LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface General Description The LM95221 is a dual remote diode temperature sensor in an 8-lead MSOP package. The 2-wire serial interface of the LM95221 is compatible with SMBus 2.0. The LM95221 can sense three temperature zones, it can measure the temperature of its own die as well as two diode connected transistors. The diode connected transistors can be a thermal diode as found in Pentium and AMD processors or can simply be a diode connected MMBT3904 transistor. The LM95221 resolution format for remote temperature readings can be programmed to be 10-bits plus sign or 11-bits unsigned. In the unsigned mode the LM95221 remote diode readings can resolve temperatures above 127˚C. Local temperature readings have a resolution of 9-bits plus sign. The temperature of any ASIC can be accurately determined using the LM95221 as long as a dedicated diode (semiconductor junction) is available on the target die. The LM95221 remote sensor accuracy of ± 1˚C is factory trimmed for a series resistance of 2.7 ohms and 1.008 non-ideality factor. Features n Accurately senses die temperature of remote ICs or diode junctions n Remote diode fault detection n On-board local temperature sensing n Remote temperature readings: — 0.125 ˚C LSb — 10-bits plus sign or 11-bits programmable resolution — 11-bits resolves temperatures above 127 ˚C n Local temperature readings: — 0.25 ˚C — 9-bits plus sign n Status register support n Programmable conversion rate allows user optimization of power consumption n Shutdown mode one-shot conversion control n SMBus 2.0 compatible interface, supports TIMEOUT n 8-pin MSOP package Key Specifications j Local Temperature Accuracy TA=0˚C to 85˚C ± 3.0 ˚C (max) j Remote Diode Temperature Accuracy TA=30˚C to 50˚C, TD=45˚C to 85˚C TA=0˚C to 85˚C, TD=25˚C to 140˚C ± 1.0 ˚C (max) ± 3.0 ˚C (max) j Supply Voltage 3.0 V to 3.6 V j Supply Current 2 mA (typ) Applications n Processor/Computer System Thermal Management (e.g. Laptop, Desktop, Workstations, Server) n Electronic Test Equipment n Office Electronics Simplified Block Diagram 20094301 Pentium™ is a trademark of Intel Corporation. © 2004 National Semiconductor Corporation DS200943 www.national.com LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface May 2004 LM95221 Connection Diagram MSOP-8 20094302 TOP VIEW Ordering Information Package Marking NS Package Number Transport Media SMBus Device Address LM95221CIMM LM95221CIMM MUA08A (MSOP-8) 1000 Units on Tape and Reel 010 1011 LM95221CIMMX LM95221CIMM MUA08A (MSOP-8) 3500 Units on Tape and Reel 010 1011 Part Number Pin Descriptions Label Pin # D1+ 1 Diode Current Source To Diode Anode. Connected to remote discrete diode-connected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A 2.2 nF diode bypass capacitor is recommended to filter high frequency noise. Place the 2.2 nF capacitor between and as close as possible to the LM95221’s D+ and D− pins. Make sure the traces to the 2.2 nF capacitor are matched. Ground this pin if this thermal diode is not used. D1− 2 Diode Return Current Sink To Diode Cathode. A 2.2 nF capacitor is recommended between D1+ and D1-. Ground this pin if this thermal diode is not used. D2+ 3 Diode Current Source To Diode Anode. Connected to remote discrete diode-connected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A 2.2 nF diode bypass capacitor is recommended to filter high frequency noise. Place the 2.2 nF capacitor between and as close as possible to the LM95221’s D+ and D− pins. Make sure the traces to the 2.2 nF capacitor are matched. Ground this pin if this thermal diode is not used. D2− 4 Diode Return Current Sink To Diode Cathode. A 2.2 nF capacitor is recommended between D2+ and D2-. Ground this pin if this thermal diode is not used. GND 5 Power Supply Ground Ground VDD 6 Positive Supply Voltage Input DC Voltage from 3.0 V to 3.6 V. VDD should be bypassed with a 0.1 µF capacitor in parallel with 100 pF. The 100 pF capacitor should be placed as close as possible to the power supply pin. Noise should be kept below 200 mVp-p, a 10 µF capacitor may be required to achieve this. www.national.com Function Typical Connection 2 LM95221 Pin Descriptions (Continued) Label Pin # Function SMBDAT 7 SMBus Bi-Directional Data Line, Open-Drain Output From and to Controller; may require an external pull-up resistor Typical Connection SMBCLK 8 SMBus Clock Input From Controller; may require an external pull-up resistor Typical Application 20094303 3 www.national.com LM95221 Absolute Maximum Ratings (Note 1) Supply Voltage Infrared (15 seconds) ESD Susceptibility (Note 4) −0.3 V to 6.0 V Voltage at SMBDAT, SMBCLK Voltage at Other Pins Human Body Model −0.5V to 6.0V 2000 V Machine Model −0.3 V to (VDD + 0.3 V) 200 V Input Current at All Other Pins (Note 2) ± 1 mA ± 5 mA Operating Ratings Package Input Current (Note 2) 30 mA (Notes 1, 5) SMBDAT Output Sink Current 10 mA D− Input Current Storage Temperature −65˚C to +150˚C Soldering Information, Lead Temperature MSOP-8 Package (Note 3) Vapor Phase (60 seconds) 220˚C 215˚C Operating Temperature Range 0˚C to +115˚C Electrical Characteristics Temperature Range TMIN≤TA≤TMAX LM95221CIMM 0˚C≤TA≤+85˚C Supply Voltage Range (VDD) +3.0V to +3.6V Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications apply for VDD=+3.0Vdc to 3.6Vdc. Boldface limits apply for TA = TJ = TMIN≤TA≤TMAX; all other limits TA= TJ=+25˚C, unless otherwise noted. TJ is the junction temperature of the LM95221. TD is the junction temperature of the remote thermal diode. Parameter Conditions Accuracy Using Local Diode TA = 0˚C to +85˚C, (Note 8) Accuracy Using Remote Diode, see (Note 9) for Thermal Diode Processor Type. TA = +30˚C to +50˚C TD = +45˚C to +85˚C TA = +0˚C to +85˚C TD = +25˚C to +140˚C Remote Diode Measurement Resolution Typical Limits Units (Note 6) (Note 7) (Limit) ±1 ±3 ±1 ˚C (max) ±3 ˚C (max) 11 Local Diode Measurement Resolution ˚C (max) Bits 0.125 ˚C 10 Bits 0.25 ˚C Conversion Time of All Temperatures at the Fastest Setting (Note 11) 66 73 ms (max) Quiescent Current (Note 10) SMBus Inactive, 15Hz conversion rate 2.0 2.6 mA (max) Shutdown 335 (D+ − D−)=+ 0.65V; high-level 188 D− Source Voltage Diode Source Current Low-Level Diode Source Current Variation over Temperature Power-On Reset Threshold www.national.com µA 0.7 V 315 µA (max) 110 µA (min) 20 µA (max) 7 µA (min) Low-level 11.75 TA = +30˚C to +50˚C +0.5 µA TA = +30˚C to +85˚C +1.5 µA Measure on VDD input, falling edge 4 2.4 1.8 V (max) V (min) DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for VDD=+3.0 to 3.6 Vdc. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA= TJ=+25˚C, unless otherwise noted. Symbol Parameter Conditions Typical Limits Units (Note 6) (Note 7) (Limit) 2.1 V (min) 0.8 V (max) SMBDAT, SMBCLK INPUTS VIN(1) Logical “1” Input Voltage VIN(0) Logical “0”Input Voltage VIN(HYST) SMBDAT and SMBCLK Digital Input Hysteresis IIN(1) Logical “1” Input Current VIN = VDD 0.005 IIN(0) Logical “0” Input Current VIN = 0 V −0.005 CIN Input Capacitance 400 mV ± 10 ± 10 µA (max) µA (max) 5 pF SMBDAT OUTPUT IOH High Level Output Current VOH = VDD 10 µA (max) 0.4 V (max) IOL = 4mA 0.6 IOL = 6mA SMBus DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for VDD=+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 = +25˚C, unless otherwise noted. The switching characteristics of the LM95221 fully meet or exceed the published specifications of the SMBus version 2.0. The following parameters are the timing relationships between SMBCLK and SMBDAT signals related to the LM95221. They adhere to but are not necessarily the SMBus bus specifications. VOL SMBus Low Level Output Voltage Symbol Parameter Conditions fSMB SMBus Clock Frequency tLOW SMBus Clock Low Time from VIN(0)max to VIN(0)max Typical Limits Units (Note 6) (Note 7) (Limit) 100 10 kHz (max) kHz (min) 4.7 25 µs (min) ms (max) tHIGH SMBus Clock High Time from VIN(1)min to VIN(1)min tR,SMB SMBus Rise Time (Note 12) 1 µs (max) tF,SMB SMBus Fall Time (Note 13) 0.3 µs (max) tOF Output Fall Time CL = 400pF, IO = 3mA, (Note 13) tTIMEOUT SMBDAT and SMBCLK Time Low for Reset of Serial Interface (Note 14) 4.0 µs (min) 250 ns (max) 25 35 ms (min) ms (max) tSU;DAT Data In Setup Time to SMBCLK High 250 ns (min) tHD;DAT Data Out Stable after SMBCLK Low 300 900 ns (min) ns (max) tHD;STA Start Condition SMBDAT Low to SMBCLK Low (Start condition hold before the first clock falling edge) 100 ns (min) tSU;STO Stop Condition SMBCLK High to SMBDAT Low (Stop Condition Setup) 100 ns (min) tSU;STA SMBus Repeated Start-Condition Setup Time, SMBCLK High to SMBDAT Low 0.6 µs (min) SMBus Free Time Between Stop and Start Conditions 1.3 µs (min) tBUF 5 www.national.com LM95221 Logic Electrical Characteristics LM95221 SMBus Communication 20094309 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 > VDD), the current at that pin should be limited to 5 mA. Parasitic components and or ESD protection circuitry are shown in the figure below for the LM95221’s pins. The nominal breakdown voltage of D4 is 6.5 V. Care should be taken not to forward bias the parasitic diode, D1, present on pins: D1+, D2+, D1−, D2−. Doing so by more than 50 mV may corrupt the temperature measurements. Pin Name PIN # VDD D1 D2 1 D3 D4 D5 D6 D7 R1 SNP x D1+ 2 x x x D1− 3 x x x D2+ 4 x x x D2- 6 x x x SMBDAT 7 x x SMBCLK 8 x x ESD CLAMP x x x x x x x x x x x x x x x x x x x x x x x Note: An “x” indicates that the component exists for the designated pin. SNP refers to a snap-back device. 20094313 FIGURE 1. ESD Protection Input Structure Note 3: See the URL ”http://www.national.com/packaging/“ for other recommendations and methods of soldering surface mount devices. Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor. Machine model, 200pF discharged directly into each pin. Note 5: Thermal resistance junction-to-ambient when attached to a printed circuit board with 2 oz. foil: – MSOP-8 = 210˚C/W Note 6: Typicals are at TA = 25˚C and represent most likely parametric norm. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 8: Local temperature accuracy does not include the effects of self-heating. The rise in temperature due to self-heating is the product of the internal power dissipation of the LM95221 and the thermal resistance. See (Note 5) for the thermal resistance to be used in the self-heating calculation. Note 9: The accuracy of the LM95221CIMM is guaranteed when using the thermal diode with a non-ideality of 1.008 and series R= 2.7Ω. When using an MMBT3904 type transistor as the thermal diode the error band will be offset by -3.25˚C Note 10: Quiescent current will not increase substantially with an SMBus. Note 11: This specification is provided only to indicate how often temperature data is updated. The LM95221 can be read at any time without regard to conversion state (and will yield last conversion result). Note 12: The output rise time is measured from (VIN(0)max + 0.15V) to (VIN(1)min − 0.15V). Note 13: The output fall time is measured from (VIN(1)min - 0.15V) to (VIN(1)min + 0.15V). Note 14: Holding the SMBDAT and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will reset the LM95221’s SMBus state machine, therefore setting SMBDAT and SMBCLK pins to a high impedance state. www.national.com 6 Thermal Diode Capacitor or PCB Leakage Current Effect Remote Diode Temperature Reading Remote Temperature Reading Sensitivity to Thermal Diode Filter Capacitance 20094305 20094307 Conversion Rate Effect on Average Power Supply Current 20094306 to sense temperatures above 127˚C. Local temperature resolution is not programmable and is always 9-bits plus sign and has a 0.25˚C LSb. The LM95221 remote diode temperature accuracy will be trimmed for the thermal diode of a Prescott processor and the accuracy will be guaranteed only when using this diode. Diode fault detection circuitry in the LM95221 can detect the presence of a remote diode: whether D+ is shorted to VDD, D- or ground, or whether D+ is floating. The LM95221 register set has an 8-bit data structure and includes: 1. Most-Significant-Byte (MSB) Local Temperature Register 2. Least-Significant-Byte (LSB) Local Temperature Register 3. MSB Remote Temperature 1 Register 4. LSB Remote Temperature 1 Register 5. MSB Remote Temperature 2 Register 6. LSB Remote Temperature 2 Register 1.0 Functional Description The LM95221 is a digital sensor that can sense the temperature of 3 thermal zones using a sigma-delta analog-to-digital converter. It can measure its local die temperature and the temperature of two diode connected MMBT3904 transistors using a ∆Vbe temperature sensing method. The 2-wire serial interface, of the LM95221, is compatible with SMBus 2.0 and I2C. Please see the SMBus 2.0 specification for a detailed description of the differences between the I2C bus and SMBus. The temperature conversion rate is programmable to allow the user to optimize the current consumption of the LM95221 to the system requirements. The LM95221 can be placed in shutdown to minimize power consumption when temperature data is not required. While in shutdown, a 1-shot conversion mode allows system control of the conversion rate for ultimate flexibility. The remote diode temperature resolution is eleven bits and is programmable to 11-bits unsigned or 10-bits plus sign. The least-significant-bit (LSb) weight for both resolutions is 0.125˚C. The unsigned resolution allows the remote diodes 7 www.national.com LM95221 Typical Performance Characteristics LM95221 1.0 Functional Description 7. specifications, the LM95221 has a 7-bit slave address. All bits A6 through A0 are internally programmed and can not be changed by software or hardware. The LM95221 has the following SMBus slave address: (Continued) Status Register: busy, diode fault 8. Configuration Register: resolution control, conversion rate control, standby control 9. 1-shot Register 10. Manufacturer ID 11. Revision ID Version A6 A5 A4 A3 A2 A1 A0 LM95221 0 1 0 1 0 1 1 1.4 TEMPERATURE DATA FORMAT Temperature data can only be read from the Local and Remote Temperature registers . 1.1 CONVERSION SEQUENCE The LM95221 takes approximately 66 ms to convert the Local Temperature, Remote Temperature 1 and 2, and to update all of its registers. Only during the conversion process the busy bit (D7) in the Status register (02h) is high. These conversions are addressed in a round robin sequence. The conversion rate may be modified by the Conversion Rate bits found in the Configuration Register (03h). When the conversion rate is modified a delay is inserted between conversions, the actual conversion time remains at 66ms (26 ms for each remote and 14 ms for local). Different conversion rates will cause the LM95221 to draw different amounts of supply current as shown in Figure 2. Remote temperature data is represented by an 11-bit, two’s complement word or unsigned binary word with an LSb (Least Significant Bit) equal to 0.125˚C. The data format is a left justified 16-bit word available in two 8-bit registers. Unused bits will always report "0". 11-bit, 2’s complement (10-bit plus sign) Temperature Digital Output Binary Hex +125˚C 0111 1101 0000 0000 7D00h +25˚C 0001 1001 0000 0000 1900h 0100h +1˚C 0000 0001 0000 0000 +0.125˚C 0000 0000 0010 0000 0020h 0˚C 0000 0000 0000 0000 0000h −0.125˚C 1111 1111 1110 0000 FFE0h −1˚C 1111 1111 0000 0000 FF00h −25˚C 1110 0111 0000 0000 E700h −55˚C 1100 1001 0000 0000 C900h 11-bit, unsigned binary Temperature +255.875˚C 20094306 Digital Output Binary Hex 1111 1111 1110 0000 FFE0h +255˚C 1111 1111 0000 0000 FF00h +201˚C 1100 1001 0000 0000 C900h FIGURE 2. Conversion Rate Effect on Power Supply Current +125˚C 0111 1101 0000 0000 7D00h +25˚C 0001 1001 0000 0000 1900h +1˚C 0000 0001 0000 0000 0100h 1.2 POWER-ON-DEFAULT STATES LM95221 always powers up to these known default states. The LM95221 remains in these states until after the first conversion. 1. Command Register set to 00h 2. Local Temperature set to 0˚C 3. Remote Diode Temperature set to 0˚C until the end of the first conversion 4. Status Register depends on state of thermal diode inputs 5. Configuration register set to 00h; continuous conversion, time = 66ms +0.125˚C 0000 0000 0010 0000 0020h 0˚C 0000 0000 0000 0000 0000h Local Temperature data is represented by a 10-bit, two’s complement word with an LSb (Least Significant Bit) equal to 0.25˚C. The data format is a left justified 16-bit word available in two 8-bit registers. Unused bits will always report "0". Local temperature readings greater than +127.875˚C are not clamped to +127.875˚C, they will roll-over to negative temperature readings. Temperature 1.3 SMBus INTERFACE The LM95221 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBDAT line is bidirectional. The LM95221 never drives the SMBCLK line and it does not support clock stretching. According to SMBus www.national.com 8 Digital Output Binary Hex +125˚C 0111 1101 0000 0000 7D00h +25˚C 0001 1001 0000 0000 1900h 0100h +1˚C 0000 0001 0000 0000 +0.125˚C 0000 0000 0010 0000 0020h 0˚C 0000 0000 0000 0000 0000h Temperature set to “00”, the location for the Read Local Temperature Register. The Command Register latches the last location it was set to. Each data register in the LM95221 falls into one of four types of user accessibility: 1. Read only 2. Write only (Continued) Digital Output Binary Hex −0.25˚C 1111 1111 1100 0000 FFE0h −1˚C 1111 1111 0000 0000 FF00h −25˚C 1110 0111 0000 0000 E700h −55˚C 1100 1001 0000 0000 C900h 3. Write/Read same address 4. Write/Read different address A Write to the LM95221 will always include the address byte and the command byte. A write to any register requires one data byte. 1.5 SMBDAT OPEN-DRAIN OUTPUT Reading the LM95221 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 Registers because that will be the data most frequently read from the LM95221), then the read can simply consist of an address byte, followed by retrieving the data byte. The SMBDAT output is an open-drain output and does not have internal pull-ups. A “high” level will not be observed on this pin until pull-up current is provided by 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 without effecting the SMBus desired data rate. This will minimize any internal temperature reading errors due to internal heating of the LM95221. The maximum resistance of the pull-up to provide a 2.1V high level, based on LM95221 specification for High Level Output Current with the supply voltage at 3.0V, is 82kΩ(5%) or 88.7kΩ(1%). 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 LM95221 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). It takes the LM95221 66 ms to measure the temperature of the remote diodes and internal diode. When retrieving all 11 bits from a previous remote diode temperature measurement, the master must insure that all 11 bits are from the same temperature conversion. This may be achieved by reading the MSB register first. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be locked in and override the previous LSB value locked-in. 1.6 DIODE FAULT DETECTION The LM95221 is equipped with operational circuitry designed to detect fault conditions concerning the remote diodes. In the event that the D+ pin is detected as shorted to GND, D−, VDD or D+ is floating, the Remote Temperature reading is –128.000 ˚C if signed format is selected and +255.875 if unsigned format is selected. In addition, the appropriate status register bits RD1M or RD2M (D1 or D0) are set. 1.7 COMMUNICATING with the LM95221 The data registers in the LM95221 are selected by the Command Register. At power-up the Command Register is 9 www.national.com LM95221 1.0 Functional Description LM95221 1.0 Functional Description (Continued) 20094310 (a) Serial Bus Write to the internal Command Register followed by a the Data Byte 20094311 (b) Serial Bus Write to the Internal Command Register 20094312 (c) Serial Bus Read from a Register with the Internal Command Register preset to desired value. 20094314 (d) Serial Bus Write followed by a Repeat Start and Immediate Read FIGURE 3. SMBus Timing Diagrams www.national.com 10 2. (Continued) 1.8 SERIAL INTERFACE RESET In the event that the SMBus Master is RESET while the LM95221 is transmitting on the SMBDAT line, the LM95221 must be returned to a known state in the communication protocol. This may be done in one of two ways: 1. When SMBDAT is HIGH, have the master initiate an SMBus start. The LM95221 will respond properly to an SMBus start condition at any point during the communication. After the start the LM95221 will expect an SMBus Address address byte. 1.9 ONE-SHOT CONVERSION The One-Shot register is used to initiate a single conversion and comparison cycle when the device is in standby mode, after which the device returns to standby. This is not a data register and it is the write operation that causes the one-shot conversion. The data written to this address is irrelevant and is not stored. A zero will always be read from this register. When SMBDAT is LOW, the LM95221 SMBus state machine resets to the SMBus idle state if either SMBDAT or SMBCLK are held low for more than 35ms (tTIMEOUT). Note that according to SMBus specification 2.0 all devices are to timeout when either the SMBCLK or SMBDAT lines are held low for 25-35ms. Therefore, to insure a timeout of all devices on the bus the SMBCLK or SMBDAT lines must be held low for at least 35ms. 2.0 LM95221 Registers 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 P6 P5 P4 P3 P2 P1 P0 Command P0-P7: Command Register Summary Name Command (Hex) Power-On Default Value (Hex) Read/Write # of used bits Comments Status Register 02h - RO 3 2 status bits and 1 busy bit Configuration Register 03h 00h R/W 4 Includes conversion rate control 1-shot 0Fh - WO - Activates one conversion for all 3 channels if the chip is in standby mode (i.e. RUN/STOP bit = 1). Data transmitted by the host is ignored by the LM95221. Local Temperature MSB 10h - RO 8 Remote Temperature 1 MSB 11h - RO 8 Remote Temperature 2 MSB 12h - RO 8 Local Temperature LSB 20h - RO 2 All unused bits will report zero Remote Temperature 1 LSB 21h - RO 3 All unused bits will report zero Remote Temperature 2 LSB 22h - RO 3 All unused bits will report zero Manufacturer ID FEh 01h RO Revision ID FFh 61h RO 11 www.national.com LM95221 1.0 Functional Description LM95221 2.0 LM95221 Registers (Continued) 2.1 STATUS REGISTER (Read Only Address 02h): D7 D6 D5 Busy D4 D3 D2 Reserved 0 0 0 0 D1 D0 RD2M RD1M 0 Bits Name Description 7 Busy When set to "1" the part is converting. 6-2 Reserved Reports "0" when read. 1 Remote diode 2 missing (RD2M) Remote Diode 2 is missing. (i.e. D2+ shorted to VDD, Ground or D2-, or D2+ is floating). Temperature Reading is FFE0h which converts to 255.875 ˚C if unsigned format is selected or 8000h which converts to –128.000 ˚C if signed format is selected. 0 Remote diode 1 missing (RD1M) Remote Diode 1 is missing. (i.e. D1+ shorted to VDD, Ground or D1-, or D1+ is floating). Temperature Reading is FFE0h which converts to 255.875 ˚C if unsigned format is selected or 8000h which converts to –128.000 ˚C if signed format is selected. 2.2 CONFIGURATION REGISTER (Read Address 03h /Write Address 03h): D7 D6 D5 D4 D3 D2 D1 D0 0 RUN/STOP CR1 CR0 0 R2DF R1DF 0 Bits Name Description 7 Reserved Reports "0" when read. 6 RUN/STOP Logic 1 disables the conversion and puts the part in standby mode. Conversion can be activated by writing to one-shot register. 5-4 Conversion Rate (CR1:CR0) 00: continuous mode 66ms, 15 Hz (typ) 01: converts every 200ms, 5 Hz (typ) 10: converts every 1 second, 1 Hz (typ) 11: converts every 3 seconds, 1⁄3 Hz (typ) Note: typically a remote diode conversion takes 26 ms and local conversion takes 14 ms. 3 Reserved Reports "0" when read. 2 Remote 2 Data Format (R2DF) Logic 0: unsigned Temperature format (0 ˚C to +255.875 ˚C) Logic 1: signed Temperature format (-128 ˚C to +127.875 ˚C) 1 Remote 1 Data Format (R1DF) Logic 0: unsigned Temperature format (0 ˚C to +255.875 ˚C) Logic 1: signed Temperature format (-128 ˚C to +127.875 ˚C) 0 Reserved Reports "0" when read. Power up default is with all bits “0” (zero) www.national.com 12 LM95221 2.0 LM95221 Registers (Continued) 2.3 LOCAL and REMOTE MSB and LSB TEMPERATURE REGISTERS Local Temperature MSB (Read Only Address 10h) 9-bit plus sign format: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value SIGN 64 32 16 8 4 2 1 Temperature Data: LSb = 1˚C. Local Temperature LSB (Read Only Address 20h) 9-bit plus sign format: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value 0.5 0.25 0 0 0 0 0 0 Temperature Data: LSb = 0.25˚C. Remote Temperature MSB (Read Only Address 11h, 12h) 10 bit plus sign format: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value SIGN 64 32 16 8 4 2 1 Temperature Data: LSb = 1˚C. (Read Only Address 11h, 12h) 11-bit unsigned format: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value 128 64 32 16 8 4 2 1 Temperature Data: LSb = 1˚C. Remote Temperature LSB (Read Only Address 21, 22h) 10-bit plus sign or 11-bit unsigned binary formats: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value 0.5 0.25 0.125 0 0 0 0 0 Temperature Data: LSb = 0.125˚C. For data synchronization purposes, the MSB register should be read first if the user wants to read both MSB and LSB registers. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be locked in and override the previous LSB value locked-in. 2.4 MANUFACTURERS ID REGISTER (Read Address FEh) The default value is 01h. 2.5 DIE REVISION CODE REGISTER (Read Address FFh) Value to be determined. This register will increment by 1 every time there is a revision to the die by National Semiconductor. 13 www.national.com LM95221 • VBE = Base Emitter Voltage drop In the active region, the -1 term is negligible and may be eliminated, yielding the following equation 3.0 Applications Hints The LM95221 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 LM95221’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 LM95221 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 LM95221’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 LM95221’s temperature. The LM95221 has been optimized to measure the remote thermal diode with a non-ideality of 1.008 and a series resistance of 2.7Ω. The thermal diode on the Pentium 4 processor on the 90 nm process has a typical non-ideality of 1.011 and a typical series resistance of 3.33Ω. Therefore, when measuring this thermal diode with the LM95221 a typical offset of +1.5˚C will be observed. This offset can be compensated for easily by subracting 1.5˚C from the LM95221’s readings. 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. 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. When measuring a diode-connected 2N3904, with an LM95221, an offset of -3.25˚C will be observed. This offset can simply be added to the LM95221’s reading: T2N3904 = TLM95221 + 3.25˚C In the above equation, η and IS are dependant upon the process that was used in the fabrication of the particular diode. By forcing two currents with a very controlled ratio (N) and measuring the resulting voltage difference, it is possible to eliminate the IS term. Solving for the forward voltage difference yields the relationship: The voltage seen by the LM95221 also includes the IFRS voltage drop of the series resistance. The non-ideality factor, η, is the only other parameter not accounted for and depends on the diode that is used for measurement. Since ∆VBE is proportional to both η and T, the variations in η 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 4 and Mobile Pentium Processor-M Intel specifies a ± 0.1% variation in η from part to part. As an example, assume a temperature sensor has an accuracy specification of ± 1˚C at room temperature of 25 ˚C and the process used to manufacture the diode has a non-ideality variation of ± 0.1%. The resulting accuracy of the temperature sensor at room temperature will be: TACC = ± 1˚C + ( ± 0.1% of 298 ˚K) = ± 1.4 ˚C The additional inaccuracy in the temperature measurement caused by η, can be eliminated if each temperature sensor is calibrated with the remote diode that it will be paired with. η, non-ideality Processor Family min typ max Pentium II 1 1.0065 1.0173 3.1 DIODE NON-IDEALITY Pentium III CPUID 67h 1 1.0065 1.0125 3.1.1 Diode Non-Ideality Factor Effect on Accuracy When a transistor is connected as a diode, the following relationship holds for variables VBE, T and If: Pentium III CPUID 1.0057 68h/PGA370Socket/Celeron where: 0.9933 1.0045 1.0368 Pentium 4, 478 pin 0.9933 1.0045 1.0368 Pentium 4 on 0.13 micron process, 2-3.06GHz 1.0011 1.0021 1.0030 3.64 Ω Pentium 4 on 90 nm process • • www.national.com AMD Athlon MP model 6 14 3.33 Ω 1.011 1.00151 1.00220 1.00289 3.06 Ω MMBT3904 q = 1.6x10−19 Coulombs (the electron charge), T = Absolute Temperature in Kelvin k = 1.38x10−23joules/K (Boltzmann’s constant), η is the non-ideality factor of the process the diode is manufactured on, IS = Saturation Current and is process dependent, If= Forward Current through the base emitter junction 1.0125 Pentium 4, 423 pin Pentium M Processor (Centrino) • • • • 1.008 Series R 1.003 1.002 1.008 1.016 possible to the LM95221’s D+ and D− pins. Make sure the traces to the 2.2nF capacitor are matched. (Continued) 3.1.2 Compensating for Diode Non-Ideality In order to compensate for the errors introduced by nonideality, the temperature sensor is calibrated for a particular processor. National Semiconductor temperature sensors are always calibrated to the typical non-ideality of a given processor type. The LM95221 is calibrated for a non-ideality of 1.008 and a series resistance of 2.7Ω. When a temperature sensor calibrated for a particular processor type is used with a different processor type or a given processor type has a non-ideality that strays from the typical, errors are introduced. Temperature errors associated with non-ideality may be reduced in a specific temperature range of concern through use of an offset calibration accomplished through software. Please send an email to [email protected] requesting further information on our recommended offset value for different processor types. 3. Ideally, the LM95221 should be placed within 10cm of the Processor diode pins with the traces being as straight, short and identical as possible. Trace resistance of 1Ω can cause as much as 1˚C of error. This error can be compensated by using simple software offset compensation. 4. 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. 5. Avoid routing diode traces in close proximity to power supply switching or filtering inductors. 6. 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 LM95221’s GND pin is as close as possible to the Processors GND associated with the sense diode. 3.2 PCB LAYOUT FOR MINIMIZING NOISE 9. 20094317 Leakage current between D+ and GND and between D+ and D− should be kept to a minimum. Thirteen nanoamperes of leakage can cause as much as 0.2˚C of error in the diode temperature reading. Keeping the printed circuit board as clean as possible will minimize leakage current. Noise coupling into the digital lines greater than 400mVp-p (typical hysteresis) and undershoot less than 500mV below GND, may prevent successful SMBus communication with the LM95221. 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 RC lowpass filter with a 3db corner frequency of about 40MHz is included on the LM95221’s SMBCLK input. Additional resistance can be added in series with the SMBDAT 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 SMBDAT and SMBCLK lines. FIGURE 4. Ideal Diode Trace Layout 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 LM95221 can cause temperature conversion errors. Keep in mind that the signal level the LM95221 is trying to measure is in microvolts. The following guidelines should be followed: 1. VDD should be bypassed with a 0.1µF capacitor in parallel with 100pF. The 100pF capacitor should be placed as close as possible to the power supply pin. A bulk capacitance of approximately 10µF needs to be in the near vicinity of the LM95221. 2. A 2.2nF diode bypass capacitor is required to filter high frequency noise. Place the 2.2nF capacitor as close as 15 www.national.com LM95221 3.0 Applications Hints LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead Molded Mini-Small-Outline Package (MSOP), JEDEC Registration Number MO-187 Order Number LM95221CIMM or LM95221CIMMX NS Package Number MUA08A 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. 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. BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. National Semiconductor Americas Customer Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: [email protected] National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: [email protected] Tel: 81-3-5639-7560 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.