LM71

LM71 SPI/MICROWIRE™ 13-Bit Plus Sign Temperature Sensor February 2005 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. n Electronic Test Equipment n Vending Machines 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 j Temperature 2.65V to 5.5V operating 300 µA (typ) 550 µA (max) Applications n n n n n System Thermal Management Personal Computers Portable Electronic Devices Disk Drives Office Electronics Accuracy j Temperature −10˚C to +65˚C −40˚C to 150˚C ± 1.5˚C (max) +3/− 2˚C (max) 31.25 m˚C Resolution Simplified Block Diagram 20031701 TRI-STATE ® is a registered trademark of National Semiconductor Corporation. © 2005 National Semiconductor Corporation DS200317 www.national.com LM71 Connection Diagrams SOT23-5 LLP-6 No Pull-Back 20031728 20031702 TOP VIEW NS Package Number MF05A TOP VIEW NS Package Number SDE06A Ordering Information Order Number LM71CIMF LM71CISD Package Marking T16C LM71C NS Package Number MF05A SDE06A Supply Voltage 2.65V to 5.5V 2.65V to 5.5V Transport Media 3000 Units in Tape and Reel 4500 Units in Tape and Reel www.national.com 2 LM71 Pin Descriptions Label CS GND SI/O SC V+ Pin Number SOT23-5 1 2 3 4 5 LLP-6 4 2, 5 3 1 6 Chip Select input Power Supply Ground Slave Input/Output - Serial bus bi-directional data line. Shmitt trigger input. Slave Clock - Serial bus clock Shmitt trigger input line Positive Supply Voltage Input From controller Connect all GND Pins to ground From and to controller From controller DC voltage from 2.65V to 5.5V. Bypass with a 0.1 µF ceramic capacitor. Function Typical Connection Typical Application 20031703 FIGURE 1. COP Microcontroller Interface 3 www.national.com LM71 Absolute Maximum Ratings (Note 1) Supply Voltage Voltage at any Pin Input Current at any Pin (Note 2) Storage Temperature SOT23-5 Package (Note 3) Vapor Phase (60 seconds) Infrared (15 seconds) LLP-6 Package (Note 3) Infrared (5 seconds) Soldering Information, Lead Temperature 215˚C 220˚C 215˚C −0.3V to 6.0V −0.3V to V+ + 0.3V 5 mA −65˚C to +150˚C ESD Susceptibility (Note 4) Human Body Model Machine Model 2000V 200V Operating Ratings Specified Temperature Range (Note 5) LM71CIMF, LM71CISD Supply Voltage Range (+VS) LM71CIMF, LM71CISD +2.65V to +5.5V TMIN to TMAX −40˚C to +150˚C 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. Parameter Conditions Typical (Note 7) LM71CIMF LM71CISD Limits (Note 8) Units (Limit) ˚C (max) ˚C (max) ˚C (max) Bits ˚C 270 550 ms (max) µA (max) Temperature Error (Note 6) TA = −10˚C to +65˚C TA = −40˚C to +85˚C TA = −40˚C to +150˚C ± 1.5 ± 2.0 +3/−2 14 0.03125 Resolution Temperature Conversion Time Quiescent Current (Note 9) Serial Bus Inactive 200 300 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 Logical “1” Input Voltage Logical “0” Input Voltage Input Hysteresis Voltage IIN(1) IIN(0) CIN VOH VOL IO_TRI-STATE Logical “1” Input Current Logical “0” Input Current All Digital Inputs High Level Output Voltage Low Level Output Voltage TRI-STATE Current ® Output Conditions Typical (Note 7) Limits (Note 8) V+ x 0.7 V+ + 0.3 −0.3 V x 0.3 + Units (Limit) V (min) V (max) V (min) V (max) V (min) µA (max) µA (min) pF V (min) V (max) µA (min) µA (max) V+ = 3.0V to 3.6V VIN = V+ VIN = 0V IOH = −400 µA IOL = +2 mA VO = GND V O = V+ 0.4 0.005 −0.005 20 0.33 3.0 −3.0 2.4 0.4 −1 +1 Leakage www.national.com 4 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 t1 t2 t3 t4 t5 t6 t7 SC (Clock) Period CS Low to SC (Clock) High Set-Up Time CS Low to Data Out (SO) Delay SC (Clock) Low to Data Out (SO) Delay CS High to Data Out (SO) TRI-STATE SC (Clock) High to Data In (SI) Hold Time Data In (SI) Set-Up Time to SC (Clock) High Parameter Conditions Typical (Note 7) Limits (Note 8) 0.16 DC 100 70 70 200 50 30 Units (Limit) µs (min) (max) ns (min) ns (max) ns (max) ns (max) ns (min) 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 LM71CIMF LM71CISD NS Package Number MF05A SDE06A Thermal Resistance (θJA) 250˚C/W 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 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 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 • 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. www.national.com 8 LM71 1.0 Functional Description 1.3 TEMPERATURE DATA FORMAT (Continued) 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 +125˚C +25˚C +0.03125˚C 0˚C −0.03125˚C −25˚C −40˚C Digital Output Binary 0100 1011 0000 0011 0011 1110 1000 0011 0000 1100 1000 0011 0000 0000 0000 0111 0000 0000 0000 0011 1111 1111 1111 1111 1111 0011 1000 0011 1110 1100 0000 0011 Hex 4B03 3E83 0C83 0007 0003 FFFF F383 EC03 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. 1.4 SHUTDOWN MODE/MANUFACTURER’S ID 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 X D14 X D13 X D12 X D11 X D10 X D9 X D8 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 D11 Bit 9 D10 Bit 8 D9 Bit 7 D8 Bit 6 D7 Bit 5 D6 Bit 4 D5 Bit 3 D4 Bit 2 D3 Bit1 D2 LSB D1 1 D0 1 Bit 12 Bit 11 Bit 10 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 1 D14 0 D13 0 D12 0 D11 0 D10 0 D9 0 D8 0 D7 0 D6 0 D5 0 D4 0 D3 1 D2 1 D1 1 D0 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 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 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- 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. 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 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. For the most current product information visit us at www.national.com. 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. 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