LM95071 SPI/MICROWIRE 13-Bit Plus Sign Temperature Sensor General Description Features The LM95071 is a low-power, high-resolution digital temperature sensor with an SPI and MICROWIRE compatible interface, available in the 5-pin SOT23. The host can query the LM95071 at any time to read temperature. Its low operating current is useful in systems where low power consumption is critical. n Small SOT23-5 package saves space n Shutdown mode conserves power between temperature readings n Operates over a full −40˚C to +150˚C range n SPI and MICROWIRE Bus interface The LM95071 has 13-bit plus sign temperature resolution (0.03125˚C per LSB) while operating over a temperature range of −40˚C to +150˚C. Key Specifications The LM95071’s 2.4V 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. j Supply Current 2.4V to 5.5V operating 280 µA (typ) shutdown 6 µA (typ) 0˚C to 70˚C ± 1˚C (max) ± 2˚C (max) j Temperature Accuracy Applications n n n n n n j Supply Voltage −40˚C to 150˚C System Thermal Management Portable Electronic Devices Personal Computers Disk Drives Office Electronics Electronic Test Equipment j Temperature 0.03125 ˚C Resolution Simplified Block Diagram 20106501 TRI-STATE ® is a registered trademark of National Semiconductor Corporation. © 2005 National Semiconductor Corporation DS201065 www.national.com LM95071 13-Bit Plus Sign SPI/MICROWIRE Temperature Sensor February 2005 LM95071 Connection Diagram SOT23-5 20106502 TOP VIEW NS Package Number MF05A Ordering Information Order Number Top Mark NS Package Number Supply Voltage Transport Media LM95071CIMFX T18C MF05A 2.4V to 5.5V 3000 Units in Tape and Reel Pin Descriptions Pin Number Symbol Name Description 1 CS Chip Select input This pin receives an active-low signal from the controller to select the device. 2 GND Ground This is the power and signal ground return. 3 SI/O Serial Input/Output This serial, bi-directional, data bus pin transmits and receives signals to and from the controller. Schmitt trigger input in the input mode. 4 SC Serial bus clock This serial clock signal comes from the controller. Schmitt trigger input. 5 VDD Positive Supply Voltage Supply a DC voltage from 2.4V to 5.5V to this pin and bypass with a 0.1 µF ceramic capacitor to ground. Typical Application 20106503 FIGURE 1. COP Microcontroller Interface www.national.com 2 Supply Voltage Operating Ratings −0.3V to 6.0V Voltage at any Pin Specified Temperature Range (Note 5) −0.3V to VDD + 0.3V Input Current at any Pin (Note 2) Storage Temperature TMIN to TMAX LM95071CIMF 5 mA −40˚C to +150˚C Supply Voltage Range (VDD) −65˚C to +150˚C ESD Susceptibility (Note 4) Human Body Model Machine Model LM95071 Absolute Maximum Ratings (Note 1) LM95071CIMF 2.4V to +5.5V 2000V 200V Soldering process must comply with National Semiconductor’s Reflow Temperature Profile specifications. Refer to www.national.com/packaging. (Note 3) Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications apply for VDD = 3.3V . Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted. Parameter Temperature Error (Note 6) Line Regulation Typical (Note 7) Conditions LM95071CIMF Limits (Note 8) Units (Limit) VDD = 3.0V to 3.6V; TA = 0˚C to +70˚C ± 1.0 ˚C (max) VDD = 3.0V to 3.6V; TA = −40˚C to +150˚C ± 2.0 ˚C (max) VDD = 3.6V to 5.5V; TA = 0˚C to +70˚C +0.3 VDD = 3.0V to 2.4V; TA = 0˚C to +70˚C -0.6 ˚C/V (max) Resolution 14 0.03125 Bits ˚C Temperature Conversion Time (Note 9) 130 228 ms (max) Quiescent Current Operating, Serial Bus Inactive 280 520 µA (max) 6 28 µA (max) Shutdown Logic Electrical Characteristics DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for VDD = 2.4 to 5.5V (Note 6). Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted. Symbol Parameter VIN(1) Logical “1” Input Voltage VIN(0) Logical “0” Input Voltage Conditions Typical (Note 7) Limits (Note 8) Units (Limit) 0.7 x VDD V (min) VDD + 0.3 V (max) −0.3 V (min) 0.3 x VDD V (max) Input Hysteresis Voltage VDD = 3.0V to 3.6V 0.4 0.33 V (min) IIN(1) Logical “1” Input Current VIN = VDD 0.005 3.0 µA (max) IIN(0) Logical “0” Input Current VIN = 0V −0.005 −3.0 µA (min) CIN All Digital Inputs 20 pF VOH High Level Output Voltage IOH = −400 µA 2.25 V (min) VOL Low Level Output Voltage IOL = +1.6 mA 0.4 V (max) IO_TRI-STATE TRI-STATE ® Output Leakage Current VO = GND VO = VDD −1 +1 µA (min) µA (max) 3 www.national.com LM95071 Logic Electrical Characteristics (Continued) SERIAL BUS DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for VDD = 2.4V to 5.5V (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) t8 SC (Clock) High to CS High Hold Time 50 ns (min) 20106504 FIGURE 2. Data Output Timing Diagram 20106505 FIGURE 3. TRI-STATE Data Output Timing Diagram 20106506 FIGURE 4. Data Input Timing Diagram www.national.com 4 LM95071 Logic Electrical Characteristics (Continued) Notes 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. Note 3: Reflow temperature profiles are different for lead-free and non-lead-free packages. 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 LM95071 will be reduced when operating at elevated temperatures. LM95071 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) LM95071CIMF MF05A 250˚C/W Note 6: The LM95071 will operate properly over the VDD supply voltage range of 2.4V 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 LM95071 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. 5 www.national.com LM95071 Electrical Characteristics 20106508 FIGURE 5. Temperature-to-Digital Transfer Function (Non-linear scale for clarity) TRI-STATE Test Circuit 20106507 FIGURE 6. www.national.com 6 LM95071 Typical Performance Characteristics Static Supply Current vs. Temperature MaximumTemperature Error 20106525 20106526 Conversion Time vs Temperature Typical Output Noise at 30˚C 20106527 20106529 7 www.national.com LM95071 Another code may place the part into a test mode. Test modes are used by National Semiconductor to thoroughly test the function of the LM95071 during production testing. Only eight bits have been defined above since only the last eight transmitted are detected by the LM95071, before CS is taken HIGH. 1.0 Functional Description The LM95071 temperature sensor incorporates a temperature sensor and 13-bit-plus-sign ∆Σ ADC (Delta-Sigma Analog-to-Digital Converter). Compatibility of the LM95071’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 Manufacturer/Device ID register identifies the LM95071 as a National Semiconductor product. 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 1.1 POWER UP AND POWER DOWN The LM95071 always powers up in a known state and in the continuous conversion mode. Immediately after power up, the LM95071 will output an erroneous code until the first temperature conversion has completed. When the supply voltage is less than about 1.6V (typical), the LM95071 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. • Take CS HIGH. Note that 228 ms (max) will have to pass for a conversion to complete before the LM95071 actually transmits temperature data. 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: 1.2 SERIAL BUS INTERFACE The LM95071 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 communication is framed by falling and rising chip select (CS) signal. The CS signal should be held high for at least one clock cycle (160 ns minimum) between communications. The transmit-only communication (register read) consists of 16 clock cycles. A complete transmit/receive communication will consist of 32 serial clocks (see Figure 7). The first 16 clocks comprise the transmit phase of communication, while the second 16 clocks are the receive phase. Temperature +150˚C 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 LM95071 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 LM95071 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 LM95071 into continuous conversion mode. Only the following codes should be transmitted to the LM95071: • 00 hex for continuous conversion • FF hex for shutdown www.national.com 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 The first data byte is the most significant byte with most significant bit first, permitting only as much data as necessary 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 ID The master controller may enable the shutdown mode for the purpose of reducing power consumption or for reading the Manufacturer/Device ID information. The shutdown mode is enabled by writing XX FF hex to the LM95071 as shown in Figure 7c. The serial bus is still active when the LM95071 is in shutdown. When in shutdown mode the LM95071 always will output 1000 0000 0000 1111. This is the Manufacturer/Device ID information. The first 5-bits of the field (1000 0XXX) are reserved for the manufacturer ID. 8 LM95071 1.0 Functional Description (Continued) 1.5 INTERNAL REGISTER STRUCTURE The LM95071 has three registers: the temperature register, the configuration register and the Manufacturer/Device identification register. The temperature and Manufacturer/Device identification registers are read only. The configuration register is write only. 1.5.1 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 XX 00 hex sets continuous-conversion mode. Note: setting D0-D15 to any other values may place the LM95071 into a manufacturer’s test mode, upon which the LM95071 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/Device ID Data. This register is accessed whenever the LM95071 is in shutdown mode. 9 www.national.com LM95071 2.0 Serial Bus Timing Diagrams 20106514 a) Reading Continuous Conversion - Single Eight-Bit Frame 20106515 b) Reading Continuous Conversion - Two Eight-Bit Frames 20106518 c) Writing Shutdown Mode 20106522 d) Writing Conversion Mode FIGURE 7. Timing Diagrams www.national.com 10 3.2 OUTPUT CONSIDERATIONS: TIGHT ACCURACY, FINE RESOLUTION AND LOW NOISE 3.1 THERMAL PATH CONSIDERATIONS The LM95071 is well suited for applications that require tight temperature measurement accuracy. In many applications, from process control to HVAC, the low temperature error can mean better system performance and, by eliminating a system calibration step, lower production cost. To get the expected results when measuring temperature with an integrated circuit temperature sensor like the LM95071, it is important to understand that the sensor measures its own die temperature. For the LM95071, the best thermal path between the die and the outside world is through the LM95071’s pins. In the SOT23 package, all the pins on the LM95071 will have an equal effect on the die temperature. Because the pins represent a good thermal path to the LM95071 die, the LM95071 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 LM95071 die. If the ambient air temperature is significantly different from the printed circuit board temperature, it will have a small effect on the measured temperature. With it’s fine digital resolution the LM95071 senses and reports very small changes in its temperature, making it ideal for applications where temperature sensitivity is important. For example, the LM95071 enables the system to quickly identify the direction of temperature change, allowing the processor to take compensating action before the system reaches a critical temperature. The LM95071 has very low output noise (see the Output Noise plot in the Typical Performance section), which makes it ideal for applications where stable thermal compensation is a priority. For example, in a temperature-compensated oscillator application, the very small deviation in successive temperature readings translates to a stable frequency output from the oscillator. 4.0 Typical Applications 20106520 FIGURE 8. Temperature monitor using Intel 196 processor 20106519 FIGURE 9. LM95071 digital input control using microcontroller’s general purpose I/O. 11 www.national.com LM95071 3.0 Application Hints LM95071 Physical Dimensions inches (millimeters) unless otherwise noted LM95071Top View SOT23-5 Package NS Package Number MF05A www.national.com 12 LM95071 13-Bit Plus Sign SPI/MICROWIRE Temperature Sensor 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. 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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