19-4385; Rev 0; 3/09
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
General Description
The LM75 temperature sensor includes a delta-sigma
analog-to-digital converter, and a digital overtempera-
ture detector. The host can query the LM75 through its
I
2
C interface to read temperature at any time. The
open-drain overtemperature output (OS) sinks current
when the programmable temperature limit is exceeded.
The OS output operates in either of two modes, com-
parator or interrupt. The host controls the temperature
at which the alarm is asserted (T
OS
) and the hysteresis
temperature below which the alarm condition is not
valid (T
HYST
). Also, the LM75’s T
OS
and T
HYST
regis-
ters can be read by the host. The address of the LM75
is set with three pins to allow multiple devices to work
on the same bus. Power-up is in comparator mode, with
defaults of T
OS
= +80°C and T
HYST
= +75°C. The 3.0V
to 5.5V supply voltage range, low supply current, and
I
2
C interface make the LM75 ideal for many applica-
tions in thermal management and protection.
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Features
SO (SOP) and µMAX
®
(µSOP) Packages
I
2
C Bus Interface
Separate Open-Drain OS Output Operates as
Interrupt or Comparator/Thermostat Input
Register Readback Capability
Power-Up Defaults Permit Stand-Alone Operation
as a Thermostat
3.0V to 5.5V Supply Voltage
Low Operating Supply Current 250µA (typ), 1mA
(max)
4µA (typ) Shutdown Mode Minimizes Power
Consumption
Up to Eight LM75s Can Be Connected to a Single
Bus
Pin- and/or Register-Compatible with Improved-
Performance Maxim Sensors Including MAX7500,
MAX6625, MAX6626, DS75LV, and DS7505
LM75
Applications
Thermal System Management
Thermal Protection
Test Equipment
Computers and Office Electronics
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Functional Diagram
+V
S
= 3.0V to 5.5V
8
3
SILICON
BANDGAP
TEMPERATURE
SENSOR
16
9-BIT DELTA-
SIGMA ADC
16
SET POINT
COMPARATOR W/
HYSTERESIS
OS
Pin Configuration
TOP VIEW
SDA
SCL
OS
GND
1
2
3
4
TOS SET POINT
REGISTER
+
LM75
CONFIGURATION
REGISTER
POINTER
REGISTER
16
8
16
T
HYST
SET
POINT REGISTER
16
1
8
7
6
5
+V
S
A0
A1
A2
7
A0
6
A1
5
A2
8
2-WIRE INTERFACE
2
4
SDA
SCL
μMAX
(μSOP), SO
Ordering Information/Selector Guide
PART
LM75BIM-3+
LM75BIMX-3+
LM75BIMM-3+
LM75BIMMX-3+
LM75BIM-5+
LM75BIMX-5+
LM75BIMM-5+
LM75BIMMX-5+
PIN-PACKAGE
8 SO (SOP)
8 SO (SOP)
8 µMAX (µSOP)
8 µMAX (µSOP)
8 SO (SOP)
8 SO (SOP)
8 µMAX (µSOP)
8 µMAX (µSOP)
PKG
Bulk
T&R
Bulk
T&R
Bulk
T&R
Bulk
T&R
SUPPLY VOLTAGE (V)
3.3
3.3
3.3
3.3
5.0
5.0
5.0
5.0
TOP MARK
LM75BIM-3
LM75BIM-3
T01B
T01B
LM75BIM-5
LM75BIM-5
T00B
T00B
Note:
Devices are specified over the -55°C to +125°C temperature range and include I
2
C noise filter.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
ABSOLUTE MAXIMUM RATINGS (Note 1)
+V
S
to GND ...........................................................-0.3V to +6.0V
OS, SDA, SCL to GND...........................................-0.3V to +6.0V
All Other Pins to GND .................................-0.3V to (+V
S
+ 0.3V)
Input Current at Any Pin (Note 2)..........................................5mA
Package Input Current (Note 2)..........................................20mA
OS Output Sink Current ......................................................10mA
Continuous Power Dissipation (T
A
= +70°C) (Note 3)
8-Pin µMAX (µSOP)
(derate 4.5mW/°C above +70°C) ..................................362mW
8-Pin SO (SOP) (derate 5.9mW/°C above +70°C) ........471mW
Junction-to-Case Thermal Resistance (θ
JC
) (Note 3)
8-Pin µMAX (µSOP) .......................................................42°C/W
8-Pin SO (SOP)..............................................................40°C/W
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 3)
8-Pin µMAX (µSOP) .....................................................221°C/W
8-Pin SO (SOP)............................................................170°C/W
ESD Protection
Human Body Model (R
D
= 1.5kΩ, C
S
= 100pF)
All Pins to GND .................................................................±2kV
Operating Temperature Range .........................-55°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifica-
tions do not apply when operating the device beyond its rated operating conditions.
Note 2:
When the input voltage (V
I
) at any pin exceeds the Absolute Maximum Ratings limits (V
I
< GND, V
I
> 6V or V
I
> +V
S
), the
current at that pin should be limited to 5mA. The 20mA maximum package input current rating limits the number of pins that
can safely exceed the power supplies with an input current of 5mA to four.
Note 3:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a single-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(+V
S
= +3.0V to +5.5V, unless otherwise noted. Temperature accuracy specifications apply for +V
S
= 3.3V for versions with “-3” in
the suffix and for +V
S
= 5V for versions with “-5” in the suffix. T
A
= -55°C to +125°C, unless otherwise noted. Typical values are at
+V
S
= +5V, T
A
= +25°C.) (Notes 4, 5)
PARAMETER
Accuracy (Six-Sigma)
Accuracy (Three-Sigma) (Note 6)
Resolution
Temperature Conversion Time
Quiescent Supply Current
+V
S
Supply Voltage Range
OS Output Saturation Voltage
OS Delay
OS Output Fall Time
T
OS
Default Temperature
T
HYST
Default Temperature
t
OF
I
OUT
= 4.0mA (Note 8)
(Note 9)
C
L
= 400pF, I
O
= 3mA (Note 10)
(Note 11)
(Note 11)
80
75
1
(Note 7)
I
2
C
inactive
Shutdown mode, +V
S
= 3V
Shutdown mode, +V
S
= 5V
3.0
SYMBOL
CONDITIONS
-25°C
≤
T
A
≤
+100°C
-55°C
≤
T
A
≤
+125°C
-25°C
≤
T
A
≤
+100°C
-55°C
≤
T
A
≤
+125°C
MIN
-2.0
-3.0
-1.5
-2.0
9
100
0.25
4
6
5.5
0.8
6
250
300
0.5
TYP
MAX
+2.0
+3.0
+1.5
+2.0
UNITS
°C
°C
Bits
ms
mA
µA
V
V
Conver-
sions
ns
°C
°C
2
_______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
ELECTRICAL CHARACTERISTICS (continued)
(+V
S
= +3.0V to +5.5V, unless otherwise noted. Temperature accuracy specifications apply for +V
S
= 3.3V for versions with “-3” in
the suffix and for +V
S
= 5V for versions with “-5” in the suffix. T
A
= -55°C to +125°C, unless otherwise noted. Typical values are at
+V
S
= +5V, T
A
= +25°C.) (Notes 4, 5)
PARAMETER
LOGIC (SDA, SCL, A0, A1, A2)
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
Input Capacitance
Output High Current
Output Low Voltage
I
2
C-COMPATIBLE TIMING (Notes 12, 13)
(Clock) SCL Period
Data In Setup Time to SCL High
Data Out Stable After SCL Low
Start Condition Setup Time
(SDA Low to SCL Low)
STOP Condition Hold Time
SDA Time Low for Reset of Serial
Interface
t
SCL
t
SU:DAT
t
HD:DAT
t
SU:STA
t
HD:STO
t
TIMEOUT
(Note 14)
Bus timeout inactive
10% of SDA to 10% of SCL
10% of SCL to 10% of SDA
90% of SCL to 90% of SDA
2.5
100
0
100
100
75
325
µs
ns
µs
ns
ns
ms
V
IH
V
IL
I
IH
I
IL
C
IN
V
IN
= 5V
V
IN
= 0V
All digital inputs
V
OH
= 5V
I
OL
= 3mA
-1.0
+V
S
x
0.7
-0.3
0.005
-0.005
20
10
0.4
+V
S
+
0.5
+V
S
x
0.3
1.0
V
V
µA
µA
pF
µA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
LM75
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
All parts operate properly over the 3V to 5.5V supply voltage range. The devices are tested and specified for rated
accuracy at their nominal supply voltage.
All parameters are measured at T
A
= +25°C. Values over the temperature range are guaranteed by design.
There is no industry-wide standard for temperature accuracy specifications. Maxim’s standard is six-sigma. The three-
sigma specification is included to allow easier comparison to products built by manufacturers who use different standards.
This specification indicates how often temperature data is updated. The devices can be read at any time without regard to
conversion state, while yielding the last conversion result.
For best accuracy, minimize output loading. Higher sink currents can affect sensor accuracy due to internal heating.
OS delay is user programmable up to 6 over-limit conversions before OS is set to minimize false tripping in noisy environ-
ments.
Guaranteed by design.
Default values set at power-up.
All timing specifications are guaranteed by design.
Unless otherwise noted, these specifications apply for +V
S
= +5VDC for LM75BIM-5 and LM75BIMM-5 and +V
S
=
+3.3VDC for LM75BIM-3 and LM75BIMM-3. C
L
(load capacitance) on output lines = 80pF, unless otherwise specified.
The switching characteristics of the LM75 fully meet or exceed the published specifications of the I
2
C bus. These parame-
ters are the timing relationships between SCL and SDA signals related to the LM75. They are not I
2
C bus specifications.
Holding the SDA line low for a time greater than t
TIMEOUT
causes the device to reset SDA to the IDLE state of the
serial bus communication (SDA set high).
_______________________________________________________________________________________
3
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
LM75 toc01
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
LM75 toc02
ACCURACY vs. TEMPERATURE
4 TYPICAL PARTS
1.5
1.0
ACCURACY (°C)
0.5
0
-0.5
-1.0
LM75 toc03
300
QUIESCENT SUPPLY CURRENT (μA)
290
280
270
260
+V
S
= +3V
250
240
230
-55
-25
5
35
65
95
+V
S
= +5V
6
SHUTDOWN SUPPLY CURRENT (μA)
5
4
3
+V
S
= +3V
2
1
0
+V
S
= +5V
2.0
-1.5
-2.0
-55
-25
5
35
65
95
125
-55
-25
5
35
65
95
125
TEMPERATURE (°C)
TEMPERATURE (°C)
125
TEMPERATURE (°C)
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
SDA
SCL
OS
GND
A2
A1
A0
+V
S
FUNCTION
Serial-Data Input/Output Line. Open drain. Connect SDA to a pullup resistor.
Serial Clock Input. Open drain. Connect SCL to a pullup resistor.
Overtemperature Shutdown Output. Open drain. Connect OS to a pullup resistor.
Ground
2-Wire Interface Address Input. Connect A2 to GND or +V
S
to set the desired I
2
C bus address. Do not
leave unconnected (see Table 1).
2-Wire Interface Address Input. Connect A1 to GND or +V
S
to set the desired I
2
C bus address. Do not
leave unconnected (see Table 1).
2-Wire Interface Address Input. Connect A0 to GND or +V
S
to set the desired I
2
C bus address. Do not
leave unconnected (see Table 1).
Positive Supply Voltage Input. Bypass to GND with a 0.1µF bypass capacitor.
4
_______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
Detailed Description
The LM75 temperature sensor measures temperature
and converts the data into digital form using a band-
gap type temperature sensor and a 9-bit delta-sigma
ADC. An I
2
C-compatible 2-wire serial interface allows
access to conversion results. The LM75 accepts stan-
dard I
2
C commands to read the data, set the overtem-
perature alarm (OS) trip thresholds, and configure other
characteristics. While reading the Temperature register,
any changes in temperature are ignored until the read
is completed. The Temperature register is updated for
the new temperature measurement upon completion of
the read operation.
Power-Up and Power-Down
The LM75 powers up to a known state, as indicated in
Table 2. Some of these settings are summarized as fol-
lowing:
• Comparator mode
• T
OS
= +80°C
• T
HYST
= +75°C
• OS active low
• Command byte pointer = 0x00
LM75
I
2
C-Compatible Bus Interface
From a software perspective, the LM75 appears as a set
of byte-wide registers that contain temperature data,
alarm threshold values, and control bits. A standard I
2
C-
compatible, 2-wire serial interface reads temperature
data and writes control bits and alarm threshold data.
Each device responds to its own I
2
C slave address,
which is selected using A0, A1, and A2. See Table 1.
T
OS
TEMPERATURE
T
HYST
OS Output, T
OS,
and T
HYST
Limits
In comparator mode (see Figure 1), the open-drain OS
output asserts when the temperature rises above the
limit programmed into the T
OS
register, and becomes
high impedance when the temperature falls below the
limit set in the T
HYST
register. In this mode the LM75
operates as a thermostat, and the OS output can be
used to take action to reduce the temperature (e.g.,
turn on a cooling fan, reduce clock speed, or shut
down the system).
In interrupt mode, exceeding T
OS
also asserts OS. OS
remains asserted until a read operation is performed on
any of the registers. Once OS has asserted due to
crossing above T
OS
and is then reset, it is asserted
again only when the temperature drops below T
HYST
.
The output then remains asserted until it is reset by a
read. It is then asserted again if the temperature rises
above T
OS
, and so on. Putting the LM75 into shutdown
mode also resets OS.
OS OUTPUT
(COMPARATOR MODE)
OS SET ACTIVE LOW
OS OUTPUT
(INTERRUPT MODE)
OS SET ACTIVE LOW
READ
OPERATION
READ
OPERATION
READ
OPERATION
Figure 1. OS Output Temperature Response Diagram
Table 1. Slave Address
BIT 7
1
BIT 6
0
BIT 5
0
BIT 4
1
BIT 3
A2
BIT 2
A1
BIT 1
A0
BIT 0
R/W
Table 2. Register Functions
REGISTER NAME
Temperature
Configuration
T
HYST
T
OS
ADDRESS
(hex)
00
01
02
03
POR STATE
(hex)
000X
00
4B0X
500X
POR STATE (binary)
0000 0000 0XXX XXXX
0000 0000
0100 1011 0XXX XXXX
0101 0000 0XXX XXXX
POR STATE (°C)
—
—
75
80
READ/
WRITE
Read only
R/W
R/W
R/W
X = Don’t care.
_______________________________________________________________________________________
5
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