Edition 2, March 2011
What’s inside? Page
Thermocouple-to-Digital Converter . . . . . . . . . . . . . 2
Fan Controllers .................................3
High-Accuracy Sensors . . . . . . . . . . . . . . . . . . . . . . . . . 7
Low-Voltage Sensors ...........................8
Page
Multichannel Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Temperature Switches . . . . . . . . . . . . . . . . . . . . . . . . . 12
LM75-Compatible Products . . . . . . . . . . . . . . . . . . . . 13
Selection Guide ...............................14
Product Guide
Thermal Management
Accurate Thermocouple-to-Digital Converter
Simplifies Designs and Cuts System Cost
2
The MAX31855 integrates all the required functions of a discrete solution, including an ADC, precision amplifier,
temperature sensor for cold-junction compensation, and a 3-wire interface. By combining these components
in a single IC, the MAX31855 simplifies design, reduces development time, and saves both component cost and
board space. The device also provides ±2.0°C accuracy for temperatures ranging from -200°C to +700°C for a K
type thermocouple, with no calibration required. The MAX31855 is ideal for industrial and temperature controls,
fuel cells, HVAC, and automotive applications.
MAX31855
VBIAS
TEMP
SENSOR
VOLTAGE
REFERENCE
IN1
IN2
THERMOCOUPLE
All these
functions in one
SO package!
TO MICROCONTROLLER
ADC
AMP
SPI is a trademark of Motorola, Inc.
Improves and Speeds System Design
• Performs cold-junction compensation
• 14-bit, 0.25°C resolution
• Versions available for K, J, N, S, T, E, and
R type thermocouples
• Simple SPI™-compatible interface
• Measures thermocouple inputs from
-270°C to +1800°C
Integrated Solution Saves Space and Cuts
BOM Cost
• Eliminates need for multiple discrete components
• Available in an 8-pin SO package
Simplified System Fault Management and
Troubleshooting Improve Reliability
• Detects thermocouple shorts to GND or VCC
• Detects open thermocouple
Industrial Controls Temperature Controllers
HVAC Systems
Choosing the Right Fan Controller
3
Maxim offers over 20 products with fan-control functions. This design note helps you to narrow the choice in
two simple steps.
Step 1: Start with the Fan
Fans are usually described by the number of wires. A 2-wire fan has just two power-supply leads. A 3-wire fan
adds an output, usually a “tachometer” output that produces a square wave with a fixed number of pulses
per fan revolution. The tachometer signal can monitor fan speed and serve as a feedback signal when closed-
loop control of speed is necessary. A 4-wire fan also includes a speed-control input that accepts a PWM signal
whose duty cycle controls the fan’s speed.
Step 2: Pick the Speed-Adjustment Method
Typically, fan control reduces the audibility of fan noise, so the preferred approach is to gradually adjust fan
speed in response to temperature changes.
If a 4-wire fan is used, it is easy to adjust the fan’s speed: just drive the speed-control input with a PWM signal
in the 20kHz to 40kHz range. In Figure 1, the MAX6639 fan controller regulates the speed of two fans by
adjusting the PWM waveforms’ duty cycles to produce the desired speed as indicated by the fans’ outputs.
In contrast, 2- and 3-wire fans require a more complex control scheme. PWM drive works, but instead of driving
the fan’s speed-control input, the PWM signal drives a power-supply pass transistor. The optimum frequency
is in the 30Hz range. Note that this approach can be noisy—each edge of the PWM waveform can cause an
audible transient due to motion of the fan motor assembly. Also, some fan manufacturers recommend against
PWM on the fan’s power supply due to reliability concerns. Be sure to check with your fan vendor before
proceeding with this approach.
Another way to control the speed of a 2- or 3-wire fan is to linearly vary the fan’s power-supply voltage. You
lose a bit of efficiency, but the approach is both quiet and reliable. A few fan controllers, such as the MAX6620
(Figure 3), can produce a variable fan supply voltage controlled over a bus such as I2C. You can also generate
an adjustable linear fan supply by using a PWM-output fan controller and adding a lowpass filter and power
amplifier, as shown in Maxim application notes "Circuit Converts PWM to Amplified and Buffered Linear Signal"
(www.maxim-ic.com/AN3149) and "Circuit Converts PWM Fan Drive to Linear and Reduces Acoustic Noise"
(www.maxim-ic.com/AN3530).
If the fan will be used infrequently or located far from users, the acoustic noise may not be important. In this
case, you can implement very simple, low-cost fan control using a temperature switch to turn a fan on and
off. In the Figure 2 example, the temperature switch’s output directly drives the control input of a 4-wire fan.
For 2- or 3-wire fans, the temperature switch in Figure 4 drives the gate of a power transistor that enables or
disables the fan’s power supply. Note that switching the fan on and off suddenly is very audible and, therefore,
is rarely appropriate for consumer or office equipment that will be located close to users.
Fan Control Type 2-Wire and 3-Wire Fans 4-Wire Fans
Control Method Maxim Solution* Control Method Maxim Solution*
Linear Control
Linear fan controller MAX6620 (Figure 3) N/A N/A
PWM fan controller + lowpass
filter + pass device
MAX6639, MAX6615,
MAX6641 (refer to app notes
3149 and 3530)
N/A N/A
PWM Control Low-frequency PWM controller
+ pass device
MAX6639, MAX6615,
MAX31782, MAX31785
High-frequency PWM
controller
MAX6639 (Figure 1),
MAX6615, MAX31782,
MAX31785
On/Off (Noise and Power-Supply
Stress Are Not Concerns)
Temperature switch +
pass device MAX6510 (Figure 4) Temperature switch MAX6510 (Figure 2)
*Single output configurable as an interrupt or square wave.
4
Choosing the Right Fan Controller (cont.)
Simple on/off
control when
acoustic noise is
not a concern
4-WIRE FAN
PWM
VFAN
2-WIRE FAN
VFAN VFAN
3-WIRE FAN
TACH OR
LOCKED ROTOR
(OPEN DRAIN)
TACH OR
LOCKED ROTOR
(OPEN DRAIN)
Variable speed control for
minimal audible noise
Using a 4-Wire Fan
2.7V TO 5.5V
PWM
TACH
OUT
HYST GND
OUTSET
SET
VFAN
Figure 1. PWM control of 4-wire fans.
Figure 2. On/off control of a 4-wire fan with a temperature switch.
OT
VCC
VCC
VCC
VCC
VCC
VCC
FANFAIL
TO SYSTEM SHUTDOWN
VFAN
TACH IN 2
TACH IN 1
PWM OUT 1
PWM OUT 2
VFAN
VFAN VFAN
THERM
ALERT
SMBCLK
SMBDATA
VCC
DXP2
DXN
DXP1
TO CLOCK
THROTTLE
TO
SMBus
MASTER
SMBus
INTERFACE
AND CONTROL
REGISTERS
TACH
FEEDBACK
AND PWM
GENERATOR
3.0V TO 5.5V
SDA
SCL
FAN_FAIL
DAC_START
SPINUP_START
WD_START
XTAL
XTAL
Variable linear drive for
minimal audible noise
TACH1
DACOUT1
DACFB1
Figure 3. Fan-speed control of a 2- or 3-wire fan
by varying the fan’s power-supply voltages.
F
A
N
1
VFAN
TACH2
DACOUT2
DACFB2
F
A
N
2
VFAN
TACH3
DACOUT3
DACFB3
F
A
N
3
VFAN
TACH4
DACOUT4
DACFB4
F
A
N
4
Figure 4. On/off control of a 2- or 3-wire fan using
a temperature switch and pass transistor.
Simple on/off control when
acoustic noise is not a concern I2C
INTERFACE,
REGISTERS,
CONTROL
LOGIC
DAC/LDO
DRIVER,
TACH
MONITOR
MAX6639
MAX6620
MAX6510
2.7V TO 5.5V
2- OR 3-WIRE
FAN
OUT
HYST GND
OUTSET
SET
VFAN
MAX6510
REMOTE
AND LOCAL
TEMP
SENSOR
Using a 2- or 3-Wire Fan
ALARM
LOGIC
Simple on/off
control when
acoustic noise is
not a concern
4-WIRE FAN
PWM
VFAN
2-WIRE FAN
VFAN VFAN
3-WIRE FAN
TACH OR
LOCKED ROTOR
(OPEN DRAIN)
TACH OR
LOCKED ROTOR
(OPEN DRAIN)
Variable speed control for
minimal audible noise
Using a 4-Wire Fan
2.7V TO 5.5V
PWM
TACH
OUT
HYST GND
OUTSET
SET
VFAN
Figure 1. PWM control of 4-wire fans.
Figure 2. On/off control of a 4-wire fan with a temperature switch.
OT
VCC
VCC
VCC
VCC VCC
VCC
FANFAIL
TO SYSTEM SHUTDOWN
VFAN
TACH IN 2
TACH IN 1
PWM OUT 1
PWM OUT 2
VFAN
VFAN VFAN
THERM
ALERT
SMBCLK
SMBDATA
VCC
DXP2
DXN
DXP1
TO CLOCK
THROTTLE
TO
SMBus
MASTER
SMBus
INTERFACE
AND CONTROL
REGISTERS
TACH
FEEDBACK
AND PWM
GENERATOR
3.0V TO 5.5V
SDA
SCL
FAN_FAIL
DAC_START
SPINUP_START
WD_START
XTAL
XTAL
Variable linear drive for
minimal audible noise
TACH1
DACOUT1
DACFB1
Figure 3. Fan-speed control of a 2- or 3-wire fan
by varying the fan’s power-supply voltages.
F
A
N
1
VFAN
TACH2
DACOUT2
DACFB2
F
A
N
2
VFAN
TACH3
DACOUT3
DACFB3
F
A
N
3
VFAN
TACH4
DACOUT4
DACFB4
F
A
N
4
Figure 4. On/off control of a 2- or 3-wire fan using
a temperature switch and pass transistor.
Simple on/off control when
acoustic noise is not a concern I2C
INTERFACE,
REGISTERS,
CONTROL
LOGIC
DAC/LDO
DRIVER,
TACH
MONITOR
MAX6639
MAX6620
MAX6510
2.7V TO 5.5V
2- OR 3-WIRE
FAN
OUT
HYST GND
OUTSET
SET
VFAN
MAX6510
REMOTE
AND LOCAL
TEMP
SENSOR
Using a 2- or 3-Wire Fan
ALARM
LOGIC
Choosing the Right Fan Controller (cont.)
5
Simple on/off
control when
acoustic noise is
not a concern
4-WIRE FAN
PWM
VFAN
2-WIRE FAN
VFAN VFAN
3-WIRE FAN
TACH OR
LOCKED ROTOR
(OPEN DRAIN)
TACH OR
LOCKED ROTOR
(OPEN DRAIN)
Variable speed control for
minimal audible noise
Using a 4-Wire Fan
2.7V TO 5.5V
PWM
TACH
OUT
HYST GND
OUTSET
SET
VFAN
Figure 1. PWM control of 4-wire fans.
Figure 2. On/off control of a 4-wire fan with a temperature switch.
OT
VCC
VCC
VCC
VCC
VCC
VCC
FANFAIL
TO SYSTEM SHUTDOWN
VFAN
TACH IN 2
TACH IN 1
PWM OUT 1
PWM OUT 2
VFAN
VFAN VFAN
THERM
ALERT
SMBCLK
SMBDATA
VCC
DXP2
DXN
DXP1
TO CLOCK
THROTTLE
TO
SMBus
MASTER
SMBus
INTERFACE
AND CONTROL
REGISTERS
TACH
FEEDBACK
AND PWM
GENERATOR
3.0V TO 5.5V
SDA
SCL
FAN_FAIL
DAC_START
SPINUP_START
WD_START
XTAL
XTAL
Variable linear drive for
minimal audible noise
TACH1
DACOUT1
DACFB1
Figure 3. Fan-speed control of a 2- or 3-wire fan
by varying the fan’s power-supply voltages.
F
A
N
1
VFAN
TACH2
DACOUT2
DACFB2
F
A
N
2
VFAN
TACH3
DACOUT3
DACFB3
F
A
N
3
VFAN
TACH4
DACOUT4
DACFB4
F
A
N
4
Figure 4. On/off control of a 2- or 3-wire fan using
a temperature switch and pass transistor.
Simple on/off control when
acoustic noise is not a concern I2C
INTERFACE,
REGISTERS,
CONTROL
LOGIC
DAC/LDO
DRIVER,
TACH
MONITOR
MAX6639
MAX6620
MAX6510
2.7V TO 5.5V
2- OR 3-WIRE
FAN
OUT
HYST GND
OUTSET
SET
VFAN
MAX6510
REMOTE
AND LOCAL
TEMP
SENSOR
Using a 2- or 3-Wire Fan
ALARM
LOGIC
PWM0
MSDA
MSCL
+3.3V
VDD
VSS
SDA
SCL
6 CHANNELS
UP TO 4
CHANNELS
TACH0
RS+0
RS-0
PWM1
TACH1
RS+1
RS-1
PWM2
TACH2
RS+2
RS-2
PWM3
TACH3
RS+3
RS-3
PWM4
TACH4
RS+4
RS-4
PWM5
TACH5
RS+5
RS-5
REMOTE
TEMPERATURE
DIODE
EACH CHANNEL
CAN READ A REMOTE
TEMPERATURE DIODE
OR A REMOTE VOLTAGE
REMOTE
VOLTAGE
A0
HOST
INTERFACE
I2C TEMP
SENSOR
CONTROL
REG18
A1/TACHSEL
REG25
SPDT
MUX
FROM
TACHSEL
OPTIONAL
SUPPORT FOR
TWO FANS
DS75LV
MAX31785
RST
ALERT
FAULT
Industry’s First 6-Channel, Intelligent Fan Controller
Optimizes System Efficiency and Reliability
6
PMBus is a trademark of SMIF, Inc.
The MAX31785 saves system power by operating fans at the lowest possible speeds to reduce audible noise,
extend fan life, and minimize system maintenance. This intelligent fan controller provides closed-loop fan
control of six independent fans, based on the measurements of up to 11 available temperature-sensing
sources. Alternately, an external host can manually command the fan speeds, while the component
automatically adjusts them. To further improve system reliability, the MAX31785 contains a fan-health-
diagnostic function to help users predict impending fan failures.
Integrates All Functions for Controlling Multiple Fans
• 6 independent channels of fan control support 3-wire and 4-wire fans
• User-selectable RPM- or PWM-based fan control eases system design
• Staggered fan spin-up eases power-supply stress
• 11 temperature-sensing sources monitor multiple hot spots
• Fault detection on all fans and temperature sensors improves reliability
• PMBus™-compliant command interface
• I2C/SMBus-compatible serial bus with bus timeout function
• Available in a 40-pin TQFN-EP package
Servers
Fan Trays
Network Switches
7
Part Interface Accuracy
(°C)
Supply Voltage
Range
(V)
Package
DS18B20 1-Wire�±0.5 (-10 to +85) 3.0 to 5.5 3-TO92, 8-µSOP (µMAX�), 8-SO
DS1620 3-wire
±0.5 (0 to +70)
2.7 to 5.5
8-SO
DS1631/DS1631A 2-wire 8-µSOP (µMAX), 8-SO
DS1626 3-wire 8-µSOP (µMAX)
DS620 2-wire 1.7 to 3.5 8-µSOP-EP (µMAX-EP)
DS600 Analog ±0.5 (-20 to +100) 2.7 to 5.5 8-µSOP-EP (µMAX-EP)
DS7505 2-wire ±0.5 (0 to +70) 1.7 to 3.7 8-µSOP (µMAX), 8-SO
MAX31723 SPI/3-wire ±0.5 (0 to +70) 1.7 to 3.7 8-µSOP (µMAX)
Industry’s Highest Accuracy Temp Sensors
We offer a broad range of temperature devices with an accuracy of ±0.5°C (max) over wide temperature and
voltage ranges. Several popular digital-communication interfaces, including analog output, support a wide
range of applications.
ERROR (°C)
REFERENCE TEMPERATURE (°C)
±0.5°C Accuracy over
Temperature and Voltage
0 10 20 30 40 50 60 70
MEAN
0.8
0.6
0.4
0.2
0
-0.2 -3
-0.4
-0.6
-0.8
+3
Network Switches/Routers
Highest Accuracy Temp Sensors
1-Wire and µMAX are registered trademarks of Maxim Integrated Products, Inc.
Temperature
Recorders
Base Stations
8
Part Interface Supply Voltage
(V)
Accuracy
(°C) Package
DS7505
2-wire
1.7 to 3.7 ±0.5 (0 to +70) 8-µSOP (µMAX), 8-SO
DS620 1.7 to 3.5 ±0.5 (0 to +70) 8-µSOP-EP (µMAX-EP)
DS75LV 1.7 to 3.7 ±2.0 (-25 to +100) 8-µSOP (µMAX), 8-SO
DS75LX 1.7 to 3.7 ±2.0 (-25 to +100) 8-µSOP (µMAX), 8-SO
MAX6607
Analog
1.8 to 3.6 ±3.5 (0 to +70) 5-SC70
MAX6608 1.8 to 3.6 ±3.5 (0 to +70) 5-SOT23
MAX6613 1.8 to 5.5 ±4.0 (0 to +50) 5-SC70
MAX31722
SPI/3-wire
1.7 to 3.7 ±2.0 (-40 to +85) 8-µSOP (µMAX)
MAX31723 1.7 to 3.7 ±0.5 (0 to +70) 8-µSOP (µMAX)
Low-Voltage Temperature Sensors
Most Complete Portfolio of Low-Voltage Temp Sensor ICs
Maxim offers a variety of temperature devices with supply voltages as low as 1.7V. Our portfolio includes both
digital and analog sensors, with several accuracy grades to choose from. The low operating voltages simplify
design in systems operating from commonly used low-voltage rails, as well as power-sensitive systems.
• Low supply voltage
• 1.7V for digital temperature sensors
• 1.8V for analog temperature sensors
• 2-wire, SPI/3-wire, and analog options
• -55°C to +125°C operating range
(up to +130°C for the MAX6613)
• No external components required
to measure temperature
• User-selectable 9- to 12-bit
resolution
• Multiple packaging options,
down to 5-pin SC70
1.8V
0001 1010
V
T
VCC
Thermostat function
– DS7505 (NV thresholds)
– DS620 (NV thresholds)
– DS75LV/LX
– MAX31722/23
Industry-standard compatibility
– DS75LV/LX (LM75)
– DS7505 (LM75)
– MAX6613 (LM20)
Tiny SC70 package
– MAX6607
– MAX6613
High accuracy (±0.5°C)
– DS7505
– DS620
– MAX31723
Analog or
digital outputs
9
OVERSAMPLING
MODULATOR
CONFIGURATION/
STATUS REGISTER
PRECISION
REFERENCE
I/O CONTROL
AND
INPUT SENSE
DIGITAL
DECIMATOR
SDI
VDD
VDD
SCLK
SDO
SERMODE
GND
CE TEMPERATURE
REGISTER
THIGH AND TLOW
REGISTERS
THERMOSTAT
COMPARATOR
MAX31723
Congurable as a
stand-alone thermostat
that requires no host
processor overhead
Choice of SPI or
3-wire interface
is user selectable
Also available in a
±2.0°C version!
Nonvolatile thermostat
registers eliminate need
for programming at
power-up
TOUT
The MAX31723 SPI/3-wire temperature sensor provides measurements within ±0.5°C over a wide temperature
range of 0° to +70°C. That accuracy, coupled with its low supply-voltage operation of 1.7V to 3.7V, aids designers
in meeting error and power budgets.
Industry’s First SPI/3-Wire Temperature Sensor Operates
from a Supply Voltage as Low as 1.7V
Accurate Temperature Sensor Enables Easy Implementation into Low-Power Systems
Highly Versatile Temp Sensor Eases System Design
• Two accuracy versions
• MAX31723: ±0.5°C from 0°C to +70°C; ±2.0°C from -55°C to +125°C
• MAX31722: ±2.0°C from -40°C to +85°C; ±3.0°C from -55°C to +125°C
• Low 1.7V to 3.7V supply-voltage operating range
• Thermostat output with NV registers
• 9- to 12-bit resolution (0.5°C to 0.0625°C)
• -55°C to +125°C operating range
• SPI or 3-wire communication, user selectable
• Available in 8-pin μMAX package
10
Using Multichannel Temperature Sensors to Save
Space and Cost
When a circuit board includes multiple hot spots, standard practice is to monitor the temperatures of those
locations to avoid performance degradation and even catastrophic failure.
A conventional approach is shown in Figure 1, where a sensor is placed near each hot spot. Monitoring
board hot spots can be done with standard local sensors (TS5–TS8). If a thermally sensitive component has a
temperature-sensing transistor (also called a “thermal diode”) integrated on the die of a high-temperature IC, a
remote-temperature sensor can use the IC’s thermal diode to accurately measure its die temperature (TS1–TS4).
Figure 2 shows the same board, but in this case, a single multichannel sensor IC monitors all of the hot spots.
The circuit uses the MAX6581 (also see Figure 3), which can measure up to seven external temperatures as
well as its own temperature. The device can monitor temperatures on ASICs, CPUs, and FPGAs using thermal
diodes, or measure board hot spots using discrete diode-connected transistors and the internal local sensor.
Using a single IC to monitor several locations reduces sensor cost. It also simplifies the design by allowing
several channels of temperature data to be read from a single I2C slave address.
Features in Multichannel Temperature Sensors
• Overtemperature Alarm Outputs. These outputs are useful if you need a signal to indicate that one of the
thermal channels has exceeded its temperature limit.
• Bus Timeout. Useful on I2C and SMBus sensors, this timeout resets the bus if the IC holds the data line low
for more than a preset limit (usually around 35ms), thus preventing the IC from locking up the bus.
• Resistance Cancellation. Excess resistance (more than a few ohms) in the remote-diode path will cause
measurement errors. These errors are predictable if you know the resistance value. If you do not, resistance
cancellation is helpful to eliminate series-resistance errors.
• Beta Compensation. Measurement errors can result when a target IC’s thermal diode has very low beta (e.g.,
less than one). If your thermal diode’s beta is low, a sensor with beta compensation will improve accuracy.
• Thermistor Inputs. A thermistor can be helpful for measuring temperature. For example, you can use a
thermistor with long leads to monitor air temperature above the surface of a board.
Maintaining Good Measurement Accuracy
• If discrete diode-connected transistors are used, either pnps or npns will work. Use small-signal
transistors with consistent beta greater than 50.
• Separate the thermal diode’s signal traces from high-speed and high-current traces to avoid noise pickup.
• Use a filter capacitor at the thermal-diode inputs (DXP and DXN). See the sensor data sheet for the
optimum value.
• Most multichannel sensors bias the thermal diode’s cathode about 0.6V. If you want to measure the
temperature of an IC with the thermal diode’s cathode grounded, use one of Maxim’s many multichannel
sensors that specifies accuracy with a grounded cathode.
11
Using Multichannel Temperature Sensors (cont.)
ASIC
TS1
REMOTE
ASIC
TS2
REMOTE
CPU
TS4
REMOTE
TS5
LOCAL
TS6
LOCAL
TS7
LOCAL
TS8
LOCAL
HOT SPOT
HOT SPOT
HOT SPOT
HOT SPOT
FPGA
TS3
REMOTE
Figure 1. The conventional way to monitor multiple hot spots is to mount
one temperature sensor at each location.
ASIC
ASIC
FPGA
CPU
HOT SPOT
HOT SPOT
HOT SPOT
HOT SPOT
MAX6581
MULTICHANNEL
SENSOR
Figure 2. The MAX6581 can monitor up to seven external temperatures
as well as its own die temperature. This approach saves space and cost
by eliminating multiple discrete sensors.
Conventional Approach Using Multiple Sensors Improved Approach Using One Multichannel Sensor
MAX6581
CPU
SMBCLK
SMBDATA
DXP2
DXN1
DXP1
GND
DXP4
DXN2
DXP3
DXN3
VCC (3.3V)
DXP7
DXN7
DXP6
DXP5
DXN6
DXN5
DXN4
HOT SPOT 4
HOT SPOT 3
HOT SPOT 2
HOT SPOT 1
FPGA
ASIC
OVERT
STBY
ALERT
Figure 3. The MAX6581 monitors a total of eight temperature locations with ±1°C accuracy.
Small,
4mm x 4mm,
24-pin TQFN
package
Highly Accurate MAX6581 Reduces Component Count
• 1 local and 7 remote temperature channels replace up to 8 individual sensors
• Remote-sensing channels monitor ASICs, FPGAs, CPUs, and board hot spots
• ±1°C remote-temperature accuracy (+60°C to +100°C)
• All remote channels have series-resistance cancellation
12
Industry’s Most Comprehensive Portfolio of
Temp Switches
Temperature switches provide simple protection from potentially damaging thermal conditions by
generating an over- or undertemperature signal when the temperature is outside the safe operating
range. Whatever kind of temperature switch you need—factory preset, resistor adjustable, pin strapped, or
remote-diode sensing—Maxim has you covered.
Factory-Preset Trip Thresholds
MAX6501–MAX6508
MAX6514–MAX6519
Resistor-Adjustable Trip Thresholds
MAX6509/MAX6510
Remote with Preset or
Pin-Strapped Thresholds
MAX6513 (Preset)
MAX6685/MAX6686 (Pin Strapped)
Local/Remote with
Pin-Strapped Local Threshold
MAX6687/MAX6688
N
CPU DXP
3.3V
12V
TO SYSTEM
SHUTDOWN
TO SYSTEM
SHUTDOWN
GND
TLOW
THIGH
RSET
DXN
S1
S2
CSMAX6685
CPU DXP
VDD
VDD
3.3V
3.3V
GND
TLOCAL
TREMOTE
DXN
S1
S2
CSMAX6687
2.7V TO 5.5V
GNDHYST GND
TOVER
MAX6515
VCC
2.7V TO 5.5V
GND
HYST
SET
TOVER
MAX6509
VCC
Industry’s
most
accurate
(±1.5°C)
N
CPU DXP
3.3V
12V
TO SYSTEM
SHUTDOWN
TO SYSTEM
SHUTDOWN
GND
TLOW
THIGH
RSET
DXN
S1
S2
CSMAX6685
CPU DXP
VDD
VDD
3.3V
3.3V
GND
TLOCAL
TREMOTE
DXN
S1
S2
CSMAX6687
2.7V TO 5.5V
GNDHYST GND
TOVER
MAX6515
VCC
2.7V TO 5.5V
GND
HYST
SET
TOVER
MAX6509
VCC
Industry’s
most
accurate
(±1.5°C)
N
CPU DXP
3.3V
12V
TO SYSTEM
SHUTDOWN
TO SYSTEM
SHUTDOWN
GND
TLOW
THIGH
RSET
DXN
S1
S2
CSMAX6685
CPU DXP
VDD
VDD
3.3V
3.3V
GND
TLOCAL
TREMOTE
DXN
S1
S2
CSMAX6687
2.7V TO 5.5V
GNDHYST GND
TOVER
MAX6515
VCC
2.7V TO 5.5V
GND
HYST
SET
TOVER
MAX6509
VCC
Industry’s
most
accurate
(±1.5°C)
N
CPU DXP
3.3V
12V
TO SYSTEM
SHUTDOWN
TO SYSTEM
SHUTDOWN
GND
TLOW
THIGH
RSET
DXN
S1
S2
CSMAX6685
CPU DXP
VDD
VDD
3.3V
3.3V
GND
TLOCAL
TREMOTE
DXN
S1
S2
CSMAX6687
2.7V TO 5.5V
GNDHYST GND
TOVER
MAX6515
VCC
2.7V TO 5.5V
GND
HYST
SET
TOVER
MAX6509
VCC
Industry’s
most
accurate
(±1.5°C)
13
Maxim Sensor Features Benefits
DS7505 ±0.5°C accuracy, NV memory, 1.7V to 3.6V supply range Better accuracy, fail-safe overtemperature detection
DS75LV 1.7V to 3.7V supply range Compatible with low-voltage, low-power designs
DS75LX 1.7V to 3.7V supply range, 27 I2C addresses Up to 27 sensors can be on a single bus
DS75 Fully compatible Accuracy guaranteed across full supply voltage
MAX7500 Fully compatible Accuracy guaranteed across full supply voltage
MAX7501–MAX7504 I2C reset input Allows controller to reset I2C interface
MAX6625/MAX6626 3mm x 3mm, 6-pin TDFN package Ideal for space-limited designs
DS1775 3mm x 3mm, 5-pin SOT23 package Ideal for space-limited designs
LM75-Compatible Temp Sensors—from Industry
Standard to Best in the Industry
Maxim offers more than a dozen “LM75-compatible” temperature sensors that give you options ranging from
industry-standard configurations to sensors with dramatically improved performance. Whether you need an
alternate source for the standard LM75 or a temperature sensor that offers best-in-class performance, you will
find what you are looking for at Maxim.
±0.5ºC Accuracy and Nonvolatile Memory
If you need better accuracy than the LM75 can achieve, select the DS7505, a pin- and register-compatible
upgrade with superior accuracy. The DS7505 features a maximum temperature-measurement error of ±0.5ºC
from 0ºC to +70ºC across its full power-supply range. The device operates from a 1.7V to 3.6V supply-voltage
range, making it ideal for low-voltage systems.
The DS7505’s conversion resolution is programmable from 0.5ºC to 0.0625ºC (9 to 12 bits). For systems
that require the OS trip threshold to be the correct value at power-up, the DS7505’s threshold is stored in
nonvolatile memory. This is an especially powerful feature when using OS for system protection—for example,
to disable the system’s power supply when the measured temperature is too high.
Other Improvements
Maxim offers other LM75-compatible digital temperature sensors with a variety of improved features. Because
temperature accuracy is guaranteed across the full supply-voltage range instead of just at 3.3V or 5.0V, all of
these products have better accuracy than the LM75 in real systems.
An example is the DS75LX, which operates from power-supply voltages as low as 1.7V. This device is ideal for
designs that require more than eight sensors on a single bus; its three address-selection inputs use three-state
logic, resulting in 27 available slave addresses.
Products such as the MAX7501–MAX7504 offer another useful feature: an input that resets the I2C interface.
Pulling this input low returns the internal registers to their default values and resets the I2C interface, thus
allowing the I2C master to reset any slaves on the board when a communications fault is detected.
Lastly, if you need a smaller footprint, choose the MAX6625, MAX6626, or DS1775. These devices are all register
compatible with the LM75 and are available in space-saving, 3mm x 3mm SOT23 or TDFN packages.
Maxim’s Industry-Standard, LM75-Compatible Temp Sensors
www.maxim-ic.com/TempSensors
†1000-up recommended resale. Prices provided are for design guidance and are FOB USA. International prices will differ due to local duties, taxes, and exchange rates. Not all packages are offered in 1k increments, and some may require minimum order quantities.
*Contact factory for pricing details.
Remote Digital Temperature Sensors www.maxim-ic.com/Thermal-Management
Part Description Interface
Remote
Sensors
Local
Sensor
Accuracy
(°C)
Accuracy
Range (°C)
Operating Temp
Range (°C)
VCC Supply
Range (V)
IDD
(µA, max) Package
Footprint
(mm2)
Price†
($) EV Kit
MAX6627/28 Remote temp sensors with SPI interface 3-wire 1 — ±1 0 to +125 -55 to +125 3.0 to 5.5 400/50 8-TDFN, 8-SOT23 9 1.78 —
MAX6682 Thermistor-to-digital converter 3-wire 1 — ±3 LSB — -55 to +125 3.0 to 5.5 300 8-µMAX 15 1.89 —
MAX6581 8-channel, ±1°C accurate temp monitor I2C/SMBus 7 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 24-TSSOP 16 * —
MAX6602 5-channel temp monitor (4 remote, 1 local) with standby I2C/SMBus 4 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 16-TSSOP 30 3.82 —
MAX6638 Remote/local temp monitor with 2 independent SMBus interfaces I2C/SMBus 1 ✓±2 +25 to +100 -40 to +125 3.0 to 5.5 950 16-TQFN 16 * ✓
MAX6642 Remote/local temp sensor with overtemp alarm I2C/SMBus 1 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 6-TDFN 9 1.15 ✓
MAX6646/47/49 Remote/local temp sensors with overtemp alarms I2C/SMBus 1 ✓±1 +60 to +145 -55 to +125 3.0 to 5.5 400 8-µMAX 15 1.96 —
MAX6648/92 Remote/local temp sensors with overtemp alarms I2C/SMBus 1 ✓±0.8 +25 to +125 -55 to +125 3.0 to 5.5 400 8-µMAX, 8-SO 15 1.96 —/✓
MAX6654 Remote/local temp sensor with resistance cancellation and overtemp alarm I2C/SMBus 1 ✓±2 +70 to +100 -55 to +125 3.0 to 5.5 1000 16-QSOP 30 2.37 ✓
MAX6655/56 2-channel remote/local temp sensors and 4-channel voltage monitors I2C/SMBus 2 ✓±1.5 +60 to +100 -55 to +125 3.0 to 5.5 1000 16-QSOP 30 2.81 ✓
/—
MAX6657/58/59 Remote/local temp sensors with overtemp alarms I2C/SMBus 1 ✓±1 +60 to +100 -55 to +125 3.0 to 5.5 1000 8-SO, 16-QSOP 30 2.02 —
MAX6680/81 Fail-safe remote/local temp sensors with overtemp alarms I2C/SMBus 1 ✓±1 +60 to +100 -55 to +125 3.0 to 5.5 1000 16-QSOP 30 2.42 —/✓
MAX6689 7-channel temp monitor (6 remote, 1 local) with standby I2C/SMBus 6 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 20-TSSOP, 20-QSOP 30 3.82 —
MAX6690 Remote/local temp sensor with resistance cancellation and overtemp alarm I2C/SMBus 1 ✓±2 +70 to +100 -55 to +125 3.0 to 5.5 70 16-QSOP 30 * —
MAX6695/96 Dual remote/local temp sensors with fixed or pin-selectable SMBus address I2C/SMBus 2 ✓±1.5 +60 to +100 -40 to +125 3.0 to 5.5 1000 10-µMAX 15 2.42 ✓
/—
MAX6697 7-channel temp monitor (6 remote, 1 local) I2C/SMBus 6 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 20-TSSOP, 20-QSOP 30 3.82 —
MAX6698 7-channel temp monitor (3 remote, 1 local, 3 thermistor) I2C/SMBus 6 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 20-TSSOP, 20-QSOP 30 3.82 ✓
MAX6699 5-channel temp monitor (4 remote, 1 local) I2C/SMBus 4 ✓±1 +60 to +100 -40 to +125 3.0 to 5.5 1000 16-TSSOP, 16-QSOP 30 3.82 —
Local Digital Temperature Sensors
Part Description Interface
Accuracy
(°C)
Accuracy
Range (°C)
Operating Temp
Range (°C)
VCC Supply
Range (V)
IDD
(µA, max) Package
Footprint
(mm2)
Price†
($) EV Kit
DS1821 Programmable digital thermostat and thermometer 1-Wire ±1 0 to +85 -55 to +125 2.7 to 5.5 1000 8-SO, PR35 30 2.01 ✓
DS1822 Econo 1-Wire digital thermometer 1-Wire ±2 -10 to +85 -55 to +125 3.0 to 5.5 1500 8-SO, TO-92 30 1.61 ✓
DS1825 Precision 1-Wire digital thermometer with 4-bit ID 1-Wire ±0.5 -10 to +85 -55 to +125 3.0 to 3.7 1500 8-µMAX 15 1.70 ✓
DS18B20 Precision digital thermometer 1-Wire ±0.5 -10 to +85 -55 to +125 3.0 to 5.5 1500 8-µSOP, 8-SO, TO-92 15 1.76 ✓
DS18S20 Precision digital thermometer 1-Wire ±0.5 -10 to +85 -55 to +125 3.0 to 5.5 1500 8-SO, TO-92 30 2.09 ✓
DS28EA00 Precision digital thermometer with sequence detect and GPIO 1-Wire ±0.5 -10 to +85 -40 to +85 3.0 to 5.5 1500 8-µSOP 15 2.25 ✓
MAX6575 Temp sensor with single-wire time-delay interface Single wire ±4.5 +85 -55 to +125 2.7 to 5.5 250 6-SOT23 9 0.79 —
MAX6576/77 Temp sensors with single-wire period output/frequency output Single wire ±4.5/±3.5 +85 -55 to +125 2.7 to 5.5 250 6-SOT23 9 0.79 —
DS1620 Precision digital thermometer and thermostat 3-wire ±0.5 0 to +70 -55 to +125 2.7 to 5.5 1000 8-SO, 8-DIP 30 2.89 ✓
DS1624 Precision digital thermometer and memory 3-wire ±0.5 0 to +70 -55 to +125 2.7 to 5.5 1000 8-SO, 8-DIP 30 3.75 ✓
DS1626 Precision digital thermometer and thermostat 3-wire ±0.5 0 to +70 -55 to +125 2.7 to 5.5 1000 8-µMAX 15 1.66 ✓
DS1720 Econo digital thermometer and thermostat 3-wire ±2.5 -55 to +125 -55 to +125 2.7 to 5.5 1000 8-SO 30 2.26 ✓
DS1722 Digital thermometer SPI/3-wire ±2 -40 to +85 -55 to +125 2.65 to 5.5 500 8-µMAX, 8-SO 15 1.10 ✓
DS1726 Digital thermometer and thermostat 3-wire ±1 -10 to +85 -55 to +125 2.7 to 5.5 400 8-µMAX 15 1.61 —
MAX6629–32 Digital temp sensors with SPI interface 3-wire ±1 0 to +70 -55 to +150 3.0 to 5.5 400/50 6-TDFN, 6-SOT23 9 1.39 ✓/—
MAX6662 12-bit + sign SPI temp sensor 3-wire ±1.6 0 to +70 -55 to +150 3.0 to 5.5 600 8-SO 30 1.44 —
DS1629 Digital thermometer and real-time clock (RTC) I2C/SMBus ±2 -10 to +85 -55 to +125 2.2 to 5.5 1000 8-SO 30 3.22 ✓
DS1631 Precision digital thermometer and thermostat I2C/SMBus ±0.5 0 to +70 -55 to +125 2.2 to 5.5 1000 8-µMAX, 8-SO 30 1.66 ✓
DS1721 Digital thermometer and thermostat I2C/SMBus ±1 -10 to +85 -55 to +125 2.7 to 5.5 1000 8-µMAX, 8-SO 30 1.61 ✓
DS1731 Digital thermometer and thermostat I2C/SMBus ±1 -10 to +85 -55 to +125 2.2 to 5.5 1000 8-µMAX 15 1.61 ✓
DS1775 Digital thermometer and thermostat I2C/SMBus ±2 -10 to +85 -55 to +125 2.7 to 5.5 1000 5-SOT23 9 0.88 ✓
DS620 Low-voltage, precision digital thermometer and thermostat I2C/SMBus ±0.5 0 to +70 -55 to +125 1.7 to 3.5 800 8-µMAX 15 1.66 ✓
DS75 Digital thermometer and thermostat I2C/SMBus ±2 -25 to +100 -55 to +125 2.7 to 5.5 1000 8-µMAX, 8-SO 15 0.90 ✓
DS75LV Low-voltage digital thermometer and thermostat I2C/SMBus ±2 -25 to +100 -55 to +125 1.7 to 3.7 1000 8-µMAX, 8-SO 15 0.90 ✓
DS75LX Digital thermometer and thermostat with extended addressing I2C/SMBus ±2 -25 to +100 -55 to +125 1.7 to 3.7 1000 8-µMAX, 8-SO 15 0.75 ✓
LM75 Digital temp sensor and thermal watchdog (LM75 second source) I2C/SMBus ±2 -25 to +100 -55 to +125 3.0 to 5.5 500 8-µMAX, 8-SO 15 0.65 —
MAX6604 Temp monitor for DDR memory modules I2C/SMBus ±2 +40 to +125 -20 to +125 2.7 to 3.6 500 8-TDFN, 8-TSSOP 6 0.95 —
MAX6625/26 Digital temp sensors with overtemp alarm I2C/SMBus ±2 0 to +70 -55 to +125 3.0 to 5.5 1000 6-TDFN, 6-SOT23 9 0.90 —
MAX6633/34/35 Digital temp sensors with overtemp alarms and 4/3/2 address pins I2C/SMBus ±1.5 -20 to +125 -55 to +150 3.0 to 5.5 350 8-SO 30 1.28 —
MAX6652/83 Digital temp sensors and 4-channel voltage monitor I2C/SMBus ±3 -20 to +80 -40 to +125 2.7 to 5.5 500 10-µMAX 15 1.84 —
MAX7500–04 Digital temp sensors with overtemp alarm (LM75 compatible) I2C/SMBus ±2 -25 to +100 -55 to +125 3.0 to 5.5 500 8-µMAX, 8-SO 15 0.72 —
MAX31722 Low-voltage, SPI/3-wire temperature sensor SPI/3-wire ±2 -40 to +85 -55 to +125 1.3 to 3.7 1200 8-µMAX 15 0.75 —
MAX31723 Low-voltage, SPI/3-wire precision temperature sensor SPI/3-wire ±0.5 0 to +70 -55 to +125 1.3 to 3.7 1200 8-µMAX 15 1.40 —
Analog Temperature Sensors
www.maxim-ic.com/Thermal-Management
Part Description
Accuracy
(°C)
Accuracy
Range (°C)
Operating Temp
Range (°C)
VCC Supply
Range (V)
IDD
(µA, max) Package
Footprint
(mm2)
Price†
($) EV Kit
DS600 Precision analog temp sensor with temp switch ±0.5 -20 to +100 -40 to +125 2.7 to 5.5 140 8-µMAX 15 1.80 ✓
MAX6605 Analog temp sensor in SC70 ±3.8 -20 to +85 -55 to +125 2.7 to 5.5 10 5-SC70 4 0.40 —
MAX6607/08 1.8V analog temp sensors in SC70/SOT23 ±5 -10 to +85 -20 to +85 1.8 to 3.6 15 5-SC70, 5-SOT23 4/9 0.59 —
MAX6610/11 Temp sensors with voltage reference in SOT23 ±3.7 -20 to +85 -40 to +125 3.0 to 5.5 250 6-SOT23 9 0.80 —
MAX6612 High-slope analog temp sensor ±4.3 +60 to +100 -55 to +150 2.4 to 5.5 35 5-SC70 4 0.59 —
MAX6613 1.8V to 5.5V analog temp sensor ±4.4 -20 to +85 -55 to +130 1.8 to 5.5 13 5-SC70 4 0.35 —
Temperature Switches
Part Description
Remote
Sensors
Local
Sensor
Accuracy
(°C)
Accuracy
Range (°C)
Operating Temp
Range (°C)
VCC Supply
Range (V)
IDD
(µA, max) Package
Footprint
(mm2)
Price†
($) EV Kit
MAX6501–04 Temp switches with factory-set thresholds (in 10°C increments) 0 ✓±6 +75 to +125 -55 to +125 2.7 to 5.5 85 5-SOT23, 7-TO-220 9 0.67 —
MAX6505–08 Dual-output temp switches with factory-set thresholds (in 5°C increments) 0 ✓±3.5 0 to +95 -55 to +125 2.5 to 5.5 1 6-SOT23 9 0.79 —
MAX6509/10 Resistor-programmable temp switches 0 ✓±4.7 0 to +125 -55 to +125 2.5 to 5.5 0 5-SOT23, 6-SOT23 9 0.70 —
MAX6513 Remote temp switch with factory-set thresholds (in 10°C increments) 1 — ±5 -40 to +85 -40 to +85 3.0 to 5.5 600 6-TDFN 9 0.85 —
MAX6514/15 Temp switches with factory-set thresholds (in 10°C increments) 0 ✓ ±2.5 +75 to +115 -55 to +125 2.7 to 5.5 40 5-SOT23 9 0.75 —
MAX6516–19 Temp switches with analog outputs, factory-set thresholds (in 10°C increments) 0 ✓ ±2.5 +75 to +115 -55 to +125 2.7 to 5.5 40 5-SOT23 9 0.75 —
MAX6685/86 Dual-output remote-junction temp switches 1 — ±1.5 0 to +125 -40 to +125 3.0 to 5.5 800 8-µMAX 15 3.31 —
MAX6687 Dual-output remote-junction temp switch 1 ✓ ±3 0 to +85 -40 to +125 3.0 to 5.5 800 8-µMAX 15 3.31 —
Fan Controllers
Part Description Interface
Remote
Sensors
Local
Sensor
Fan
Outputs
Tach
Inputs
Operating Temp
Range (°C)
VCC Supply
Range (V)
IDD
(µA, max) Package
Footprint
(mm2)
Price†
($) EV Kit
MAX6665 Temp switch with factory-programmed threshold and fan on/off driver Analog 0 ✓1 — -40 to +125 2.7 to 5.5 200 8-SO 30 1.32 —
DS1780 2-channel hardware monitor with DAC output I2C/SMBus 0 ✓ 1 — -40 to +125 2.8 to 5.75 1000 24-TSSOP 52 2.21 ✓
MAX6615/16 2-channel temp monitors/fan-speed controllers with thermistor inputs I2C/SMBus 2 ✓ 2 2 -40 to +125 3.0 to 5.5 — 16-QSOP/24-QSOP 30 1.95 —/✓
MAX6620 Quad linear fan controller with RPM control I2C/SMBus 0 — 4 4 -40 to +125 3.0 to 5.5 500 28-TQFN 25 2.50 ✓
MAX6639 2-channel temp monitor with dual PWM fan-speed control I2C/SMBus 1 ✓ 2 2 -40 to +125 3.0 to 3.6 1000 16-TQFN, 16-QSOP 25 1.22 —/✓
MAX6650/51 Fan-speed regulators and monitors (single/quad) I2C/SMBus 0 — 1 1/4 -40 to +85 3.0 to 5.5 10,000 10-µMAX 15 2.10 —/✓
MAX6653/63/64 Local/remote temp monitors and PWM fan controllers I2C/SMBus 1 ✓ 1 1 -40 to +125 3.0 to 5.5 — 16-QSOP 30 2.02 ✓/—
MAX6660 Remote temp monitor and fan-speed controller I2C/SMBus 1 — 1 1 -40 to +125 3.0 to 5.5 500 16-QSOP 30 3.26 ✓
MAX6661 Remote-junction, temp-controlled fan-speed regulator I2C/SMBus 1 — 1 1 -40 to +125 3.0 to 5.5 700 16-QSOP 30 3.46 —
MAX6678 2-channel temp monitor with dual-PWM fan controller and 5 GPIOs I2C/SMBus 2 ✓ 2 — -40 to +125 3.0 to 5.5 1000 20-TQFN, 20-QSOP 25 1.82 —
MAX6684 Fan-failure detector and power switch for 2-wire fans Logic 0 — 1 — -40 to +85 3.0 to 5.5 3400 8-SO 30 1.06 —
MAX31782 System management microcontroller I2C/SMBus 6 ✓6 6 -40 to +85 2.7 to 5.5 2340 40-TQFN 36 3.45 ✓
MAX31785 6-channel intelligent fan controller I2C/SMBus 10 ✓6 6 -40 to +85 2.7 to 5.5 3000 40-TQFN 36 3.45 ✓
Other Thermal Products
Part Description Interface
Operating Temp
Range (°C)
VCC Supply
Range (V)
IDD
(µA, max) Package
Footprint
(mm2)
Price†
($) EV Kit
DS1682 Total-elapsed-time recorder with alarm I2C/SMBus -40 to +85 2.5 to 5.5 300 8-SO 30 1.73 —
DS2422 1-Wire temp/data logger with 8KB data-log memory 1-Wire -40 to +85 2.8 to 3.6 350 24-SO 166 27.25 —
MAX6603 2-channel platinum RTD-to-voltage signal conditioner Analog -40 to +125 3.0 to 5.5 5500 10-TDFN 9 1.50 ✓
MAX6618 PECI-to-I2C translator I2C/SMBus -20 to +120 3.0 to 3.6 7000 10-µMAX 15 * —
MAX6674/75 K-thermocouple-to-digital converters (0°C to +128°C and 0°C to +1024°C) 3-wire -20 to +85 3.0 to 5.5 1500 8-SO 30 3.82 ✓
MAX6684 Fan-failure detector and power switch for 2-wire fans Logic -40 to +85 3.0 to 5.5 3400 8-SO 30 1.06 —
MAX31855 Thermocouple-to-digital converter for K, J, N, T, R, E, and S type thermocouples SPI -40 to +125 3.0 to 3.6 1500 8-SO 30 3.10 ✓
†1000-up recommended resale. Prices provided are for design guidance and are FOB USA. International prices will differ due to local duties, taxes, and exchange rates. Not all packages are offered in 1k increments, and some may require minimum order quantities.
*Contact factory for pricing details.
