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LM75B, LM75C
SNIS153D – JULY 2009 – REVISED OCTOBER 2015
LM75x Digital Temperature Sensor and Thermal Watchdog With Two-Wire Interface
1 Features
3 Description
•
•
•
The LM75B and LM75C are industry-standard digital
temperature sensors with an integrated Sigma-Delta
analog-to-digital converter and I2C interface. The
LM75 provides 9-bit digital temperature readings with
an accuracy of ±2°C from -25°C to 100°C and ±3°C
over –55°C to 125°C.
1
•
•
•
No External Components Required
Shutdown Mode to Minimize Power Consumption
Up to Eight LM75s Can be Connected to a Single
Bus
Power Up Defaults Permit Stand-alone Operation
as Thermostat
UL Recognized Component (LM75B and LM75C)
Key Specifications:
– Supply Voltage
– LM75B, LM75C: 3 V to 5.5 V
– Supply Current
– Operating: 280 μA (typical)
– Shutdown: 4 μA (typical)
– Temperature Accuracy
– −25°C to 100°C: ±2°C (maximum)
– −55°C to 125°C: ±3°C (maximum)
Communication is accomplished over a 2-wire
interface which operates up to 400kHz. The LM75
has three address pins, allowing up to eight LM75
devices to operate on the same 2-wire bus. The
LM75 has a dedicated over-temperature output (O.S.)
with programmable limit and hystersis. This output
has programmable fault tolerance, which allows the
user to define the number of consecutive error
conditions that must occur before O.S. is activated.
The wide temperature and supply range and I2C
interface make the LM75 ideal for a number of
applications including base stations, electronic test
equipment, office electronics, personal computers,
and any other system where thermal management is
critical to performance. The LM75B and LM75C are
available in an SOIC package or VSSOP package.
2 Applications
•
•
•
•
General System Thermal Management
Communications Infrastructure
Electronic Test Equipment
Environmental Monitoring
Device Information(1)
PART NUMBER
LM75B
PACKAGE
BODY SIZE (NOM)
SOIC (8)
4.90 mm x 3.91 mm
VSSOP (8)
3.00 mm x 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Typical Application
+VS
100 nF (typ) unless mounted
close to processor
8
A0
Address
A1
(Set as desired)
A2
Interface
SDA
SCL
7
6
5
LM75
3
O.S.
To Processor
Interrupt Line
1
O.S. set to active low
IRUZLUH25¶GPXOWLSOH
interrupt line
2
4
GND
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM75B, LM75C
SNIS153D – JULY 2009 – REVISED OCTOBER 2015
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Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
7
1
1
1
2
3
3
Absolute Maximum Ratings ...................................... 3
ESD Ratings ............................................................ 4
Recommended Operating Conditions....................... 4
Thermal Information .................................................. 4
Temperature-to-Digital Converter Characteristics..... 5
Digital DC Characteristics ......................................... 5
I2C Digital Switching Characteristics......................... 7
Typical Characteristics ............................................ 11
Detailed Description ............................................ 12
7.1 Overview ................................................................. 12
7.2 Functional Block Diagram ....................................... 12
7.3 Feature Description................................................. 12
7.4 Device Functional Modes........................................ 13
7.5 Programming........................................................... 13
7.6 Register Maps ......................................................... 16
8
Application and Implementation ........................ 18
8.1 Application Information............................................ 18
8.2 Typical Application .................................................. 18
8.3 System Examples ................................................... 19
9 Power Supply Recommendations...................... 21
10 Layout................................................................... 21
10.1 Layout Guidelines ................................................. 21
10.2 Layout Example .................................................... 22
11 Device and Documentation Support ................. 23
11.1
11.2
11.3
11.4
11.5
Related Links ........................................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
23
23
23
23
23
12 Mechanical, Packaging, and Orderable
Information ........................................................... 23
4 Revision History
Changes from Revision C (January 2015) to Revision D
Page
•
Updated Thermal Information table. ...................................................................................................................................... 4
•
Corrected UNIT error in I2C Digital Switching Characteristics table....................................................................................... 7
•
Added Community Resources section. ................................................................................................................................ 23
Changes from Revision B (March 2013) to Revision C
•
Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional
Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device
and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1
Changes from Revision A (March 2013) to Revision B
•
2
Page
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 20
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5 Pin Configuration and Functions
D and DGK Packages
8-Pin SOIC, VSSOP
Top View
Pin Functions
PIN
NO.
1
2
DESCRIPTION
NAME
SDA
I2C Serial Bi-Directional Data Line.
Open Drain.
2
TYPICAL CONNECTION
From Controller, tied to a pullup resistor or current source
SCL
I C Clock Input
From Controller, tied to a pullup resistor or current source
3
O.S.
Over temperature Shutdown.
Open Drain Output
Pullup Resistor, Controller Interrupt Line
4
GND
Power Supply Ground
Ground
5
A2
6
A1
User-Set I2C Address Inputs
Ground (Low, 0) or +VS (High, 1)
7
A0
8
+VS
Positive Supply Voltage Input
DC Voltage from 3 V to 5.5 V; 100-nF bypass capacitor with 10-µF
bulk capacitance in the near vicinity
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
Supply Voltage Pin (+VS)
Voltage at A0, A1and A2 Pins
Voltage at O.S., SCL and SDA Pins
MIN
MAX
UNIT
−0.3
6.5
V
−0.3
(+VS + 0.3) and must
be ≤ 6.5
V
−0.3
6.5
V
Input Current at any Pin (2)
5
mA
Package Input Current (2)
20
mA
O.S. Output Sink Current
10
mA
150
°C
Storage temperature, Tstg
(1)
(2)
–65
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.
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. The 20-mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input
current of 5 mA to four.
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6.2 ESD Ratings
VALUE
UNIT
LM75B
Electrostatic discharge (1)
V(ESD)
Human-body model (HBM)
±2500
Machine model
±250
Human-body model (HBM)
±1500
Machine Model
±100
V
LM75C
Electrostatic discharge (1)
V(ESD)
(1)
V
Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin. The
Charged Device Model (CDM) is a specified circuit characterizing an ESD event that occurs when a device acquires charge through
some triboelectric (frictional) or electrostatic induction processes and then abruptly touches a grounded object or surface.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1) (2)
Specified Temperature Range
Supply Voltage Range (+VS) LM75B, LM75C
(1)
(2)
MIN
MAX
TMIN
TMAX
UNIT
–55
125
°C
3
5.5
V
Soldering process must comply with Texas Instruments Incorporated Reflow Temperature Profile specifications. Refer to
Reflow temperature profiles are different for lead-free and non-lead-free packages.
6.4 Thermal Information
LM75B
THERMAL METRIC (1)
D (SOIC)
DGK (VSSOP)
UNIT
8 PINS
8 PINS
RθJA
Junction-to-ambient thermal resistance
115.2
158.7
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
62.2
52.3
°C/W
RθJB
Junction-to-board thermal resistance
56.4
78.8
°C/W
ψJT
Junction-to-top characterization parameter
10.2
5.3
°C/W
ψJB
Junction-to-board characterization parameter
55.8
77.5
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
N/A
N/A
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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6.5 Temperature-to-Digital Converter 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 (1). TA = TJ = 25°C, unless
otherwise noted. (2)
PARAMETER
TEST CONDITIONS
Accuracy
MIN (3)
TYP (4)
TA = −25°C to 100°C
–2
2
TA = −55°C to 125°C
–3
3
Resolution
LM75B
Quiescent Current
4
Shutdown Mode, +VS = 5 V
6
4
Shutdown Mode, +VS = 5 V
6
See
(6)
See
(7)
mA
1
Shutdown Mode, +VS = 3 V
O.S. Delay
(6)
(7)
μA
0.25
I2C Inactive, –55°C ≤ TA ≤ 125°C
IOUT = 4.0 mA, –55°C ≤ TA ≤
125°C
THYST Default Temperature
mA
0.5
Shutdown Mode, +VS = 3 V
O.S. Output Saturation Voltage
TOS Default Temperature
ms
0.25
I2C Inactive, –55°C ≤ TA ≤ 125°C
I2C Inactive
LM75C
Bits
300
I2C Inactive
(3)
(4)
(5)
°C
100
See (5), –55°C ≤ TA ≤ 125°C
(2)
UNIT
9
See (5)
Temperature Conversion Time
(1)
MAX (3)
μA
0.8
, –55°C ≤ TA ≤ 125°C
1
6
V
Conversions
80
°C
75
All part numbers of the LM75 will operate properly over the +VS supply voltage range of 3 V to 5.5 V. The devices are tested and
specified for rated accuracy at their nominal supply voltage. Accuracy will typically degrade 1°C/V of variation in +VS as it varies from
the nominal value.
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.
Limits are specified to AOQL (Average Outgoing Quality Level).
Typicals are at TA = 25°C and represent most likely parametric norm.
The conversion-time specification is provided to indicate how often the temperature data is updated. The LM75 can be accessed at any
time and reading the Temperature Register will yield result from the last temperature conversion. When the LM75 is accessed, the
conversion that is in process will be interrupted and it will be restarted after the end of the communication. Accessing the LM75
continuously without waiting at least one conversion time between communications will prevent the device from updating the
Temperature Register with a new temperature conversion result. Consequently, the LM75 should not be accessed continuously with a
wait time of less than 300 ms.
O.S. Delay is user programmable up to 6 “over limit” conversions before O.S. is set to minimize false tripping in noisy environments.
Default values set at power up.
6.6 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 (1). TA = TJ = 25°C, unless
otherwise noted.
PARAMETER
TEST CONDITIONS
MIN (2)
TYP (3)
MAX (2)
UNIT
VIN(1)
Logical “1” Input Voltage
–55°C ≤ TA ≤ 125°C
+VS × 0.7
+VS + 0.3
V
VIN(0)
Logical “0” Input Voltage
–55°C ≤ TA ≤ 125°C
−0.3
+VS × 0.3
V
IIN(1)
Logical “1” Input Current
VIN = +VS
0.005
VIN = +VS, –55°C ≤ TA ≤
125°C
IIN(0)
Logical “0” Input Current
VIN = 0 V
VIN = 0 V, –55°C ≤ TA ≤
125°C
(1)
(2)
(3)
1
μA
−0.005
−1
μA
All part numbers of the LM75 will operate properly over the +VS supply voltage range of 3 V to 5.5 V. The devices are tested and
specified for rated accuracy at their nominal supply voltage. Accuracy will typically degrade 1°C/V of variation in +VS as it varies from
the nominal value.
Limits are specified to AOQL (Average Outgoing Quality Level).
Typicals are at TA = 25°C and represent most likely parametric norm.
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Digital DC Characteristics (continued)
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(1). TA = TJ = 25°C, unless
otherwise noted.
PARAMETER
CIN
IOH
MIN (2)
All Digital Inputs
High Level Output
Current
VOL
Low Level Output Voltage
tOF
Output Fall Time
6
TEST CONDITIONS
TYP (3)
MAX (2)
5
UNIT
pF
LM75B
VOH = 5 V, –55°C ≤ TA ≤
125°C
10
μA
LM75C
VOH = 5 V, –55°C ≤ TA ≤
125°C
100
μA
IOL = 3 mA, –55°C ≤ TA ≤
125°C
0.4
V
CL = 400 pF IO = 3 mA,
–55°C ≤ TA ≤ 125°C
250
ns
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6.7 I2C Digital Switching 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, CL (load capacitance) on
output lines = 80 pF unless otherwise specified. TA = TJ = 25°C, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN (1) (2) TYP (3)
MAX (1) (2)
UNIT
t1
SCL (Clock) Period, See Figure 1
–55°C ≤ TA ≤ 125°C
2.5
µs
t2
Data in Set-Up Time to SCL High, See Figure 1
–55°C ≤ TA ≤ 125°C
100
ns
t3
Data Out Stable after SCL Low, See Figure 1
–55°C ≤ TA ≤ 125°C
0
ns
t4
SDA Low Set-Up Time to SCL Low (Start Condition),
See Figure 1
–55°C ≤ TA ≤ 125°C
100
t5
SDA High Hold Time after SCL High (Stop Condition),
See Figure 1
–55°C ≤ TA ≤ 125°C
100
–55°C ≤ TA ≤ 125°C
75
tTIMEOUT
SDA Time Low for Reset of Serial Interface (4)
LM75B
(1)
(2)
(3)
(4)
LM75C
ns
ns
325
ms
Not
Applicable
Limits are specified to AOQL (Average Outgoing Quality Level).
Timing specifications are tested at the bus input logic levels (Vin(0)=0.3xVA for a falling edge and Vin(1)=0.7xVA for a rising edge) when
the SCL and SDA edge rates are similar.
Typicals are at TA = 25°C and represent most likely parametric norm.
Holding the SDA line low for a time greater than tTIMEOUT will cause the LM75B to reset SDA to the IDLE state of the serial bus
communication (SDA set High).
Figure 1. Timing Diagram
Figure 2. Temperature-to-Digital Transfer Function (Non-Linear Scale for Clarity)
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LM75C θJA (thermal resistance, junction-to-ambient) when attached to a printed circuit board with 2 oz. foil similar to
the one shown. Summarized below:
Device Number
LM75BIM-3, LM75BIM-5, LM75CIM-3,
LM75CIM-5
LM75BIMM-3, LM75BIMM-5,
LM75CIMM-3, LM75CIMM-5
Package Number
Thermal Resistance (θJA)
D (R-PDSO-G8)
200°C/W
DGK (S-PDSO-G8)
250°C/W
Figure 3. Printed Circuit Board Used for Thermal Resistance Specifications
8
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Figure 4. I2C Timing Diagrams
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Figure 5. I2C Timing Diagrams (Continued)
10
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6.8 Typical Characteristics
Figure 6. Static Quiescent Current vs Temperature (LM75C)
Figure 7. Dynamic Quiescent Current vs Temperature
(LM75C)
Figure 8. Accuracy vs Temperature (LM75C)
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7 Detailed Description
7.1 Overview
The LM75 temperature sensor incorporates a band-gap type temperature sensor and 9-bit ADC (Sigma-Delta
Analog-to-Digital Converter). The temperature data output of the LM75 is available at all times via the I2C bus. If
a conversion is in progress, it will be stopped and restarted after the read. A digital comparator is also
incorporated that compares a series of readings, the number of which is user-selectable, to user-programmable
setpoint and hysteresis values. The comparator trips the O.S. output line, which is programmable for mode and
polarity.
The LM75B contains all the functionality of the LM75C, plus two additional features:
• The LM75B has an integrated low-pass filter on both the SDA and the SCL line. These filters increase
communications reliability in noisy environments.
• The LM75B also has a bus fault timeout feature. If the SDA line is held low for longer than tTIMEOUT (see I2C
Digital Switching Characteristics) the LM75B will reset to the IDLE state (SDA set to high impedance) and
wait for a new start condition. The TIMEOUT feature is not functional in Shutdown Mode.
7.2 Functional Block Diagram
+VS
8
Ð
1-Bit
D/A
Temperature
10-Bit
Digital
Decimation
Filter
TOS Set Point
Register
A0
A1
Set Point
Comparator
A2
Reset
Configuration
Register
Pointer
Register
5
THYST Set
Point Register
1
7
6
O.S.
Threshold
9-Bit Sigma-Delta ADC
Silicon Bandgap
Temperature
Sensor
3
Two-Wire Interface
2
SDA
SCL
4
GND
7.3 Feature Description
7.3.1 Digital Temperature Sensor
The LM75 is an industry-standard digital temperature sensor with an integrated Sigma-Delta analog-to-digital
converter and I2C interface. The LM75 provides 9-bit digital temperature readings with an accuracy of ±2°C from
–25°C to 100°C and ±3°C over –55°C to 125°C.
The LM75 operates with a single supply from 2.7 V to 5.5 V. Communication is accomplished over a 2-wire
interface which operates up to 400kHz. The LM75 has three address pins, allowing up to eight LM75 devices to
operate on the same 2-wire bus. The LM75 has a dedicated over-temperature output (O.S.) with programmable
limit and hysteresis. This output has programmable fault tolerance, which allows the user to define the number of
consecutive error conditions that must occur before O.S. is activated.
12
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7.4 Device Functional Modes
In Comparator mode the O.S. Output behaves like a thermostat. The output becomes active when temperature
exceeds the TOS limit, and leaves the active state when the temperature drops below the THYST limit. In this mode
the O.S. output can be used to turn a cooling fan on, initiate an emergency system shutdown, or reduce system
clock speed. Shutdown mode does not reset O.S. state in a comparator mode.
In Interrupt mode exceeding TOS also makes O.S. active but O.S. will remain active indefinitely until reset by
reading any register via the I2C interface. Once O.S. has been activated 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.
The LM75B always powers up in a known state. The power up default conditions are:
1. Comparator mode
2. TOS = 80°C
3. THYST = 75°C
4. O.S. active low
5. Pointer = “00”
When the supply voltage is less than about 1.7V, the LM75 is considered powered down. As the supply voltage
rises above the nominal 1.7V power up threshold, the internal registers are reset to the power up default values
listed above.
If the LM75 is not connected to the I2C bus on power up, it will act as a stand-alone thermostat with the power up
default conditions listed above. It is optional, but recommended, to connect the address pins (A2, A1, A0) and
the SCL and SDA pins together and to a 10k pull-up resistor to +VS for better noise immunity. Any of these pins
may also be tied high separately through a 10k pull-up resistor.
7.5 Programming
7.5.1
I2C Bus Interface
The LM75 operates as a slave on the I2C bus, so the SCL line is an input (no clock is generated by the LM75)
and the SDA line is a bi-directional serial data path. According to I2C bus specifications, the LM75 has a 7-bit
slave address. The four most significant bits of the slave address are hard wired inside the LM75 and are “1001”.
The three least significant bits of the address are assigned to pins A2–A0, and are set by connecting these pins
to ground for a low, (0); or to +VS for a high, (1).
Therefore, the complete slave address is:
1
0
0
1
A2
MSB
A1
A0
LSB
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These interrupt mode resets of O.S. occur only when LM75 is read or placed in shutdown. Otherwise, O.S. would
remain active indefinitely for any event.
Figure 9. O.S. Output Temperature Response Diagram
7.5.2 Temperature Data Format
Temperature data can be read from the Temperature, TOS Set Point, and THYST Set Point registers; and written to
the TOS Set Point, and THYST Set Point registers. Temperature data is represented by a 9-bit, two's complement
word with an LSB (Least Significant Bit) equal to 0.5°C:
Temperature
Digital Output
Binary
Hex
125°C
0 1111 1010
0FAh
25°C
0 0011 0010
032h
0.5°C
0 0000 0001
001h
0°C
0 0000 0000
000h
−0.5°C
1 1111 1111
1FFh
−25°C
1 1100 1110
1CEh
−55°C
1 1001 0010
192h
7.5.3 Shutdown Mode
Shutdown mode is enabled by setting the shutdown bit in the Configuration register via the I2C bus. Shutdown
mode reduces power supply current significantly. See specified quiescent current specification in the
Temperature-to-Digital Converter Characteristics table. In Interrupt mode O.S. is reset if previously set and is
undefined in Comparator mode during shutdown. The I2C interface remains active. Activity on the clock and data
lines of the I2C bus may slightly increase shutdown mode quiescent current. TOS, THYST, and Configuration
registers can be read from and written to in shutdown mode.
For the LM75B, the TIMEOUT feature is turned off in Shutdown Mode.
7.5.4 Fault Queue
A fault queue of up to 6 faults is provided to prevent false tripping of O.S. when the LM75 is used in noisy
environments. The number of faults set in the queue must occur consecutively to set the O.S. output.
14
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7.5.5 Comparator and Interrupt Mode
As indicated in the O.S. Output Temperature Response Diagram, Figure 9, 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.
7.5.6 O.S. Output
The O.S. output is an open-drain output and does not have an internal pull-up. A “high” level will not be observed
on this pin until pull-up current is provided from some external source, typically a pull-up resistor. Choice of
resistor value depends on many system factors but, in general, the pull-up resistor should be as large as
possible. This will minimize any errors due to internal heating of the LM75. The maximum resistance of the pull
up, based on LM75 specification for High Level Output Current, to provide a 2V high level, is 30 kΩ.
7.5.7
O.S. Polarity
The O.S. output can be programmed via the configuration register to be either active low (default mode), or
active high. In active low mode the O.S. output goes low when triggered exactly as shown on the O.S. Output
Temperature Response Diagram, Figure 9. Active high simply inverts the polarity of the O.S. output.
7.5.8 Internal Register Structure
SCL
2
I C Interface
SDA
Data
Address
Pointer Register
(Selects register for
communication)
Temperature
(Read-Only)
Pointer = 00000000
Configuration
(Read-Write)
Pointer = 00000001
TOS Set Point
(Read-Write)
Pointer = 00000011
THYST Set Point
(Read-Write)
Pointer = 00000010
Figure 10. Iternal Register Structure
There are four data registers in the LM75B and LM75C selected by the Pointer register. At power-up the Pointer
is set to “000”; 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 a read only.
A write to the LM75 will always include the address byte and the Pointer byte. A write to the Configuration
register requires one data byte, and the TOS and THYST registers require two data bytes.
Reading the LM75 can take place either of two ways: If the location latched in the Pointer is correct (most of the
time it is expected that the Pointer will point to the Temperature register because it will be the data most
frequently read from the LM75), then the read can simply consist of an address byte, followed by retrieving the
corresponding number of data bytes. If the Pointer needs to be set, then an address byte, pointer byte, repeat
start, and another address byte will accomplish a read.
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 indicates an overtemperature condition, the host processor could immediately take action to remedy the
excessive temperatures. At the end of a read, the LM75 can accept either Acknowledge or No Acknowledge from
the Master (No Acknowledge is typically used as a signal for the slave that the Master has read its last byte).
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An inadvertent 8-bit read from a 16-bit register, with the D7 bit low, can cause the LM75 to stop in a state where
the SDA line is held low as shown in Figure 11. This can prevent any further bus communication until at least 9
additional clock cycles have occurred. Alternatively, the master can issue clock cycles until SDA goes high, at
which time issuing a “Stop” condition will reset the LM75.
Figure 11. Inadvertent 8-Bit Read from 16-Bit Register where D7 is Zero (“0”)
7.6 Register Maps
7.6.1 Pointer Register (Selects Which Registers Will Be Read From or Written to):
P7
P6
P5
P4
P3
0
0
0
0
0
P2
P1
P2
P1
P0
0
0
0
Temperature (Read only) (Power-up default)
0
0
1
Configuration (Read/Write)
0
1
0
THYST (Read/Write)
0
1
1
TOS (Read/Write)
P0
Register Select
P0-P1: Register Select:
Register
P3–P7: Must be kept zero.
7.6.2 Temperature Register (Read Only):
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
X
X
X
X
X
X
X
D0–D6: Undefined.
D7–D15: Temperature Data. One LSB = 0.5°C. Two's complement format.
7.6.3 Configuration Register (Read/Write):
D7
D6
D5
0
0
0
D4
D3
Fault Queue
D2
D1
D0
O.S. Polarity
Cmp/Int
Shutdown
Power up default is with all bits “0” (zero).
D0: Shutdown: When set to 1 the LM75 goes to low power shutdown mode.
D1: Comparator/Interrupt mode: 0 is Comparator mode, 1 is Interrupt mode.
D2: O.S. Polarity: 0 is active low, 1 is active high. O.S. is an open-drain output under all conditions.
D3–D4: Fault Queue: Number of faults necessary to detect before setting O.S. output to avoid false tripping due
to noise. Faults are determind at the end of a conversion. See specified temperature conversion time in the
Temperature-to-Digital Converter Characteristics table.
16
D4
D3
Number of Faults
0
0
1 (Power-up default)
0
1
2
1
0
4
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D4
D3
Number of Faults
1
1
6
D5–D7: These bits are used for production testing and must be kept zero for normal operation.
7.6.4 THYST and TOS Register (Read/Write):
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
X
X
X
X
X
X
X
D0–D6: Undefined
75°C
D7–D15: THYST Or TOS Trip Temperature Data. Power up default is TOS = 80°C, THYST =
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The wide temperature and supply range and I2C interface make the LM75 ideal for a number of applications
including base stations, electronic test equipment, office electronics, personal computers, and any other system
where thermal management is critical to performance.
8.2 Typical Application
8.2.1 Simple Fan Controller, Interface Optional
+VS
+12V
Optional but
Recommended
Pull-up
In Stand-alone
Mode
C1
100 nF
R3
10k
R1
10k
R2
10k
+12V/300 mA
Fan Motor
8
A0 7
A1 6
3 O.S.
A2 5
Q1
2N3904
Q2
NDP410A
series
LM75
SDA 1
SCL 2
4
GND
When using the two-wire interface: program O.S. for active high and connect O.S. directly to Q2's gate.
Figure 12. Simple Fan Controller, Interface Optional
8.2.1.1 Design Requirements
The LM75 requires a positive supply voltage of 2.7 V to 5.5 V to be applied between +Vs and GND. For best
results, bypass capacitors of 100 nF and 10 µF are recommended. Pull-up resistors of 10 kΩ are required on
SCL and SDA.
8.2.1.2 Detailed Design Procedure
Accessing the conversion result of the LM75 consists of writing an address byte followed by retrieving the
corresponding number of data bytes. The first data byte is the most significant byte with the 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 indicates an overtemperature condition, the host processor could
immediately take action to remedy the excessive temperatures. At the end of a read, the LM75 can accept either
Acknowledge or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave
that the Master has read its last byte). Temperature data is two's complement format and one LSB is equivalent
to 0.5°C.
18
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Typical Application (continued)
8.2.1.3 Application Curve
Figure 13. Temperature Accuracy
8.3 System Examples
8.3.1 Simple Thermostat, Interface Optional
+ 5 VDC
Heater
Heater
Supply
Optional but
Recommended
Pull-up In
Stand-alone
Mode
R2
10k
C1
100 nF
8
R1
+VS 10k
K1
5V
Relay
D1
1N4001
A0 7
A1 6
A2 5
LM75
3
O.S.
Q1
2N2222A
SDA 1
SCL 2
4
GND
Figure 14. Simple Thermostat, Interface Optional
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System Examples (continued)
8.3.2 Temperature Sensor with Loudmouth Alarm (Barking Watchdog)
+VS
Optional but
Recommended
Pull-up
In Stand-alone
Mode
R3
10k
C6
100 nF
R1
10k
8
A0 7
A1 6
3
A2 5
LM75
SDA 1
SCL 2
4
GND
SHUTDOWN Vo2
BYPASS
C1
100 nF
C2
100 nF
GND
VDD
+IN
LM4861M
-IN
Vo1
R5 200k
O.S.
C3
6.8 nF
C4
6.8 nF
C5
6.8 nF
R2
10k
R3
10k
R4
10k
Figure 15. Temperature Sensor with Loudmouth Alarm (Barking Watchdog)
20
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9 Power Supply Recommendations
The LM75 is specified for operation from 2.7 V to 5.5 V. Place a 100-nF and 10-µF capacitor close to +Vs in
order to reduce errors coupling in from noisy or high impedance supplies.
10 Layout
10.1 Layout Guidelines
To achieve the expected results when measuring temperature with an integrated circuit temperature sensor like
the LM75, it is important to understand that the sensor measures its own die temperature. For the LM75, the best
thermal path between the die and the outside world is through the LM75's pins. In the VSSOP package for the
LM75B and LM75C, the GND pin is directly connected to the die, so the GND pin provides the best thermal path.
If the other pins are at different temperatures (unlikely, but possible), they will affect the die temperature, but not
as strongly as the GND pin. In the SOIC package, none of the pins is directly connected to the die, so they will
all contribute similarly to the die temperature. Because the pins represent a good thermal path to the LM75 die,
the LM75 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 LM75 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.
In probe-type applications, the LM75 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 LM75 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 LM75 or its
connections.
10.1.1 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.
Excessive noise coupling into the SDA and SCL lines on the LM75C-specifically noise with amplitude greater
than 400 mVpp (the LM75’s typical hysteresis), overshoot greater than 300 mV above +Vs, and undershoot more
than 300 mV below GND-may prevent successful serial communication with the LM75C. Serial bus noacknowledge is the most common symptom, causing unnecessary traffic on the bus. The layout procedures
mentioned above apply also to the LM75C. Although the serial bus maximum frequency of communication is only
400 kHz, care must be taken to ensure proper termination within a system with long printed circuit board traces
or multiple parts on the bus. Resistance can be added in series with the SDA and SCL lines to further help filter
noise and ringing. A 5 kΩ resistor should be placed in series with the SCL line, placed as close as possible to the
SCL pin on the LM75C. This 5 kΩ resistor, with the 5 pF to 10 pF stray capacitance of the LM75 provides a 6
MHz to 12 MHz low pass filter, which is sufficient filtering in most cases.
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10.2 Layout Example
Figure 16. Typical Layout
22
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11 Device and Documentation Support
11.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 1. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LM75B
Click here
Click here
Click here
Click here
Click here
LM75C
Click here
Click here
Click here
Click here
Click here
11.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.3 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
18-Dec-2021
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM75BIM-3
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-55 to 125
LM75
BIM-3
LM75BIM-3/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
LM75
BIM-3
LM75BIM-5
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-55 to 125
LM75
BIM-5
LM75BIM-5/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
LM75
BIM-5
LM75BIMM-3
NRND
VSSOP
DGK
8
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-55 to 125
T01B
LM75BIMM-3/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
T01B
LM75BIMM-5/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
T00B
LM75BIMMX-3/NOPB
ACTIVE
VSSOP
DGK
8
3500
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
T01B
LM75BIMMX-5/NOPB
ACTIVE
VSSOP
DGK
8
3500
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
T00B
LM75BIMX-3
NRND
SOIC
D
8
2500
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-55 to 125
LM75
BIM-3
LM75BIMX-3/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
LM75
BIM-3
LM75BIMX-5
NRND
SOIC
D
8
2500
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-55 to 125
LM75
BIM-5
LM75BIMX-5/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 125
LM75
BIM-5
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
18-Dec-2021
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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