LM75BIMM-5+T [MAXIM]
Sensor/Transducer, CMOS, 8 Pin, Plastic/epoxy;
| 型号： | LM75BIMM-5+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Sensor/Transducer, CMOS, 8 Pin, Plastic/epoxy 传感器 换能器 温度传感器 输出元件 |
| 文件： | 总12页 (文件大小：266K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4385; Rev 0; 3/09
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
General Description
Features
o SO (SOP) and µMAX® (µSOP) Packages
o I2C Bus Interface
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
o Separate Open-Drain OS Output Operates as
2
I C interface to read temperature at any time. The
Interrupt or Comparator/Thermostat Input
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
o Register Readback Capability
o Power-Up Defaults Permit Stand-Alone Operation
as a Thermostat
o 3.0V to 5.5V Supply Voltage
at which the alarm is asserted (T ) and the hysteresis
OS
temperature below which the alarm condition is not
o Low Operating Supply Current 250µA (typ), 1mA
valid (T
). Also, the LM75’s T
and T
regis-
HYST
HYST
OS
(max)
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
o 4µA (typ) Shutdown Mode Minimizes Power
Consumption
o Up to Eight LM75s Can Be Connected to a Single
defaults of T
= +80°C and T
= +75°C. The 3.0V
OS
HYST
Bus
to 5.5V supply voltage range, low supply current, and
2
I C interface make the LM75 ideal for many applica-
o Pin- and/or Register-Compatible with Improved-
Performance Maxim Sensors Including MAX7500,
MAX6625, MAX6626, DS75LV, and DS7505
tions in thermal management and protection.
Applications
Thermal System Management
Thermal Protection
Functional Diagram
+V = 3.0V to 5.5V
S
Test Equipment
Computers and Office Electronics
8
3
OS
16
16
SILICON
BANDGAP
TEMPERATURE
SENSOR
SET POINT
COMPARATOR W/
HYSTERESIS
9-BIT DELTA-
SIGMA ADC
µMAX is a registered trademark of Maxim Integrated Products, Inc.
TOS SET POINT
REGISTER
Pin Configuration
TOP VIEW
POINTER
REGISTER
CONFIGURATION
REGISTER
T
SET
HYST
POINT REGISTER
+
SDA
SCL
OS
1
2
3
4
8
7
6
5
+V
A0
A1
A2
S
8
16
8
16
16
LM75
7
6
5
1
2
A0
A1
A2
SDA
SCL
2-WIRE INTERFACE
4
GND
μMAX (μSOP), SO
Ordering Information/Selector Guide
PART
LM75BIM-3+
PIN-PACKAGE
8 SO (SOP)
PKG
Bulk
T&R
Bulk
T&R
Bulk
T&R
Bulk
T&R
SUPPLY VOLTAGE (V)
TOP MARK
LM75BIM-3
LM75BIM-3
T01B
3.3
3.3
3.3
3.3
5.0
5.0
5.0
LM75BIMX-3+
LM75BIMM-3+
LM75BIMMX-3+
LM75BIM-5+
8 SO (SOP)
8 µMAX (µSOP)
8 µMAX (µSOP)
8 SO (SOP)
T01B
LM75BIM-5
LM75BIM-5
T00B
LM75BIMX-5+
LM75BIMM-5+
LM75BIMMX-5+
8 SO (SOP)
8 µMAX (µSOP)
8 µMAX (µSOP)
5.0
2
T00B
Note: Devices are specified over the -55°C to +125°C temperature range and include I 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
ABSOLUTE MAXIMUM RATINGS (Note 1)
+V to GND ...........................................................-0.3V to +6.0V
S
Junction-to-Ambient Thermal Resistance (θ ) (Note 3)
JA
OS, SDA, SCL to GND...........................................-0.3V to +6.0V
8-Pin µMAX (µSOP).....................................................221°C/W
8-Pin SO (SOP)............................................................170°C/W
ESD Protection
All Other Pins to GND.................................-0.3V to (+V + 0.3V)
S
Input Current at Any Pin (Note 2)..........................................5mA
Package Input Current (Note 2)..........................................20mA
OS Output Sink Current ......................................................10mA
LM75
Human Body Model (R = 1.5kΩ, C = 100pF)
D
S
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
Continuous Power Dissipation (T = +70°C) (Note 3)
A
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 ) (Note 3)
JC
8-Pin µMAX (µSOP).......................................................42°C/W
8-Pin SO (SOP)..............................................................40°C/W
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 ) at any pin exceeds the Absolute Maximum limits (V < GND, V > 6V or V > +V ), the current at
I
I
I
I
S
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 = +3.0V to +5.5V, unless otherwise noted. Temperature accuracy specifications apply for +V = 3.3V for versions with “-3” in
S
S
the suffix and for +V = 5V for versions with “-5” in the suffix. T = -55°C to +125°C, unless otherwise noted. Typical values are at
S
A
+V = +5V, T = +25°C.) (Notes 4, 5)
S
A
PARAMETER
SYMBOL
CONDITIONS
MIN
-2.0
-3.0
-1.5
-2.0
TYP
MAX
+2.0
+3.0
+1.5
+2.0
UNITS
-25°C ≤ T ≤ +100°C
A
Accuracy (6 σ)
°C
-55°C ≤ T ≤ +125°C
A
-25°C ≤ T ≤ +100°C
A
Accuracy (3 σ) (Note 6)
°C
-55°C ≤ T ≤ +125°C
A
Resolution
9
100
0.25
4
Bits
ms
Temperature Conversion Time
(Note 7)
I2C inactive
300
0.5
mA
Quiescent Supply Current
Shutdown mode, +V = 3V
S
µA
Shutdown mode, +V = 5V
6
S
+V Supply Voltage Range
S
3.0
1
5.5
0.8
V
V
OS Output Saturation Voltage
I
= 4.0mA (Note 8)
OUT
Conver-
sions
OS Delay
(Note 9)
6
OS Output Fall Time
t
C = 400pF, I = 3mA (Note 10)
250
ns
°C
°C
OF
L
O
T
T
Default Temperature
(Note 11)
80
75
OS
Default Temperature
(Note 11)
HYST
2
_______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
ELECTRICAL CHARACTERISTICS (continued)
(+V = +3.0V to +5.5V, unless otherwise noted. Temperature accuracy specifications apply for +V = 3.3V for versions with “-3” in
S
S
the suffix and for +V = 5V for versions with “-5” in the suffix. T = -55°C to +125°C, unless otherwise noted. Typical values are at
S
A
+V = +5V, T = +25°C.) (Notes 4, 5)
S
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
LOGIC (SDA, SCL, A0, A1, A2)
+V
0.7
x
+V
0.5
+
x
S
S
Input High Voltage
V
V
V
IH
+V
0.3
S
Input Low Voltage
V
-0.3
-1.0
IL
Input High Current
Input Low Current
Input Capacitance
Output High Current
Output Low Voltage
I
V
V
= 5V
= 0V
0.005
-0.005
20
1.0
µA
µA
pF
µA
V
IH
IN
IN
I
IL
C
All digital inputs
= 5V
IN
V
10
OH
I
= 3mA
0.4
OL
I2C-COMPATIBLE TIMING (Notes 12, 13)
(Clock) SCL Period
t
Bus timeout inactive
2.5
100
0
µs
ns
µs
SCL
Data In Setup Time to SCL High
Data Out Stable After SCL Low
t
10% of SDA to 10% of SCL
10% of SCL to 10% of SDA
SU:DAT
HD:DAT
t
Start Condition Setup Time
(SDA Low to SCL Low)
t
90% of SCL to 90% of SDA
100
100
75
ns
ns
SU:STA
STOP Condition Hold Time
t
HD:STO
SDA Time Low for Reset of Serial
Interface
t
(Note 14)
325
ms
TIMEOUT
Note 4: 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.
Note 5: All parameters are measured at T = +25°C. Values over the temperature range are guaranteed by design.
A
Note 6: There is no industry-wide standard for temperature accuracy specifications. Maxim’s standard is 6-σ. The 3-σ specifica-
tion is included to allow easier comparison to products built by manufacturers who use different standards.
Note 7: 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.
Note 8: For best accuracy, minimize output loading. Higher sink currents can affect sensor accuracy due to internal heating.
Note 9: OS delay is user programmable up to 6 over-limit conversions before OS is set to minimize false tripping in noisy environ-
ments.
Note 10: Guaranteed by design.
Note 11: Default values set at power-up.
Note 12: All timing specifications are guaranteed by design.
Note 13: Unless otherwise noted, these specifications apply for +V = +5VDC for LIM75BIM-5 and LIM75BIMM-5 and +V =
S
S
+3.3VDC for LIM75BIM-3 and LIM75BIMM-3. C (load capacitance) on output lines = 80pF, unless otherwise specified.
L
2
The switching characteristics of the LM75 fully meet or exceed the published specifications of the I C bus. These parame-
2
ters are the timing relationships between SCL and SDA signals related to the LM75. They are not I C bus specifications.
Note 14: Holding the SDA line low for a time greater than t
causes the device to reset SDA to the IDLE state of the
TIMEOUT
serial bus communication (SDA set high).
_______________________________________________________________________________________
3
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
QUIESCENT SUPPLY CURRENT
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
vs. TEMPERATURE
ACCURACY vs. TEMPERATURE
LM75
300
6
5
4
3
2
1
0
2.0
1.5
1.0
0.5
0
4 TYPICAL PARTS
290
+V = +5V
S
280
270
260
250
240
230
+V = +5V
S
+V = +3V
S
-0.5
-1.0
-1.5
-2.0
+V = +3V
S
-55
-25
5
35
65
95
125
-55
-25
5
35
65
95
125
-55
-25
5
35
65
95
125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE ( C)
°
Pin Description
PIN
1
NAME
FUNCTION
SDA
SCL
OS
Serial-Data Input/Output Line. Open drain. Connect SDA to a pullup resistor.
Serial-Data Clock Input. Open drain. Connect SCL to a pullup resistor.
2
3
Overtemperature Shutdown Output. Open drain. Connect OS to a pullup resistor.
Ground
4
GND
2-Wire Interface Address Input. Connect A2 to GND or +V to set the desired I2C bus address. Do not
leave unconnected (see Table 1).
S
5
6
A2
A1
A0
2-Wire Interface Address Input. Connect A1 to GND or +V to set the desired I2C bus address. Do not
S
leave unconnected (see Table 1).
2-Wire Interface Address Input. Connect A0 to GND or +V to set the desired I2C bus address. Do not
S
7
8
leave unconnected (see Table 1).
+V
Positive Supply Voltage Input. Bypass to GND with a 0.1µF bypass capacitor.
S
4
_______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
Power-Up and Power-Down
Detailed Description
The LM75 powers up to a known state, as indicated in
The LM75 temperature sensor measures temperature
Table 2. Some of these settings are summarized as fol-
lowing:
and converts the data into digital form using a band-
gap type temperature sensor and a 9-bit sigma-delta
ADC. An I2C-compatible 2-wire serial interface allows
access to conversion results. The LM75 accepts stan-
dard I2C 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.
• Comparator mode
• T = +80°C
OS
• T
= +75°C
HYST
• OS active low
• Command byte pointer = 0x00
I2C-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 I2C-
compatible, 2-wire serial interface reads temperature
data and writes control bits and alarm threshold data.
Each device responds to its own I2C slave address,
which is selected using A0, A1, and A2. See Table 1.
OS Output, T
and T
Limits
HYST
OS,
In comparator mode (see Figure 1), the open-drain OS
output asserts when the temperature rises above the
limit programmed into the T
register, and becomes
OS
high impedance when the temperature falls below the
limit set in the T register. In this mode the LM75
HYST
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).
T
OS
TEMPERATURE
T
In interrupt mode, exceeding T
also asserts OS. OS
HYST
OS
remains asserted until a read operation is performed on
any of the registers. Once OS has asserted due to
OS OUTPUT
(COMPARATOR MODE)
OS SET ACTIVE LOW
crossing above T
and is then reset, it is asserted
OS
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 , and so on. Putting the LM75 into shutdown
OS
mode also resets OS.
OS OUTPUT
(INTERRUPT MODE)
OS SET ACTIVE LOW
READ
READ
READ
OPERATION
OPERATION
OPERATION
Figure 1. OS Output Temperature Response Diagram
Table 1. Slave Address
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
1
0
0
1
A2
A1
A0
RD/W
Table 2. Register Functions
ADDRESS
REGISTER NAME
(hex)
POR STATE
READ/
WRITE
POR STATE (binary)
POR STATE (°C)
(hex)
Temperature
Configuration
00
01
02
03
000X
00
0000 0000 0XXX XXXX
0000 0000
—
—
75
80
Read only
R/W
T
HYST
T
OS
4B0X
500X
0100 1011 0XXX XXXX
0101 0000 0XXX XXXX
R/W
R/W
X = Don’t care.
_______________________________________________________________________________________
5
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
SDA
t
BUF
LM75
t
SU:DAT
t
SU:STA
t
SU:STO
t
HD:DAT
t
t
LOW
HD:STA
SCL
t
HIGH
t
HD:STA
t
R
t
F
START
CONDITION
(S)
REPEATED START
CONDITION
(SR)
ACKNOWLEDGE
STOP
CONDITION
(P)
START
CONDITION
(S)
(A)
PARAMETERS ARE MEASURED FROM 10% TO 90%.
Figure 2. Serial Bus Timing
Table 3. Temperature, THYST, and TOS Register Definition
UPPER BYTE
LOWER BYTE
D15
Sign bit
1= Negative
0 = Positive
D14
D13
D12
D11
D10
4°C
D9
D8
D7
D6
X
D5
X
D4
D3
D2
X
D1
X
D0
X
MSB
64°C
LSB
0.5°C
32°C 16°C
8°C
2°C
1°C
X
X
X = Don’t care.
Table 4. Temperature Data Output Format
DIGITAL OUTPUT
0111 1101 0
TEMPERATURE (°C)
BINARY
HEX
7D0X
190X
008X
000X
FF8X
E70X
C90X
+125
+25
+0.5
0
0111 1101 0XXX XXXX
0001 1001 0XXX XXXX
0000 0000 1XXX XXXX
0000 0000 0XXX XXXX
1111 1111 1XXX XXXX
1110 0111 0XXX XXXX
1100 1001 0XXX XXXX
0001 1001 0
0000 0000 1
0000 0000 0
-0.5
-25
1111 1111 1
1110 0111 0
1100 1001 0
-55
X = Don’t care.
-55
-25
-0.5
LOCAL
TEMPERATURE ( C)
0
+0.5
+25
+125
Figure 3. Temperature-to-Digital Transfer Function
6
_______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
2
Figure 4. I C-Compatible Timing Diagram (Read)
_______________________________________________________________________________________
7
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
2
Figure 5. I C-Compatible Timing Diagram (Write)
8
_______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
bytes are written, the second data byte overrides the
first. The T and T registers require 1 address
byte, 1 pointer byte, and 2 data bytes. If only 1 data
byte is written, it is saved in bits D15–D8 of the respec-
tive register. If more than 2 data bytes are written, only
the first 2 bytes are recognized while the remaining
bytes are ignored.
Temperature Data Format
Temperature data is stored in the Temperature, T Set
OS
HYST
OS
Point, and T
Set Point registers. The temperature
HYST
data format is 9 bits, two’s complement, and the register
is read out in 2 bytes: an upper byte and a lower byte.
Bits D15–D7 contain the temperature data, with the LSB
representing 0.5°C and the MSB representing the sign
bit (see Table 3). The MSB is transmitted first. The last 7
bits of the lower byte, bits D6–D0, are don’t cares.
Read from the LM75 in one of two ways. If the location
latched in the Pointer register is set from the previous
read, the new read consists of an address byte, fol-
lowed by retrieving the corresponding number of data
bytes. If the Pointer register needs to be set to a new
address, perform a read operation by writing an
address byte, pointer byte, repeat start, and another
address byte.
Shutdown
Set bit D0 in the Configuration register to 1 to place the
LM75 in shutdown mode and reduce supply current to
4µA. In interrupt mode, entering shutdown resets the
OS output. While in shutdown, the I2C remains active
and T
and T
limit registers along with the
HYST
OS
An inadvertent 8-bit read from a 16-bit register, with the
D7 bit low, can cause the device to stop in a state
where the SDA line is held low. Ordinarily, this would
prevent any further bus communication until the master
sends nine additional clock cycles or SDA goes high.
At that time, a stop condition resets the device. If the
additional clock cycles are not generated by the mas-
ter, the LM75 bus resets and unlocks after the bus time-
out period has elapsed.
Configuration register remain accessible to the master.
Fault Queue
The fault queue prevents OS false tripping in noisy
environments. The number of faults set in the queue (up
to 6) must occur to trip the OS output.
Comparator/Interrupt Mode
The events that trigger OS are identical between com-
parator and interrupt modes. In comparator mode, OS
is asserted when the temperature rises above the T
OS
+V
S
value. OS is deasserted when the temperature drops
below the T value. In interrupt mode, OS is assert-
HYST
ed when the temperature rises above the T
value or
OS
falls below the T
value. OS is deasserted only after
HYST
performing a read operation.
A0
A1
OS Output
A2/RESET
SDA
LM75
The OS output is an open-drain output without an inter-
SMBus™
INTERFACE
BLOCK
nal pullup. Connect a pullup resistor from OS to +V .
S
Using larger resistance values reduces any tempera-
ture errors due to self heating from current entering OS.
OS
SCL
DATA
ADDRESS
OS Polarity
The OS polarity can be programmed for active-low or
active-high operation. In active-low operation, OS goes
low when triggered by a temperature event.
POINTER REGISTER
(SELECTS REGISTER
FOR COMMUNICATION)
REGISTER SELECT
TEMPERATURE
(READ ONLY)
POINTER = 0000 0000
CONFIGURATION
(READ/WRITE)
POINTER = 0000 0001
Internal Registers
The LM75’s Pointer register selects between four data
registers (see Figure 6). At power-up, the pointer is set
to read the Temperature register at address 0x00. The
Pointer register latches the last location to which it was
set. All registers are read and write, except the
Temperature register, which is read only.
T
OS
SET POINT
T
SET POINT
HYST
(READ/WRITE)
POINTER = 0000 0011
(READ/WRITE)
POINTER = 0000 0010
GND
Write to the Configuration register by writing an address
byte, a data pointer byte, and a data byte. If 2 data
Figure 6. Block Diagram
SMBus is a trademark of Intel Corp.
_______________________________________________________________________________________
9
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
Table 5. Configuration Register Definition
D7
D6
D5
D4
D3
D2
D1
D0
Comparator/
Interrupt
0
0
0
Fault Queue
Fault Queue
OS Polarity
Shutdown
LM75
Configuration Register
Table 6. Configuration Register Fault
Queue Bits
The 8-bit Configuration register sets the fault queue, OS
polarity, shutdown control, and whether the OS output
functions in comparator or interrupt mode. When writing
to the Configuration register, set bits D7, D6, and D5 to
zero (see Table 5).
D4
D3
NUMBER OF FAULTS
0
0
1 (POR state)
0
1
2
4
6
Bits D4 and D3, the fault queue bits, determine the
number of faults necessary to trigger an OS condition
(see Table 6). The number of faults set in the queue
must occur consecutively to trip the OS output. The
fault queue prevents OS false tripping in noisy environ-
ments.
1
0
1
1
through the leads. Because of this, the LM75 most easi-
ly measures the PCB temperature. For ambient temper-
ature measurements, mount the LM75 on a separate
PCB away from high power sources. Temperature
errors due to self heating of the LM75 die is minimal
due to the low supply current.
Set bit D2, the OS polarity bit, to zero to force the OS
output polarity to active low. Set bit D2 to 1 to set the
OS output polarity to active high. OS is an open-drain
output under all conditions and requires a pullup resis-
tor to output a high voltage (see Figure 1).
Digital Noise Issues
The lowpass filters in the SCL and SDA digital lines miti-
gate the effects of bus noise, and make communica-
tions in noisy environments more robust. Good layout
practices also help. Keep switching power supplies
away from digital lines, and arrange for high-speed dig-
ital traces to cross SCL and SDA at right angles.
Properly terminate long PCB traces and bus traces
connected to multiple slaves.
Set bit D1, the comparator/interrupt bit to zero to oper-
ate OS in comparator mode. In comparator mode, OS
is asserted when the temperature rises above the T
OS
value. OS is deasserted when the temperature drops
below the T value (see Figure 1). Set bit D1 to 1 to
HYST
operate OS in interrupt mode. OS is asserted in inter-
rupt mode when the temperature rises above the T
OS
value or falls below the T
value. OS is deasserted
HYST
Serial bus no-acknowledge (which causes unnecessary
bus traffic) is the most common symptom of excessive
noise coupling into the SDA and SCL lines. Noise with
amplitude greater than the LM75’s hysteresis (400mV
typ), overshoot greater than 300mV above +V , and
undershoot more than 300mV below GND may prevent
successful serial communication.
only after performing a read operation.
Set bit D0, the shutdown bit, to zero for normal opera-
tion. Set bit D0 to 1 to shutdown the LM75’s internal
blocks. The I2C interface remains active as long as the
,
P-P
S
shutdown bit is set. The T , T
, and Configuration
OS HYST
registers can still be written to and read from while in
shutdown.
Resistance can be added in series with the SDA and
SCL lines to help filter noise and ringing. A 5kΩ resistor
placed in series with the SCL line and as close as pos-
sible to the SCL pin, with the 5pF to 10pF stray capaci-
tance of the device, provides a 6MHz to 12MHz
lowpass filter, which is sufficient filtering in many cases.
Applications Information
LM75 measures the temperature of its own die. The
thermal path between the die and the outside world
determines the accuracy of temperature measure-
ments. Most of the heat flows in to or out of the die
10 ______________________________________________________________________________________
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
LM75
3V to
5.5V
3V to
5.5V
12V
12V 300mA
FAN MOTOR
R3
10kΩ
R2
10kΩ
+V
S
R1
10kΩ
R2
10kΩ
R3
10kΩ
GND
A0
A1
A2
OS
N
or +V
+V
s
LM75
GND
SCL
SDA
SCL
SDA
OS
LM75
GND
TO
Microcontroller
OS
2
Figure 7. I C Controlled Temperature Sensor
Figure 8. Fan Control
SHDN
3V to
5.5V
C1
0.1μF
OUT-
GND
BIAS
IN+
MAX4364
V
CC
R1
10kΩ
OUT+
IN-
C2
0.1μF
R5
200kΩ
+V
s
C4
6.8nF
C5
6.8nF
C3
6.8nF
LM75
GND
R2
10kΩ
R3
10kΩ
R4
10kΩ
Figure 9. Temperature Sensor with Audible Alarm
______________________________________________________________________________________ 11
Digital Temperature Sensor and Thermal
Watchdog with 2-Wire Interface
Package Information
Chip Information
For the latest package outline information and land patterns,
PROCESS: CMOS
go to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
LM75
8 SO (SOP)
S8-2
U8-1
21-0041
21-0036
8 µMAX (µSOP)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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