 111 = 8 secs <5:3> PWM 2 Frequency Read/Write These bits allow programmability of the nominal PWM 2 output frequency driving Fan 2. (Default = 31 Hz.) 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 <7:6> Speed Range, N Read/Write Speed Range 00 = 1 01 = 2 10 = 4 11 = 8

REV. 0 ADM1031 –27– Table XXI. Register 0x22 Fan Speed Config Register Power-On Default = 55H Bit Name R/ W Description <3:0> Normal/Min Spd 1 Read/Write This nibble contains the normal speed value for Fan 1. When in Automatic Fan Speed Control Mode, this nibble contains the minimum speed at which Fan 1 will run. Default is 0x05 for 33% PWM duty cycle. <7:4> Normal/Min Spd 2 Read/Write This nibble contains the normal speed value for Fan 2. When in Automatic Fan Speed Control Mode, this nibble contains the minimum speed at which Fan 2 will run. Default is 0x05 for 33% PWM duty cycle. Table XXII. Register 0x23 Fan Filter Register Power-On Default = 50H Bit Name R/ W Description <7> Spin-Up Disable Read/Write When set to 1, disables fan spin-up. <6:5> Ramp Rate Read/Write These bits set the ramp rate. 00 = 1 01 = 2 10 = 4 (Default) 11 = 8 <4:2> ADC Sample Rate Read/Write These bits set the sampling rate for the ADC. 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 <1> Fan 2 Filter En Read/Write This bit enables fan filtering for Fan 2. <0> Fan1 Filter En Read/Write This bit enables fan filtering for Fan 1. Table XXIII. Register 0x24 Local Temp TMIN/TRANGE Power-On Default = 41H Bit Name R/ W Description <7:3> Local Temp T MIN Read/Write Contains the minimum temperature value for Automatic Fan Speed Control based on Local Temperature Readings. T MIN 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 <2:0> Local Temp T RANGE Read/Write This nibble contains the temperature range value for Automatic Fan Speed Control based on the Local Temp Readings. 000 = 5°C 001 = 10°C (Default) 010 = 20°C 011 = 40°C 100 = 80°C

REV. 0 ADM1031 –28– Table XXIV. Register 0x25 Remote 1 Temp TMIN/TRANGE Power-On Default = 61H Bit Name R/ W Description <7:3> Remote 1 Temp T MIN Read/Write Contains the minimum temperature value for Automatic Fan Speed Control based on Remote 1 Temperature Readings. T MIN can be programmed to positive values only in 4 °C increments. Default is 48 °C. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C 01100 = 48°C (Default) 11110 = 120°C 11111 = 124°C <2:0> Remote 1 Temp T RANGE Read/Write 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 Table XXV. Register 0x26 Remote 2 Temp TMIN/TRANGE Power-On Default = 61H Bit Name R/ W Description <7:3> Remote 2 Temp T MIN Read/Write Contains the minimum temperature value for Automatic Fan Speed Control based on Remote 2 Temperature Readings. T MIN can be programmed to positive values only in 4 °C increments. Default is 48 °C. 00000 = 0°C 00001 = 4°C 00010 = 8°C 00011 = 12°C 01100 = 48°C (Default) 11110 = 120°C 11111 = 124°C <2:0> Remote 2 Temp T RANGE Read/Write 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 Table XXVI. Register 0x3F Therm Behavior/Revision Power-On Default = 80H Bit Name R/ W Description <7> Therm-to-Fan En Read/Write 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. Clear- ing 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). <3:0> Revision Read Only This nibble contains the revision number for the ADM1031.

REV. 0 ADM1031 –29– Table XXVII. Register 0x0D Local Temp Offset Power-On Default = 00H Bit Name R/ W Description <7> Sign Read/Write When this bit is 0, the local offset will be added to the Local Temp Reading. When this bit is set to 1, the local offset will be subtracted from the L ocal Temp Reading. <3:0> Local Offset Read/Write 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 XXVIII. Register 0x0E Remote 1 Temp Offset Power-On Default = 00H Bit Name R/ W Description <7> Sign Read/Write When this bit is 0, the remote offset will be added to the Remote 1 Temp Reading. When this bit is set to 1, the remote offset will be subtracted from the Remote 1 Temp Reading. <6.4> Unused Read/Write Unused. Read back 0. <3:0> Remote 1 Offset Read/Write T hese 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. Table XXIX. Register 0x0F Remote 2 Temp Offset Power-On Default = 00H Bit Name R/ W Description <7> Sign Read/Write When this bit is 0, the remote offset will be added to the Remote 2 Temp Reading. When this bit is set to 1, the remote offset will be subtracted from the Remote 2 Temp Reading. <6.4> Unused Read/Write Unused. Read back 0. <3:0> Remote 2 Offset Read/Write 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.

REV. 0 ADM1031 –30– OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 16-Lead QSOP Package (RQ-16) 16 9 0.197 (5.00) 0.189 (4.80) 0.244 (6.20) 0.228 (5.79) PIN 1 0.157 (3.99) 0.150 (3.81) SEATING PLANE 0.010 (0.25) 0.004 (0.10) 0.012 (0.30) 0.008 (0.20) 0.025 (0.64) BSC 0.059 (1.50) MAX 0.069 (1.75) 0.053 (1.35) 0.010 (0.20) 0.007 (0.18) 0.050 (1.27) 0.016 (0.41) 8/H11543 0/H11543

–31–

–32– C02402–2.5–4/01(0) PRINTED IN U.S.A.