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| LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire Interface November 1999 LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire Interface General Description The LM83 is a digital temperature sensor with a 2 wire serial interface that senses the voltage and thus the temperature of three remote diodes using a Delta-Sigma analog-to-digital converter with a digital over-temperature detector. The LM83 accurately senses its own temperature as well as the temperature of three external devices, such as Pentium II (R) Processors or diode connected 2N3904s. The temperature of any ASIC can be detected using the LM83 as long as a dedicated diode (semiconductor junction) is available on the die. Using the SMBus interface a host can access the LM83's registers at any time. Activation of a T_CRIT_A output occurs when any temperature is greater than a programmable comparator limit, T_CRIT. Activation of an INT output occurs when any temperature is greater than its corresponding programmable comparator HIGH limit. The host can program as well as read back the state of the T_CRIT register and the four T_HIGH registers. Three state logic inputs allow two pins (ADD0, ADD1) to select up to 9 SMBus address locations for the LM83. The sensor powers up with default thresholds of 127C for T_CRIT and all T_HIGHs. The LM83 is pin for pin and register compatible with the LM84 as well as the Maxim MAX1617 and the Analog Devices ADM1021. n On-board local temperature sensing n SMBus and I2C compatible interface, supports SMBus 1.1 TIMEOUT n Two interrupt outputs: INT and T_CRIT_A n Register readback capability n 7 bit plus sign temperature data format, 1 C resolution n 2 address select pins allow connection of 9 LM83s on a single bus Key Specifications n Supply Voltage n Supply Current 0C to +85C 3.0V to 3.6V 0.8mA (max) n Local Temp Accuracy (includes quantization error) 3.0C (max) n Remote Diode Temp Accuracy (includes quantization error) +25C to +100C 0C to +125C 3C (max) 4C (max) Applications n n n n n System Thermal Management Computers Electronic Test Equipment Office Electronics HVAC Features n Accurately senses die temperature of 3 remote ICs, or diode junctions Simplified Block Diagram DS101058-1 SMBusTM is a trademark of the Intel Corporation. Pentium II (R) is a registered trademark of the Intel Corporation. I2C (R) is a registered trademark of the Philips Corporation. (c) 1999 National Semiconductor Corporation DS101058 www.national.com LM83 Connection Diagram QSOP-16 Ordering Information Order Number LM83CIMQA NS Package Number MQA16A (QSOP-16) MQA16A (QSOP-16) Transport Media 95 Units in Rail 2500 Units on Tape and Reel LM83CIMQAX DS101058-2 TOP VIEW Typical Application DS101058-3 Pin Description Label Pin # Function Diode Current Source D1+, D2+, D3+ 1, 3, 5 Typical Connection To Diode Anode. Connected to remote discrete diode junction or to the diode junction on a remote IC whose die temperature is being sensed. When not used they should be left floating. DC Voltage from 3.0 V to 3.6 V VCC 2 Positive Supply Voltage Input www.national.com 2 LM83 Pin Description Label D- ADD0-ADD1 GND (Continued) Pin # 4 10, 6 7, 8 Function Diode Return Current Sink User-Set SMBus (I2C) Address Inputs Power Supply Ground Manufacturing test pins. Typical Connection To all Diode Junction Cathodes using a star connection to pin. Must float when not used. Ground (Low, "0"), VCC (High, "1") or open ("TRI-LEVEL") Ground Left floating. PC board traces may be routed through the pads for these pins, although the components that drive these traces should share the same supply as the LM83 so that the Absolute Maximum Rating, Voltage at Any Pin, is not violated. Pull Up Resistor, Controller Interrupt or Alert Line From and to Controller, Pull-Up Resistor NC 9, 13, 15 INT 11 Interrupt Output, open-drain SMBus (I2C) Serial Bi-Directional Data Line, open-drain output SMBus (I2C) Clock Input Critical Temperature Alarm, open-drain output SMBData SMBCLK T_CRIT_A 12 14 16 From Controller, Pull-Up Resistor Pull Up Resistor, Controller Interrupt Line or System Shutdown 3 www.national.com LM83 Absolute Maximum Ratings (Note 1) Supply Voltage Voltage at Any Pin -0.3 V to 6.0 V -0.3 V to (VCC + 0.3 V) 1 mA D- Input Current Input Current at All Other Pins (Note 2) 5 mA Package Input Current (Note 2) 20 mA SMBData, T_CRIT_A, INT Output Sink Current 10 mA SMBCLK, SMBData, T_CRIT_A, INT Output Voltage 6.0 V Storage Temperature -65C to +150C Soldering Information, Lead Temperature QSOP Package (Note 3) Vapor Phase (60 seconds) Infrared (15 seconds) ESD Susceptibility (Note 4) Human Body Model Machine Model 215C 220C 2000 V 200 V Operating Ratings (Notes 1, 5) Specified Temperature Range LM83 Supply Voltage Range (VCC) TMIN to TMAX -40C to +125C +3.0V to +3.6V Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications apply for VCC = +3.0Vdc to 3.6Vdc. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25C, unless otherwise noted. Parameter Temperature Error using Local Diode ((Note 8)) Conditions TA = 0 C to +85C, VCC = +3.3V TA = -40 C to +125C, VCC = +3.3V TA = +60 C to +100C, VCC = +3.3V TA = 25 C to +100C, VCC = +3.3V TA = 0 C to +125C, VCC = +3.3V Typical (Note 6) Limits (Note 7) Units (Limit) C (max) C (max) 1 3 4 3 3 4 Temperature Error using Remote Diode ((Note 8)) C (max) C (max) C (max) C Bits C Diode Channel to Channel Matching Resolution Conversion Time of All Temperatures Quiescent Current (Note 9) D- Source Voltage Diode Source Current (D+ - D-) = + 0.65V; high level Low level T_CRIT_A and INT Output Saturation Voltage Power-On Reset Threshold Local and Remote T_CRIT and HIGH Default Temperature settings IOUT = 3.0 mA On VCC input, falling edge (Note 11) (Note 10) SMBus (I2C) Inactive 0 8 1 460 0.500 0.7 125 60 15 5 0.4 2.3 1.8 +127 600 0.80 ms (max) mA (max) V A (max) A (min) A (max) A (min) V (max) V (max) V (min) C www.national.com 4 LM83 Logic Electrical Characteristics DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for VCC = +3.0 to 3.6 Vdc. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25C, unless otherwise noted. Symbol SMBData, SMBCLK VIN(1) VIN(0) VIN(HYST) IIN(1) IIN(0) ADD0, ADD1 VIN(1) VIN(0) IIN(1) IIN(0) CIN IOH VOL Logical "1" Input Voltage Logical "0"Input Voltage Logical "1" Input Current Logical "0" Input Current Input Capacitance High Level Output Current SMBus Low Level Output Voltage VOH = VCC IOL = 3 mA IOL = 6 mA VIN = VCC VIN = 0 V 20 100 0.4 0.6 VCC GND 1.5 0.6 2 -2 V (min) V (max) A (max) A (max) pF A (max) V (max) Logical "1" Input Voltage Logical "0"Input Voltage SMBData and SMBCLK Digital Input Hysteresis Logical "1" Input Current Logical "0" Input Current VIN = VCC VIN = 0 V 300 0.005 -0.005 1.5 1.5 2.1 0.8 V (min) V (max) mV A (max) A (max) Parameter Conditions Typical (Note 6) Limits (Note 7) Units (Limit) ALL DIGITAL INPUTS ALL DIGITAL OUTPUTS 5 www.national.com LM83 Logic Electrical Characteristics (Continued) SMBus DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for VCC = +3.0 Vdc to +3.6 Vdc, CL (load capacitance) on output lines = 80 pF. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25C, unless otherwise noted. The switching characteristics of the LM83 fully meet or exceed the published specifications of the SMBus or I2C bus. The following parameters are the timing relationships between SMBCLK and SMBData signals related to the LM83. They are not the I2C or SMBus bus specifications. Symbol fSMB tLOW Parameter SMBus Clock Frequency SMBus Clock Low Time 10 % to 10 % Conditions Typical (Note 6) Limits (Note 7) 100 10 1.3 25 10 90 % to 90% 10% to 90% 90% to 10% CL = 400 pF, IO = 3 mA 1 0.3 250 25 40 10 100 300 TBD 100 100 0.6 1.3 0.6 Units (Limit) kHz (max) kHz (min) s (min) ms (max) ms (max) s (min) s (max) ns (max) ns (max) ms (min) ms (max) s (min) ns (min) ns (min) ns (max) ns (min) ns (min) s (min) s (min) tLOWMEXT Cumulative Clock Low Extend Time tHIGH tR,SMB tF,SMB tOF tTIMEOUT t1 t2, tSU;DAT t3, tHD;DAT t4, tHD;STA t5, tSU;STO t6, tSU;STA tBUF SMBus Clock High Time SMBus Rise Time SMBus Fall Time Output Fall Time SMBData and SMBCLK Time Low for Reset of Serial Interface (Note 12) SMBCLK (Clock) Period Data In Setup Time to SMBCLK High Data Out Stable after SMBCLK Low SMBData Low Setup Time to SMBCLK Low SMBData High Delay Time after SMBCLK High (Stop Condition Setup) SMBus Start-Condition Setup Time SMBus Free Time SMBus Communication DS101058-4 www.national.com 6 LM83 Logic Electrical Characteristics (Continued) SMBus TIMEOUT DS101058-7 See drawing DS10105807 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions. Note 2: When the input voltage (VI) at any pin exceeds the power supplies (VI < GND or VI > VCC), 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. Parasitic components and or ESD protection circuitry are shown in the figure below for the LM83's pins. The nominal breakdown voltage of the zener D3 is 6.5 V. Care should be taken not to forward bias the parasitic diode, D1, present on pins: D+, D-, ADD1 and ADD0. Doing so by more than 50 mV may corrupt a temperature or voltage measurement. Pin Name VCC D+ D- ADD0, ADD1 D1 D2 D3 x D4 Pin Name T_CRIT_A & INT SMBData NC (pins 9 & 15) D1 D2 x x D3 x x x x D4 x x x x x x x x x x x x x x SMBCLK NC (pin 13) Note: An x indicates that the diode exists. DS101058-13 FIGURE 1. ESD Protection Input Structure Note 3: See AN-450 "Surface Mounting Methods and Their Effect on Product Reliability" or the section titled "Surface Mount" found in a current National Semiconductor Linear Data Book for other methods of soldering surface mount devices. Note 4: Human body model, 100 pF discharged through a 1.5 k resistor. Machine model, 200 pF discharged directly into each pin. Note 5: Thermal resistance of the QSOP-16 package is xyzC/W, junction-to-ambient when attached to a printed circuit board with 2 oz. foil as shown in Figure 3 . 7 www.national.com LM83 Logic Electrical Characteristics (Continued) Note 6: Typicals are at TA = 25C and represent most likely parametric norm. Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level). Note 8: The Temperature Error will vary less than 1.0 C for a variation in VCC of 3 V to 3.6 V from the nominal of 3.3 V. Note 9: Quiescent current will not increase substantially with an active SMBus. Note 10: This specification is provided only to indicate how often temperature data is updated. The LM83 can be read at any time without regard to conversion state (and will yield last conversion result). Note 11: Default values set at power up. Note 12: Holding the SMBData and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will cause the LM83 to reset SMBData and SMBCLK to the IDLE state of an SMBus communication (SMBCLK and SMBData set High). DS101058-5 FIGURE 2. Temperature-to-Digital Transfer Function (Non-linear scale for clarity) DS101058-24 FIGURE 3. Printed Circuit Board Used for Thermal Resistance Specifications 1.0 Functional Description The LM83 temperature sensor incorporates a band-gap type temperature sensor using a Local or three Remote diodes and an 8-bit ADC (Delta-Sigma Analog-to-Digital Converter). The LM83 is compatible with the serial SMBus and I2C two wire interfaces. Digital comparators compare Local (LT) and Remote (D1RT, D2RT and D3RT) temperature readings to user-programmable setpoints (LHS, D1RHS, D2RHS, D3RHS and TCS). Activation of the INT output indicates that a comparison is greater than the limit preset in a HIGH register. The T_CRIT setpoint (TCS) interacts with all the temperature readings. Activation of the T_CRIT_A output indicates that any or all of the temperature readings have exceed the T_CRIT setpoint. 1.1 CONVERSION SEQUENCE The LM83 converts its own temperature as well as 3 remote diode temperatures in the following sequence: 1. Local Temperature (LT) 1. Remote Diode 2 (D2RT) 2. Remote Diode 1 (D1RT) 3. Remote Diode 3 (D3RT) This round robin sequence takes approximately 480 ms to complete as each temperature is digitized in approximately 120 ms. 1.2 INT OUTPUT and T_HIGH LIMITS Each temperature reading (LT, D1RT, D2RT, and D3RT) is associated with a T_HIGH setpoint register (LHS, D1RHS, D2RHS, D3RHS). At the end of a temperature reading a digital comparison determines whether that reading has exceed its HIGH setpoint. If the temperature reading is greater than the HIGH setpoint, a bit is set in one of the Status Registers, to indicate which temperature reading, and the INT output is activated. Local and remote temperature diodes are sampled in sequence by the A/D converter. The INT output and the Status 8 www.national.com LM83 1.0 Functional Description (Continued) Register flags are updated at the completion of a conversion, which occurs approximately 60 ms after a temperature diode is sampled. INT is deactivated when the Status Register, containing the set bit, is read and a temperature reading is less than or equal to it's corresponding HIGH setpoint, as shown in Figure 4. Figure 5shows a simplified logic diagram for the INT output and related circuitry. Local and remote temperature diodes are sampled in sequence by the A/D converter. The T_CRIT_A output and the Status Register flags are updated at the completion of a conversion. T_CRIT_A and the Status Register flags are reset only after the Status Register is read and if a temperature conversion is below the T_CRIT setpoint, as shown in Figure 6. Figure 7 shows a simplified logic diagram of the T_CRIT_A and related circuitry. DS101058-6 * Note: Status Register Bits are reset by a read of Status Register where bit is located. DS101058-14 * Note: Status Register Bits are reset by a read of Status Register where FIGURE 6. T_CRIT_A Temperature Response Diagram with remote diode 1 and local temperature masked. bit is located. FIGURE 4. INT Temperature Response Diagram with D2RHS and D3RHS set to 127C. DS101058-21 FIGURE 5. INT output related circuitry logic diagram The INT output can be disabled by setting the INT mask bit, D7, of the configuration register. INT can be programmed to be active high or low by the state of the INT inversion bit, D1, in the configuration register. A "0" would program INT to be active low. INT is an open-drain output. 1.3 T_CRIT_A OUTPUT and T_CRIT LIMIT T_CRIT_A is activated when any temperature reading is greater than the limit preset in the critical temperature setpoint register (T_CRIT), as shown in Figure 6. The Status Registers can be read to determine which event caused the alarm. A bit in the Status Registers is set high to indicate which temperature reading exceeded the T_CRIT setpoint temperature and caused the alarm, see Section 2.3. 9 DS101058-20 FIGURE 7. T_CRIT_A output related circuitry logic diagram Located in the Configuration Register are the mask bits for each temperature reading, seeSection 2.5. When a mask bit is set, its corresponding status flag will not propagate to the T_CRIT_A output, but will still be set in the Status Registers. Setting all four mask bits or programming the T_CRIT setpoint to 127C will disable the T_CRIT_A output. 1.4 POWER ON RESET DEFAULT STATES LM83 always powers up to these known default states: 1. 2. Command Register set to 00h Local Temperature set to 0C www.national.com LM83 1.0 Functional Description 3. (Continued) Diode 1, Diode 2, and Diode 3 Remote Temperature set to 0C until the LM83 senses a diode present between the D+ and D- input pins. 4. Status Registers 1 and 2 set to 00h. 5. Configuration Register set to 00h; INT enabled and all T_CRIT setpoints enabled to activate T_CRIT_A. 6. Local and all Remote T_CRIT set to 127C 1.6 TEMPERATURE DATA FORMAT Temperature data can be read from the Local and Remote Temperature, T_CRIT, and HIGH setpoint registers; and written to the T_CRIT and HIGH setpoint registers. Temperature data is represented by an 8-bit, two's complement byte with an LSB (Least Significant Bit) equal to 1C: Temperature +125C Digital Output Binary 0111 1101 0001 1001 0000 0001 0000 0000 1111 1111 1110 0111 1100 1001 +25C +1C 0C -1C -25C -55C Hex 7Dh 19h 01h 00h FFh E7h C9h 1.5 SMBus INTERFACE The LM83 operates as a slave on the SMBus, so the SMBCLK line is an input (no clock is generated by the LM83) and the SMBData line is bi-directional. According to SMBus specifications, the LM83 has a 7-bit slave address. Bit 4 (A3) of the slave address is hard wired inside the LM83 to a 1. The remainder of the address bits are controlled by the state of the address select pins ADD1 and ADD0, and are set by connecting these pins to ground for a low, (0) , to VCC for a high, (1), or left floating (TRI-LEVEL). Therefore, the complete slave address is: A6 MSB and is selected as follows: Address Select Pin State ADD0 0 0 0 TRI-LEVEL TRI-LEVEL TRI-LEVEL 1 1 1 ADD1 0 TRI-LEVEL 1 0 TRI-LEVEL 1 0 TRI-LEVEL 1 LM83 SMBus Slave Address A6:A0 binary 001 1000 001 1001 001 1010 010 1001 010 1010 010 1011 100 1100 100 1101 100 1110 A5 A4 1 A2 A1 A0 LSB 1.7 OPEN-DRAIN OUTPUTS The SMBData, INT and T_CRIT_A outputs are open-drain outputs and do not have internal pull-ups. A "high" level will not be observed on these pins until pull-up current is provided from some external source, typically a pull-up resistor. Choice of resistor value depends on many system factors but, in general, the pull-up resistor should be as large as possible. This will minimize any internal temperature reading errors due to internal heating of the LM83. The maximum resistance of the pull up, based on LM83 specification for High Level Output Current, to provide a 2.1V high level, is 30k. 1.8 DIODE FAULT DETECTION Before each external conversion the LM83 goes through an external diode fault detection sequence. If a D+ input is shorted to VCC or floating then the temperature reading will be +127 C, and its OPEN bit in the Status Register will be set. If the T_CRIT setpoint is set to less than +127 C then the D+ inputs RTCRIT bit in the Status Register will be set which will activate the T_CRIT_A output, if enabled. If a D+ is shorted to GND or D-, its temperature reading will be 0 C and its OPEN bit in the Status Register will not be set. The LM83 latches the state of the address select pins during the first read or write on the SMBus. Changing the state of the address select pins after the first read or write to any device on the SMBus will not change the slave address of the LM83. www.national.com 10 LM83 1.0 Functional Description 1.9 COMMUNICATING with the LM83 (Continued) DS101058-9 There are 19 data registers in the LM83, selected by the Command Register. At power-up the Command Register is set to "00", the location for the Read Local Temperature Register. The Command Register latches the last location it was set to. Reading the Status Register resets T_CRIT_A and INT, so long as a temperature comparison does not signal a fault (see Sections 1.2 and 1.3). All other registers are predefined as read only or write only. Read and write registers with the same function contain mirrored data. A Write to the LM83 will always include the address byte and the command byte. A write to any register requires one data byte. Reading the LM83 can take place either of two ways: 1. If the location latched in the Command Register is correct (most of the time it is expected that the Command Register will point to one of the Read Temperature Reg11 isters because that will be the data most frequently read from the LM83), then the read can simply consist of an address byte, followed by retrieving the data byte. 2. If the Command Register needs to be set, then an address byte, command byte, repeat start, and another address byte will accomplish a read. The data byte has the most significant bit first. At the end of a read, the LM83 can accept either Acknowledge or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master has read its last byte). 1.10 SERIAL INTERFACE ERROR RECOVERY The LM83 SMBus lines will be reset to the SMBus idle state if the SMBData or SMBCLK lines are held low for 40 ms or more (tTIMEOUT). The LM83 may or may not reset the state of www.national.com LM83 1.0 Functional Description (Continued) the serial interface logic if either of the SMBData or SMBCLK lines are held low between 25 ms and 40 ms. TIMEOUT allows a clean recovery in cases where the master may be reset while the LM83 is transmitting a low bit thus preventing possible bus lock up. Whenever the LM83 sees the start condition its serial interface will reset to the beginning of the communication, thus the LM83 will expect to see an address byte next. This simplifies recovery when the master is reset while the LM83 is transmitting a high. www.national.com 12 LM83 1.0 Functional Description 2.0 LM83 REGISTERS (Continued) 2.1 COMMAND REGISTER Selects which registers will be read from or written to. Data for this register should be transmitted during the Command Byte of the SMBus write communication. P7 0 P0-P7: Command Select Command Select Address Power On Default State Register Name Register Function P6 P5 P4 P3 P2 P1 P0 Command Select 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah 0Bh 0Ch 0Dh 0Eh-2Fh 30h 31h 32h-34h 35h 36h-37h 38h 39h 3Ah 3Bh-41h 42h 43h-4Fh 50h 51h 52h 53h-59h 5Ah 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0111 1111 0111 1111 0000 0000 0111 1111 0111 1111 127 127 WC WD2LHS WD2RHS 0000 0000 0000 0000 0 0 RD1RT RD3RT 0000 0000 0111 1111 0 127 RSR2 RD1RHS 0111 1111 127 RD3RHS 0111 1111 0111 1111 127 127 RTCS WD1RHS 0111 1111 127 WD3RHS 0111 1111 127 WTCS 13 www.national.com LM83 1.0 Functional Description Command Select Address (Continued) Register Name Register Function Power On Default State 5Ch-6Fh and F0h-FDh FEh FFh 0000 0001 1 RMID RSR Read Manufacturers ID Read Stepping or Die Revision Code 2.2 LOCAL and D1, D2 and D3 REMOTE TEMPERATURE REGISTERS (LT, D1RT, D2RT, and D3RT) (Read Only Address 00h, 01h, 30h and 31h): D7 MSB D6 Bit 6 D5 Bit 5 D4 Bit 4 D3 D2 D1 D0 Bit 3 Bit 2 Bit 1 LSB D7-D0: Temperature Data. One LSB = 1C. Two's complement format. 2.3 STATUS REGISTERS 1 and 2 2.3.1 Status Register 1 (SR1) (Read Only Address 02h): D7 0 D6 LHIGH D5 0 D4 D2RHIGH D3 0 D2 D2OPEN D1 D2CRIT D0 LCRIT Power up default is with all bits "0" (zero). D0: LCRIT: When set to a 1 indicates an Local Critical Temperature alarm. D1: D2CRIT: When set to a 1 indicates a Remote Diode 2 Critical Temperature alarm. D2: D2OPEN: When set to 1 indicates a Remote Diode 2 disconnect. D4: D2RHIGH: When set to 1 indicates a Remote Diode 2 HIGH Temperature alarm. D6: LHIGH: When set to 1 indicates a Local HIGH Temperature alarm. D7, D5, and D3: These bits are always set to 0 and reserved for future use. Status Register 2 2.3.2 Status Register 2 (SR2) (Read Only Address 35h): D7 D1RHIGH D6 0 D5 D1OPEN D4 D3RHIGH D3 0 D2 D3OPEN D1 D3CRIT D0 D1CRIT Power up default is with all bits "0" (zero). D0: D1CRIT, when set to 1 indicates a Remote Diode 1 Critical Temperature alarm. D1: D3CRIT, when set to 1 indicates a Remote Diode 3 Critical Temperature alarm. D2: D3OPEN, when set to 1 indicates a Remote Diode 3 disconnect. D4: D3RHIGH, when set to 1 indicates a Remote Diode 3 HIGH Temperature alarm. D5: D1OPEN, when set to 1 indicates a Remote Diode 1 disconnect. D7: D1RHIGH, when set to 1 indicates a Remote Diode 1 HIGH Temperature alarm. D6, and D3: These bits are always set to 0 and reserved for future use. 2.4 MANUFACTURERS ID REGISTER (Read Address FEh) Default value 01h. 2.5 CONFIGURATION REGISTER (Read Address 03h/Write Address 09h): D7 INT mask D6 0 D5 D1 T_CRIT_A mask D4 D2 T_CRIT_A mask D3 D3 T_CRIT_A mask D2 Local T_CRIT_A mask D1 INT Inversion D0 0 Power up default is with all bits "0" (zero). D7: INT mask: When set to 1 INT interrupts are masked. www.national.com 14 LM83 1.0 Functional Description (Continued) D5: T_CRIT mask for Diode 1, when set to 1 a Diode 1 temperature reading that exceeds T_CRIT setpoint will not activate the T_CRIT_A pin. D4: T_CRIT mask for Diode 2, when set to 1 a Diode 2 temperature reading that exceeds T_CRIT setpoint will not activate the T_CRIT_A pin. D3: T_CRIT mask for Diode 3, when set to 1 a Diode 3 temperature reading that exceeds T_CRIT setpoint will not activate the T_CRIT_A pin. D2: T_CRIT mask for Local reading, when set to 1 a Local temperature reading that exceeds T_CRIT setpoint will not activate the T_CRIT_A pin. D1: INT active state inversion. When INT Inversion is set to a 1 the active state of the INT output will be a logical high. A low would then select an active state of a logical low. D6 and D0: These bits are always set to 0 and reserved for future use. A write of 1 will return a 0 when read. 2.6 LOCAL, DIODE 1, DIODE 2 and DIODE 3 HIGH SETPOINT REGISTERS (LHS, D1RHS, D2RHS and D3RHS) (Read Address 05h, 07h, 38h, 3Ah /Write Address 0Bh, 0Dh, 50h, 52h): D7 MSB D6 Bit 6 D5 Bit 5 D4 Bit 4 D3 Bit 3 D2 Bit 2 D1 Bit 1 D0 LSB D7-D0: HIGH setpoint temperature data. Power up default is LHIGH = RD1HIGH = RD2HIGH = RD3HIGH = 127C. 2.7 T_CRIT REGISTER (TCS) (Read Address 42h/Write Address 5Ah): D7 MSB D6 Bit 6 D5 Bit 5 D4 Bit 4 D3 Bit 3 D2 Bit 2 D1 Bit 1 D0 LSB D7-D0: T_CRIT setpoint temperature data. Power up default is T_CRIT = 127C. 15 www.national.com LM83 3.0 SMBus Timing Diagrams DS101058-10 (a) Serial Bus Write to the internal Command Register followed by a the Data Byte DS101058-11 (b) Serial Bus Write to the internal Command Register DS101058-12 (c) Serial Bus Read from a Register with the internal Command Register preset to desired value. FIGURE 8. Serial Bus Timing Diagrams www.national.com 16 LM83 4.0 Application Hints The LM83 can be applied easily in the same way as other integrated-circuit temperature sensors, and its remote diode sensing capability allows it to be used in new ways as well. It can be soldered to a printed circuit board, and because the path of best thermal conductivity is between the die and the pins, its temperature will effectively be that of the printed circuit board lands and traces soldered to the LM83's pins. This presumes that the ambient air temperature is almost the same as the surface temperature of the printed circuit board; if the air temperature is much higher or lower than the surface temperature, the actual temperature of the of the LM83 die will be at an intermediate temperature between the surface and air temperatures. Again, the primary thermal conduction path is through the leads, so the circuit board temperature will contribute to the die temperature much more strongly than will the air temperature. To measure temperature external to the LM83's die, use a remote diode. This diode can be located on the die of a target IC, allowing measurement of the IC's temperature, independent of the LM83's temperature. The LM83 has been optimized to measure the remote diode of a Pentium II processor as shown in Figure 9. A discrete diode can also be used to sense the temperature of external objects or ambient air. Remember that a discrete diode's temperature will be affected, and often dominated, by the temperature of its leads. where: * is the non-ideality factor of the process the diode is manufactured on, * q is the electron charge, * k is the Boltzmann's constant, * N is the current ratio, * T is the absolute temperature in K. The temperature sensor then measures VBE and converts to digital data. In this equation, k and q are well defined universal constants, and N is a parameter controlled by the temperature sensor. The only other parameter is , which depends on the diode that is used for measurement. Since VBE is proportional to both and T, the variations in cannot be distinguished from variations in temperature. Since the non-ideality factor is not controlled by the temperature sensor, it will directly add to the inaccuracy of the sensor. For the Pentium II Intel specifies a 1% variation in from part to part. As an example, assume a temperature sensor has an accuracy specification of 3 C at room temperature of 25 C and the process used to manufacture the diode has a non-ideality variation of 1%. The resulting accuracy of the temperature sensor at room temperature will be: TACC = 3C + (1% of 298 K) = 6 C. The additional inaccuracy in the temperature measurement caused by , can be eliminated if each temperature sensor is calibrated with the remote diode that it will be paired with. 3.2 PCB LAYOUT for MINIMIZING NOISE In a noisy environment, such as a processor mother board, layout considerations are very critical. Noise induced on traces running between the remote temperature diode sensor and the LM83 can cause temperature conversion errors. The following guidelines should be followed: 1. Place a 0.1 F power supply bypass capacitor as close as possible to the VCCpin and the recommended 2.2 nF capacitor as close as possible to the D+ and D- pins. Make sure the traces to the 2.2nF capacitor are matched. 2. The recommended 2.2nF diode bypass capacitor actually has a range of 200pF to 3.3nF. The average temperature accuracy will not degrade. Increasing the capacitance will lower the corner frequency where differential noise error affects the temperature reading thus producing a reading that is more stable. Conversely, lowering the capacitance will increase the corner frequency where differential noise error affects the temperature reading thus producing a reading that is less stable. 3. Ideally, the LM83 should be placed within 10cm of the Processor diode pins with the traces being as straight, short and identical as possible. Trace resistance of 1 can cause as much as 1C of error. Diode traces should be surrounded by a GND guard ring to either side, above and below if possible. This GND guard should not be between the D+ and D- lines. In the event that noise does couple to the diode lines it would be ideal if it is coupled common mode. That is equally to the D+ and D- lines.(See Figure 10) Avoid routing diode traces in close proximity to power supply switching or filtering inductors. www.national.com DS101058-15 Pentium or 3904 Temperature vs LM83 Temperature Reading Most silicon diodes do not lend themselves well to this application. It is recommended that a 2N3904 transistor base emitter junction be used with the collector tied to the base. A diode connected 2N3904 approximates the junction available on a Pentium microprocessor for temperature measurement. Therefore, the LM83 can sense the temperature of this diode effectively. 3.1 ACCURACY EFFECTS OF DIODE NON-IDEALITY FACTOR The technique used in today's remote temperature sensors is to measure the change in VBE at two different operating points of a diode. For a bias current ratio of N:1, this difference is given as: 4. 5. 17 LM83 4.0 Application Hints 6. (Continued) Avoid running diode traces close to or parallel to high speed digital and bus lines. Diode traces should be kept at least 2cm. apart from the high speed digital traces. 7. If it is necessary to cross high speed digital traces, the diode traces and the high speed digital traces should cross at a 90 degree angle. 8. The ideal place to connect the LM83's GND pin is as close as possible to the Processors GND associated with the sense diode. For the Pentium II this would be pin A14. 9. Leakage current between D+ and GND should be kept to a minimum. One nano-ampere of leakage can cause as much as 1C of error in the diode temperature reading. Keeping the printed circuit board as clean as possible will minimize leakage current. DS101058-17 FIGURE 10. Ideal Diode Trace Layout Noise coupling into the digital lines greater than 300mVp-p (typical hysteresis), overshoot greater than 500mV above VCC, and undershoot less than 500mV below GND, may prevent successful SMBus communication with the LM83. SMBus no acknowledge is the most common symptom, causing unnecessary traffic on the bus. Although, the SMBus maximum frequency of communication is rather low (100kHz max) care still needs to be taken to ensure proper termination within a system with multiple parts on the bus and long printed circuit board traces. An R/C lowpass filter with a 3db corner frequency of about 40MHz has been included on the LM83's SMBCLK input. Additional resistance can be added in series with the SMBData and SMBCLK lines to further help filter noise and ringing. Minimize noise coupling by keeping digital traces out of switching power supply areas as well as ensuring that digital lines containing high speed data communications cross at right angles to the SMBData and SMBCLK lines. 4.0 Typical Applications DS101058-22 FIGURE 11. LM83 Demo Board Diode Layout www.national.com 18 LM83 4.0 Typical Applications (Continued) DS101058-23 Any two or three D+ inputs can be connected in parallel to increase the number of High temperature setpoints for a particular temperature reading. If all three D+ inputs are tied as shown here, D1+, D2+ and D3+ temperature readings will be identical, unless affected by PCB D+ trace resistance differences. FIGURE 12. Connecting all Three LM83 Diode Inputs in Parallel will Increase the Number of HIGH Setpoints for a Single Temperature Reading to Three. 19 www.national.com LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire Interface Physical Dimensions inches (millimeters) unless otherwise noted 16-Lead QSOP Package Order Number LM83CIMQA or LM83CIMQAX NS Package Number MQA16 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 Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Francais Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 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: sea.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. |
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