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LM75

Digital Temperature Sensor and Thermal Watchdog with

Two-Wire Interface

General Description

The LM75 is a temperature sensor, Delta-Sigma

analog-to-digital converter, and digital over-temperature de-

tector with I

interface. The host can query the LM75 at

any time to read temperature. The open-drain Overtempera-

ture Shutdown (O.S.) output becomes active when the tem-

perature exceeds a programmable limit. This pin can operate

in either “Comparator” or “Interrupt” mode.

The host can program both the temperature alarm threshold

) and the temperature at which the alarm condition goes

away (T

HYST

). In addition, the host can read back the con-

tents of the LM75’s T

and T

HYST

registers. Three pins (A0,

A1, A2) are available for address selection. The sensor

powers up in Comparator mode with default thresholds of

80˚C T

and 75˚C T

HYST

The LM75’s 3.0V to 5.5V supply voltage range, low supply

current and I

C interface make it ideal for a wide range of

applications. These include thermal management and pro-

tection applications in personal computers, electronic test

equipment, and office electronics.

Features

n SOP-8 and Mini SOP-8 (MSOP) packages save space

n I

C Bus interface

n Separate open-drain output pin operates as interrupt or

comparator/thermostat output

n Register readback capability

n Power up defaults permit stand-alone operation as

thermostat

n Shutdown mode to minimize power consumption

n Up to 8 LM75s can be connected to a single bus

Key Specifications

Supply Voltage 3.0V to 5.5V

Supply Current operating 250 µA (typ)

1 mA (max)

shutdown 4 µA (typ)

Temperature Accuracy −25˚C to 100˚C

2˚C(max)

−55˚C to 125˚C

3˚C(max)

Applications

n System Thermal Management

n Personal Computers

n Office Electronics

n Electronic Test Equipment

Simplified Block Diagram

01265801

is a registered trademark of Philips Corporation.

October 2002

LM75 Digital Temperature Sensor and Thermal Watchdog with Two-Wire Interface

Summary of content (18 pages)

PAGE 1
LM75 Digital Temperature Sensor and Thermal Watchdog with Two-Wire Interface General Description The LM75 is a temperature sensor, Delta-Sigma analog-to-digital converter, and digital over-temperature detector with I2C ® interface. The host can query the LM75 at any time to read temperature. The open-drain Overtemperature Shutdown (O.S.) output becomes active when the temperature exceeds a programmable limit. This pin can operate in either “Comparator” or “Interrupt” mode.
PAGE 2
LM75 Connection Diagram SOP-8 and Mini SOP-8 01265802 Ordering Information Order Number Package Marking NS Package Number Supply Voltage Transport Media Noise Filter on SDA and SCL LM75BIM-3 LM75BIM-3 M08A (SOP-8) 3.3V 95 Units in Rail Yes LM75BIMX-3 LM75BIM-3 M08A (SOP-8) 3.3V 2500 Units on Tape and Reel Yes LM75BIMM-3 T01B MUA08A (MSOP-8) 3.3V 1000 Units on Tape and Reel Yes LM75BIMMX-3 T01B MUA08A (MSOP-8) 3.
PAGE 3
LM75 Pin Description (Continued) 01265803 FIGURE 1. Typical Application 3 www.national.
PAGE 4
LM75 Absolute Maximum Ratings Supply Voltage ESD Susceptibility (Note 4) (Note 1) Human Body Model −0.3V to 6.5V Voltage at any Pin Machine Model −0.3V to +VS + 0.3V Input Current at any Pin (Note 2) LM75B LM75C 2500V 1500V 250V 100V 5 mA Package Input Current (Note 2) 20 mA Operating Ratings O.S. Output Sink Current 10 mA Specified Temperature Range O.S. Output Voltage 6.5V Storage Temperature (Note 5) −65˚C to +150˚C TMIN to TMAX −55˚C to +125˚C Supply Voltage Range (+VS) +3.
PAGE 5
(Continued) DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS = +5 Vdc for LM75BIM-5, LM75BIMM-5, LM75CIM-5, and LM75CIMM-5 and +VS = +3.3 Vdc for LM75BIM-3, LM75BIMM-3, LM75CIM-3, and LM75CIMM-3 (Note 6). Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted.
PAGE 6
LM75 Note 5: LM75 θJA (thermal resistance, junction-to-ambient) when attached to a printed circuit board with 2 oz. foil similar to the one shown in Figure 3 is summarized in the table below: Device Number NS Package Number Thermal Resistance (θJA) LM75BIM-3, LM75BIM-5, LM75CIM-3, LM75CIM-5 M08A 200˚C/W LM75BIMM-3, LM75BIMM-5, LM75CIMM-3, LM75CIMM-5 MUA08A 250˚C/W Note 6: All part numbers of the LM75 will operate properly over the +VS supply voltage range of 3V to 5.5V.
PAGE 7
LM75 01265806 FIGURE 3. Printed Circuit Board Used for Thermal Resistance Specifications Typical Performance Characteristics Static Quiescent Current vs Temperature Dynamic Quiescent Current vs Temperature 01265816 01265817 2. 1.0 Functional Description The LM75 temperature sensor incorporates a band-gap type temperature sensor and 9-bit ADC (Delta-Sigma Analog-to-Digital Converter). The temperature data output of the LM75 is available at all times via the I2C bus.
PAGE 8
LM75 1.0 Functional Description above the nominal 1.7V power up threshold, the internal registers are reset to the power up default values listed above. (Continued) by crossing TOS, then reset, it can be activated again only by Temperature going below THYST. Again, it will remain active indefinitely until being reset by a read. Placing the LM75 in shutdown mode also resets the O.S. Output. 1.
PAGE 9
1.7 COMPARATOR/INTERRUPT MODE As indicated in the O.S. Output Temperature Response Diagram, Figure 4, the events that trigger O.S. are identical for either Comparator or Interrupt mode. The most important difference is that in Interrupt mode the O.S. will remain set indefinitely once it has been set. To reset O.S. while in Interrupt mode, perform a read from any register in the LM75. (Continued) 1.
PAGE 10
LM75 1.0 Functional Description 1.10 INTERNAL REGISTER STRUCTURE (Continued) 01265808 There are four data registers in the LM75, selected by the Pointer register. At power-up the Pointer is set to “00”; the location for the Temperature Register. The Pointer register latches whatever the last location it was set to. In Interrupt Mode, a read from the LM75, or placing the device in shutdown mode, resets the O.S. output. All registers are read and write, except the Temperature register which is read only.
PAGE 11
LM75 1.0 Functional Description (Continued) 1.11 POINTER REGISTER (Selects which registers will be read from or written to): P7 P6 P5 P4 P3 P2 0 0 0 0 0 0 P1 P0 Register Select P0-P1: Register Select: P1 P0 0 0 Temperature (Read only) (Power-up default) Register 0 1 Configuration (Read/Write) 1 0 THYST (Read/Write) 1 1 TOS (Read/Write) P2–P7: Must be kept zero. 1.
PAGE 12
www.national.com 12 2.0 I2C Timing Diagrams FIGURE 6.
PAGE 13
2.0 I2C Timing Diagrams (Continued) FIGURE 7. Timing Diagrams (Continued) 01265811 LM75 13 www.national.
PAGE 14
LM75 Digital Noise Issues The LM75B features an integrated low-pass filter on both the SCL and the SDA digital lines to mitigate the effects of bus noise. Although this filtering makes the LM75B communication robust in noisy environments, good layout practices are always recommended. Minimize noise coupling by keeping digital traces away from switching power supplies. Also, ensure that digital lines containing high-speed data communications cross at right angles to the SDA and SCL lines. 3.
PAGE 15
LM75 4.0 Typical Applications (Continued) 01265813 FIGURE 9. Data Acquisition System with Temperature Input via I2C Bus 01265814 FIGURE 10. Simple Thermostat, Interface Optional 15 www.national.
PAGE 16
LM75 4.0 Typical Applications (Continued) 01265815 FIGURE 11. Temperature Sensor with Loudmouth Alarm (Barking Watchdog) www.national.
PAGE 17
LM75 Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead (0.150" Wide) Molded Small Outline Package (SOP), JEDEC Order Number LM75CIM-3, LM75CIMX-3, LM75CIM-5, LM75CIMX-5, LM75BIM-3, LM75BIMX-3, LM75BIM-5, or LM75BIMX-5 NS Package Number M08A 17 www.national.
PAGE 18
LM75 Digital Temperature Sensor and Thermal Watchdog with Two-Wire Interface Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Lead Molded Mini Small Outline Package (MSOP) (JEDEC REGISTRATION NUMBER M0-187) Order Number LM75CIMM-3, LM75CIMMX-3, LM75CIMM-5, LM75CIMMX-5, LM75BIMM-3, LM75BIMMX-3, LM75BIMM-5, or LM75BIMMX-5 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