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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 con-

version rate, low supply current, and simple SPI interface

make it ideal for a wide range of applications.

Applications

n System Thermal Management

n Personal Computers

n Portable Electronic Devices

n Disk Drives

n Office Electronics

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

Supply Voltage 2.65V to 5.5V

Supply Current operating 300 µA (typ)

550 µA (max)

Temperature

Accuracy −10˚C to +65˚C

1.5˚C (max)

−40˚C to 150˚C +3/− 2˚C (max)

Temperature

Resolution

31.25 m˚C

Simplified Block Diagram

20031701

TRI-STATE

is a registered trademark of National Semiconductor Corporation.

February 2005

LM71 SPI/MICROWIRE

™

13-Bit Plus Sign Temperature Sensor

Summary of content (13 pages)

PAGE 1
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.
PAGE 2
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.
PAGE 3
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.
PAGE 4
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.
PAGE 5
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.
PAGE 6
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.
PAGE 7
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.
PAGE 8
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.
PAGE 9
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.
PAGE 10
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.
PAGE 11
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.
PAGE 12
LM71 Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM71Top View CIMF NS Package Number MF05A www.national.
PAGE 13
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.