MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 1 of 49 Data Sheet
Rev 006 September 30, 2010
Features and Benefits
Small size, low cost
Easy to integrate
Factory calibrated in wide temperature range:
-40…+125 ˚C for sensor temperature and
-70…+380 ˚C for object temperature.
High accuracy of 0.5°C over wide temperature
range (0…+50°C for both Ta and To)
High (medical) accuracy calibration
Measurement resolution of 0.02°C
Single and dual zone versions
SMBus compatible digital interface
Customizable PWM output for continuous
reading
Available in 3V and 5V versions
Simple adaptation for 8…16V applications
Sleep mode for reduced power consumption
Different package options for applications and
measurements versatility
Automotive grade
Applications Examples
High precision non-contact temperature
measurements;
Thermal Comfort sensor for Mobile Air
Conditioning control system;
Temperature sensing element for residential,
commercial and industrial building air
conditioning;
Windshield defogging;
Automotive blind angle detection;
Industrial temperature control of moving parts;
Temperature control in printers and copiers;
Home appliances with temperature control;
Healthcare;
Livestock monitoring;
Movement detection;
Multiple zone temperature control – up to 100
sensors can be read via common 2 wires
Thermal relay / alert
Body temperature measurement
Ordering Information
Part No.
MLX90614
Temperature Code
E (-40°C to 85°C)
K (-40°C to 125°C)
Package Code
SF (TO-39) - Option Code
- X X X
(1) (2) (3)
(1) Supply Voltage/
Accuracy
A - 5V
B - 3V
C - Reserved
D - 3V medical accuracy
Example:
MLX90614ESF-BAA
(2) Number of thermopiles:
A – single zone
B – dual zone
C – gradient compensated*
* : See page 2
(3) Package options:
A – Standard package
B – Reserved
C – 35° FOV
D/E – Reserved
F – 10° FOV
G – Reserved
H – 12° FOV (refractive lens)
I – 5° FOV
1 Functional diagram
J1
CON1
SCL
SDA
GND
Vdd
C1 value and type may differ
in different applications
for optimum EMC
U1
MLX90614
1
PW M
SDA
C1
MLX 90 6 14 co nnectio n to SM Bus
4
Vss
SCL
Vz
M LX90614Ax x: Vdd=4.5...5.5V
3
2
Vdd
0.1uF
Figure 1: Typical application schematics
2 General Description
The MLX90614 is an Infra Red thermometer for non
contact temperature measurements. Both the IR sensitive
thermopile detector chip and the signal conditioning ASSP
are integrated in the same TO-39 can.
Thanks to its low noise amplifier, 17-bit ADC and powerful
DSP unit, a high accuracy and resolution of the
thermometer is achieved.
The thermometer comes factory calibrated with a digital
PWM and SMBus (System Management Bus) output.
As a standard, the 10-bit PWM is configured to
continuously transmit the measured temperature in range
of -20…120 ˚C, with an output resolution of 0.14 ˚C.
The factory default POR setting is SMBus.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 2 of 49 Data Sheet
Rev 006 September 30, 2010
General description (continued)
The MLX90614 is built from 2 chips developed and manufactured by Melexis:
•
The Infra Red thermopile detector MLX81101
•
The signal conditioning ASSP MLX90302, specially designed to process the output of IR sensor.
The device is available in an industry standard TO-39 package.
Thanks to the low noise amplifier, high resolution 17-bit ADC and powerful DSP unit of MLX90302 high
accuracy and resolution of the thermometer is achieved. The calculated object and ambient temperatures are
available in RAM of MLX90302 with resolution of 0.01 ˚C. They are accessible by 2 wire serial SMBus
compatible protocol (0.02°C resolution) or via 10-bit PWM (Pulse Width Modulated) output of the device.
The MLX90614 is factory calibrated in wide temperature ranges: -40…125 ˚C for the ambient temperature
and -70…382.19 ˚C for the object temperature.
The measured value is the average temperature of all objects in the Field Of View of the sensor. The
MLX90614 offers a standard accuracy of ±0.5ºC around room temperatures. A special version for medical
applications exists offering an accuracy of ±0.1ºC in a limited temperature range around the human body
temperature.
It is very important for the application designer to understand that these accuracies are only guaranteed and
achievable when the sensor is in thermal equilibrium and under isothermal conditions (there are no
temperature differences across the sensor package). The accuracy of the thermometer can be influenced by
temperature differences in the package induced by causes like (among others): Hot electronics behind the
sensor, heaters/coolers behind or beside the sensor or by a hot/cold object very close to the sensor that not
only heats the sensing element in the thermometer but also the thermometer package.
This effect is especially relevant for thermometers with a small FOV like the -XXC and -XXF as the energy
received by the sensor from the object is reduced. Therefore, Melexis has introduced the -XCX version of the
MLX90614. In these MLX90614-XCX, the thermal gradients are measured internally and the measured
temperature is compensated for them. In this way, the –XCX version of the MLX90614 is much less sensitive
to thermal gradients, but the effect is not totally eliminated. It is therefore important to avoid the causes of
thermal gradients as much as possible or to shield the sensor from them.
As a standard, the MLX90614 is calibrated for an object emissivity of 1. It can be easily customized by the
customer for any other emissivity in the range 0.1…1.0 without the need of recalibration with a black body.
The 10-bit PWM is as a standard configured to transmit continuously the measured object temperature for an
object temperature range of -20…120 ˚C with an output resolution of 0.14 ˚C. The PWM can be easily
customized for virtually any range desired by the customer by changing the content of 2 EEPROM cells. This
has no effect on the factory calibration of the device.
The PWM pin can also be configured to act as a thermal relay (input is To), thus allowing for an easy and
cost effective implementation in thermostats or temperature (freezing / boiling) alert applications. The
temperature threshold is user programmable. In a SMBus system this feature can act as a processor interrupt
that can trigger reading all slaves on the bus and to determine the precise condition.
The thermometer is available in 2 supply voltage options: 5V compatible or 3V (battery) compatible. The 5V
can be easily adopted to operate from a higher supply voltage (8…16V, for example) by use of few external
components (refer to “Applications information” section for details).
An optical filter (long-wave pass) that cuts off the visible and near infra-red radiant flux is integrated in the
package to provide ambient and sunlight immunity. The wavelength pass band of this optical filter is from 5.5
till 14µm.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 3 of 49 Data Sheet
Rev 006 September 30, 2010
3 Table of Contents
1 Functional diagram ..........................................................................................................................................................................................1
2 General Description .........................................................................................................................................................................................1
General description (continued) .........................................................................................................................................................................2
3 Table of Contents............................................................................................................................................................................................. 3
4 Glossary of Terms............................................................................................................................................................................................ 4
5 Maximum ratings.............................................................................................................................................................................................. 4
6 Pin definitions and descriptions.......................................................................................................................................................................5
7 Electrical Specifications................................................................................................................................................................................... 6
7.1 MLX90614Axx..........................................................................................................................................................................................6
7.2 MLX90614Bxx, MLX90614Dxx................................................................................................................................................................ 8
8 Detailed description .......................................................................................................................................................................................10
8.1 Block diagram.........................................................................................................................................................................................10
8.2 Signal processing principle....................................................................................................................................................................10
8.3 Block description ....................................................................................................................................................................................11
8.3.1 Amplifier.......................................................................................................................................................................................... 11
8.3.2 Supply regulator and POR .............................................................................................................................................................11
8.3.3 EEPROM ........................................................................................................................................................................................11
8.3.4 RAM ................................................................................................................................................................................................ 14
8.4 SMBus compatible 2-wire protocol........................................................................................................................................................14
8.4.1 Functional description ....................................................................................................................................................................14
8.4.2 Differences with the standard SMBus specification (reference [1])..............................................................................................15
8.4.3 Detailed description........................................................................................................................................................................15
8.4.4 AC specification for SMBus............................................................................................................................................................17
8.4.5 Bit transfer ......................................................................................................................................................................................18
8.4.6 Commands ..................................................................................................................................................................................... 18
8.4.7 Sleep Mode.....................................................................................................................................................................................19
8.4.8 MLX90614 SMBus specific remarks..............................................................................................................................................20
8.5 PWM.......................................................................................................................................................................................................21
8.5.1 Single PWM format......................................................................................................................................................................... 22
8.5.2 Extended PWM format ................................................................................................................................................................... 23
8.5.3 Customizing the temperature range for PWM output....................................................................................................................24
8.6 Switching Between PWM and SMBus communication.........................................................................................................................25
8.6.1 PWM is enabled .............................................................................................................................................................................25
8.6.2 Request condition........................................................................................................................................................................... 25
8.6.3 PWM is disabled.............................................................................................................................................................................25
8.7 Computation of ambient and object temperatures................................................................................................................................ 26
8.7.1 Ambient temperature Ta ................................................................................................................................................................26
8.7.2 Object temperature To ...................................................................................................................................................................26
8.7.3 Calculation flow ..............................................................................................................................................................................26
8.8 Thermal relay .........................................................................................................................................................................................28
9 Unique Features ............................................................................................................................................................................................29
10 Performance Graphs ...................................................................................................................................................................................30
10.1 Temperature accuracy of the MLX90614............................................................................................................................................30
10.1.1 Standard accuracy .......................................................................................................................................................................30
10.1.2 Medical accuracy..........................................................................................................................................................................31
10.1.3 Temperature reading dependence on V
DD
..................................................................................................................................31
10.2 Field Of View (FOV).............................................................................................................................................................................33
11 Applications Information ..............................................................................................................................................................................37
11.1 Use of the MLX90614 thermometer in SMBus configuration............................................................................................................. 37
11.2 Use of multiple MLX90614s in SMBus configuration..........................................................................................................................37
11.3 PWM output operation ......................................................................................................................................................................... 38
11.4 Thermal alert / thermostat....................................................................................................................................................................38
11.5 High voltage source operation.............................................................................................................................................................39
12 Application Comments.................................................................................................................................................................................40
13 Standard information regarding manufacturability of Melexis products with different soldering processes.............................................42
14 ESD Precautions..........................................................................................................................................................................................42
15 FAQ .............................................................................................................................................................................................................. 43
16 Package Information.................................................................................................................................................................................... 45
16.1 MLX90614XXA..................................................................................................................................................................................... 45
16.2 MLX90614XCC ....................................................................................................................................................................................45
16.3 MLX90614XCF..................................................................................................................................................................................... 46
16.4 MLX90614XCH ....................................................................................................................................................................................46
16.5 MLX90614XCI......................................................................................................................................................................................47
16.6 Part marking.........................................................................................................................................................................................47
17 Table of figures ............................................................................................................................................................................................ 48
18 References................................................................................................................................................................................................... 49
19 Disclaimer .................................................................................................................................................................................................... 49
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 4 of 49 Data Sheet
Rev 006 September 30, 2010
4 Glossary of Terms
PTAT Proportional To Absolute Temperature sensor (package temperature)
PTC Positive Temperature Coefficient sensor (package temperature)
POR Power On Reset
HFO High Frequency Oscillator (RC type)
DSP Digital Signal Processing
FIR Finite Impulse Response. Digital filter
IIR Infinite Impulse Response. Digital filter
IR Infra-Red
PWM Pulse With Modulation
DC Duty Cycle (of the PWM) ; Direct Current (for settled conditions specifications)
FOV Field Of View
SDA,SCL Serial DAta, Serial CLock – SMBus compatible communication pins
Ta Ambient Temperature measured from the chip – (the package temperature)
To Object Temperature, ‘seen’ from IR sensor
ESD Electro-Static Discharge
EMC Electro-Magnetic Compatibility
ASSP Application Specific Standard Product
TBD To Be Defined
Note: sometimes the MLX90614xxx is referred to as “the module”.
5 Maximum ratings
Parameter MLX90614ESF-Axx
MLX90614ESF-Bxx
MLX90614ESF-Dxx MLX90614KSF-Axx
Supply Voltage, V
DD
( ov er v oltage)
7 V
5V
7 V
Supply Voltage, V
DD
( oper ati n g)
5. 5 V
3 . 6 V
5. 5V
R ev er s e Voltage
0 .
4
V
O per ati n g T em per atur e R an ge, T
A
-
40…
+
8
5
°
C
-
4 0 …+
1 25
° C
Stor age T em per atur e R an ge, T
S
-
4 0
…+1
2
5
°
C
-
4 0
…+1
2
5° C
E SD Sen s i ti v i ty ( A
E C Q 1 0 0 0 0 2)
2k V
D C c ur r en t i n to SCL
/
Vz ( Vz m od e)
2 m A
D C s i n k c ur r en t, SD A /
P W M pi n
25 m A
D C s our c e c ur r en t, SD A
/
P W M pi n
25 m A
D C c lam p c ur r en t, SD A
/
P W M pi n
25 m A
D C c lam p c ur r en t, SCL pi n 25 m A
Table 1: Absolute maximum ratings for MLX90614
Exceeding the absolute maximum ratings may cause permanent damage. Exposure to absolute-maximum-
rated conditions for extended periods may affect device reliability.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 5 of 49 Data Sheet
Rev 006 September 30, 2010
6 Pin definitions and descriptions
Bottom view
2 - SDA / PWM
4 - VSS
3 - VDD
1 - SCL / Vz
Figure 2: Pin description
Pin Name Function
SCL / Vz Ser i al c loc k i n put f or 2 w i r e c om m un i c ati on s pr otoc ol. 5. 7 V z en er i s av ai lab le at th i s pi n f or c on n ec ti on
of ex ter n al b i polar tr an s i s tor to M L X 9 0 6 1 4 A to s upply th e d ev i c e f r om ex ter n al 8 …1 6 V s our c e.
SD A / P W M
D i gi tal i n put / output. I n n or m al m od e th e m eas ur ed ob j ec t tem per atur e i s av ai lab le at th i s pi n P uls e
W i d th M od ulated .
I n SM B us c om pati b le m od e autom ati c ally c on f i gur ed as open d r ai n N M O S.
VD D E x ter n al s upply v oltage.
VSS G r oun d . T h e m etal c an i s als o c on n ec ted to th i s pi n .
Table 2: Pin description MLX90614
Note:
for +12V (+8…+16V) powered operation refer to the Application information section. For EMC and
isothermal conditions reasons it is highly recommended not to use any electrical connection to the metal can
except by the VSS pin.
With the SCL / Vz and PWM / SDA pins operated in 2-wire interface mode, the input Schmidt trigger function
is automatically enabled.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 6 of 49 Data Sheet
Rev 006 September 30, 2010
7 Electrical Specifications
7.1 MLX90614Axx
All parameters are preliminary for T
A
= 25 ˚C, V
DD
=5V (unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Units
Supplies
External supply V
DD
4.5 5 5.5 V
Supply current I
DD
No load 1 2 mA
Supply current
(programming) I
DDpr
No load, erase/write EEPROM
operations 1.5 2.5 mA
Zener voltage Vz Iz = 75…1000uA (Ta=room) 5.5 5.7 5.9 V
Zener voltage Vz(Ta) Iz = 70…1000uA,
full temperature range 5.15 5.75 6.24 V
Power On Reset
POR level V
POR_up
Power-up (full temp range) 1.4 1.75 1.95 V
POR level V
POR_down
Power –down (full temp range) 1.3 1.7 1.9 V
POR hysteresis V
POR_hys
Full temp range 0.08 0.1 1.15 V
V
DD
rise time (10% to 90%
of specified supply voltage)
T
POR
Ensure POR signal 20 ms
Output valid (result in RAM)
Tvalid After POR 0.15 s
Pulse width modulation
1
PWM resolution PWMres Data band 10 bit
PWM output period PWM
T,def
Factory default, internal oscillator
factory calibrated 1.024 ms
PWM period stability dPWM
T
Internal oscillator factory
calibrated, over the entire
operation range and supply
voltage
-4 +4 %
Output high Level PWM
HI
I
source
= 2 mA V
DD
-0.2
V
Output low Level PWM
LO
I
sink
= 2 mA V
SS
+0.2 V
Output drive current Idrive
PWM
Vout,H = V
DD
- 0.8V 7 mA
Output sink current Isink
PWM
Vout,L = 0.8V 13.5 mA
Continued next page
.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 7 of 49 Data Sheet
Rev 006 September 30, 2010
Parameter Symbol Test Conditions Min Typ Max Units
SMBus compatible 2-wire interface
2
Input high voltage V
IH
(Ta, V) Over temperature and supply 3 V
Input low voltage V
IL
(Ta, V) Over temperature and supply 0.6 V
Output low voltage V
OL
SDA pin in open drain mode,
over temperature and supply,
Isink = 2mA 0.2 V
SCL leakage I
SCL
, leak V
SCL
=4V, Ta=+85°C 30 uA
SDA leakage I
SDA
, leak V
SDA
=4V, Ta=+85°C 0.3 uA
SCL capacitance C
SCL
10 pF
SDA capacitance C
SDA
10 pF
Slave address SA Factory default 5A hex
Wake up request t
wake
SDA low 33 ms
SMBus Request t
REQ
SCL low 1.44 ms
Timeout, low T
imeout,L
SCL low 27 33 ms
Timeout, high T
imeout,H
SCL high 45 55 us
Acknowledge setup time Tsuac(MD) 8-th SCL falling edge, Master 0.5 1.5 us
Acknowledge hold time Thdac(MD) 9-th SCL falling edge, Master 1.5 2.5 us
Acknowledge setup time Tsuac(SD) 8-th SCL falling edge, Slave 2.5 us
Acknowledge hold time Thdac(SD) 9-th SCL falling edge, Slave 1.5 us
EEPROM
Data retention Ta = +85°C 10 years
Erase/write cycles Ta = +25°C 100,000
Times
Erase/write cycles Ta = +125°C 10,000 Times
Erase cell time Terase 5 ms
Write cell time Twrite 5 ms
Table 3: Electrical specification MLX90614AXX
Notes: All the communication and refresh rate timings are given for the nominal calibrated HFO frequency and will vary
with this frequency’s variations.
1. All PWM timing specifications are given for single PWM output (factory default for MLX90614xAx). For the extended
PWM output (factory default for the MLX90614xBx) each period has twice the timing specifications (refer to the PWM
detailed description section). With large capacitive load lower PWM frequency is recommended. Thermal relay output
(when configured) has the PWM DC specification and can be programmed as push-pull, or NMOS open drain. PWM is
free-running, power-up factory default is SMBus, refer to 7.6, “Switching between PWM and SMBus communication” for
details..
2. For SMBus compatible interface on 12V application refer to Application information section. SMBus compatible
interface is described in details in the SMBus detailed description section. Maximum number of MLX90614xxx devices on
one bus is 127, higher pull-up currents are recommended for higher number of devices, faster bus data transfer rates,
and increased reactive loading of the bus.
MLX90614xxx is always a slave device on the bus. MLX90614xxx can work in both low-power and high-power SMBus
communication.
All voltages are referred to the Vss (ground) unless otherwise noted.
Sleep mode is not available on the 5V version (MLX90614Axx).
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 8 of 49 Data Sheet
Rev 006 September 30, 2010
7.2 MLX90614Bxx, MLX90614Dxx
All parameters are preliminary for T
A
= 25 ˚C, V
DD
=3V (unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Units
Supplies
External supply V
DD
2.6 3 3.6 V
Supply current I
DD
No load 1 2 mA
Supply current
(programming) I
DDpr
No load, erase/write EEPROM
operations 1.5 2.5 mA
Sleep mode supply
current Isleep no load 1 2.5 5 uA
Sleep mode supply
current Isleep Full temperature range 1 2.5 6 uA
Power On Reset
POR level V
POR_up
Power-up (full temp range) 1.4 1.75 1.95 V
POR level V
POR_down
Power –down (full temp range) 1.3 1.7 1.9 V
POR hysteresis V
POR_hys
Full temp range 0.08 0.1 1.15 V
V
DD
rise time (10% to
90% of specified
supply voltage)
T
POR
Ensure POR signal 20 ms
Output valid Tvalid After POR 0.15 s
Pulse width modulation
1
PWM resolution PWMres Data band 10 bit
PWM output period PWM
T,def
Factory default, internal oscillator
factory calibrated 1.024 ms
PWM period stability dPWM
T
Internal oscillator factory
calibrated, over the entire
operation range and supply
voltage
-4 +4 %
Output high Level PWM
HI
I
source
= 2 mA V
DD
-0.25 V
Output low Level PWM
LO
I
sink
= 2 mA V
SS
+0.25 V
Output drive current Idrive
PWM
Vout,H = V
DD
- 0.8V 4.5 mA
Output sink current Isink
PWM
Vout,L = 0.8V 11 mA
Continued next page
.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 9 of 49 Data Sheet
Rev 006 September 30, 2010
Parameter Symbol Test Conditions Min Typ Max Units
SMBus compatible 2-wire interface
2
Input high voltage V
IH
(Ta,V) Over temperature and supply VDD-0.1 V
Input low voltage V
IL
(Ta,V) Over temperature and supply 0.6 V
Output low voltage V
OL
SDA pin in open drain mode,
over temperature and supply,
Isink = 2mA 0.25 V
SCL leakage I
SCL
,leak V
SCL
=3V, Ta=+85°C 20 uA
SDA leakage I
SDA
,leak V
SDA
=3V, Ta=+85°C 0.25 uA
SCL capacitance C
SCL
10 pF
SDA capacitance C
SDA
10 pF
Slave address SA Factory default 5A hex
Wake up request t
wake
SDA low 33 ms
SMBus Request t
REQ
SCL low 1.44 ms
Timeout,low T
imeout,L
SCL low 27 33 ms
Timeout, high T
imeout,H
SCL high 45 55 us
Acknowledge setup
time
Tsuac(MD
)
8-th SCL falling edge, Master 0.5 1.5 us
Acknowledge hold
time
Thdac(MD
)
9-th SCL falling edge, Master 1.5 2.5 us
Acknowledge setup
time
Tsuac(SD)
8-th SCL falling edge, Slave 2.5 us
Acknowledge hold
time
Thdac(SD
)
9-th SCL falling edge, Slave 1.5 us
EEPROM
Data retention Ta = +85°C 10 years
Erase/write cycles Ta = +25°C 100,000 Times
Erase/write cycles Ta = +125°C 10,000 Times
Erase cell time Terase 5 ms
Write cell time Twrite 5 ms
Table 4: Electrical specification MLX90614BXX, DXX
Note: refer to MLX90614Axx notes.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 10 of 49 Data Sheet
Rev 006 September 30, 2010
8 Detailed description
8.1 Block diagram
Figure 3: Block diagram
8.2 Signal processing principle
The operation of the MLX90614 is controlled by an internal state machine, which controls the measurements
and calculations of the object and ambient temperatures and does the post-processing of the temperatures to
output them through the PWM output or the SMBus compatible interface.
The ASSP supports 2 IR sensors (second one not implemented in the MLX90614xAx).The output of the IR
sensors is amplified by a low noise low offset chopper amplifier with programmable gain, converted by a
Sigma Delta modulator to a single bit stream and fed to a powerful DSP for further processing. The signal is
treated by programmable (by means of EEPROM contend) FIR and IIR low pass filters for further reduction of
the band width of the input signal to achieve the desired noise performance and refresh rate. The output of
the IIR filter is the measurement result and is available in the internal RAM. 3 different cells are available:
One for the on-board temperature sensor (on chip PTAT or PTC) and 2 for the IR sensors.
Based on results of the above measurements, the corresponding ambient temperature Ta and object
temperatures To are calculated. Both calculated temperatures have a resolution of 0.01 ˚C. The data for Ta
and To can be read in two ways: Reading RAM cells dedicated for this purpose via the 2-wire interface
(0.02°C resolution, fixed ranges), or through the PWM digital output (10 bit resolution, configurable range).
In the last step of the measurement cycle, the measured Ta and To are rescaled to the desired output
resolution of the PWM) and the recalculated data is loaded in the registers of the PWM state machine, which
creates a constant frequency with a duty cycle representing the measured data.
81101
OPA
ADC
DSP
PWM
STATE MACHINE
t°
Voltage
Regulator
90302
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 11 of 49 Data Sheet
Rev 006 September 30, 2010
8.3 Block description
8.3.1 Amplifier
A low noise, low offset amplifier with programmable gain is used for amplifying the IR sensor voltage. By
carefully designing the input modulator and balanced input impedance, an offset below 0.5µV is achieved.
8.3.2 Supply regulator and POR
The module can operate from 3 different supplies:
VDD= 5V => MLX90614Axx
VDD=3.3V => MLX90614Bxx (battery or regulated supply)
VDD=8…16V => MLX90614Axx few external components are necessary please refer to “Applications
information” section for information about adopting higher voltage supplies.
The Power On Reset (POR) is connected to Vdd supply. The on-chip POR circuit provides an active (high)
level of the POR signal when the Vdd voltage rises above approximately 0.5V and holds the entire
MLX90614xxx in reset until the Vdd is higher than the specified POR threshold V
POR
(note that this level is
different for MLX90614Axx and MLX90614Bxx). During the time POR is active, the POR signal is available as
an open drain at the PWM/SDA pin. After the MLX90614xxx exits the POR condition, the function
programmed in EEPROM takes precedence for that pin.
8.3.3 EEPROM
A limited number of addresses in the EEPROM memory can be changed by the customer. The whole
EEPROM can be read through the SMBus interface.
EEPROM (32X16)
Name Address Write
access
To
max
0x000 Yes
To
min
0x001 Yes
PWMCTRL 0x002 Yes
Ta range
0x003 Yes
Emissivity correction coefficient 0x004 Yes
Config Register1 0x005 Yes
Melexis reserved 0x006 No
… … …
Melexis reserved 0x00D No
SMBus address 0x00E Yes
Melexis reserved 0x00F Yes
Melexis reserved 0x010 No
… … …
Melexis reserved 0x018 No
Melexis reserved 0x019 Yes
Melexis reserved 0x01A No
Melexis reserved 0x01B No
ID number 0x01C No
ID number 0x01D No
ID number 0x01E No
ID number 0x01F No
Table 5: EEPROM table
The addresses To
max
, To
min
and Ta range are for customer dependent object and ambient temperature
ranges. For details see section 8.5.3 below in this document
The address Emissivity contains the object emissivity (factory default 1.0 = 0xFFFF), 16 bit.
Emissivity = dec2hex[ round( 65535 x
ε
) ]
Where dec2hex[ round( X ) ] represents decimal to hexadecimal conversion with round-off to nearest value
(not truncation). In this case the physical emissivity values are
ε
= 0.1…1.0.
Erase (write 0) must take place before write of desired data is made.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 12 of 49 Data Sheet
Rev 006 September 30, 2010
PWM period configuration: Period in extended PWM mode is twice the period in single PWM mode.
In single PWM mode period is T = 1.024*P [ms], where P is the number, written in bits 15…9 PWMCTRL.
Maximum period is then 131.072 ms for single and 262.144 ms for extended. These values are typical and
depend on the on-chip RC oscillator absolute value. The duty cycle must be calculated instead of working
only with the high time only in order to avoid errors from the period absolute value deviations.
The address PWMCTRL consists of control bits for configuring the PWM/SDA pin as follows:
* Values are valid for nominal HFO frequency
Table 6: PWM control bits
The address ConfigRegister1 consists of control bits for configuring the analog and digital parts:
Note: The following bits/registers should not be altered (except with special tools – contact Melexis for such
tools availability) in order to keep the factory calibration relevant:
Ke [15..0] ; Config Register1 [13..11;7;3] ; addresses 0x00F and 0x019.
Table 7: Configuration register 1
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 13 of 49 Data Sheet
Rev 006 September 30, 2010
Check www.melexis.com for latest application notes with details on EEPROM settings.
On-chip filtering and settling time:
The MLX90614 features configurable on-chip digital filters. They allow customization for speed or noise.
Factory default configurations and the typical settling time and noise for the MLX90614 family are given
below. Device Settling time, sec Typical noise, °C rms Spike limit
MLX90614 AAA, BAA, DAA 0.10 0.05 100%
MLX90614 ABA, BBA 0.14 0.07 100%
MLX90614 ACC, BCC 0.14 0.18 100%
MLX90614 ACF, BCF 1.33 0.10 50%
Table 8: factory default IIR and FIR configuration, settling time and typical noise
Details on the filters are given in the application note “Understanding MLX90614 on-chip digital signal filters”
available from www.melexis.com .
The evaluation board, EVB90614 supported by PC SW allows easy configuration of the filters, while not
requiring in-depth understanding of the EEPROM.
The available filter settings and the settling times they give are listed below. Settling time depends on three
configurations: single/dual zone, IIR filter settings and FIR filter settings. The FIR filter has a straightforward
effect on noise (a 4 times decrease of settling time increases the noise 2 times and vice versa). The IIR filter
provides an additional, spike limiting, feature. Spike limit is also listed and defines to what level the magnitude
of a spike would be limited – for example, 25% denotes that if a 20°C temperature delta spike is measured
the temperature reading by the MLX90614 will spike only 5°C. More details are available in the application
notes from www.melexis.com.
IIR setting FIR setting Settling time (s)
90614xAx Settling time (s)
90614xBx, 90614xCx Spike limit
xxx 000…011 Not recommended
100 100 0.04 0.06 100.0%
100 101 0.05 0.07 100.0%
100 110 0.06 0.10 100.0%
100 111 0.10 0.14 100.0%
101 100 0.12 0.20 80.0%
101 101 0.16 0.24 80.0%
101 110 0.22 0.34 80.0%
101 111 0.35 0.54 80.0%
110 100 0.24 0.38 66.7%
110 101 0.30 0.48 66.7%
110 110 0.43 0.67 66.7%
110 111 0.70 1.10 66.7%
111 100 0.26 0.42 57.0%
111 101 0.34 0.53 57.0%
111 110 0.48 0.75 57.0%
111 111 0.78 1.20 57.0%
000 100 0.30 0.47 50.0%
000 101 0.37 0.60 50.0%
000 110 0.54 0.84 50.0%
000 111 0.86 1.33 50.0%
001 100 0.70 1.10 25.0%
001 101 0.88 1.40 25.0%
001 110 1.30 2.00 25.0%
001 111 2.00 3.20 25.0%
010 100 1.10 1.80 16.7%
010 101 1.40 2.20 16.7%
010 110 2.00 3.20 16.7%
010 111 3.30 5.00 16.7%
011 100 1.50 2.40 12.5%
011 101 1.90 3.00 12.5%
011 110 2.80 4.30 12.5%
011 111 4.50 7.00 12.5%
Table 9: possible IIR and FIR settings
Note: Settling time is in seconds and depends on internal oscillator absolute value.
100% spike limit appears with the IIR filter bypassed, and there is no spike limitation.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 14 of 49 Data Sheet
Rev 006 September 30, 2010
8.3.4 RAM
It is not possible to write into the RAM memory. It can only be read and only a limited number of RAM
registers are of interest to the customer.
RAM (32x17)
Name Address Read access
Melexis reserved 0x000 Yes
… … …
Melexis reserved 0x003 Yes
Raw data IR channel 1 0x004
Raw data IR channel 2 0x005
T
A
0x006 Yes
T
OBJ1
0x007 Yes
T
OBJ2
0x008 Yes
Melexis reserved 0x009 Yes
… … …
Melexis reserved 0x01F Yes
Table 10: Ram addresses
8.4 SMBus compatible 2-wire protocol
The chip supports a 2 wires serial protocol, build with pins PWM/SDA and SCL.
• SCL – digital input, used as the clock for SMBus compatible communication. This pin has the
auxiliary function for building an external voltage regulator. When the external voltage regulator is
used, the 2-wire protocol is available only if the power supply regulator is overdriven.
• PWM/SDA – Digital input/output, used for both the PWM output of the measured object
temperature(s) or the digital input/output for the SMBus. The pin can be programmed in EEPROM to
operate as Push/Pull or open drain NMOS (open drain NMOS is factory default). In SMBus mode
SDA is forced to open drain NMOS I/O, push-pull selection bit defines PWM/Thermal relay operation.
SMBus communication with MLX90614 is covered in details in application notes, available from
www.melexis.com
8.4.1 Functional description
The SMBus interface is a 2-wire protocol, allowing communication between the Master Device (MD) and one
or more Slave Devices (SD). In the system only one master can be presented at any given time [1]. The
MLX90614 can only be used as a slave device.
Generally, the MD initiates the start of data transfer by selecting a SD through the Slave Address (SA).
The MD has read access to the RAM and EEPROM and write access to 9 EEPROM cells (at addresses
0x20h, 0x21h, 0x22h, 0x23h, 0x24h, 0x25h*, 0x2Eh, 0x2Fh, 0x39h). If the access to the MLX90614 is a read
operation it will respond with 16 data bits and 8 bit PEC only if its own slave address, programmed in internal
EEPROM, is equal to the SA, sent by the master. The SA feature allows connecting up to 127 devices with
only 2 wires, unless the system has some of the specific features described in paragraph 5.2 of reference [1].
In order to provide access to any device or to assign an address to a SD before it is connected to the bus
system, the communication must start with zero SA followed by low RWB bit. When this command is sent
from the MD, the MLX90614 will always respond and will ignore the internal chip code information.
Special care must be taken not to put two MLX90614 devices with the same SD addresses on the
same bus as MLX90614 does not support ARP [1].
The MD can force the MLX90614 into low consumption mode “sleep mode” (3V version only).
Read flags like “EEBUSY” (1 – EEPROM is busy with executing the previous write/erase), “EE_DEAD” (1 –
there is fatal EEPROM error and this chip is not functional**).
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 15 of 49 Data Sheet
Rev 006 September 30, 2010
Note*: This address is readable and writable. Bit 3 should not be altered as this will cancel the factory
calibration.
Note**: EEPROM error signaling is implemented in automotive grade parts only.
8.4.2 Differences with the standard SMBus specification (reference [1])
There are eleven command protocols for standard SMBus interface. The MLX90614 supports only two of
them. Not supported commands are:
• Quick Command
• Byte commands - Sent Byte, Receive Byte, Write Byte and Read Byte
• Process Call
• Block commands – Block Write and Write-Block Read Process Call
Supported commands are:
• Read Word
• Write Word
8.4.3 Detailed description
The PWM/SDA pin of MLX90614 can operate also as PWM output, depending on the EEPROM settings. If
PWM is enabled, after POR the PWM/SDA pin is directly configured as PWM output. The PWM mode can be
avoided and the pin can be restored to its Data function by a special command. That is why hereafter both
modes are treated separately.
8.4.3.1 Bus Protocol
Figure 4: SMBus packet element key
After every 8 bits received by the SD an ACK/NACK takes place. When a MD initiates communication, it first
sends the address of the slave and only the SD which recognizes the address will ACK, the rest will remain
silent. In case the SD NACKs one of the bytes, the MD should stop the communication and repeat the
message. A NACK could be received after the PEC. This means that there is an error in the received
message and the MD should try sending the message again. The PEC calculation includes all bits except the
S
Wr
Slave Address
A
Data Byte
A
P
S
Start Condition
Sr
Repeated Start Condition
Rd
Read (bit value of 1)
Wr
Write (bit value of 0)
A
Acknowledge (this bit can be 0 for ACK and 1 for NACK)
S
Stop Condition
PEC
Packet Error Code
Master-to-Slave
Slave-to-Master
1
1
7
1
8
1
1
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 16 of 49 Data Sheet
Rev 006 September 30, 2010
START, REPEATED START, STOP, ACK, and NACK bits. The PEC is a CRC-8 with polynomial
X8+X2+X1+1. The Most Significant Bit of every byte is transferred first.
8.4.3.1.1 Read Word (depending on the command – RAM or EEPROM)
Figure 5: SMBus read word format
8.4.3.1.2 Write Word (depending on the command – RAM or EEPROM)
Figure 6: SMBus write word format
Figure 7: SMBus communication examples (Read RAM and Write EEPROM)
S
Wr
Slave Address
A
Data Byte Low
A
P
Command
A
Sr
Slave Address
Rd
1
7
1
1
8
1
1
7
1
8
1
1
………..
………..
A
1
Data Byte High
A
8
1
PEC
A
8
1
S
Wr
Slave Address
A
Data Byte Low
A
P
Command
A
1
7
1
1
8
1
8
1
1
………..
………..
Data Byte High
A
8
1
PEC
A
8
1
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 17 of 49 Data Sheet
Rev 006 September 30, 2010
8.4.4 AC specification for SMBus
8.4.4.1 Timing
The MLX90614 meets all the timing specifications of the SMBus [1]. The maximum frequency of the
MLX90614 SMBus is 100 KHz and the minimum is 10 KHz.
The specific timings in MLX90614’s SMBus are:
SMBus Request (t
R E Q
) is the time that the SCL should be forced low in order to switch MLX90614 from PWM
mode to SMBus mode – at least 1.44ms;
Timeout L is the maximum allowed time for SCL to be low. After this time the MLX90614 will reset its
communication block and will be ready for new communication – not more than 45us;
Timeout H is the maximum time for which it is allowed for SCL to be high during communication.
After this
time MLX90614 will reset its communication block assuming that the bus is idle (according to the SMBus
specification) – not more than 27ms.
Tsuac(SD) is the time after the eighth falling edge of SCL that MLX90614 will force PWM/SDA low to
acknowledge the last received byte – not more than 2,5µs.
Thdac(SD) is the time after the ninth falling edge of SCL that MLX90614 will release the PWM/SDA (so the
MD can continue with the communication) – not more than 1,5µs.
Tsuac(MD) is the time after the eighth falling edge of SCL that MLX90614 will release PWM/SDA (so that the
MD can acknowledge the last received byte) – not more than 0,5µs.
Thdac(MD) is the time after the ninth falling edge of SCL that MLX90614 will take control of the PWM/SDA
(so it can continue with the next byte to transmit) – not more than 1,5µs.
The indexes MD and SD for the latest timings are used – MD when the master device is making
acknowledge; SD when the slave device is making acknowledge. For other timings see [1].
PWM/SDA
SCL
T
suac
T
hdac
T
imeout,L
T
imeout,H
> 27ms > 47us
SD<2,5us
MD<0,5us SD<1,5us
MD<1,5us
Figure 8: SMBus timing
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 18 of 49 Data Sheet
Rev 006 September 30, 2010
8.4.5 Bit transfer
PWM/SDA
SCL
Sampling
data
Changing
data
Figure 9: Bit transfer on SMBus
The data on PWM/SDA must be changed when SCL is low (min 300ns after the falling edge of SCL). The
data is fetched by both MD and SDs on the rising edge of the SCL. The recommended timing for changing
data is in the middle of the period when the SCL is low.
8.4.6 Commands
RAM and EEPROM can be read both with 32x16 sizes. If the RAM is read, the data are divided by two, due
to a sign bit in RAM (for example,
T
OBJ1 - RAM address 0x07h will sweep between 0x27ADh to 0x7FFF as the
object temperature rises from -70.01°C to +382.19°C). The MSB read from RAM is an error flag (active high)
for the linearized temperatures (TOBJ1,
TOBJ2 and T
a
). The MSB for the raw data (e.g. IR sensor1 data) is a sign
bit (sign and magnitude format). A write of 0x0000 must be done prior to writing in EEPROM in order to erase
the EEPROM cell content. Refer to EEPROM detailed description for factory calibration EEPROM locations
that need to be kept unaltered.
Opcode Command
000x xxxx* RAM Access
001x xxxx* EEPROM Access
1111_0000** Read Flags
1111_1111 Enter SLEEP mode
Table 11: SMBus commands
Note*: The xxxxx represent the 5 LSBits of the memory map address to be read/written.
Note**: Behaves like read command. The MLX90614 returns PEC after 16 bits data of which only 4 are
meaningful and if the MD wants it, it can stop the communication after the first byte. The difference between
read and read flags is that the latter does not have a repeated start bit.
Flags read are:
Data[7] - EEBUSY - the previous write/erase EEPROM access is still in progress. High active.
Data[6] - Unused
Data[5] - EE_DEAD - EEPROM double error has occurred. High active.
Data[4] - INIT - POR initialization routine is still ongoing. Low active.
Data[3] - Not implemented.
Data[2..0] and Data[8..15] - All zeros.
Flags read is a diagnostic feature. The MLX90614 can be used regardless of these flags.
For details and examples for SMBus communication with the MLX90614 check the www.melexis.com
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 19 of 49 Data Sheet
Rev 006 September 30, 2010
8.4.7 Sleep Mode
The MLX90614 can enter in Sleep Mode via the command “Enter SLEEP mode” sent via the SMBus
interface. This mode is not available for the 5V supply version. To limit the current consumption to 2.5uA
(typical), the SCL pin should be kept low during sleep. MLX90614 goes back into power-up default mode (via
POR reset) by setting SCL pin high and then PWM/SDA pin low for at least t
DDq
=80ms. If EEPROM is
configured for PWM (EN_PWM is high), the PWM interface will be selected after awakening and if
PWM control [2], PPODB is 1 the MLX90614 will output a PWM pulse train with push-pull output.
8.4.7.1 Enter Sleep Mode
Sleep
command
Stop
condition
Stop
Sleep
SCL
PWM/SDA
Figure 10: Enter sleep
8.4.7.2 Exit from Sleep Mode
Sleep Awake
SCL
PWM/SDA
twake
> 33ms
Figure 11: Exit Sleep Mode
First data is available 0.25 seconds (typ) after exit from Sleep is done. On-chip IIR filter is skipped for the very
first measurement. All measurements afterwards pass the embedded digital filtering as configured in
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 20 of 49 Data Sheet
Rev 006 September 30, 2010
EEPROM. Details on embedded filtering are available in application note “Understanding MLX90614 on-chip
digital signal filters”, available from www.melexis.com
SCL line is kept low in order to reduce current leakage trough the pin (artificial Zener diode is connected to
that pin).
8.4.8 MLX90614 SMBus specific remarks
The auxiliary functions of the SCL pin (zener diode) add undershoot to the clock pulse (5V devices only) as
shown in the picture below (see Fig 9). This undershoot is caused by the transient response of the on-chip
synthesized Zener diode. Typical duration of undershoot is approximately 15µs. An increased reactance of
the SCL line is likely to increase this effect. Undershoot does not affect the recognition of the SCL rising edge
by the MLX90914, but may affect proper operation of non-MLX90614 slaves on the same bus.
Figure 12: Undershoot of SCL line due to on chip synthesized Zener diode (5V versions only)
Continuous SMBus readings can introduce and error. As the SCL line inside TO39 package is passing
relatively close to the sensor input and error signal is induced to the sensor output. The manifestation of the
problem is wrong temperature readings. This is especially valid for narrow FOV devices. Possible solution is
to keep SDA and SCL line quite for period longer than refresh rate and settling time defined by internal
settings of MLX90614 prior reading the temperature or switch to PWM signal and completely disconnect from
SDA and SCL line.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 21 of 49 Data Sheet
Rev 006 September 30, 2010
8.5 PWM
The MLX90614 can be read via PWM or SMBus compatible interface. Selection of PWM output is done in
EEPROM configuration (factory default is SMBus). PWM output has two programmable formats, single and
dual data transmission, providing single wire reading of two temperatures (dual zone object or object and
ambient). The PWM period is derived from the on-chip oscillator and is programmable.
Config Register[5:4] PWM1 data PWM2 data Tmin,1 Tmax,1 Tmin,2 Tmax,2
00 Ta T
obj1
Ta
range
,L Ta
range
,H To
min
To
max
01 Ta T
obj2
Ta
range
,L Ta
range
,H To
min
To
max
11 T
obj1
T
obj2
To
min
To
max
To
min
To
max
10* T
obj2
Undefined To
min
To
max
N.A. N.A.
Table 12: PMW configuration table
Note: Serial data functions (2-wire / PWM) are multiplexed with a thermal relay function (described in the
“Thermal relay” section).
* not recommended for extended PWM format operation
t1 t2
t3
t4
FE
Valid data band
Error band
Start Stop
0
T
5
8
T
1
8T
13
16 T
7
8T
t1 t2
t3
t4
FE
Sensor 1
Error band
Start Stop
0
T
1
16 TT
5
16 T
7
16 T
8
16
Valid data band
t5 t6
Sensor 1
t7
FE
Error band
Sensor 2
Sensor 2
Valid data band
t8
T
9
16 T
13
16 T
15
16
Figure 13: PWM timing single (above) and extended PWM (bellow)
PWM type t1 t2 t3 t4 t5 t6 t7 t8
Single 1/8 – high 4/8 - var 2/8 1/8 – low NA NA NA NA
Extended - S1 1/16 - high 4/16 - var 2/16 1/16 - low 1/16 - low 4/16 – low 2/16 - low 1/16 - low
Extended - S2 1/16 - high 4/16 - high 2/16 - high 1/16 - high 1/16 - high 4/16 - var 2/16 1/16 - low
Table 13: PMW timing
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 22 of 49 Data Sheet
Rev 006 September 30, 2010
8.5.1 Single PWM format
In single PWM output mode the settings for PWM1 data only are used. The temperature reading can be
calculated from the signal timing as:
( )
MINOMINOMAXOOUT TTT
T
t
T___
2
2+
−=
where Tmin and Tmax are the corresponding rescale coefficients in EEPROM for the selected temperature
output (Ta, object temperature range is valid for both Tobj1 and Tobj2 as specified in the previous table) and
T is the PWM period. Tout is T
obj1
, T
obj2
or T
a
according to Config Register [5:4] settings.
The different time intervals t
1
…t
4
have following meaning:
t
1
: Start buffer. During this time the signal is always high. t
1
= 0.125*T (T is the PWM period, refer to fig. 13).
t
2
: Valid Data Output Band, 0…1/2T. PWM output data resolution is 10 bit.
t
3
: Error band – information for fatal error in EEPROM (double error detected, not correctable). t
3
= 0.25 * T.
Therefore a PWM pulse train with a duty cycle of 0.875 will indicate a fatal error in EEPROM (for single PWM
format). FE means Fatal Error.
Example:
Figure 14: PWM example single mode
To_
min
= 0°C => To
min
[EEPROM] = 100 * (to
min
+ 273.15) = 0x6AB3
To_
max
= +50°C => To
max
[EEPROM] = 100 * (to
max
+ 273.15) = 0x7E3B
Captured PWM period is T = 1004µs
Captured high duration is t = 392 µs
Calculated duty cycle is:
3904.0
1004
392 ===
T
t
D
or
%04.39
The temperature is calculated as follows:
(
)
(
)
CT
O
°==+−−=
54.2650*2554.0*20050*125.03904.0*2
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 23 of 49 Data Sheet
Rev 006 September 30, 2010
8.5.2 Extended PWM format
The PWM format for extended PWM is shown in Figure 15. Note that with bits DUAL[5:1]>00h each period
will be outputted 2N+1 times, where N is the decimal value of the number written in DUAL[5:1] (DUAL[5:1]
=PWM control & clock [8:4] ), like shown on Figure 15.
Figure 15: Extended PWM format with DUAL [5:1] = 01h (2 repetitions for each data)
The temperature transmitted in Data 1 field can be calculated using the following equation:
( )
111
2
1*
4TminTminTmax
T
t
Tout +
−=
For Data 2 field the equation is:
( )
222
5
2*
4TminTminTmax
T
t
Tout +
−=
Time bands are: t
1
=0.0625*T (Start1), t
3
=0.125*T and t
4
=0.5625*T (Start2 = Start1 + Valida_data1 +
error_band1 + stop1 + start2). As shown in Figure 13, in extended PWM format the period is twice the period
for the single PWM format. All equations provided herein are given for the single PWM period T. The
EEPROM Error band signaling will be 43.75% duty cycle for Data1 and 93.75% for Data2.
Note: EEPROM error signaling is implemented in automotive grade parts only.
t3
t1 t2
Start
0
T
1
16 TT
8
16 T
15
16
t=16.875ms
T=100ms (PWM = 10Hz)
t1 t2
Start
0
T
1
16 TT
8
16 T
15
16
t=73.125ms
T=100ms (PWM = 10Hz)
Extended PWM mode sensor 1
Extended PWM mode sensor 2
Figure 16: Example: Extended PWM mode readings – sensor 1 above and sensor 2 bellow
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 24 of 49 Data Sheet
Rev 006 September 30, 2010
Example (see Figure 15 above):
Configuration: Sensor1 = Ta, Sensor2 = T
obj1
=> Config Reg[5:4] = 00b,
Ta
min
= 0°C => Ta
range
, L [EEPROM] = 100*(Ta
min
+38.2)/64 = 0x3C,
Ta
max
= +60°C => Ta
range
,H [EEPROM] = 100*(Ta
max
+38.2)/64 = 0x99,
Ta
range
[EEPROM 0x03]=0x993C
To
min
= 0°C => To
min
[EEPROM 0x01] = 100 * (To
min
+ 273.15) = 0x6AB3
To
max
= +50°C => To
max
[EEPROM 0x00] = 100 * (To
max
+ 273.15) = 0x7E3B
Captured high durations are:
Sensor 1 – t = 16.875ms at period T = 100ms thus the duty cycle is 16875.0
100
875.16
1
==
S
Duty
Sensor 2 – t = 73.125ms at period T = 100ms thus the duty cycle is 73125.0
100
125.73
2
==
S
Duty
The temperature is calculated as follows:
(
)
(
)
(
)
(
)
CTTTStartDutyT
MINAMINAMAXASambient
°=+−−=+−−= 5.2500600625.016875.0.4.1.4
___1
(
)
(
)
(
)
(
)
CTTTStartDutyT
MINOMINOMAXOSobject
°=+−−=+−−= 75.3300505625.073125.0.4.2.4
___21
8.5.3 Customizing the temperature range for PWM output
The calculated ambient and object temperatures are stored in RAM with a resolution of 0.01 °C (16 bit). The
PWM operates with a 10-bit word so the transmitted temperature is rescaled in order to fit in the desired
range.
For this goal 2 cells in EEPROM are foreseen to store the desired range for To (To
min
and To
max
) and one for
Ta (Ta
range
: the 8MSB are foreseen for Ta
max
and the 8LSB for Ta
min
).
Thus the output range for To can be programmed with an accuracy of 0.01 °C, while the corresponding Ta
range can be programmed with an accuracy of 0.64 °C.
The object data for PWM is rescaled according to the following equation:
1023
,
EEPROMEEPROMEEPROM
obj
MINMAX
obj
PWM
obj
PWM
MINRAM
PWM
TT
K
K
TT
T
−
=
−
=
The T
RAM
is the linearized Tobj, 16-bit (0x0000…0xFFFF, 0x0000 for -273.15°C and 0xFFFF for +382.2°C)
and the result is a 10-bit word, in which 0x000h corresponds to To
MIN
[°C], 0x3FFh corresponds to To
MAX
[°C]
and 1LSB corresponds to
1023
MINMAX
ToTo
−
[°C]
100∗=
MINMIN
TT
EEPORM
LSB
100∗=
MAXMAX
TT
EEPORM
LSB
The ambient data for PWM is rescaled according to the following equation:
1023
,
EEPROMEEPROM
ambient
EEPROM
ambient
MINMAX
ambient
PWM
PWM
MINRAM
PWM
TT
K
K
TT
T
−
=
−
=
The result is a 10-bit word, where 000h corresponds to -38.2 °C (lowest Ta that can be read via PWM), 3FFh
corresponds to 125 °C (highest Ta that can be read via PWM) and 1LSB corresponds to
1023
MINMAX
TT
−
[°C]
( )
[ ]
64
100
2.38
∗−−=
MINMIN
TT
EEPORM
LSB
( )
[ ]
64
100
2.38
∗−−=
MAXMAX
TT
EEPORM
LSB
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 25 of 49 Data Sheet
Rev 006 September 30, 2010
8.6 Switching Between PWM and SMBus communication
8.6.1 PWM is enabled
The diagram below illustrates the way of switching to SMBus if PWM is enabled (factory programmed POR
default for MLX90614 is SMBus, PWM disabled). Note that the SCL pin needs to be kept high in order to use
PWM.
SCL
PWM/SDA
Start Stop
t
REQ
PWM mode SMBus mode
>1.44ms
Figure 17: Switching from PWM mode to SMBus
8.6.2 Request condition
SCL
SMBus Request
t
REQ
>1,44ms
Figure 18: Request (switch to SMBus) condition
If PWM is enabled, the MLX90614’s SMBus Request condition is needed to disable PWM and reconfigure
PWM/SDA pin before starting SMBus communication. Once PWM is disabled, it can be only enabled by
switching the supply OFF – ON or exit from Sleep Mode. The MLX90614’s SMBus request condition requires
forcing LOW the SCL pin for period longer than the request time (t
REQ
) >1,44ms. The SDA line value is
ignored in this case.
8.6.3 PWM is disabled
If PWM is disabled by means of EEPROM the PWM/SDA pin is directly used for the SMBus purposes after
POR. Request condition should not be sent in this case.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 26 of 49 Data Sheet
Rev 006 September 30, 2010
8.7 Computation of ambient and object temperatures
The IR sensor consists of serial connected thermo-couples with cold junctions placed at thick chip substrate
and hot junctions, placed over thin membrane. The IR radiation absorbed from the membrane heats (or
cools) it. The thermopile output signal is:
(
)
(
)
44
., TaToAToTaV
ir
−=
,
Where To is the object temperature absolute (Kelvin) temperature, Ta is the sensor die absolute (Kelvin)
temperature, and A is the overall sensitivity.
An on board temperature sensor is needed to measure the chip temperature. After measurement of the
output of both sensors, the corresponding ambient and object temperatures can be calculated. These
calculations are done by the internal DSP, which produces digital outputs, linearly proportional to measured
temperatures.
8.7.1 Ambient temperature Ta
The Sensor die temperature is measured with a PTC or a PTAT element. All the sensors conditioning and
data processing is handled on-chip and the linearized sensor die temperature Ta is made available in
memory.
The resolution of the calculated temperature is 0.02 ˚C. The sensor is factory calibrated for the full automotive
range (-40…+125 ˚C). In RAM cell 006h, 2DE4h corresponds to -38.2 ˚C (linearization output lower limit) and
4DC4h (19908d) corresponds to 125 ˚C. The conversions from RAM contend to real Ta is easy using the
following relation:
02.0][
×
=
°
TaregKTa
, or 0.02 °K / LSB.
8.7.2 Object temperature To
The result has a resolution of 0.02 ˚C and is available in RAM. To is derived from RAM as:
02.0][
×
=
°
ToregKTo
, or 0.02 °K / LSB.
Please note that 1LSB corresponds to 0,02Deg and the MSB bit is error flag (if “1” then error).
Example:
1. 0x0000 => -273,15˚C (no error) - min possible value returned by MLX90614
2. 0x0001 => -273.13˚C (no error)
3. 0x0002 => -273,11˚C (no error) and so on
4. 0x3AF7 => 28,75˚C (no error)
5. 0x7FFF => 382,19˚C (no error) - max possible value returned by MLX90614
The result is calculated by following expressions:
1. Convert it to decimal value i.e 0x3AF7 = 15095d
2. Divide by 50 (or multiply by 0,02) i.e. 15095/50=301,9K (result is in Kelvin)
3. Convert K -> ˚C i.e. 301,9-273,15=28,75˚C
8.7.3 Calculation flow
The measurement, calculation and linearization are held by core, which executes a program form ROM.
After POR the chip is initialized with calibration data from EEPROM. During this phase the number of IR
sensors is selected and it is decided which temperature sensor will be used. Measurements, compensation
and linearization routines run in a closed loop afterwards.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 27 of 49 Data Sheet
Rev 006 September 30, 2010
Processing ambient temperature includes:
Offset measurement with fixed length FIR filter
Additional filtering with fixed length IIR filter. The result is stored into RAM as T
OS
Temperature sensor measurement using programmable length FIR *.
Offset compensation
Additional processing with programmable length IIR **. The result is stored into RAM as T
D
.
Calculation of the ambient temperature. The result is stored into RAM as T
A
Processing of the object temperature consists of three parts. The first one is common for both IR sensors, the
third part can be skipped if only one IR sensor is used.
IR offset:
Offset measurement with a fixed length FIR
Additional filtering with a fixed length IIR. The result is stored into RAM as IR
OS
.
Gain measurement with fixed length FIR filter
Offset compensation
Additional gain filtering with fixed length IIR, storing the result into RAM as IR
G
.
Gain compensation calculation, the result is stored into RAM as K
G
Object temperature:
IR1 sensor:
IR sensor measurement with programmable length FIR filter *.
Offset compensation
Gain compensation
Filtering with programmable length IIR filter**, storing the result into RAM as IR1
D
.
Calculation of the object temperature. The result is available in RAM as T
OBJ1
.
IR2 sensor:
IR sensor measurement with programmable length FIR filter *.
Offset compensation
Gain compensation
Filtering with programmable length IIR filter**, storing the result into RAM as IR2
D
Calculation of the object temperature. The result is available in RAM as T
OBJ2
.
PWM calculation:
Recalculate the data for PWM with 10 bit resolution
Load data into PWM module
Note*: The measurements with programmable filter length for FIR filter use the same EEPROM cells for N.
Note**: The IIR filter with programmable filter length uses the same EEPROM cells for L.
Initialization
T
A
Offset meas
OS
Ta
= meas(N
Tos
)
filtering
T
OS
= IIR(L
Tos
,OS
Ta
)
T
A
meas
T
DATA
= meas(N
Ta
)
Offset comp
T
DATAcomp
= T
DATA
-T
OS
filtering
T
D
= IIR(L
Ta
,T
DATAcomp
)
T
A
calculation
TA
IR Offset meas
OS
IR
= meas(N
IRos
)
filtering
IR
OS
= IIR(L
IRos
,OS
IR
)
IR1 meas
IR1
D
= meas(N
IR
)
Offset comp
IR1
Dcomp
= IR1
D
- IR
OS
filtering
IR1
D
= IIR(L
IR
,IR1
Dg
)
T
OBJ1
calculation
Gain drift
IR
Gm
= meas(N
IRg
)
Offset comp
IR
Gcomp
= IR
Gm
- IR
OS
filtering
IR
G
= IIR(L
G
,IR
Gcomp
)
K
G
calculation
IR offset
Gain comp
IR1
Dg
= IR1
Dcomp
*K
G
IR2 meas
IR2
D
= meas(N
IR
)
Offset comp
IR2
Dcomp
= IR2
D
- IR
OS
filtering
IR2
D
= IIR(L
IR
,IR2
Dg
)
T
OBJ2
calculation
Gain comp
IR2
Dg
= IR2
Dcomp
*K
G
TOBJ1
TOBJ2
PWM
calculation
Load PWM
registers
1
123
23
Figure 19: Software flow
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 28 of 49 Data Sheet
Rev 006 September 30, 2010
8.8 Thermal relay
The MLX90614 can be configured to behave as a thermo relay with programmable threshold and hysteresis
on the PWM/SDA pin. The input for the comparator unit of the relay is the object temperature from sensor 1
The output of the MLX90614 is NOT a relay driver but a logical output which should be connected to a
relay driver if necessary.
The output driver is one and the same for PWM and Thermal relay.
In order to configure the MLX90614 to work as thermal relay two conditions must be met:
o Set bit TRPWMB high at address 002h in EEPROM
o Enable PWM output i.e. EN_PWM is set high
The PWM/SDA pin can be programmed as a push-pull or open drain NMOS (via bit PPODB in EEPROM
PWMCTRL), which can trigger an external device. The temperature threshold data is determined by
EEPROM at address 021h (Tomin) and the hysteresis at address 020h (To
max
).
The logical state of the PWM/SDA pin is as follows:
PWM/SDA pin is high if
hysteresisthresholdT
obj
+≥1
PWM/SDA pin is low if
hysteresisthresholdT
obj
−≤1
threshold
hysteresis hysteresis
T
“0”
“1”
Figure 20: Thermal relay : “PWM” pin versus Tobj
The MLX90614 preserves its normal operation when configured as a thermal relay (PWM configuration and
specification applies as a general rule also for the thermal relay) and therefore it can be read using the
SMBus (entering the SMBus mode from both PWM and thermal relay configuration is the same).
For example, the MLX90614 can generate a wake-up alert for a system upon reaching a certain temperature
and then be read as a thermometer. A reset condition (enter and exit Sleep, for example) will be needed in
order to return to the thermal relay configuration.
Example:
Threshold = 5 °C(5 + 273.15)*100 = 27815 EEPROM 0x0001= 0x6CA7
Hysteresis = 1°C1*100=100 EEPROM 0x0000= 0x0064 (smallest possible hysteresis is 0,01°C or 0x0001)
PWM/SDA pin will be low at object temperature below 4 °C
PWM/SDA pin will be high at object temperature higher that 6 °C
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 29 of 49 Data Sheet
Rev 006 September 30, 2010
9 Unique Features
• The MLX90614 is a ready-to use low-cost non contact thermometer provided from Melexis with
output data linearly dependent on the object temperature with high accuracy and extended
resolution.
• The high thermal stability of the MLX90614-XCX make this part highly suited in applications where
secondary heat sources can heat up the sensor. These sensors also have a very short stabilization
time compared to other types of thermopile sensors, which is of importance if one needs an accurate
measurement in conditions where the ambient temperature can change quickly.
• The MLX90614 supports versatile customization to a very wide range of temperatures, power
supplies and refresh rates.
• The user can program the internal object emissivity correction for objects with a low emissivity. An
embedded error checking and correction mechanism provides high memory reliability.
• The sensors are housed in an industry standard TO39 package for both single- and dual-zone IR
thermometers. The thermometer is available in automotive grade and can use two different packages
for wider applications’ coverage.
• The low power consumption during operation and the low current draw during sleep mode make the
thermometer ideally suited for handheld mobile applications.
• The digital sensor interface can be either a power-up-and-measure PWM or an enhanced access
SMBus compatible protocol. Systems with more than 100 devices can be built with only two signal
lines. Dual zone non contact temperature measurements are available via a single line (extended
PWM).
• A build-in thermal relay function further extends the easy implementation of wide variety of
freezing/boiling prevention and alert systems, as well as thermostats (no MCU is needed).
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 30 of 49 Data Sheet
Rev 006 September 30, 2010
10 Performance Graphs
10.1 Temperature accuracy of the MLX90614
10.1.1 Standard accuracy
All accuracy specifications apply under settled isothermal conditions only. Furthermore, the accuracy is only
valid if the object fills the FOV of the sensor completely.
-70
-20 0
Ta,
o
C
50 100 125-40
-40
0
60
120
180
240
300
380
To,
o
C
± 1
o
C
± 1
o
C
± 1
o
C
± 1
o
C
± 2
o
C
± 3
o
C
± 2
o
C± 2
o
C
± 3
o
C
± 3
o
C
± 2
o
C± 3
o
C
± 3
o
C± 4
o
C
± 4
o
C
± 4
o
C± 3
o
C
± 4
o
C
± 3
o
C± 2
o
C
± 1
o
C
± 1
o
C± 2
o
C
± 2
o
C
± 2
o
C± 2
o
C
± 3
o
C
± 0.5
o
C
Figure 21: Accuracy of MLX90614 (Ta,To)
All accuracy specifications apply under settled isothermal conditions only.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 31 of 49 Data Sheet
Rev 006 September 30, 2010
10.1.2 Medical accuracy
A version of the MLX90614 with accuracy suited for medical applications is available. The accuracy in the
range Ta 10ºC - 40ºC and To 32ºC - 42ºC is shown in diagram below. The accuracy for the rest of the
temperature ranges is the same as in previous diagram. Medical accuracy specification is only available for
the MLX90614DAA version.
40302010
36
45
32
39
42
± 0.1
o
C
± 0.2
o
C
± 0.2
o
C
± 0.3
o
C± 0.3
o
C
30
Ta,
o
C
To,
o
C
Figure 22: Accuracy of MLX90614DAA (Ta,To) for medical applications.
Accuracy of the MLX90614DCH and DCI for VDD = 3V (see paragraph 10.1.3)
Versions MLX90614DCI and MLX90614DCH comply with ASTM standard section 5.3.1.2 (Designation: E
1965 – 98 (Re-approved 2009) - Standard Specification for Infrared Thermometers for Intermittent
Determination of Patient Temperature
It is very important for the application design to understand that the accuracy specified in Figure 21 and
Figure 22 are only guaranteed when the sensor is in thermal equilibrium and under isothermal conditions
(there are no temperature differences across the sensor package). The accuracy of the thermometer can be
influenced by temperature differences in the package induced by causes like (among others): Hot electronics
behind the sensor, heaters/coolers behind or beside the sensor or when the measured object is so close to
the sensor that it not only radiates on the sensing element in the thermometer but also heats the thermometer
casing.
This effect is especially relevant for thermometers with a small Field Of View (FOV) like the -XXC and -XXF
as the energy received by the sensor from the object is reduced. Therefore, Melexis has introduced the -
XCX version of the MLX90614. In these MLX90614-XCC and -XCF, the thermal gradients are measured
internally and the measured temperature is compensated for them. In this way, the MLX90614–XCX is much
less sensitive to thermal gradients induced from outside, but the effect is not totally eliminated. It is therefore
important to avoid introducing strong heat sources close to the sensor or to shield the sensor from them.
10.1.3 Temperature reading dependence on V
DD
In case of medical applications where high accuracy is required and the supply is provided by means of a
battery, a compensation of temperature readings from VDD dependence should be done by the
microcontroller. The dependence is very repeatable and compensation can easily be implemented. As this
dependence comes from the ambient temperature it is the same for all type of devices regardless of FOV and
optics used and it directly translates in the same compensation for object temperature.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 32 of 49 Data Sheet
Rev 006 September 30, 2010
The VDD dependence of the ambient and object temperature is 0.6°C/V.
Typical Ta=f(VDD) dependance
-0.50
-0.40
-0.30
-0.20
-0.10
0.00
0.10
0.20
0.30
0.40
0.50
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8
VDD, V
Ta error, DegC
Sensor1
Sensor2
Sensor3
Sensor4
Sensor5
Sensor6
Sensor7
Sensor8
Sensor9
Sensor10
Sensor11
Sensor12
Sensor13
Sensor14
Sensor15
Sensor16
Figure 23: Typical Ta dependence from supply voltage
Example: As the devices are calibrated at VDD=3V the error at VDD=3V is smallest one. The error in ambient
channel is directly transferred as object channel error (see Figure 23 bellow).
Typical To=f(VDD) dependance
-0.50
-0.40
-0.30
-0.20
-0.10
0.00
0.10
0.20
0.30
0.40
0.50
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8
VDD, V
To error, DegC
Sensor1
Sensor2
Sensor3
Sensor4
Sensor5
Sensor6
Sensor7
Sensor8
Sensor9
Sensor10
Sensor11
Sensor12
Sensor13
Sensor14
Sensor15
Sensor16
Figure 24: Typical To dependence from supply voltage (practically the same as Ta dependence error
In order to compensate for this error we measure supply voltage and by applying following equation
compensate the result.
6.0*)3(_*)(
0_
−−=−−= VDDTdependenceTypicalVDDVDDTT
OOdcompensateO
Compensated VDD dependence
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8
VDD, V
To_compensated error, degC
Sensor1
Sensor2
Sensor3
Sensor4
Sensor5
Sensor6
Sensor7
Sensor8
Sensor9
Sensor10
Sensor11
Sensor12
Sensor13
Sensor14
Sensor15
Sensor16
Figure 25: Typical To compensated dependence error
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 33 of 49 Data Sheet
Rev 006 September 30, 2010
10.2 Field Of View (FOV)
Figure 26: Field Of View measurement
Parameter MLX90614xAA MLX90614xBA MLX90614xCC MLX90614xCF
MLX90614xCH
MLX90614xCI
Peak
zone 1 ±0° -25° ±0° ±0° ±0° ±0°
Width
zone 1 90° 70° 35° 10° 12° 5°
Peak
zone 2 -25°
Width
zone 2
Not applicable 70° Not applicable Not applicable Not applicable Not applicable
Table 14: FOV summary table
Point heat source
Rotated
sensor
Angle of incidence
100%
50%
Sensitivity
Field Of View
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 34 of 49 Data Sheet
Rev 006 September 30, 2010
0.00
0.25
0.50
0.75
1.00
-80° -60° -40° -20° 0° 20° 40° 60° 80°
Angle, Deg
Figure 27: Typical FOV of MLX90614xAA
0.00
0.25
0.50
0.75
1.00
-80° -60° -40° -20° 0° 20° 40° 60° 80°
Angle, Deg
Figure 28: Typical FOV of MLX90614xBA Figure 29: Identification of
zone 1&2 relative to alignment
tab
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 35 of 49 Data Sheet
Rev 006 September 30, 2010
0.00
0.25
0.50
0.75
1.00
-80° -60° -40° -20° 0° 20° 40° 60° 80°
Angle, Deg
Figure 30: Typical FOV of MLX90614xCC
0.00
0.25
0.50
0.75
1.00
-80° -60° -40° -20° 0° 20° 40° 60° 80°
Angle, Deg
Figure 31: Typical FOV of MLX90614xCF
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 36 of 49 Data Sheet
Rev 006 September 30, 2010
0.00
0.25
0.50
0.75
1.00
-80º -60º -40º -20º 0º 20º 40º 60º 80º
Angle, Deg
Figure 32: Typical FOV of MLX90614xCH
0.00
0.25
0.50
0.75
1.00
-80º -60º -40º -20º 0º 20º 40º 60º 80º
Angle, Deg
Figure 33: Typical FOV of MLX90614xCI
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 37 of 49 Data Sheet
Rev 006 September 30, 2010
11 Applications Information
11.1 Use of the MLX90614 thermometer in SMBus configuration
SCL
Vz
Vdd
R2
2
C1
0.1uF
3
U1 MCU
SCL
SDA
GND
Vdd
4
+3.3V
PW M
SDA
U2 MLX90614Bxx
R1
1
SMBus
Vss
Figure 34: MLX90614 SMBus connection
Error! Reference source not found. shows the connection of a MLX90614 to a SMBus with 3.3V power
supply. The MLX90614 has diode clamps SDA/SCL to Vdd so it is necessary to provide MLX90614 with
power in order not to load the SMBus lines.
11.2 Use of multiple MLX90614s in SMBus configuration
R2
U1 MLX90614Bxx
4
1
2
SCL
Vz
U1 MLX90614Bxx
C4
Cbus2
U1 MCU
SCL
SDA
GND
Vdd
1
I1
Ipu1
C2
0.1uF
SCL
Vz
3
SDA
C3
Cbus1
R1
3
SCL
4
C1
0.1uF
Vss
+3.3V
I2
Ipu2
Vdd
Vdd
2
SMBus
Vss
Current source or resistor
pull-ups of the bus
PW M
SDA
PW M
SDA
Figure 35: Use of multiple MLX90614 devices in SMBus network
The MLX90614 supports a 7-bit slave address in EEPROM, thus allowing up to 127 devices to be read via
two common wires. With the MLX90614BBx this results in 254 object temperatures measured remotely and
an additional 127 ambient temperatures which are also available. Current source pull-ups may be preferred
with higher capacitive loading on the bus (C3 and C4 represent the lines’ parasitics), while simple resistive
pull-ups provide the obvious low cost advantage.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 38 of 49 Data Sheet
Rev 006 September 30, 2010
11.3 PWM output operation
Using the PWM output mode of the MLX90614 is very simple, as shown in Figure 36.
J1
CON1
PWM
Vdd
GND
2
0.1uF
Vdd U1
MLX90614
Vss
PWM
SDA
1
C1
SCL
Vz
3
Figure 36: Connection of MLX90614 for PWM output mode
The PWM mode is free-running after POR when configured in EEPROM. The SCL pin must be forced high
for PWM mode operation (can be shorted to V
DD
pin).
A pull-up resistor can be used to preserve the option for SMBus operation while having PWM as a default as
is shown on Figure 37.
PWM
SDA
10k
3
1
Vdd
2
R1
SCL
Vz
J1
CON1
SCL
PWM/SDA
GND
Vdd
U1
MLX90614
Vss
0.1uF
C1
Figure 37: PWM output with SMBus available
Again, the PWM mode needs to be written as the POR default in EEPROM. Then for PWM operation the
SCL line can be high impedance, forced high, or even not connected. The pull-up resistor R1 will ensure
there is a high level on the SCL pin and the PWM POR default will be active. SMBus is still available (for
example – for further reconfiguration of the MLX90614, or sleep mode power management) as there are pull-
up resistors on the SMBus lines anyway.
PWM can be configured as open drain NMOS or a push-pull output. In the case of open drain external pull-up
will be needed. This allows cheap level conversion to lower logic high voltage. Internal pull-ups present in
many MCUs can also be used.
11.4 Thermal alert / thermostat
U2
AC line
R1
3
C2
10uF
C1
0.1uF
U1 MCU
SCL
SDA
GND
Vdd
2
SCL
Vz
C*
2
SCL
Vz
U1
MLX90614Axx
U1 MLX90614Bxx
Vss
Vdd
1 1
SMBus
R2
Vdd
4
Q1
4
1
+5V
U1 MLX90614Axx
Vdd
Vss
+3.3V R1
C3
0.1uF
SCL
Vz
3
R2
+24V
Vss
C1
0.1uF
PWM
SDA
PWM
SDA
3
4
PW M
SDA
D1
Alert dev ice
+
-
2
Figure 38: Thermal alert/thermostat applications of MLX90614
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 39 of 49 Data Sheet
Rev 006 September 30, 2010
The MLX90614 can be configured in EEPROM to operate as a thermal relay. A non contact freezing or
boiling prevention with 1 mA quiescent current can be built with two components only – the MLX90614 and a
capacitor. The PWM/SDA pin can be programmed as a push-pull or open drain NMOS, which can trigger an
external device, such as a relay (refer to electrical specifications for load capability), buzzer, RF transmitter or
a LED. This feature allows very simple thermostats to be built without the need of any MCU and zero design
overhead required for firmware development. In conjunction with a MCU, this function can operate as a
system alert that wakes up the MCU. Both object temperature and sensor die temperature can also be read
in this configuration.
11.5 High voltage source operation
As a standard, the module MLX90614Axx works with a supply voltage of 5Volt. In addition, thanks to the
integrated internal reference regulator available at pin SCL/Vz, this module can easily be powered from
higher voltage source (like VDD=8…16V). Only a few external components as depicted in the diagram below
are required to achieve this.
2.2uF
1
Vdd
Vss
PWM
SDA
U1
5.7V
C* +12V
J1
CON1
PWM
V+
GND
3
Equivalent schematics
Q1
Q1
U1
MLX90614
2
C1
SCL
Vz
MLX90614Axx: V=8...16V
+5V
4
R1
R1
Figure 39: 12V regulator implementation
With the second (synthesized Zener diode) function of the SCL/Vz pin used, the 2-wire interface function is
available only if the voltage regulator is overdriven (5V regulated power is forced to Vdd pin).
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 40 of 49 Data Sheet
Rev 006 September 30, 2010
12 Application Comments
Significant contamination at the optical input side (sensor filter) might cause unknown additional
filtering/distortion of the optical signal and therefore result in unspecified errors.
IR sensors are inherently susceptible to errors caused by thermal gradients. There are physical reasons for
these phenomena and, in spite of the careful design of the MLX90614xxx, it is recommended not to subject
the MLX90614 to heat transfer and especially transient conditions.
Upon power-up the MLX90614 passes embedded checking and calibration routines. During these routines
the output is not defined and it is recommended to wait for the specified POR time before reading the module.
Very slow power-up may cause the embedded POR circuitry to trigger on inappropriate levels, resulting in
unspecified operation and this is not recommended.
The MLX90614xxx is designed and calibrated to operate as a non contact thermometer in settled
conditions. Using the thermometer in a very different way will result in unknown results.
Capacitive loading on a SMBus can degrade the communication. Some improvement is possible with use
of current sources compared to resistors in pull-up circuitry. Further improvement is possible with specialized
commercially available bus accelerators. With the MLX90614xxx additional improvement is possible by
increasing the pull-up current (decreasing the pull-up resistor values). Input levels for SMBus compatible
mode have higher overall tolerance than the SMBus specification, but the output low level is rather low even
with the high-power SMBus specification for pull-up currents. Another option might be to go for a slower
communication (clock speed), as the MLX90614xxx implements Schmidt triggers on its inputs in SMBus
compatible mode and is therefore not really sensitive to rise time of the bus (it is more likely the rise time to
be an issue than the fall time, as far as the SMBus systems are open drain with pull-up).
For ESD protection there are clamp diodes between the Vss and Vdd and each of the other pins. This
means that the MLX90614 might draw current from a bus in case the SCL and/or SDA is connected and the
Vdd is lower than the bus pull-ups’ voltage.
In 12V powered systems SMBus usage is constrained because the SCL pin is used for the Zener diode
function. Applications where the supply is higher than 5V should use the PWM output or an external
regulator. Nevertheless, in the 12V powered applications MLX90614 can be programmed (configured and
customized) by forcing the Vdd to 5V externally and running the SMBus communication.
A sleep mode is available in the MLX90614Bxx. This mode is entered and exited via the SMBus compatible
2-wire communication. On the other hand, the extended functionality of the SCL pin yields in increased
leakage current through that pin. As a result, this pin needs to be forced low in sleep mode and the pull-up on
the SCL line needs to be disabled in order to keep the overall power drain in sleep mode really small. During
sleep mode the sensor will not perform measurements.
The PWM pin is not designed for direct drive of inductive loads (such as electro-magnetic relays). Some
drivers need to be implemented for higher load, and auxiliary protection might be necessary even for light but
inductive loading.
It is possible to use the MLX90614xxx in applications, powered directly from the AC line (transformer less). In
such cases it is very important not to forget that the metal package of the sensor is not isolated and
therefore may occur to be connected to that line, too. Melexis can not be responsible for any application like
this and highly recommends not using the MLX90614xxx in that way.
Power dissipation within the package may affect performance in two ways: by heating the “ambient”
sensitive element significantly beyond the actual ambient temperature, as well as by causing gradients over
the package that will inherently cause thermal gradient over the cap. Loading the outputs also causes
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 41 of 49 Data Sheet
Rev 006 September 30, 2010
increased power dissipation. In case of using the MLX90614Axx internal Zener voltage feature, the regulating
external transistor should also not cause heating of the TO39 package.
High capacitive load on a PWM line will result in significant charging currents from the power supply,
bypassing the capacitor and therefore causing EMC, noise, level degradation and power dissipation
problems. A simple option is adding a series resistor between the PWM/SDA pin and the capacitive loaded
line, in which case timing specifications have to be carefully reviewed. For example, with a PWM output that
is set to 1.024 ms and the output format that is 11 bit, the time step is 0.5 µs and a settling time of 2 µs would
introduce a 4 LSB error.
Power supply decoupling capacitor is needed as with most integrated circuits. MLX90614 is a mixed-signal
device with sensors, small signal analog part, digital part and I/O circuitry. In order to keep the noise low
power supply switching noise needs to be decoupled. High noise from external circuitry can also affect noise
performance of the device. In many applications a 100nF SMD ceramic capacitor close to the Vdd and Vss
pins would be a good choice. It should be noted that not only the trace to the Vdd pin needs to be short, but
also the one to the Vss pin. Using MLX90614 with short pins improves the effect of the power supply
decoupling.
Severe noise can also be coupled within the package from the SCL (in worst cases also from the SDA) pin.
This issue can be solved by using PWM output. Also the PWM output can pass additional filtering (at lower
PWM frequency settings). With a simple LPF RC network added also increase of the ESD rating is possible.
Check www.melexis.com for most recent application notes about MLX90614.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 42 of 49 Data Sheet
Rev 006 September 30, 2010
13 Standard information regarding manufacturability of Melexis
products with different soldering processes
Our products are classified and qualified regarding soldering technology, solderability and moisture sensitivity
level according to following test methods:
Wave Soldering THD’s (Through Hole Devices)
• EIA/JEDEC JESD22-B106 and EN60749-15
Resistance to soldering temperature for through-hole mounted devices
Iron Soldering THD’s (Through Hole Devices)
• EN60749-15
Resistance to soldering temperature for through-hole mounted devices
Solderability THD’s (Through Hole Devices)
• EIA/JEDEC JESD22-B102 and EN60749-21
Solderability
For all soldering technologies deviating from above mentioned standard conditions (regarding peak
temperature, temperature gradient, temperature profile etc) additional classification and qualification tests
have to be agreed upon with Melexis.
Melexis is contributing to global environmental conservation by promoting lead free solutions. For more
information on qualifications of RoHS compliant products (RoHS = European directive on the Restriction Of
the use of certain Hazardous Substances) please visit the quality page on our website:
http://www.melexis.com/quality.aspx
The MLX90614 is RoHS compliant
14 ESD Precautions
Electronic semiconductor products are sensitive to Electro Static Discharge (ESD).
Always observe Electro Static Discharge control procedures whenever handling semiconductor products.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 43 of 49 Data Sheet
Rev 006 September 30, 2010
15 FAQ
When I measure aluminum and plastic parts settled at the same conditions I get significant errors on
aluminum. Why?
Different materials have different emissivity. A typical value for aluminum (roughly polished) is 0.18 and for
plastics values of 0.84…0.95 are typical. IR thermometers use the radiation flux between the sensitive
element in the sensor and the object of interest, given by the equation
(
)
(
)
2
4
22ba1
4
111
ATFATq ........ σεσαε −=
−
,
Where:
ε
1
and ε
2
are the emissivities of the two objects,
α
1
is the absorptivity of the sensor (in this case),
σ is the Stefan-Boltzmann constant,
A
1
and A
2
are the surface areas involved in the radiation heat transfer,
F
a-b
is the shape factor,
T
1
and T
2
are known temperature of the sensor die (measured with specially integrated and calibrated
element) and the object temperature that we need.
Note that these are all in Kelvin, heat exchange knows only physics.
When a body with low emissivity (such as aluminum) is involved in this heat transfer, the portion of the
radiation incident to the sensor element that really comes from the object of interest decreases – and the
reflected environmental IR emissions take place. (This is all for bodies with zero transparency in the IR band.)
The IR thermometer is calibrated to stay within specified accuracy – but it has no way to separate the
incoming IR radiation into real object and reflected environmental part. Therefore, measuring objects with low
emissivity is a very sophisticated issue and infra-red measurements of such materials are a specialized field.
What can be done to solve that problem? Look at paintings – for example, oil paints are likely to have
emissivity of 0.85…0.95 – but keep in mind that the stability of the paint emissivity has inevitable impact on
measurements.
It is also a good point to keep in mind that not everything that looks black is “black” also for IR. For example,
even heavily oxidized aluminum has still emissivity as low as 0.30.
How high is enough? Not an easy question – but, in all cases the closer you need to get to the real object
temperature the higher the needed emissivity will be, of course.
With the real life emissivity values the environmental IR comes into play via the reflectivity of the object (the
sum of Emissivity, Reflectivity and Absorptivity gives 1.00 for any material). The larger the difference between
environmental and object temperature is at given reflectivity (with an opaque for IR material reflectivity equals
1.00 minus emissivity) the bigger errors it produces.
After I put the MLX90614 in the dashboard I start getting errors larger than specified in spite that the
module was working properly before that. Why?
Any object present in the FOV of the module provides IR signal. It is actually possible to introduce error in the
measurements if the module is attached to the dashboard with an opening that enters the FOV. In that case
portion of the dashboard opening will introduce IR signal in conjunction with constraining the effective FOV
and thus compromising specified accuracy. Relevant opening that takes in account the FOV is a must for
accurate measurements. Note that the basic FOV specification takes 50% of IR signal as threshold (in order
to define the area, where the measurements are relevant), while the entire FOV at lower level is capable of
introducing lateral IR signal under many conditions.
When a hot (cold) air stream hits my MLX90614 some error adds to the measured temperature I read.
What is it?
IR sensors are inherently sensitive to difference in temperatures between the sensitive element and
everything incident to that element. As a matter of fact, this element is not the sensor package, but the sensor
die inside. Therefore, a thermal gradient over the sensor package will inevitably result in additional IR flux
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 44 of 49 Data Sheet
Rev 006 September 30, 2010
between the sensor package and the sensor die. This is real optical signal that can not be segregated from
the target IR signal and will add errors to the measured temperature.
Thermal gradients with impact of that kind are likely to appear during transient conditions. The sensor used is
developed with care about sensitivity to this kind of lateral phenomena, but their nature demands some care
when choosing place to use the MLX90614 in order to make them negligible.
I measure human body temperature and I often get measurements that significantly differ from the
+37°C I expect.
IR measurements are true surface temperature measurements. In many applications this means that the
actual temperature measured by an IR thermometer will be temperature of the clothing and not the skin
temperature. Emissivity (explained first in this section) is another issue with clothes that has to be considered.
There is also the simple chance that the measured temperature is adequate – for example, in a cold winter
human hand can appear at temperatures not too close to the well known +37°C.
I consider using MLX90614AAA to measure temperature within car compartment, but I am
embarrassed about the Sun light that may hit the module. Is it a significant issue?
Special care is taken to cut off the visible light spectra as well as the NIR (near IR) before it reaches the
sensitive sensor die. Even more, the glass (in most cases) is not transparent to the IR radiation used by the
MLX90614. Glass has temperature and really high emissivity in most cases – it is “black” for IR of interest.
Overall, Sun behind a window is most likely to introduce relatively small errors. Why is it not completely
eliminated after all? Even visible light partially absorbed in the filter of the sensor has some heating potential
and there is no way that the sensor die will be “blind” for that heating right in front of it.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 45 of 49 Data Sheet
Rev 006 September 30, 2010
16 Package Information
16.1 MLX90614XXA
The MLX90614 is packaged in an industry standard TO – 39 can.
Figure 40: MLX90614XXA package
Note: All dimensions are in mm
16.2 MLX90614XCC
Figure 41: MLX90614XCC package
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 46 of 49 Data Sheet
Rev 006 September 30, 2010
16.3 MLX90614XCF
Figure 42: MLX90614XCF package
16.4 MLX90614XCH
Figure 43: MLX90614XCH package
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 47 of 49 Data Sheet
Rev 006 September 30, 2010
16.5 MLX90614XCI
Figure 44: MLX90614XCI package
16.6 Part marking
The MLX90614 is laser marked with 10 symbols. First 3 letters define device version (AAA, BCC, etc), and
the last 7 are the lot number. Example: “ACC9307308” – MLX90614ACC from lot 9307308.
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 48 of 49 Data Sheet
Rev 006 September 30, 2010
17 Table of figures
Figure 1: Typical application schematics........................................................................................................1
Figure 2: Pin description................................................................................................................................5
Figure 3: Block diagram...............................................................................................................................10
Figure 4: SMBus packet element key...........................................................................................................15
Figure 5: SMBus read word format ..............................................................................................................16
Figure 6: SMBus write word format ..............................................................................................................16
Figure 7: SMBus communication examples (Read RAM and Write EEPROM) .............................................16
Figure 8: SMBus timing ...............................................................................................................................17
Figure 9: Bit transfer on SMBus...................................................................................................................18
Figure 10: Enter sleep .................................................................................................................................19
Figure 11: Exit Sleep Mode..........................................................................................................................19
Figure 12: Undershoot of SCL line due to on chip synthesized Zener diode (5V versions only).....................20
Figure 13: PWM timing single (above) and extended PWM (bellow).............................................................21
Figure 14: PWM example single mode.........................................................................................................22
Figure 15: Extended PWM format with DUAL [5:1] = 01h (2 repetitions for each data)..................................23
Figure 16: Example: Extended PWM mode readings – sensor 1 above and sensor 2 bellow.......................23
Figure 17: Switching from PWM mode to SMBus.........................................................................................25
Figure 18: Request (switch to SMBus) condition..........................................................................................25
Figure 19: Software flow..............................................................................................................................27
Figure 20: Thermal relay : “PWM” pin versus Tobj........................................................................................28
Figure 21: Accuracy of MLX90614 (Ta,To)...................................................................................................30
Figure 22: Accuracy of MLX90614DAA (Ta,To) for medical applications. Accuracy of the MLX90614DCH and
DCI for VDD = 3V (see paragraph 10.1.3).............................................................................................31
Figure 23: Typical Ta dependence from supply voltage................................................................................32
Figure 24: Typical To dependence from supply voltage (practically the same as Ta dependence error.........32
Figure 25: Typical To compensated dependence error.................................................................................32
Figure 26: Field Of View measurement........................................................................................................33
Figure 27: Typical FOV of MLX90614xAA....................................................................................................34
Figure 28: Typical FOV of MLX90614xBA....................................................................................................34
Figure 29: Identification of zone 1&2 relative to alignment tab......................................................................34
Figure 30: Typical FOV of MLX90614xCC ...................................................................................................35
Figure 31: Typical FOV of MLX90614xCF....................................................................................................35
Figure 32: Typical FOV of MLX90614xCH ...................................................................................................36
Figure 33: Typical FOV of MLX90614xCI.....................................................................................................36
Figure 34: MLX90614 SMBus connection ....................................................................................................37
Figure 35: Use of multiple MLX90614 devices in SMBus network.................................................................37
Figure 36: Connection of MLX90614 for PWM output mode.........................................................................38
Figure 37: PWM output with SMBus available..............................................................................................38
Figure 38: Thermal alert/thermostat applications of MLX90614 ....................................................................38
Figure 39: 12V regulator implementation......................................................................................................39
Figure 40: MLX90614XXA package .............................................................................................................45
Figure 41: MLX90614XCC package.............................................................................................................45
Figure 42: MLX90614XCF package .............................................................................................................46
Figure 44: MLX90614XCI package ..............................................................................................................47
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 49 of 49 Data Sheet
Rev 006 September 30, 2010
18 References
[1] System Management Bus (SMBus) Specification Version 2.0 August 3, 2000
SBS Implementers Forum Copyright . 1994, 1995, 1998, 2000
Duracell, Inc., Energizer Power Systems, Inc., Fujitsu, Ltd., Intel Corporation, Linear Technology
Inc., Maxim Integrated Products, Mitsubishi Electric Semiconductor Company, PowerSmart, Inc.,
Toshiba Battery Co. Ltd., Unitrode Corporation, USAR Systems, Inc.
19 Disclaimer
Devices sold by Melexis are covered by the warranty and patent indemnification provisions appearing in its
Term of Sale. Melexis makes no warranty, express, statutory, implied, or by description regarding the
information set forth herein or regarding the freedom of the described devices from patent infringement.
Melexis reserves the right to change specifications and prices at any time and without notice. Therefore, prior
to designing this product into a system, it is necessary to check with Melexis for current information. This
product is intended for use in normal commercial applications. Applications requiring extended temperature
range, unusual environmental requirements, or high reliability applications, such as military, medical life-
support or life-sustaining equipment are specifically not recommended without additional processing by
Melexis for each application.
The information furnished by Melexis is believed to be correct and accurate. However, Melexis shall not be
liable to recipient or any third party for any damages, including but not limited to personal injury, property
damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequential
damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical
data herein. No obligation or liability to recipient or any third party shall arise or flow out of Melexis’ rendering
of technical or other services.
© 2010 Melexis NV. All rights reserved.
For the latest version of this document, go to our website at
www.melexis.com
Or for additional information contact Melexis Direct:
Europe, Africa, Asia: America:
Phone: +32 1367 0495 Phone: +1 603 223 2362
E-mail: sales_europe@melexis.com E-mail: sales_usa@melexis.com
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