LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor General Description The LM81 is a highly integrated data acquisition system for hardware monitoring of servers, Personal Computers, or virtually any microprocessor-based system. In a PC, the LM81 can be used to monitor power supply voltages, temperatures, and fan speeds. Actual values for these inputs can be read at any time. Programmable WATCHDOG limits in the LM81 activate a fully programmable and maskable interrupt system with two outputs (INT and T_CRIT_). The LM81 has an on-chip digital output temperature sensor with 9-bit or 12-bit resolution, a 6 analog input ADC with 8-bit resolution and an 8-bit DAC. Two fan tachometer outputs can be measured with the LM81's FAN1 and FAN2 inputs. The DAC, with a 0 to 1.25V output voltage range, can be used for fan speed control. Additional inputs are provided for Chassis Intrusion detection circuits, and VID monitor inputs. The LM81 has a Serial Bus interface that is compatible with SMBusTM. n Chassis Intrusion detector input n WATCHDOG comparison of all monitored values n SMBus 1.0 (LM81C) and 1.1 (LM81B) Serial Bus interface compatibility n LM81B has improved voltage monitoring accuracy n VID0-VID4 monitoring inputs Key Specifications j Voltage Monitoring Error +2% or 1.2% (max) j Temperature Error 3C (max) -40C to +125C j Supply Voltage Range 2.8V to 3.8V j Supply Current 0.4 mA (typ) j ADC and DAC Resolution 8 Bits j Temperature Resolution 0.5C Applications Features n Temperature sensing n 6 positive voltage inputs with scaling resistors to monitor +5V, +12V, +3.3V, +2.5V, Vccp power supplies directly n 8-bit DAC output for controlling fan speed n 2 fan speed monitoring inputs n System Thermal and Hardware Monitoring for Servers and PCs n Office Electronics n Electronic Test Equipment and Instrumentation Typical Application DS100072-1 # Indicates Active Low ("Not") (c) 2002 National Semiconductor Corporation DS100072 www.national.com LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor February 2002 LM81 Ordering Information Temperature Range -40C TA +125C NS Package Number SMBus Revision Level Voltage Monitoring Error Order Number Device Marking LM81BIMT-31 LM81BIMT-3 MTC24B 1.1 LM81BIMTX-3 LM81BIMT-3 MTC24B 1.1 1.2% 1.2% LM81CIMT-31 LM81CIMT-3 MTC24B 1.0 +2% LM81CIMTX-32 LM81CIMT-3 MTC24B 1.0 +2% 2 Note: 1-Rail transport media, 62 parts per rail 2 -Tape and reel transport media, 3400 parts per reel Connection Diagram DS100072-3 www.national.com 2 LM81 Block Diagram DS100072-2 Pin Description Pin Name(s) A0/NTEST_OUT Pin Number Number of Pins 1 1 Digital I/0 The lowest order programmable bit of the serial bus address. This pin functions as an output during NAND Tree tests (board-level connectivity testing). Refer to SECTION 11 on NAND Tree testing. Type Description A1 2 1 Digital Input The highest order programmable bit of the serial bus address. SMBData 3 1 Digital I/O Serial Bus bidirectional Data. Open-drain output. SMBCLK 4 1 Digital Input Serial Bus Clock. FAN1-FAN2 5-6 2 Digital Inputs Schmitt Trigger fan tachometer inputs. CI 7 1 Digital I/O An active high input from an external circuit which latches a Chassis Intrusion event. This line can go high without any clamping action regardless of the powered state of the LM81. There is also an internal open-drain output on this line, controlled by Bit 6 of the Configuration Register (40h) or Bit 7 CI Clear Register (46h), to provide a minimum 20 ms reset pulse. See Section 3.3 and Section 9.0. T_CRIT_A 8 1 Digital Output Critical Temperature Alarm active low open-drain output. This pin can be grounded when not used. V+ (+2.8V to +3.8V) 9 1 POWER +3.3V V+ power. Bypass with the parallel combination of 10 F (electrolytic or tantalum) and 0.1 F (ceramic) bypass capacitors. 3 www.national.com LM81 Pin Description Pin Name(s) (Continued) Pin Number Number of Pins Type Description INT 10 1 Digital Output Interrupt active low open-drain output. This output is enabled when Bit 1 in the Configuration Register is set to 1. The default state is disabled. DACOut/NTEST_IN 11 1 Analog Output/Digital Input 0V to +1.25V amplitude 8-bit DAC output. When forced high by an external voltage the NAND Tree Test mode is enabled which provides board-level connectivity testing. Refer to Section 11.0 on NAND Tree testing. RESET 12 1 Digital I/O Master Reset, 5 mA driver (open-drain), active low output with a 20 ms minimum pulse width. Available when enabled via Bit 4 in the Configuration register. It acts as an active low power on RESET input. GND 13 1 GROUND Internally connected to all circuitry. The ground reference for all analog inputs and the DAC output. This pin needs to be connected to a low noise analog ground plane for optimum performance of the DAC output. Vccp2 14 1 Analog Input Analog input for monitoring -12V or Vccp2. Selectable by choosing the appropriate external resistor divider values such that the input to the LM81 is scaled to +2.5V. See Section 4.0. +12Vin 15 1 Analog Input Analog input for monitoring +12V. +5Vin 16 1 Analog Input Analog input for monitoring +5V. +3.3Vin 17 1 Analog Input Analog input for monitoring +3.3V. +2.5Vin 18 1 Analog Input Analog input for monitoring +2.5V. Vccp1 19 1 Analog Input Analog input for monitoring Vccp, a processor voltage that is nominally at +2.5V. 20-24 5 Digital Inputs Supply Voltage readouts from the Pentium/PRO power supplies that indicate the operating voltage or the processor (e.g. 1.5V to 2.9V). The values are read in the VID/Fan Divisor Register and the VID4 Register. VID4-VID0 TOTAL PINS www.national.com 24 4 Soldering Information MTC Package (Note 7) : Vapor Phase (60 seconds) Infrared (15 seconds) Storage Temperature If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Positive Supply Voltage (V+) Voltage on Any Input or Output Pin: +12Vin, T_CRIT_A A0, A1, DACOut +2.5Vin, +3.3Vin All other pins Input Current at any Pin (Note 4) Package Input Current (Note 4) Maximum Junction Temperature (TJ max) ESD Susceptibility (Note 6) Human Body Model Machine Model LM81 Absolute Maximum Ratings (Notes 1, 2) +6.0V 215C 235C -65C to +150C Operating Ratings (Notes 1, 2) -0.3V to +15V -0.3V to (V++ 0.3V) (Note 3) -0.3V to +6V 5 mA 20 mA Operating Temperature Range TMIN TA TMAX LM81 -40C TA +125C Specified Temperature Range TMIN TA TMAX LM81 -40C TA +125C Junction to Ambient Thermal Resistance (JA (Note 5)) NS Package Number: MTC24B 95C/W +2.8V to +3.8V Supply Voltage (V+) VIN Voltage Range: +12Vin -0.05V to +15V +5Vin -0.05V to +6.8V +3.3Vin -0.05V to +4.6V +2.5Vin -0.05V to +3.6V VID0 - VID4, Vccp, FAN1-FAN2 -0.05V to +6.0V All other inputs -0.05V to (V+ + 0.05V) 150C 2000V 200V DC Electrical Characteristics The following specifications apply for +2.8VDC V+ +3.8VDC, RS = 500, unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25C. (Note 8) Symbol Parameter Conditions Typical Limits LM81BIM Limits LM81CIM Units (Note 9) (Note 10) (Note 10) (Limits) 0.4 1.4 0.9 mA (max) 3 3 C (max) 0.5 0.0625 0.5 0.0625 C (min) C (min) POWER SUPPLY CHARACTERISTICS I+ Supply Current Interface Inactive TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS -40C TA +125C Error Resolution 9-bit mode 12-bit mode LM81 ANALOG-TO-DIGITAL CONVERTER CHARACTERISTICS Resolution TUE Total Unadjusted Error 8 (Notes 11, 12) +1.2 -1.2 +2 +0.8 % (max) % (min) Vccp1, Vccp2 (Note 11) +1.2 -1.2 +2.4 0 % (max) % (min) +12Vin (Notes 11, 12) +1.2 -1.2 +3.1 +1.2 % (max) % (min) 1 1 LSB (max) DNL Differential Non-Linearity PSS Power Supply Sensitivity tC bits +2.5Vin, +3.3Vin, +5Vin Total Monitoring Cycle Time 0.4 (Note 13) 9-bit Temp Resolution 12-bit Temp Resolution %/V 0.4 0.82 1.2 0.82 1.2 sec sec (max) sec (max) 90 90 k (min) ADC INPUT CHARACTERISTICS Input Resistance (All analog inputs except Vccp1 and Vccp2) 115 Vccp1 and Vccp2 DC Input Current 1 5 A www.national.com LM81 DC Electrical Characteristics (Continued) The following specifications apply for +2.8VDC V+ +3.8VDC, RS = 500, unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25C. (Note 8) Symbol Parameter Conditions Typical Limits LM81BIM Limits LM81CIM Units (Note 9) (Note 10) (Note 10) (Limits) 5 5 62.5 10 125 62.5 DAC CHARACTERISTICS Resolution DAC Error 8 + V = 3.3V DAC Error Temperature Sensitivity 100 DAC Error Power Supply Sensitivity RL Output Load Resistance CL Output Load Capacitance Bits 0.5 VO = 1.25V % (max) mV (max) % (max) mV (max) 100 ppm/C (max) 0.725 % (max) 625 625 (min) 20 20 pF (max) 10 15 20 10 15 20 % (max) 255 255 (max) FAN RPM-TO-DIGITAL CONVERTER Fan RPM Error +25C TA +75C -10C TA +100C -40C TA +125C Full-scale Count FAN1 and FAN2 Nominal Input RPM (See Section 6.0) Internal Clock Frequency www.national.com % (max) % (max) Divisor = 1, Fan Count = 153 (Note 14) 8800 RPM Divisor = 2, Fan Count = 153 (Note 14) 4400 RPM Divisor = 3, Fan Count = 153 (Note 14) 2200 RPM Divisor = 4, Fan Count = 153 (Note 14) 1100 RPM +25C TA +75C 22.5 -10C TA +100C 22.5 -40C TA +125C 22.5 6 20.2 20.2 kHz (min) 24.8 24.8 kHz (max) 19.1 19.1 kHz (min) 25.9 25.9 kHz (max) 18 27 18 27 kHz (min) kHz (max) LM81 DC Electrical Characteristics (Continued) The following specifications apply for +2.8VDC V+ +3.8VDC, RS = 500, unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25C. (Note 8) Symbol Parameter Conditions Typical Limits LM81BIM Limits LM81CIM Units (Note 9) (Note 10) (Note 10) (Limits) DIGITAL OUTPUTS (NTEST_OUT) VOUT(1) Logical "1" Output Voltage IOUT = 3.0 mA at V+ = +2.8V 2.4 2.4 V (min) VOUT(0) Logical "0" Output Voltage IOUT = 3.0 mA at V+ = +3.8V 0.4 0.4 V (max) OPEN- DRAIN DIGITAL OUTPUTS (SMBData, RESET, CI, INT, T_CRIT_A) VOUT(0) Logical "0" Output Voltage IOUT = -3.0 mA IOH High Level Output Current VOUT = V+ RESET and Chassis Intrusion 0.4 0.4 V (min) 0.1 100 100 A (max) 45 20 20 ms (min) Pulse Width DIGITAL INPUTS: VID0-VID4, NTEST_IN, A0/NTEST_OUT, A1, Chassis Intrusion (CI) VIN(1) Logical "1" Input Voltage 2.0 2.0 V (min) VIN(0) Logical "0" Input Voltage 0.8 0.8 V (max) SMBus DIGITAL INPUTS (SMBCLK, SMBData) VIN(1) Logical "1" Input Voltage 2.1 1.4 V (min) VIN(0) Logical "0" Input Voltage 0.8 0.6 V (max) Tach Pulse Logic Inputs (FAN1, FAN2) VIN(1) VIN(0) Logical "1" Input Voltage 0.7 x V+ 0.7 x V+ V (min) Logical "0" Input Voltage + 0.3 x V+ V (max) 0.3 x V ALL DIGITAL INPUTS IIN(1) Logical "1" Input Current VIN = V+ -0.005 -1 -1 A (min) IIN(0) Logical "0" Input Current VIN = 0 VDC 0.005 1 1 A (max) CIN Digital Input Capacitance 20 7 pF www.national.com LM81 AC Electrical Characteristics The following specifications apply for +2.8VDC V+ +3.8VDC on SMBCLK and SMBData, unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25C. (Note 15) Symbol Parameter Conditions Typical Limits Units (Note 9) (Note 10) (Limits) SERIAL BUS TIMING CHARACTERISTICS t1 2.5 s (min) trise SMBCLK and SMBData Rise Time 1 s (max) tfall SMBCLK and SMBData Fall Time 300 ns (max) t2 Data In Setup Time to SMBCLK High 100 ns (min) t3 Data Out Stable After SMBCLK Low 0 ns (min) t4 SMBData Low Setup Time to SMBCLK Low (start) 100 ns (min) t5 SMBData High Hold Time After SMBCLK High (stop) 100 ns (min) 25 35 ms ms (min) ms (max) 400 pF (max) tTIMEOUT CL SMBCLK (Clock) Period SMBData or SMBCLK low time required to reset the Serial Bus Interface to the Idle State 31 Capacitive Load on SMBCLK and SMBData DS100072-4 FIGURE 1. Serial Bus Timing Diagram www.national.com 8 LM81 AC Electrical Characteristics (Continued) Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions. Note 2: All voltages are measured with respect to GND, unless otherwise specified. Note 3: The Absolute maximum input range for : +2.5Vin - -0.3V to (1.4 x V+ + 0.42V or 6V, whichever is smaller +3.3Vin - -0.3V to (1.8 x V+ + 0.55V or 6V, whichever is smaller. Note 4: When the input voltage (VIN) at any pin exceeds the power supplies (VIN < GND or VIN > V+), the current at that pin should be limited to 5 mA. The 20 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four. Note 5: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax, JA and the ambient temperature, TA. The maximum allowable power dissipation at any temperature is PD = (TJ max-TA)/JA. Note 6: The human body model is a 100 pF capacitor discharged through a 1.5 k resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. Note 7: See the section titled "Surface Mount" found in any post 1986 National Semiconductor Linear Data Book for other methods of soldering surface mount devices. Note 8: Parasitics and or ESD protection circuitry are shown in the figure below for the LM81's pins. The nominal breakdown voltage of the zener D3 is 6.5V. Care should be taken not to forward bias the parasitic diode, D1, present on pins: A0/NTEST_OUT, A1 and DACOut/NTEST_IN. Doing so by more than 50 mV may corrupt a temperature or voltage measurement. D2 D3 INT Pin Name D1 x x CI x D4 R1 R2 0 +12Vin Pin Name D1 D2 x x x 0 x 0 Vccp1, Vccp2 FAN1-FAN2 +5Vin x x SMBCLK x 0 +3.3Vin, +2.5Vin x x x x 0 T_CRIT_A SMBData RESET x x 0 A0/NTEST_OUT x x x 0 A1 x x x 0 x D3 DACOut/NTEST_IN x R1 R2 x R1+R2 120k x R1+R2 120k x 0 x x VID4-VID0 D4 R1+R2 120k x 0 x x 0 x x 0 DS100072-5 An x indicates that the diode exists. FIGURE 2. ESD Protection Input Structure Note 9: Typicals are at TJ = TA = 25C and represent most likely parametric norm. Note 10: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level). Note 11: TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC. Note 12: Guaranteed at 3/4 scale 15%. Note 13: Total Monitoring Cycle Time includes temperature conversion, 6 analog input voltage conversions and 2 tachometer readings. Each 9-bit temperature and 8-bit input voltage conversion takes 50 ms typical and 56 ms maximum. Twelve bit temperature conversion takes 400 ms. Fan tachometer readings take 20 ms typical, at 4400 rpm, and 200 ms maximum. Note 14: The total fan count is based on 2 pulses per revolution of the fan tachometer output. Note 15: Timing specifications are tested at the specified logic levels, VIL for a falling edge and VIH for a rising edge. 9 www.national.com LM81 Test Circuit DS100072-6 FIGURE 3. Digital Output Load Test Circuitry Functional Description * CI Clear Register: Allows transmitting a 20 ms low pulse on the chassis intrusion pin (CI). 1.0 GENERAL DESCRIPTION The LM81 provides 6 analog inputs, a temperature sensor, a Delta-Sigma ADC (Analog-to-Digital Converter), a DAC output, 2 fan speed counters, WATCHDOG registers, and a variety of inputs and outputs on a single chip. A two wire Serial Bus interface is included. The LM81 performs power supply, temperature, fan control and fan monitoring for personal computers. The analog inputs are useful for monitoring several power supplies present in a typical computer. The LM81 includes internal resistor dividers that scale and/or offset external Vccp, +2.5V, +3.3V, +5.0V and +12V power supply voltages to a 3/4 scale nominal ADC output. The LM81 ADC then continuously converts the scaled inputs to 8-bit digital words. Measurement of negative voltages (such as -5V and -12V power supplies) can be accommodated with an external resistor divider applied to the Vccp2 input. Temperature is converted to a 9-bit or 12-bit two's-complement digital word with a 0.5C LSB or 0.0625C LSB, respectively. Fan inputs measure the period of tachometer pulses from the fans, providing a higher count for lower fan speeds. The fan inputs are Schmitt-Trigger digital inputs with an acceptable range of 0V to V+ and a transition level of approximately V+/2. Full scale fan counts are 255 (8-bit counter) and this represents a stopped or very slow fan. Nominal speeds, based on a count of 153, are programmable from 1100 to 8800 RPM on FAN1 and FAN2. Schmitt-Trigger input circuitry is included to accommodate slow rise and fall times. A 0V to 1.25V DAC output voltage range can be used for control of fan speed. The LM81 has several internal registers, as shown in Figure 4, Table 1 and Section 13.0. These include: * VID/Fan Divisor Register: This register contains the state of the VID0-VID3 input lines and the divisor bits for FAN1 and FAN2 inputs. * Serial Bus Address Register: Contains the Serial Bus address. At power on it assumes the default value of 01011XX binary, and can be altered by the state of A0 and A1. * * VID4 Register: Contains the state of the VID4 input. * Extended Mode Registers: Enable and control the Extended Mode which includes the LSBs of the 12-bit temperature reading, T_CRIT, and THYST * Configuration Register: figuration. * Interrupt Status Registers: Two registers to provide status of each WATCHDOG limit or Interrupt event. * Interrupt Mask Registers: Allows masking of individual Interrupt sources, as well as separate masking for each of the two hardware Interrupt outputs. www.national.com * Temperature Configuration Register: Selects the interrupt mode and contains the 0.5C LSB of the temperature reading. Value RAM: The DAC digital input, monitoring results (temperature, voltages, fan counts), WATCHDOG limits, and Company/Stepping IDs are all contained in the Value RAM. The Value RAM consists of a total of 34 bytes, addresses 15h - 3Fh, containing: -- byte 1 at address 15h a manufacturers test register -- locations 16h - 18h are unassigned and do not have associated registers -- byte 2 at address 19h contains the DAC Data Register -- locations 1Ah - 1Fh are unassigned and do not have associated registers -- the next 10 bytes at addresses 20h -29h contain all of the results, with address 26h reserved -- the next 18 bytes at addresses 2Bh-3Ch are the WATCHDOG limits -- the last 2 bytes at addresses 3Eh and 3Fh contain the Company ID and Stepping ID numbers, respectively When the LM81 is started, it cycles through each measurement in sequence, and it continuously loops through the sequence approximately once every 400 ms. Each measured value is compared to values stored in WATCHDOG, or Limit registers. When the measured value violates the programmed limit the LM81 will set a corresponding Interrupt in the Interrupt Status Registers. The hardware Interrupt line INT is fully programmable with separate masking of each Provides control and con- 10 purpose allows for the fastest possible response time to a thermal runaway event. This output can be enabled by setting bit 4 of Extended Mode Register 1. (Continued) Interrupt source. In addition, the Configuration Register has a control bit to enable or disable the hardware Interrupt. Another hardware Interrupt line available T_CRIT_A (Critical Temperature Alarm Output) is used to signal a catastrophic overtemperature event. Having a dedicated interrupt for this The Chassis Intrusion input is designed to accept an active high signal from an external circuit that latches when the case is removed from the computer. 2.0 INTERFACE DS100072-7 FIGURE 4. LM81 Register Structure 11 www.national.com LM81 Functional Description LM81 Functional Description (Continued) 2.1 Internal Registers of the LM81 TABLE 1. The internal registers and their corresponding internal LM81 addresses are as follows: Register LM81 Internal Hex Address Power on Value Configuration Register 40h 0000 1000 Interrupt Status Register 1 41h 0000 0000 Interrupt Status Register 2 42h 0000 0000 Interrupt Mask Register 1 43h 0000 0000 Interrupt Mask Register 2 44h 0000 0000 CI Clear Register 46h 0000 0000 VID/Fan Divisor Register 47h 0101 XXXX The upper four bits set the divisor for Fan Counters 1 and 2. The lower four bits reflect the state of the VID0-VID3 inputs. Serial Bus Address Register 48h 0010 11XX The lower 2 bits reflect the state of A1 and A0, the Serial Bus address input pins. VID4 Register 49h 1000 000X The lower bit reflects the state of VID4 input. Temperature Configuration Register 4Bh 0000 0001 Extended Mode Register 1 4Ch 0100 0100 Extended Mode Register 2 4Dh 0000 0000 Value RAM DAC Data Register 19h 1111 1111 Value RAM www.national.com 20h-3Fh Notes Contains: monitoring results (temperature, voltages, fan counts), WATCHDOG limits, and Company/Stepping IDs 12 LM81 Functional Description (Continued) 2.2 Serial Bus Interface DS100072-8 (a) Serial Bus Write to the Internal Address Register followed by the Data Byte DS100072-9 (b) Serial Bus Write to the Internal Address Register Only DS100072-10 (c) Serial Bus Read from a Register with the Internal Address Register Preset to Desired Location FIGURE 5. Serial Bus Timing Bus Interface Address byte, followed by the Internal Address Register byte. Then restart the Serial Communication with a Read consisting of the Serial Bus Interface Address byte, followed by the data byte read from the LM81. The default Serial Bus address of the LM81 is set to 010 11(A1)(A0). All bits, except for A0 and A1, can be changed by writing to the Serial Bus address register. A0 and A1 will always reflect the state of the A0 and A1 input pins. All of these communications are depicted in the Serial Bus Interface Timing Diagrams as shown in Figure 5. Serial Bus Timeout can be initiated by holding the SMBCLK and/or SMBData lines low for greater than tTIMEOUT (35 ms max). Serial Bus Timeout resets the serial bus interface circuitry to the idle state and readies the LM81 for a new serial bus communication. The Serial Bus control lines consist of the SMBData (serial data), SMBCLK (serial clock) and A0-A1 (address) pins. The LM81 can operate only as a slave. The SMBCLK line only controls the serial interface, all other clock functions within LM81 such as the ADC and fan counters are done with a separate asynchronous internal clock. When using the Serial Bus Interface a write will always consist of the LM81 Serial Bus Interface Address byte, followed by the Internal Address Register byte, then the data byte. There are two cases for a read: 1. If the Internal Address Register is known to already be at the desired Address, simply read the LM81 with the Serial Bus Interface Address byte, followed by the data byte read from the LM81. 2. If the Internal Address Register value is unknown, or if it is not the desired value, write to the LM81 with the Serial 13 www.national.com LM81 Functional Description Bit 0 of the Configuration Register controls the monitoring loop of the LM81. Setting Bit 0 low stops the LM81 monitoring loop and puts the LM81 in shutdown mode, reducing power consumption. Serial Bus communication can take place with any register in the LM81 although activity on the SMBData and SMBCLK lines will increase shutdown current, up to as much as maximum rated supply current, while the activity takes place. Taking Bit 0 high starts the monitoring loop, described in more detail subsequently. Bit 1 of the Configuration Register enables the INT Interrupt hardwire output when this bit is taken high. Bit 3 of the Configuration Register clears the INT output when set high, without affecting the contents of the Interrupt Status Registers. The LM81 will stop monitoring. It will resume upon clearing of this bit. Bit 4 of the Configuration Register provides an active low 20 ms pulse at the RESET output when set high. (Continued) 3.0 USING THE LM81 3.1 Power On When power is first applied, the LM81 performs a "power on reset" on several of its registers. The power on condition of the LM81's registers in shown in Table 1 Registers whose power on values are not shown have power on conditions that are indeterminate (this includes the value RAM ,exclusive of the DAC data, and WATCHDOG limits). When power is first applied the ADC is inactive. In most applications, usually the first action after power on is usually to write WATCHDOG limits into the Value RAM. Register values can be returned to their default values after power is applied to the LM81 by taking RESET low for at least 50 ns. 3.2 Resets Configuration Register INITIALIZATION accomplishes the same function as power on reset on most registers. The Value RAM conversion results, and Value RAM WATCHDOG limits are not Reset and will be indeterminate immediately after power on. If the Value RAM contains valid conversion results and/or Value RAM WATCHDOG limits have been previously set, they will not be affected by a Configuration Register INITIALIZATION. Power on reset, or Configuration Register INITIALIZATION, clear or initialize the following registers (the initialized values are shown on Table 1: * * * * * * * The CI_Clear provides an active low 20 ms pulse at the CI output pin when set high. This is intended for resetting the Chassis Intrusion circuitry. The INITIALIZATION bit resets the internal registers of the LM81 as described in Section 3.2. 3.4 Starting Conversions The monitoring function (Analog inputs, temperature, and fan speeds) in the LM81 is started by writing to the Configuration Register and setting INT_Clear (Bit 3), low, and Start (bit 0), high. The LM81 then performs a "round-robin" monitoring of all analog inputs, temperature, and fan speed inputs approximately once every 400 ms. The sequence of items being monitored corresponds to locations in the Value RAM and is: 1. Temperature 2. Vccp2 3. +12Vin 4. +5Vin 5. +3.3Vin 6. Vccp1 7. +2.5Vin 8. Fan 1 9. Fan 2 DACOut immediately changes after the DAC Data Register in the Value RAM has been updated. For a zero to full scale transition DACOut will typically settle within 100 sec of the stop by master in the write to the DAC Data Register Serial Bus transaction. The DAC Data Register is not reset by the INITIALIZATION bit found in the Configuration Register. Configuration Register Interrupt Status Register 1 Interrupt Status Register 2 INT Mask Register 1 INT Mask Register 2 VID/Fan Divisor Register Serial Bus Address Register (Power on reset only, not reset by Configuration Register INITIALIZATION) * VID4 Register * Temperature Configuration Register * Extended Mode Register 1 * Extended Mode Register 2 Configuration Register INITIALIZATION is accomplished by setting Bit 7 of the Configuration Register high. This bit automatically clears after being set. 3.3 Using the Configuration Register The Configuration Register controls the LM81 operation. At power on, the ADC is stopped and INT_Clear is asserted, clearing the INT hardwire output. The Configuration Register starts and stops the LM81, enables and disables interrupt output, and provides the Reset function described in Section 3.2. www.national.com 14 shown in the table below for the circuit of Figure 6 will provide approximately 1.25V at the Vccp analog inputs of the LM81 for a nominal reading of 89. (Continued) 3.5 Reading Conversion Results The conversion results are available in the Value RAM. Conversions can be read at any time and will provide the result of the last conversion. Because the ADC stops, and starts a new conversion whenever it is read, reads of any single value should not be done more often than once every 56 ms. When reading all values, allow at least 0.82 seconds between reading groups of values. Reading more frequently than once every 0.82 seconds can also prevent complete updates of Interrupt Status Registers and Interrupt Output's. A typical sequence of events upon power on of the LM81 would consist of: 1. Set WATCHDOG Limits 2. Set Interrupt Masks 3. Start the LM81 monitoring process 3.6 Digital Communication Noise Considerations The SMBData and SMBCLK logic input levels were changed in the SMBus 1.1 specification. SMBus 1.0 levels were set to 1.4V for a logic high and 0.6V for a logic low. In SMBus 1.1 they were changed to 2.1V for a logic high and 0.8V for a logic low. Devices that meet the SMBus 1.0 specification have issues in that the logic levels did not allow for enough noise immunity for some pcb layouts. This has changed with the SMBus 1.1 specification because the higher logic levels allow for more hysteresis in the schmitt trigger inputs stages and thus more noise immunity. It may be required in some cases to add a series 5.1k resistor connected at the SMBCLK pin of the LM81C to improve its noise immunity. In addition to meeting the SMBus 1.1 logic levels, the LM81B has a built-in glitch filter that rejects 100MHz or greater to make it impervious to noise. LSB size Vin for 192 Vin for 255 2.5 Vin 13 mV 2.5V 3.320V 3.3 Vin 17.2 mV 3.3V 4.383V 5 Vin 26 mV 5V 6.641V 12 Vin 62.5 mV 12V 15.93V Vccp1, Vccp2 14.1 mV 2.7V 3.586V R2 R1 V+ Voltage at Analog Inputs (ADC code 89) -12V 40 k 141 k +5V +1.25V -5V 40 k 66.7 k +5V +1.25V DS100072-11 FIGURE 6. Input Examples. Resistor values shown in table provide approximately 1.25V at the Vccp inputs. The resistors were selected by setting R2 = 40 k and then calculating R2 using the following equation: 4.0 ANALOG INPUTS All analog input voltages are digitized to 8-bits of resolution. All analog inputs, except for Vccp1 and Vccp2, include internal resistor attenuators. The theoretical LSB size, theoretical voltage input required for an ADC reading of 192 (3/4 scale) and 255 (full scale) for each analog input is detailed in the table below: Input Voltage Measurements (VS) R1 = [(1.25V - VS) / (V+ - 1.25V)] x 40 k The maximum R1 can be is restricted by the DC input current of a Vccp input. Inputs with internal resistor dividers (+2.5 Vin, +3.3 Vin or +5 Vin, +12 Vin) can have voltage applied that exceeds the power supply up to: 3.6V for +2.5 Vin, 4.6V for +3.3 Vin, 6.8V for +5 Vin, and 15V for +12 Vin. The Vccp inputs have a parasitic diode to the positive supply, so care should be taken not to forward bias this diode. All analog inputs have internal diodes that clamp the input voltage when going below ground thus limiting the negative analog input voltage range to -50 mV. Violating the analog input voltage range of any analog input has no detrimental effect on the other analog inputs. External resistors should be included to limit input currents to the values given in the ABSOLUTE MAXIMUM RATINGS for Input Current At Any Pin whenever exceeding the analog input voltage range, even on an un-powered LM81. Inputs with external attenuator networks will usually meet these requirements. If it is possible for inputs without attenuators (such as Vccp1 and Vccp2) to be turned on while LM81 is powered off, additional resistors of about 10 k should be added in series with the inputs to limit the input current. Thus monitoring power supplies within a system can be easily accomplished by tying the Vccp, +2.5 Vin, +3.3 Vin, +5 Vin and +12 Vin analog inputs to the corresponding system supply. A digital reading can be converted to a voltage by simply multiplying the decimal value of the reading by the LSB size. For inputs with attenuators the input impedance is greater than 90 k. Vccp inputs do not have resistor attenuators and are are directly tied to the ADC, therefore having a much larger input impedance. A negative power supply voltage can be applied to a Vccp input through a resistor divider referenced to a known positive DC voltage as show in Figure 6. The resistor values 4.1 Analog Input Interrupts A WATCHDOG window comparison on the analog inputs can activate the INT interrupt output. A converted input voltage that is above its respective HIGH limit or less than or 15 www.national.com LM81 Functional Description LM81 Functional Description If fans can be powered while the power to the LM81 is off, the LM81 inputs will provide diode clamping. Limit input current to the Input Current at Any Pin specification shown in the ABSOLUTE MAXIMUM RATINGS section. In most cases, open collector outputs with pull-up resistors inherently limit this current. If this maximum current could be exceeded, either a larger pull up resistor should be used or resistors connected in series with the fan inputs. The Fan Inputs gate an internal 22.5 kHz oscillator for one period of the Fan signal into an 8-bit counter (maximum count = 255). The default divisor, located in the VID/Fan Divisor Register, is set to 2 (choices are 1, 2, 4, and 8) providing a nominal count of 153 for a 4400 rpm fan with two pulses per revolution. Typical practice is to consider 70% of normal RPM a fan failure, at which point the count will be 219. Determine the fan count according to: (Continued) equal to its LOW limit will cause a flag to be set in its Interrupt Status Register. This flag will activate the INT output when its mask bit is set low. Mask bits are found in the Interrupt Mask Registers. 5.0 LAYOUT AND GROUNDING A separate, low-impedance ground plane for analog ground, which provides a ground point for both GND pins, voltage dividers and other analog components, will provide best performance but is not mandatory. Analog components such as voltage dividers should be located physically as close as possible to the LM81. The power supply bypass, the parallel combination of 10 F (electrolytic or tantalum) and 0.1 F (ceramic) bypass capacitors connected between pin 12 and ground, should also be located as close as possible to the LM81. 6.0 FAN INPUTS The FAN1 and FAN2 inputs accept signals from fans equipped with tachometer outputs. These are logic-level inputs with an approximate threshold of V+/2. Signal conditioning in the LM81 accommodates the slow rise and fall times typical of fan tachometer outputs. The maximum input signal range is 0 to V+. In the event these inputs are supplied from fan outputs which exceed 0 to V+, either resistive division or diode clamping must be included to keep inputs within an acceptable range, as shown in Figure 7. R2 is selected so that it does not develop excessive voltage due to input leakage. R1 is selected based on R2 to provide a minimum input of 2V and a maximum of V+. R1 should be as low as possible to provide the maximum possible input up to V+ for best noise immunity. Alternatively, use a shunt reference or zener diode to clamp the input level. www.national.com Note that Fan 1 and Fan 2 Divisors are programmable via the VID/Fan Divisor Register. Fan tachometer outputs that provide one pulse per revolution should use a divisor setting twice that of outputs that provide two pulses per revolution. For example, a 4400 RPM fan that provides one pulse per revolution should have the divisor set to 4 such that the nominal counter output is 153. 16 LM81 Functional Description (Continued) DS100072-12 (a) Fan with Tach Pull-Up to +5V DS100072-13 (b) Fan with Tach Pull-Up to +12V, or Totem-Pole Output and Resistor Attenuator DS100072-14 (c) Fan with Tach Pull-Up to +12V and Diode Clamp DS100072-15 (d) Fan with Strong Tach Pull-Up or Totem Pole Output and Diode Clamp FIGURE 7. Alternatives for Fan Inputs Counts are based on 2 pulses per revolution tachometer outputs. RPM Time per Revolution Counts for "Divide by 2" Comments 4400 13.64 ms 153 counts Typical RPM 3080 19.48 ms 219 counts 70% RPM 2640 22.73 ms 255 counts 60% RPM (Default) in Decimal (maximum counts) Mode Select Nominal RPM Counts for the Time per Revolution 70% RPM Given Speed in Decimal Time per Revolution for 70% RPM Divide by 1 8800 6.82 ms 153 6160 9.74 ms Divide by 2 4400 13.64 ms 153 3080 19.48 ms Divide by 4 2200 27.27 ms 153 1540 38.96 ms Divide by 8 1100 54.54 ms 153 770 77.92 ms 17 www.national.com LM81 Functional Description The output of the amplifier can be configured to provide a high or low side pass transistor. A high side pass transistor simplifies the coupling of tachometer outputs to the tachometer inputs of the LM81 since the fan remains grounded. Low side drive will require AC coupling along with clamping at the LM81 input to prevent negative excursions. (Continued) 7.0 DAC OUTPUT The LM81 provides an 8-bit DAC (Digital-to-Analog Converter) with an output range of 0 to 1.25 volts (4.88 mV LSB). This DAC can be used in any way, but in most applications of the LM81 the DAC will be used for fan control. Typically the DAC output would be amplified to provide the up to 12 volt drive required by the fan. At power-on the DAC provides full output, insuring that full fan speed is the default condition. Care should be taken such that the analog circuitry tied to this pin does not drive this pin above 2.5V. Doing so will place the LM81 in NAND tree test mode which will make all pins inputs, thus disabling any response from the LM81. Fans do not start reliably at reduced voltages, so operation at a reduced voltage should be preceded by a brief (typically 1 second) excursion to full operating voltage, then reduce the voltage. Most fans do not operate at all below 5 to 7 volts. At those lower voltages the fan will simply consume current, dissipate power, and not operate and such conditions should be avoided. A typical circuit for fan drive is shown in Figure 8. R4 is used when a negative power supply is available to eliminate offset in the amplifier and provide a 0 to 11.5 volt output (actually 12 volts less saturation). Omitting R4 will create a "dead zone" between approximately 0 to 6 volts output (a potentially unusable region anyway). In many applications protecting the pass transistor Q2 from faults such as a shorted fan can be accomplished by taking advantage of the current limit already existing on the 12 volt supply. Q2 will have to be heat-sunk accordingly. Otherwise, use the suggested current limit circuit as shown. DS100072-28 FIGURE 8. Amplifier circuit for connection between DAC output and fan. www.national.com 18 8.1 Temperature Data Format (Continued) Temperature data can be read from the Temperature, THIGH setpoint, THIHYST setpoint, TLOW setpoint, TC setpoint and THYST Offset registers; and written to the THIGH setpoint, THIHYST, TLOW setpoint, T_CRIT setpoint and THYST offset registers. THIGH setpoint, TLOW setpoint, T_CRIT setpoint temperature data is represented by an 8-bit, two's complement word with an LSB (Least Significant Bit) equal to 1C: 8.0 TEMPERATURE MEASUREMENT SYSTEM The LM81 temperature sensor and ADC produce 9-bit or 12-bit two's-complement temperature data. A digital comparator compares the temperature data to the user-programmable High, Low, Critical setpoints and Hysteresis values. Temperature Digital Output Binary Hex +125C 0111 1101 7Dh +25C 0001 1001 19h +1.0C 0000 0001 01h +0C 0000 0000 00h -1.0C 1111 1111 FFh -25C 1110 0111 E7h -40C 1101 1000 D8h By default Temperature Register data is represented by a 9-bit two's complement digital word with the LSB having a resolution of 0.5C: Temperature Digital Output Binary Hex +125C 0 1111 1010 0 FAh +25C 0 0011 0010 0 32h +1.5C 0 0000 0011 0 03h DS100072-24 (Non-Linear Scale for Clarity) FIGURE 9. 9-bit Temperature-to-Digital Transfer Function +0C 0 0000 0000 0 00h -0.5C 1 1111 1111 1 FFh -25C 1 1100 1110 1 CEh -40C 1 1011 0000 1 B0h In the extended mode temperature Register data can also be represented by a 12-bit two's complement digital word with an LSB of 0.0625C: Temperature Digital Output Binary Hex +125C 0111 1100 0000 7 D0h +25C 0001 1001 0000 1 90h +1.0C 0000 0001 0000 0 10h +0.0625C 0000 0000 0001 0 01h 0C 0000 0000 0000 0 00h -0.0625C 1111 1111 1111 F FFh -1.0C 1111 1111 0000 F F0h -25C 1110 0111 0000 E 70h -40C 1101 1000 0000 D 80h DS100072-27 THYST Offset temperature data is represented by a 3-bit word with an LSB (Least Significant Bit) equal to 1C. (Non-Linear Scale for Clarity) FIGURE 10. 12-bit Temperature-to-Digital Transfer Function 19 www.national.com LM81 Functional Description LM81 Functional Description Normal One-Time Interrupt Mode is shown in Figure 12 and operates in the following way: T_CRIT_A is disabled. Exceeding THIGH causes an interrupt that will remain active indefinitely until reset by reading Interrupt Status Register 1. Another interrupt will not occur until the temperature drops to less than or equal to THIHYST and then exceeds THIGH during a subsequent conversion. After power up this mode is selected as default. (Continued) 8.2 Temperature Interrupts INT and T_CRIT_A outputs are provided for temperature interrupt. Temperature interrupts have a normal and an extended option of operation. Each option has three different modes of operation: Repetitive Interrupt, One-Time Interrupt and Comparator. Normal Repetitive Interrupt Mode is shown in Figure 11 and operates in the following way: T_CRIT_A is disabled. Exceeding THIGH causes an interrupt that will remain active indefinitely until reset by reading Interrupt Status Register 1. Once reset if the temperature remains above the THIHYST setpoint the interrupt will again be activated at the completion of another conversion cycle. If temperature is less than or equal to THIHYST the interrupt will not be activated. DS100072-17 *Note: Interrupt resets occur only when interrupt Status Register 1 is read. FIGURE 12. One-Time Interrupt Response Diagram Normal Comparator Mode is shown in Figure 13 and operates in the following way: T_CRIT_A is disabled. Exceeding THIGH causes an interrupt that will remain activated until the temperature is less than or equal to THIGH. TLOW is disabled. DS100072-16 *Note: Interrupt resets occur only when interrupt Status Register 1 is read. FIGURE 11. Normal Repetitive Interrupt Response Diagram DS100072-18 *Note: Interrupt resets occur only when interrupt Status Register 1 is read. FIGURE 13. Normal Comparator Mode www.national.com 20 Extended Comparator Mode is shown in Figure 16 and operates in the following way: Interrupt is activated when the data from a temperature conversion is less than or equal to TLOW. Interrupt is reset when the data from a temperature conversion exceeds (TLOW + THIGH). Exceeding THIGH will activate interrupt. This interrupt will be reset when data from a temperature conversion is less than or equal to (THIGH - THYST). T_CRIT_A interrupt is activated when the temperature exceeds T_CRIT. T_CRIT_A remains active until the data from a temperature conversion is less than or equal to (T_CRIT - THYST) resets it. (Continued) Extended Repetitive Interrupt Mode is shown in Figure 14 and operates in the following way: Once activated, all interrupts remain activated until reset by a read of the Interrupt Status Register 1. Once activated all T_CRIT_A interrupts remain activated until reset by a read of the Extended Mode Register 1. Temperature conversion data less than or equal to TLOW will activate interrupt. Interrupt will continue to be activated until the temperature data exceeds (TLOW + THYST). Exceeding THIGH activates interrupt. Interrupt will continue to be activated at the end of a conversion until the temperature data is less than or equal to (THIGH - THYST). T_CRIT_A interrupts are activated when the temperature exceeds T_CRIT. T_CRIT_A interrupts will no longer be activated if the temperature data at the end of a conversion is less than or equal to( T_CRIT - THYST). DS100072-19 *Note: Interrupt resets occur only when interrupt Status Register 1 is read. FIGURE 16. Extended Comparator Mode DS100072-20 *Note: Interrupt resets occur only when interrupt Status Register 1 is read. FIGURE 14. Extended Repetitive Interrupt Mode Extended One-Time Interrupt Mode is shown in Figure 15 and operates in the following way: Once activated all interrupts remain activated until reset by a read of the Interrupt Status Register 1. Once activated all T_CRIT_A interrupts remain activated until reset by a read of the Extended Mode Register 1. An interrupt will be activated when the data of a temperature conversion is less than or equal to TLOW. Interrupt cannot again be activated until the data from a temperature conversion is greater than (TLOW + THYST). An interrupt will be activated when the data of a temperature conversion is greater than THIGH. Interrupt cannot again be activated until the data of a temperature conversion is less than or equal to (THIGH - THYST). T_CRIT_A interrupt is activated when the data from a temperature conversion is greater than T_CRIT. Activation of an T_CRIT_A interrupt cannot occur until the data from a temperature conversion is less than or equal to ( T_CRIT - THYST). DS100072-21 *Note: Interrupt resets occur only when interrupt Status Register 1 is read. FIGURE 15. Extended One-Time Interrupt 21 www.national.com LM81 Functional Description LM81 Functional Description (Continued) 9.0 THE LM81 INTERRUPT STRUCTURE DS100072-22 FIGURE 17. Interrupt Structure Figure 17 depicts the Interrupt Structure of the LM81. The LM81 can generate Interrupts as a result of each of its internal WATCHDOG registers on the analog, temperature, and fan inputs. External Interrupts can come from the following source. While the label suggests a specific type or source of Interrupt, this label is not a restriction of its usage, and it could come from any desired source: * Chassis Intrusion: any type of device intrusion violations. chanically, optically, www.national.com to the LM81 is expected to latch the event. The design of the LM81 allows this input to go high even with no power applied to the LM81, and no clamping or other interference with the line will occur. This line can also be pulled low for at least 20 ms by the LM81 to reset a typical Chassis Intrusion circuit. Accomplish this reset by setting Bit 7 of CI Clear Register (45h) high. The bit in the Register is self-clearing. All interrupts are indicated in the two Interrupt Status Registers. The INT output has two mask registers, and individual This is an active high interrupt from that detects and captures chassis This could be accomplished meor electrically, and circuitry external 22 ration Register high outputs a least 20 ms low on this line, at the end of which Bit 4 in the Configuration Register automatically clears. Again, the label for this pin is only its suggested use. In applications where the RESET capability is not needed it can be used for any type of digital control that requires a 20 ms active low open-drain output. (Continued) masks for each Interrupt. As described in Section 3.3, the hardware Interrupt line can also be enabled/disabled in the Configuration Register. T_CRIT_A interrupt is dedicated to temperature and is indicated in Extended Mode Register 1. Extended Mode Register 1 controls T_CRIT_A. RESET operates as an input when not activated by the Configuration Register. Setting this line low will reset all of the registers in the LM81 to their power on default state. All Value RAM locations will not be affected except for the DAC Data Register. 9.1 Interrupt Clearing Reading a Status Register will output the contents of the Register, and reset the Register. A subsequent read done before the analog "round-robin" monitoring loop is complete will indicate a cleared Register. Allow at least 820 ms to allow all Registers to be updated between reads. In summary, the Interrupt Status Register clears upon being read, and requires at least 400 ms to be updated. When the Interrupt Status Register clears, the hardware interrupt line will also clear until the Registers are updated by the monitoring loop. The hardware Interrupt line (INT) is cleared with the INT_Clear bit, which is Bit 3 of the Configuration Register. When this bit is high, the LM81 monitoring loop will stop. It will resume when the bit is low. 11.0 NAND TREE TESTS A NAND tree is provided in the LM81 for Automated Test Equipment (ATE) board level connectivity testing. DACOut/ NTEST_IN, T_CRIT_A, V+ and GND pins are excluded from NAND tree testing. Taking DACOut/NTEST_IN high before the first write to the configuration register activates the NAND Tree test mode. After the first write to the configuration register the NAND Tree test mode cannot be reactivated. To perform a NAND tree test all pins included in the NAND tree should be driven to 1 forcing the A0/ NTEST_OUT high. Each individual pin starting with A1 and concluding with SMBData (excluding DACOut/NTEST_IN, T_CRIT_A, V+ and GND) can be taken low with the resulting toggle observed on the A0/NTEST_OUT pin. Allow for a typical propagation delay of 500 ns. 10.0 RESET I/O RESET is intended to provide a master reset to devices connected to this line. INT Mask Register 2, Bit 7, must be set high to enable this function. Setting Bit 4 in the Configu- DS100072-29 23 www.national.com LM81 Functional Description LM81 Functional Description (Continued) 12.0 FAN MANUFACTURERS Manufacturers of cooling fans with tachometer outputs are listed below: NMB Tech 9730 Independence Ave. Chatsworth, California 91311 818 341-3355 818 341-8207 Model Number Frame Size Airflow CFM 2408NL 2.36 in sq. X 0.79 in 9-16 (60 mm sq. X 20 mm) 2410ML 2.36 in sq. X 0.98 in 14-25 (60 mm sq. X 25 mm) 3108NL 3.15 in sq. X 0.79 in 25-42 (80 mm sq. X 20 mm) 3110KL 3.15 in sq. X 0.98 in 25-40 (80 mm sq. X 25 mm) Mechatronics Inc. P.O. Box 20 Mercer Island, WA 98040 800 453-4569 Various sizes available with tach output option. Sanyo Denki America, Inc. 468 Amapola Ave. Torrance, CA 90501 310 783-5400 Model Number Frame Size Airflow CFM 109P06XXY601 2.36 in sq. X 0.79 in 11-15 (60 mm sq. X 20 mm) 109R06XXY401 2.36 in sq. X 0.98 in 13-28 (60 mm sq. X 25 mm) 109P08XXY601 3.15 in sq. X 0.79 in 23-30 (80 mm sq. X 20 mm) 109R08XXY401 3.15 in sq. X 0.98 in 21-42 (80 mm sq. X 25 mm) www.national.com 24 LM81 Functional Description (Continued) 13.0 REGISTERS AND RAM 13.1 Address Register The main register is the ADDRESS Register. The bit designations are as follows: Bit 7-0 Name Read/ Write Address Pointer Bit 7 Description Write Bit 6 Address of RAM and Registers. See the tables below for detail. Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 A2 A1 A0 Address Pointer (Power On default 00h) A7 A6 A5 A4 A3 13.2 Address Pointer Index (A7-A0) Registers and RAM A6-A0 in Hex Power On Value of Registers: Notes < 7:0 > in Binary Configuration Register 40h 0000 1000 Interrupt Status Register 1 41h 0000 0000 Interrupt Status Register 2 42h 0000 0000 Interrupt Mask Register 1 43h 0000 0000 Interrupt Mask Register 2 44h 0000 0000 CI Clear Register 46h 0000 0000 VID/Fan Divisor Register 47h Serial Bus Address Register 48h < 7:4 > = 0101; < 3:0 > = VID3-VID0 < 7:2 > =0010 11; < 1:0 > =(A1)(A0) VID4 Register 49h < 7:1 > =1000 000; < 0 > =VID4 Temperature Configuration Register 4Bh 0000 0001 Extended Mode Register 1 4Ch 0100 0100 Extended Mode Register 2 4Dh 0000 0000 Value RAM 19h-3Dh Company ID 3Eh 0000 0001 This default designates National Semiconductor. Stepping 3Fh 0000 0011 Revisions of this device will start with 1 and increment by one. Address 19h default=1111 1111 25 www.national.com LM81 Functional Description (Continued) 13.3 Configuration Register -- Address 40h Power on default - < 7:0 > = 00001000 binary Bit 0 Name Start Read/ Write Read/Write Description A one enables startup of monitoring operations, a zero puts the part in standby mode. Note: The outputs of Interrupt pins will not be cleared if the user writes a zero to this location after an interrupt has occurred unlike "INT_Clear" bit. At start up, limit checking functions and scanning begin. Note, all limits should be set in the Value RAM before setting this bit HIGH. 1 INT Enable Read/Write 2 Reserved Read/Write 3 INT_Clear Read/Write A one disables the INT output without affecting the contents of Interrupt Status Registers. The device will stop monitoring. It will resume upon clearing of this bit. 4 RESET Read/Write A one outputs at least a 20 ms active low reset signal at RESET. This bit is cleared once the pulse has gone inactive. 5 Reserved Read/Write 6 CI_Clear Read/Write A one outputs a minimum 20 ms active low pulse on the CI pin. The register bit self clears after the pulse has been output. This bit is mirrored in the CI Clear Register bit 7. 7 INITIALIZATION Read/Write A one restores power on default value to the Configuration Register, Interrupt Status Registers, Interrupt Mask Registers, CI Clear Register, VID/Fan Divisor Register, VID4, Temperature Configuration Register, and the Extended Mode Registers. This bit clears itself since the power on default is zero. www.national.com A one enables the INT Interrupt output. 26 LM81 Functional Description (Continued) 13.4 Interrupt Status Register 1 -- Address 41h Power on default - < 7:0 > = 0000 0000 binary Bit Name Read/Write Description 0 +2.5Vin Read Only A one indicates a High or Low limit has been exceeded. 1 Vccp1 Read Only A one indicates a High or Low limit has been exceeded. 2 +3.3Vin Read Only A one indicates a High or Low limit has been exceeded. 3 +5Vin Read Only A one indicates a High or Low limit has been exceeded. 4 Temperature Read Only A one indicates a HIGH or HIHYST temperature error, see SECTION 8.2. 5 Reserved Read Only 6 FAN1 Read Only A one indicates the fan count limit has been exceeded. 7 FAN2 Read Only A one indicates the fan count limit has been exceeded. 13.5 Interrupt Status Register 2 -- Address 42h Power on default - < 7:0 > = 0000 0000 binary Bit Name Read/Write Description 0 +12Vin Read Only A one indicates a High or Low limit has been exceeded. 1 Vccp2 Read Only A one indicates a High or Low limit has been exceeded. 2 Reserved Read Only 3 Reserved Read Only 4 CI Read Only 5 Reserved Read Only 6 Reserved Read Only 7 TLOW Read Only A one indicates CI (Chassis Intrusion) has gone high. A one indicates LOW temperature error in EXTENDED MODE ONLY, see SECTION 8.2. 13.6 Interrupt Mask Register 1 -- Address 43h Power on default - < 7:0 > = 0000 0000 binary Bit Name Read/ Write Description 0 +2.5Vin Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 1 Vccp1 Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 2 +3.3Vin Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 3 +5Vin Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 4 Temperature Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 5 Reserved Read/Write 6 FAN1 Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 7 FAN2 Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 27 www.national.com LM81 Functional Description (Continued) 13.7 Interrupt Mask Register 2 -- Address 44h Power on default - < 7:0 > = 0000 0000 binary Bit Name Read/ Write Description 0 +12Vin Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 1 Vccp2 Read/Write A one disables the corresponding interrupt status bit for INT interrupt. 2 Reserved Read/Write 3 Reserved Read/Write 4 Chassis Intrusion Read/Write 5 Reserved Read/Write 6 Reserved Read/Write 7 RESET Enable Read/Write A one disables the corresponding interrupt status bit for INT interrupt. < 7 > = 1 in INT Mask Register 2 enables the RESET in the Configuration Register. 13.8 Reserved Register -- Address 45h Power on default - < 7:0 > = 00h. Read/Write for backwards compatibility. 13.9 CI Clear Register -- Address 46h Power on default - < 7:0 > = 0000 0000 binary Bit Name Read/ Write 0-6 Reserved Read/Write 7 CI Clear Read/Write www.national.com Description A one outputs a minimum 20 ms active low pulse on the Chassis Intrusion pin. The register bit self clears after the pulse has been output. This bit is mirrored in Configuration Register bit 6. 28 LM81 Functional Description (Continued) 13.10 VID/Fan Divisor Register -- Address 47h Power on default - < 7:4 > is 0101, and < 3:0 > is mapped to VID < 3:0 > Bit Name 0-3 VID < 3:0 > Read/Write Read Only Description The VID < 3:0 > inputs from the Pentium/PRO power supplies that indicate the operating voltage (e.g. 1.5V to 2.9V). 4-5 FAN1 RPM Control Read/Write FAN1 Speed Control. < 5:4 > < 5:4 > < 5:4 > < 5:4 > 6-7 FAN2 RPM Control Read/Write = 00 - divide by 1; = 01 - divide by 2; = 10 - divide by 4; = 11 - divide by 8. FAN2 Speed Control. < 7:6 > < 7:6 > < 7:6 > < 7:6 > = 00 - divide by 1; = 01 - divide by 2; = 10 - divide by 4; = 11 - divide by 8. 13.11 Serial Bus Address Register -- Address 48h Power on default - Serial Bus address < 6:0 > = 010 11(A1)(A0) and < 7 > = 0 binary Bit Name Read/Write Description Serial Bus Address Read Only Serial Bus address < 1:0 > = A1 A0 2-6 Serial Bus Address Read/Write Serial Bus address < 6:2 > = 010 11 7 Reserved Read/Write 0-1 13.12 VID4 Register -- Address 49h Power on default - < 7:1 > = 100 000, < 0 > = VID4. Bit 0 1-7 Name Read/Write VID4 Read Only Reserved Read/Write Description VID4 input from Pentium/PRO power supply that indicate the operating voltage of the processor (e.g. 1.5V to 2.9V). 13.13 Temperature Configuration Register -- Address 4Bh Power on default - < 7:0 > = 0000 0001 binary Bit Name Read/Write 0-1 Temperature Interrupt Mode Select Bits Read/Write 2-6 Reserved Read/Write Temperature Resolution Read Only 7 Description The state of these bits select the interrupt mode for INT as described below. < 1:0 > = 00 or < 1:0 > = 11: Repetitive Interrupt Mode < 1:0 > = 01: One-Time Interrupt Mode < 1:0 > = 10: Comparator Mode For 8-bit plus sign temperature resolution: < 7 > = LSB ( 0.5C) 29 www.national.com LM81 Functional Description (Continued) 13.14 Extended Mode Register 1 -- Address 4Ch Power on default - < 7:0 > = 0100 0100 binary Bit Name Read/Write Description 0 Extended Mode Enable Read/Write A one enables the Extended Interrupt Modes, the T_CRIT_A output and all the functions listed in the Extended Mode Registers. Bit 7 of the Interrupt Status register will be activated to reflect the interrupt status of the LOW limit comparison result. 1 LOW Limit Mask Bit Read/Write A mask bit for the LOW limit Interrupt. A one disables the interrupt from propagating to the INT pin. T_CRIT_A Interrupt Mode Select Read/Write The state of these bits select the interrupt mode for T_CRIT_A as described below. < 3:2 > = 00 or < 3:2 > = 11: Repetitive Interrupt Mode < 3:2 > = 01: One-Time Interrupt Mode < 3:2 > = 10: Comparator Mode 4 T_CRIT_A Enable Read/Write A one enables the T_CRIT_A pin. 5 T_CRIT_A Polarity Read/Write A one sets the T_CRIT_A pin active HIGH. A zero sets the T_CRIT_A pin active LOW. 6 T_CRIT_A Mask Enable Read/Write A one prevents the T_CRIT_A interrupt from propagating to the INT output pin. 7 T_CRIT_A Status Bit Read A one indicates that a T_CRIT_A interrupt has occurred. 2-3 13.15 Extended Mode Register 2 -- Address 4Dh Power on default - < 7:0 > = 0000 0000 binary Bit Name Read/Write Description 0-2 Hysteresis Offset Value Read/Write THYST value. 3 12-bit Temperature Resolution Enable Read/Write A one sets the temperature resolution to 12 bits. 4-7 12-bit Temperature Data Read Only 12-bit temperature data least significant bits. Bit 7 mirrors bit 7 in the temperature configuration register (4Bh) and has a weight of 0.5C; bits 6-4 have a weight of 0.25, 0.125, and 0.0625C, respectively. www.national.com 30 LM81 Functional Description (Continued) 13.16 Value RAM -- Address 15h-3Fh Address A6-A0 Description 15h Manufacturers Test Register 19h DAC data register; power on default < 7:0 > =1111 1111 binary 20h +2.5Vin reading 21h Vccp1 reading 22h +3.3Vin reading 23h +5Vin reading 24h +12Vin reading 25h Vccp2 reading 26h Reserved reading 27h Temperature reading (8 MSBs) 28h FAN1 reading Note: This location stores the number of counts of the internal clock per revolution. 29h FAN2 reading 2Ah Reserved Note: This location stores the number of counts of the internal clock per revolution. 2Bh +2.5Vin High Limit 2Ch +2.5Vin Low Limit 2Dh Vccp1 High Limit 2Eh Vccp1 Low Limit 2Fh +3.3Vin High Limit 30h +3.3Vin Low Limit 31h +5Vin High Limit 32h +5Vin Low Limit 33h +12Vin High Limit 34h +12Vin Low Limit 35h Vccp2 High Limit 36h Vccp2 Low Limit 37h T_CRIT Limit (Extended Mode) 38h LOW Limit (Extended Mode) 39h HIGH Temperature Limit 3Ah HIHYST Temperature Limit 3Bh FAN1 Fan Count Limit Note: It is the number of counts of the internal clock for the Low Limit of the fan speed. 3Ch FAN2 Fan Count Limit Note: It is the number of counts of the internal clock for the Low Limit of the fan speed. 3Dh Reserved 3Eh Company Identification. The number in this register identifies National Semiconductor (0000 0001) 3Fh Stepping Register LM81 revision number (0000 0011) Note: Setting all ones to the high limits for voltages and fans (0111 1111 binary for temperature) means interrupts will never be generated except the case when voltages go below the low limits. For voltage input high limits, the device is doing a greater than comparison. For low limits, however, it is doing a less than or equal to comparison. 31 www.national.com LM81 Typical Application DS100072-23 FIGURE 19. In this PC application the LM81 monitors temperature, fan speed for 2 fans, and 6 power supply voltages. It also monitors an optical chassis intrusion detector. The LM81 provides a DAC output that can be used to control fan speed. www.national.com 32 inches (millimeters) unless otherwise noted 24-Lead TSSOP Order Number LM81BIMT-3, LM81BIMTX-3, LM81CIMT-3 or LM81CIMTX-3 NS Package Number MTC24B LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Email: support@nsc.com www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor Physical Dimensions