LM71 SPI/MICROWIRE™ 13-Bit Plus Sign Temperature Sensor General Description The LM71 is a low-power, high-resolution digital temperature sensor with an SPI and MICROWIRE compatible interface, available in the 5-pin SOT23 or the 6-pin LLP (no pull back) package. The host can query the LM71 at any time to read temperature. Its low operating current is useful in systems where low power consumption is critical. The LM71 has 13-bit plus sign temperature resolution (0.03125˚C per LSB) while operating over a temperature range of −40˚C to +150˚C. The LM71’s 2.65V to 5.5V supply voltage range, fast conversion rate, low supply current, and simple SPI interface make it ideal for a wide range of applications. Features n SOT23-5 or No-Pull-Back LLP-6 Packages n Operates over a full −40˚C to +150˚C range n SPI and MICROWIRE Bus interface Key Specifications j Supply Voltage j Supply Current 2.65V to 5.5V operating 300 µA (typ) 550 µA (max) j Temperature Applications n n n n n n Electronic Test Equipment n Vending Machines Accuracy System Thermal Management Personal Computers Portable Electronic Devices Disk Drives Office Electronics −10˚C to +65˚C ± 1.5˚C (max) −40˚C to 150˚C +3/− 2˚C (max) j Temperature 31.25 m˚C Resolution Simplified Block Diagram 20031701 MICROWIRE™ is a trademark of National Semiconductor Corporation. TRI-STATE ® is a registered trademark of National Semiconductor Corporation. © 2004 National Semiconductor Corporation DS200317 www.national.com LM71 SPI/MICROWIRE 13-Bit Plus Sign Temperature Sensor March 2004 LM71 Connection Diagrams SOT23-5 LLP-6 No Pull-Back 20031728 TOP VIEW NS Package Number SDE06A 20031702 TOP VIEW NS Package Number MF05A Ordering Information Order Number Package Marking NS Package Number Supply Voltage Transport Media LM71CIMF T16C MF05A 2.65V to 5.5V 3000 Units in Tape and Reel LM71CISD LM71C SDE06A 2.65V to 5.5V 4500 Units in Tape and Reel www.national.com 2 LM71 Pin Descriptions Label Pin Number SOT23-5 Function Typical Connection LLP-6 CS 1 4 GND 2 2, 5 SI/O 3 SC V+ Chip Select input From controller Power Supply Ground Connect all GND Pins to ground 3 Slave Input/Output - Serial bus bi-directional data line. Shmitt trigger input. From and to controller 4 1 Slave Clock - Serial bus clock Shmitt trigger input line From controller 5 6 Positive Supply Voltage Input DC voltage from 2.65V to 5.5V. Bypass with a 0.1 µF ceramic capacitor. Typical Application 20031703 FIGURE 1. COP Microcontroller Interface 3 www.national.com LM71 Absolute Maximum Ratings (Note 1) Supply Voltage ESD Susceptibility (Note 4) Human Body Model Machine Model −0.3V to 6.0V −0.3V to V+ + 0.3V Voltage at any Pin Input Current at any Pin (Note 2) 5 mA Storage Temperature 2000V 200V Operating Ratings −65˚C to +150˚C Soldering Information, Lead Temperature Specified Temperature Range (Note 5) SOT23-5 Package (Note 3) Vapor Phase (60 seconds) Infrared (15 seconds) 215˚C 220˚C LLP-6 Package (Note 3) Infrared (5 seconds) 215˚C TMIN to TMAX LM71CIMF, LM71CISD −40˚C to +150˚C Supply Voltage Range (+VS) LM71CIMF, LM71CISD +2.65V to +5.5V Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications apply for V+ = 2.65V to 3.6V (Note 6). Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted. LM71CIMF LM71CISD Limits (Note 8) Units (Limit) TA = −10˚C to +65˚C ± 1.5 ˚C (max) TA = −40˚C to +85˚C ± 2.0 ˚C (max) TA = −40˚C to +150˚C +3/−2 ˚C (max) Parameter Temperature Error (Note 6) Typical (Note 7) Conditions Resolution 14 0.03125 Bits ˚C Temperature Conversion Time (Note 9) 200 270 ms (max) Quiescent Current Serial Bus Inactive 300 550 µA (max) Logic Electrical Characteristics DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for V+ = 2.65V to 3.6V (Note 6). Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted. Symbol VIN(1) VIN(0) Parameter Conditions Typical (Note 7) Logical “1” Input Voltage Logical “0” Input Voltage Limits (Note 8) V+ x 0.7 V (min) V+ + 0.3 V (max) −0.3 V (min) + V x 0.3 Input Hysteresis Voltage V+ = 3.0V to 3.6V IIN(1) Logical “1” Input Current IIN(0) Logical “0” Input Current CIN All Digital Inputs VOH High Level Output Voltage VOL Low Level Output Voltage IO_TRI-STATE www.national.com TRI-STATE Current ® Output V (max) 0.4 0.33 V (min) VIN = V+ 0.005 3.0 µA (max) VIN = 0V −0.005 −3.0 µA (min) IOH = −400 µA 2.4 V (min) IOL = +2 mA 0.4 V (max) VO = GND V O = V+ −1 +1 µA (min) µA (max) 20 Leakage Units (Limit) 4 pF LM71 Logic Electrical Characteristics (Continued) SERIAL BUS DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for V+ = 2.65V to 3.6V (Note 6); CL (load capacitance) on output lines = 100 pF unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted. Symbol Parameter Conditions Typical (Note 7) Limits (Note 8) Units (Limit) µs (min) (max) t1 SC (Clock) Period 0.16 DC t2 CS Low to SC (Clock) High Set-Up Time 100 ns (min) t3 CS Low to Data Out (SO) Delay 70 ns (max) t4 SC (Clock) Low to Data Out (SO) Delay 70 ns (max) t5 CS High to Data Out (SO) TRI-STATE 200 ns (max) t6 SC (Clock) High to Data In (SI) Hold Time 50 ns (min) t7 Data In (SI) Set-Up Time to SC (Clock) High 30 ns (min) 20031704 FIGURE 2. Data Output Timing Diagram 20031705 FIGURE 3. TRI-STATE Data Output Timing Diagram 5 www.national.com LM71 Logic Electrical Characteristics (Continued) 20031706 FIGURE 4. Data Input Timing Diagram 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 > +VS) the current at that pin should be limited to 5 mA. 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 kΩ resistor. Machine model, 200 pF discharged directly into each pin. Note 5: The life expectancy of the LM71 will be reduced when operating at elevated temperatures. LM71 θJA (thermal resistance, junction-to-ambient) when attached to a printed circuit board with 2 oz. foil is summarized in the table below: Device Number NS Package Number Thermal Resistance (θJA) LM71CIMF MF05A 250˚C/W LM71CISD SDE06A 57.6˚C/W Note 6: The LM71 will operate properly over the V+ supply voltage range of 2.65V to 5.5V. Note 7: Typicals are at TA = 25˚C and represent most likely parametric norm. Note 8: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 9: This specification is provided only to indicate how often temperature data is updated. The LM71 can be read at any time without regard to conversion state (and will yield last conversion result). A conversion in progress will not be interrupted. The output shift register will be updated at the completion of the read and a new conversion restarted. Note 10: For best accuracy, minimize output loading. Higher sink currents can affect sensor accuracy with internal heating. This can cause an error of 0.64˚C at full rated sink current and saturation voltage based on junction-to-ambient thermal resistance. www.national.com 6 LM71 Electrical Characteristics 20031708 FIGURE 5. Temperature-to-Digital Transfer Function (Non-linear scale for clarity) TRI-STATE Test Circuit 20031707 FIGURE 6. 7 www.national.com LM71 Typical Performance Characteristics Static Supply Current vs. Temperature Temperature Error 20031796 20031797 time during the transmit phase. If CS is brought low in the middle of a conversion the LM71 will complete the conversion and the output shift register will be updated after CS is brought back high. The receive phase of a communication starts after 16 SC periods. CS can remain low for 32 SC cycles. The LM71 will read the data available on the SI/O line on the rising edge of the serial clock. Input data is to an 8-bit shift register. The part will detect the last eight bits shifted into the register. The receive phase can last up to 16 SC periods. All ones must be shifted in order to place the part into shutdown. All zeros must be shifted in order to place the LM71 into continuous conversion mode. Only the following codes should be transmitted to the LM71: • 00 hex for continuous conversion • FF hex for shutdown Another code may place the part into a test mode. Test modes are used by National Semiconductor to thoroughly test the function of the LM71 during production testing. Only eight bits have been defined above since only the last eight transmitted are detected by the LM71, before CS is taken HIGH. The following communication can be used to determine the Manufacturer’s/Device ID and then immediately place the part into continuous conversion mode. With CS continuously low: • Read 16 bits of temperature data • Write 16 bits of data commanding shutdown • Read 16 bits of Manufacture’s/Device ID data 1.0 Functional Description The LM71 temperature sensor incorporates a temperature sensor and 13-bit plus sign ∆Σ ADC (Delta-Sigma Analog-toDigital Converter). Compatibility of the LM71’s three wire serial interface with SPI and MICROWIRE allows simple communications with common microcontrollers and processors. Shutdown mode can be used to optimize current drain for different applications. A Manufacture’s/Device ID register identifies the LM71 as National Semiconductor product. 1.1 POWER UP AND POWER DOWN The LM71 always powers up in a known state. The power up default condition is continuous conversion mode. Immediately after power up the LM71 will output an erroneous code until the first temperature conversion has completed. When the supply voltage is less than about 1.6V (typical), the LM71 is considered powered down. As the supply voltage rises above the nominal 1.6V power up threshold, the internal registers are reset to the power up default state described above. 1.2 SERIAL BUS INTERFACE The LM71 operates as a slave and is compatible with SPI or MICROWIRE bus specifications. Data is clocked out on the falling edge of the serial clock (SC), while data is clocked in on the rising edge of SC. A complete transmit/receive communication will consist of 32 serial clocks. The first 16 clocks comprise the transmit phase of communication, while the second 16 clocks are the receive phase. When CS is high SI/O will be in TRI-STATE. Communication should be initiated by taking chip select (CS) low. This should not be done when SC is changing from a low to high state. Once CS is low the serial I/O pin (SI/O) will transmit the first bit of data. The master can then read this bit with the rising edge of SC. The remainder of the data will be clocked out by the falling edge of SC. CS can be taken high at any www.national.com • Write 8 to 16 bits of data commanding Conversion Mode • Take CS HIGH. Note that 300 ms will have to pass for a conversion to complete before the LM71 actually transmits temperature data. 8 sary to be read to determine temperature condition. For instance, if the first four bits of the temperature data indicate an overtemperature condition, the host processor could immediately take action to remedy the excessive temperatures. (Continued) 1.3 TEMPERATURE DATA FORMAT Temperature data is represented by a 14-bit, two’s complement word with an LSB (Least Significant Bit) equal to 0.03125˚C: Temperature +150˚C 1.4 SHUTDOWN MODE/MANUFACTURER’S ID Digital Output Binary Hex 0100 1011 0000 0011 4B03 +125˚C 0011 1110 1000 0011 3E83 +25˚C 0000 1100 1000 0011 0C83 +0.03125˚C 0000 0000 0000 0111 0007 0˚C 0000 0000 0000 0011 0003 −0.03125˚C 1111 1111 1111 1111 FFFF −25˚C 1111 0011 1000 0011 F383 −40˚C 1110 1100 0000 0011 EC03 Shutdown mode is enabled by writing XX FF to the LM71 as shown in Figure 7c. The serial bus is still active when the LM71 is in shutdown. When in shutdown mode the LM71 always will output 1000 0000 0000 1111. This is the manufacturer’s/Device ID information. The first 5-bits of the field (1000 0XXX) are reserved for manufacturer’s ID. 1.5 INTERNAL REGISTER STRUCTURE The LM71 has three registers, the temperature register, the configuration register and the manufacturer’s/device identification register. The temperature and manufacturer’s/device identification registers are read only. The configuration register is write only. The first data byte is the most significant byte with most significant bit first, permitting only as much data as neces1.5.1 Configuration Register (Selects shutdown or continuous conversion modes): (Write Only): D15 D14 D13 D12 D11 D10 D9 D8 X X X X X X X X D7 D6 D5 D4 D3 D2 D1 D0 Shutdown D0–D15 set to XX FF hex enables shutdown mode. D0–D15 set to 00 00 hex sets Continuous conversion mode. Note: setting D0-D15 to any other values may place the LM70 into a manufacturer’s test mode, upon which the LM71 will stop responding as described. These test modes are to be used for National Semiconductor production testing only. See Section 1.2 Serial Bus Interface for a complete discussion. 1.5.2 Temperature Register (Read Only): D15 MSB D14 D13 D12 Bit 12 Bit 11 Bit 10 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit1 LSB 1 1 D0–D1: Logic 1 will be output on SI/0. D2–D15: Temperature Data. One LSB = 0.03125˚C. Two’s complement format. 1.5.3 Manufacturer/Device ID Register (Read Only): D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 1 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 D0–D1: Logic 1 will be output on SI/0. D2–D15: Manufacturer’s/Device ID Data. This register is accessed whenever the LM71 is in shutdown mode. 9 www.national.com LM71 1.0 Functional Description LM71 2.0 Serial Bus Timing Diagrams 20031714 a) Reading Continuous Conversion - Single Eight-Bit Frame 20031715 b) Reading Continuous Conversion - Two Eight-Bit Frames 20031718 c) Writing Shutdown Control FIGURE 7. Timing Diagrams cantly different from the printed circuit board temperature, it will have a small effect on the measured temperature. In probe-type applications, the LM71 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LM71 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold temperatures where condensation can occur. Printed-circuit coatings and varnishes such as Humiseal and epoxy paints or dips are often used to insure that moisture cannot corrode the LM71 or its connections. 3.0 Application Hints To get the expected results when measuring temperature with an integrated circuit temperature sensor like the LM71, it is important to understand that the sensor measures its own die temperature. For the LM71, the best thermal path between the die and the outside world is through the LM71’s pins. In the SOT23 package, all the pins on the LM71 will have an equal effect on the die temperature. Because the pins represent a good thermal path to the LM71 die, the LM71 will provide an accurate measurement of the temperature of the printed circuit board on which it is mounted. There is a less efficient thermal path between the plastic package and the LM71 die. If the ambient air temperature is signifi- www.national.com 10 LM71 4.0 Typical Applications 20031720 FIGURE 8. Temperature monitor using Intel 196 processor 20031719 FIGURE 9. LM71 digital input control using micro-controller’s general purpose I/O. 11 www.national.com LM71 Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM71Top View CIMF NS Package Number MF05A www.national.com 12 LM71 SPI/MICROWIRE 13-Bit Plus Sign Temperature Sensor Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Order Number LM71Bottom View CISD NS Package Number SDE06A 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. 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