ETC MLX90614

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
Features and Benefits
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
Small size, low cost
Easy to integrate
Factory calibrated in wide temperature range:
-40 to 125 ˚C for sensor temperature and
-70 to 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 optional
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 to 16V applications
Power saving mode
Different package options for applications and
measurements versatility
Automotive grade
Ordering Information
Part No. MLX90614 X X X
(1) (2) (3)
(1) Supply Voltage:
A - 5V power
(adaptable for 12V)
B - 3V power
1 Functional diagram
MLX90614Axx: Vdd=4.5...5.5V
1 MLX90614
J1
SCL
U1
SCL
Vz
P WM
4
Vss
SDA
2 SDA
Vdd
GND
Vdd
3
C1
0.1uF
CON1
C1 value and type may differ
in different applications
for optimum EMC
MLX90614 connection to SMBus
Figure 1 Typical application schematics
3901090614
Rev 1.0
(2) Number of thermopiles:
A – single zone
B – dual zone
(3) Package type:
A – Filter inside
B – Filter outside
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 output.
As a standard, the 10-bit PWM is configured to
continuously transmit the measured temperature in range
of -20 to 120 ˚C, with an output resolution of 0.14 ˚C.
The POR default is SMBus interface
Page 1 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
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 to 125 ˚C for the ambient temperature
and -70 to 382.2 ˚C for the object temperature. The 10-bit PWM is as a standard configured to transmit
continuously the measured object temperature for an object temperature range of -20 to 120 ˚C with an
output resolution of 0.14 ˚C. The PWM can be easily customized for virtually any range desired by 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 an 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.
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 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 sunlight immunity.
3901090614
Rev 1.0
Page 2 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
Table of Contents
1 Functional diagram .....................................................................................................................................1
2 General Description ....................................................................................................................................1
General description (continued) .....................................................................................................................2
3 Glossary of Terms ......................................................................................................................................4
4 Maximum ratings ........................................................................................................................................4
5 Pin definitions and descriptions...................................................................................................................5
6 Electrical Specifications ..............................................................................................................................6
6.1 MLX90614Axx......................................................................................................................................6
6.2 MLX90614Bxx......................................................................................................................................8
7 Detailed description ..................................................................................................................................10
7.1 Block diagram ....................................................................................................................................10
7.2 Signal processing principle.................................................................................................................10
7.3 Block description ................................................................................................................................11
7.3.1 Amplifier ......................................................................................................................................11
7.3.2 Supply regulator and POR ...........................................................................................................11
7.3.3 EEPROM.....................................................................................................................................11
7.3.4 RAM ............................................................................................................................................13
7.4 SMBus compatible 2-wire protocol......................................................................................................13
7.4.1 Functional description ..................................................................................................................13
7.4.2 Differences with the standard SMBus specification (reference [1]) ................................................14
7.4.3 Detailed description .....................................................................................................................14
7.4.4 AC specification for SMBus..........................................................................................................15
7.4.5 Bit transfer ...................................................................................................................................16
7.4.6 Commands ..................................................................................................................................16
7.4.7 Sleep Mode .................................................................................................................................17
7.5 PWM..................................................................................................................................................18
7.5.1 Single PWM format ......................................................................................................................18
7.5.2 Extended PWM format .................................................................................................................19
7.5.3 Customizing the temperature range for PWM output ....................................................................20
7.6 Switching Between PWM and SMBus communication ........................................................................21
7.6.1 PWM is enabled...........................................................................................................................21
7.6.2 Request condition ........................................................................................................................21
7.6.3 PWM is disabled ..........................................................................................................................21
7.7 Computation of ambient and object temperatures ...............................................................................22
7.7.1 Ambient temperature Ta...............................................................................................................22
7.7.2 Object temperature To .................................................................................................................22
7.7.3 Calculation flow............................................................................................................................22
7.8 Thermal relay .....................................................................................................................................24
8 Unique Features.......................................................................................................................................24
9 Performance Graphs ................................................................................................................................25
9.1 Temperature accuracy of the MLX90601AAA .....................................................................................25
9.2 Field Of View (FOV) ...........................................................................................................................27
10 Applications Information..........................................................................................................................28
10.1 Use of the MLX90614 thermometer in SMBus configuration .............................................................28
10.2 Use of multiple MLX90614s in SMBus configuration .........................................................................28
10.3 Thermal alert / thermostat.................................................................................................................29
10.4 High voltage source operation ..........................................................................................................29
11 Application Comments............................................................................................................................30
12 ESD Precautions ....................................................................................................................................32
13 FAQ........................................................................................................................................................32
14 Package Information...............................................................................................................................34
15 References .............................................................................................................................................35
16 Disclaimer...............................................................................................................................................35
3901090614
Rev 1.0
Page 3 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3 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)
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
TBD
To Be Defined
Note: sometimes the MLX90614xxx is referred to as “the module”.
4 Maximum ratings
Parameter.
MLX90614AAA
MLX90614ABA
MLX90614BAA
MLX90614BBA
MLX90614AAB
MLX90614ABB
MLX90614BAB
MLX90614BBB
Supply Voltage, VDD (over voltage)
7V
5V
7V
5V
Supply Voltage, VDD (operating)
5.5 V
3.6V
5.5V
3.6V
Reverse Voltage
0.4 V
Operating Temperature Range, TA
-40…+85°C
-40 to +125°C
Storage Temperature Range, TS
-40…+105°C
-40…+125 °C
ESD Sensitivity (AEC Q100 002)
2kV
DC current into SCL/Vz (Vz mode)
2 mA
DC sink current, SDA /PWM pin
25 mA
DC source current, SDA/PWM pin
25 mA
DC clamp current, SDA/PWM pin
25 mA
DC clamp current, SCL pin
25 mA
Table 1: Absolute maximum ratings for MLX90614
Exceeding the absolute maximum ratings may cause permanent damage. Exposure to absolute-maximumrated conditions for extended periods may affect device reliability.
3901090614
Rev 1.0
Page 4 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
5 Pin definitions and descriptions
2 - PWM/
SDA
1 - SCL/
Vz
3 - VDD
4 - VSS
Top view
Figure 2: Pin description
Pin Name
VSS
SCL / Vz
PWM / SDA
VDD
Function
Ground. The metal can is also connected to this pin.
Serial clock input for 2 wire communications protocol. 5.7V zener
is available at this pin for connection of external bipolar transistor
to MLX90614A to supply the device from external 8 -16V source.
Digital input / output. In normal mode the measured object
temperature is available at this pin Pulse Width Modulated.
External supply voltage.
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.
3901090614
Rev 1.0
Page 5 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
6 Electrical Specifications
6.1 MLX90614Axx
All parameters are preliminary for TA = 25 ˚C, VDD =5V (unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Units
4.5
5
5.5
V
Supplies
External supply
VDD
Supply current
IDD
No load
1
mA
Supply current
(programming)
IDDpr
No load, erase/write EEPROM
operations
1.5
mA
Zener voltage
Vz
Iz = 75…400 uA
5.6
5.75
5.8
V
Zener voltage
Vz(Ta)
Iz=70…400uA, full temperature
range
5.15
5.75
6.24
V
POR level
V POR
Power-up, power-down and
brown-out
2.7
3.0
3.3
V
VDD rise time
TPOR
Ensure POR signal
3
ms
Output valid (result in RAM)
Tvalid
After POR
Power On Reset
Pulse width modulation
0.15
s
1
PWM resolution
PWMres
Data band
10
bit
PWM output period
PWMT,def
Factory default, internal oscillator
factory calibrated
1.024
ms
PWM period stability
dPWMT
Internal oscillator factory
calibrated, over the entire
operation range and supply
voltage
-4
Output high Level
PWMHI
Isource = 2 mA
VDD-0.2
Output low Level
PWMLO
Isink = 2 mA
Output drive current
IdrivePWM
Vout,H = VDD - 0.8V
20
mA
Output sink current
Isink PWM
Vout,L = 0.8V
20
mA
Output settling time
Tset
100 pF capacitive load, full
operating Ta range
500
Output settling time
TsetRC
220 Ohm in series with 47nF load
on the wire, full Ta operating
range
3901090614
Rev 1.0
Page 6 of 35
+4
V
VSS+0.2
20
%
V
TBD
ns
50
us
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
Parameter
Symbol
Test Conditions
Min
Typ
Max
Units
2
SMBus compatible 2-wire interface
Input high voltage
Input high voltage
VIH
VIH(Ta,V)
1.8
1.6
2
Over temperature and supply
2.2
2.4
V
V
Input low voltage
Input low voltage
V IL
VIL(Ta,V)
0.7
0.5
1.0
Over temperature and supply
1.3
1.5
V
V
0.2
V
Output low voltage
VOL
SDA pin in open drain mode,
over temperature and supply,
Isink = 2mA
SCL leakage
ISCL,leak
V SCL=4V, Ta=+85°C
30
uA
SDA leakage
SCL capacitance
ISDA,leak
C SCL
V SDA=4V, Ta=+85°C
0.3
10
uA
pF
SDA capacitance
C SDA
10
pF
Slave address
SMBus Request
tREQ
SA
SCL low
Factory default
5Ah
hex
Timeout, low
Timeout,L
SCL low
30
ms
Timeout, high
Timeout,H
SCL high
50
us
Acknowledge setup time
Acknowledge hold time
Tsuac(MD)
Thdac(MD)
8-th SCL falling edge, Master
9-th SCL falling edge, Master
0.5
1.5
1.5
2.5
us
Acknowledge setup time
Acknowledge hold time
Tsuac(SD)
Thdac(SD)
8-th SCL falling edge, Slave
9-th SCL falling edge, Slave
2.5
1.5
1.024
ms
us
us
us
EEPROM
Data retention
Ta = +85°C
10
years
Erase/write cycles
Ta = +25°C
100,000
Ta = +125°C
10,000
Times
Times
Erase/write cycles
Erase cell time
Terase
5
Write cell time
Twrite
5
ms
ms
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 pullup 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 voltage are with respect to the Vss (ground) unless otherwise noted.
Power saving mode is not available on the 5V version (MLX90614Axx).
3901090614
Rev 1.0
Page 7 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
6.2 MLX90614Bxx
All parameters are preliminary for TA = 25 ˚C, VDD =3V (unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Units
2.4
3
3.6
V
Supplies
External supply
VDD
Supply current
IDD
No load
1
mA
Supply current
(programming)
IDDpr
No load, erase/write EEPROM
operations
1.5
mA
Power-down supply
current
Isleep
no load
1
2.5
5
uA
Power-down supply
current
Isleep
Full temperature range
1
2.5
6
uA
POR level
V POR
Power-up, power-down and
brown-out
1.6
1.85
2.1
V
VDD rise time
TPOR
Ensure POR signal
1
ms
Output valid
Tvalid
After POR
Power On Reset
Pulse width modulation
0.15
s
1
PWM resolution
PWMres
Data band
10
bit
PWM output period
PWMT,def
Factory default, internal oscillator
factory calibrated
1.024
ms
PWM period stability
dPWMT
Internal oscillator factory
calibrated, over the entire
operation range and supply
voltage
-4
Output high Level
PWMHI
Isource = 2 mA
V DD-0.25
Output low Level
PWMLO
Isink = 2 mA
Output drive current
IdrivePWM
Vout,H = V DD - 0.8V
15
mA
Output sink current
IsinkPWM
Vout,L = 0.8V
15
mA
Output settling time
Tset
100 pF capacitive load, full
operating Ta range
Output settling time
TsetRC
220 Ohm in series with 47nF
load on the wire, full Ta operating
range
3901090614
Rev 1.0
Page 8 of 35
+4
%
V
VSS+0.25
500
V
150
ns
TBD
ns
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
Parameter
Symbol
Test Conditions
Min
Typ
SMBus compatible 2-wire interface
Max
Units
2
Input high voltage
Input high voltage
V IH
V IH(Ta,V)
Over temperature and supply
1.6
1.2
2
2
2.4
2.8
V
V
Input low voltage
Input low voltage
V IL
V IL(Ta,V)
Over temperature and supply
0.7
0.5
1.0
1.0
1.3
1.5
V
V
0.25
V
Output low voltage
SDA pin in open drain mode,
over temperature and supply,
Isink = 2mA
VOL
SCL leakage
ISCL,leak
VSCL=3V, Ta=+85°C
20
uA
SDA leakage
SCL capacitance
ISDA,leak
CSCL
V SDA=3V, Ta=+85°C
0.25
10
uA
pF
SDA capacitance
CSDA
10
pF
Slave address
SMBus Request
SA
tREQ
SCL low
Timeout,low
Timeout,L
SCL low
30
ms
Timeout, high
Timeout,H
SCL high
50
Acknowledge setup
time
Acknowledge hold
Tsuac(MD 8-th SCL falling edge, Master
)Thdac(MD 9-th SCL falling edge, Master
)Tsuac(SD) 8-th SCL falling edge, Slave
time
Acknowledge setup
time
Acknowledge hold
time
Thdac(SD
)
Factory default
hex
ms
0.5
1.5
us
us
1.5
2.5
us
2.5
us
1.5
us
Ta = +85°C
Ta = +25°C
10
100,000
Times
Ta = +125°C
10,000
9-th SCL falling edge, Slave
Data retention
Erase/write cycles
5Ah
1.024
EEPROM
years
Erase/write cycles
Erase cell time
Terase
5
ms
Write cell time
Twrite
5
ms
Times
Note: refer to MLX90614Axx notes.
3901090614
Rev 1.0
Page 9 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7 Detailed description
7.1 Block diagram
81101
OPA
ADC
DSP
PWM
t°
STATE MACHINE
Voltage
Regulator
90302
Figure 3: block diagram
7.2 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.
3901090614
Rev 1.0
Page 10 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.3 Block description
7.3.1 Amplifier
A low noise low offset amplifier with programmable gain is implemented for amplification of the IR sensor
voltage. With a carefully designed input modulator and balanced input impedance, an offset as low as 0.5µV
is achieved.
7.3.2 Supply regulator and POR
The module can operate from 2 different supplies:
VDD= 5V => MLX90614Axx
VDD=3.3V => MLX90614Bxx (battery or regulated supply)
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 VPOR (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 (active high) at the PWM/SDA pin. After the MLX90614xxx exits the POR condition, the
function programmed in EEPROM takes precedence for that pin.
7.3.3 EEPROM
A limited number of addresses in the EEPROM memory can be changed by the customer. The whole
EEPROM can be read via SMBus interface.
EEPROM (32X16)
Name
Address
Write acces
Tomax
Tomin
PWMCTRL
Ta range
Ke
Config Register1
Melexis reserved
…
Melexis reserved
SMBus address
Melexis reserved
Melexis reserved
…
Melexis reserved
Melexis reserved
Melexis reserved
Melexis reserved
ID number
ID number
ID number
ID number
000h
001h
002h
003h
004h
005h
006h
…
00Dh
00Eh
00Fh
010h
…
018
019h
01Ah
01Bh
01Ch
01Dh
01Eh
01Fh
Yes
Yes
Yes
Yes
Yes
Yes
No
…
No
Yes
Yes
No
…
No
Yes
No
No
No
No
No
No
The addresses Tomax, Tomin and Ta range are for customer dependent object and ambient temperature
ranges. For details see point 7.5.3 below in this document
3901090614
Rev 1.0
Page 11 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
The address PWMCTRL consists of control bits for configuring the PWM/SDA pin:
Bit 0
Select the type of 1 - Single PWM, factory default for
0 – Extended PWM, factory default
PWM mode:
MLX90614xAx
for MLX90614xBx
Bit 1
Enable/disable
1 - Enable PWM, disable SMBus
0 - Disable PWM (Enable SMBus),
the PWM:
Factory default
Bit 2
Configuration of
1 - Push-Pull,
0 – OpenDrain NMOS, factory default
the pin PWM:
Bit 3
Mode selection
1 - ThermoRelay,
0 - PWM, Factory default
Bits[8:4]
Extemded PWM
Number of repetitions divided by 2 of sensor 1 and 2 in Extended PWM
definition
mode. The number of repetitions can vary from 0 to 64 times.
Bits[15:9] PWM clock
2MHz divided by number written in this place. (128 in case the number is 0.)
configuration
A single PWM period consists of 2048 clocks and extended PWM of 4096
clocks for each period (2T in figure 6). The 2 MHz clock is valid for the
nominal HFO frequency.
The address ConfigRegister1 consist of control bits for configuring the analog and digital parts:
Bits[2:0]
– Configure coefficients of IIR
Bit 2
Bit 1
Bit 0
a1
b1
0
x
x
0.5
0.5
digital filter:
Bit 3
Bits[5:4]
Bit 6
Bit 7
Bits[10:8]
Bits[13:11]
Bit 14
Bit 15
1
1
1
1
1
1
0
0
– Configure the type of
ambient temperature sensor:
– Configure the type of data
transmitted through PWM:
1 - PTC,
– Define the number IR
sensors:
– Define the sign Ks
(Ks=dAlpha/dTobj) :
– Configure coefficient N of
FIR digital filter:
1 – 2 sensors,
– Configure the gain of
amplifier:
Bit 5
1
0
1
0
Bit 4
0
0
1
1
0
1
1
0
0.571428571
0.666(6)
0.8
1
0 – PTAT.
0.428571428
0.333(3)
0.2
0 (IIR bypassed)
Data 1
Data 2
Ta
Ta
IR 1
IR 2
0 -1 sensor.
IR 1
IR 2
IR 2
Undefined*
Factory calibration, do not alter
Bit 10
Bit 9
Bit 8
Bit 13
Bit 12
Bit 11
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
N
8
16
32
64
128
256
512
1024
Gain
1 (preamplifier bypassed)
3
6
12.5
25
50
100
100
Unused
– Define the sign of thermo1 - negative,
0 – positive.
shock compensation:
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 00Fh and 019h.
* not recommended for extended PWM mode
3901090614
Rev 1.0
Page 12 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.3.4 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.
Name
RAM (32x17)
Address
Melexis reserved
…
Melexis reserved
TA
TOBJ1
TOBJ2
Melexis reserved
…
Melexis reserved
000h
…
005h
006h
007h
008h
009h
…
01Fh
Read access
Yes
…
Yes
Yes
Yes
Yes
Yes
…
Yes
7.4 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).
7.4.1 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**).
Note*: This address is readable and writable. Bit 3 should not be altered as this will cancel the factory
calibration.
Note**: EEPROM error signalling is implemented in automotive grade parts only.
3901090614
Rev 1.0
Page 13 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.4.2 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
7.4.3 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.
7.4.3.1 Bus Protocol
1
7
1
S
Slave Address
1
Wr A
S
Start Condition
Sr
Repeated Start Condition
Rd
Read (bit value of 1)
Wr
Write (bit value of 0)
8
1
1
Data Byte
A
P
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
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. If 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 error in the received message and the MD
should try sending the message again. The PEC calculation includes all bits except the 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.
3901090614
Rev 1.0
Page 14 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.4.3.1.1 Read Word (depending on the command – RAM or EEPROM)
1
S
7
1
Slave Address
………..
1
8
Wr A
1
1
Command
A Sr
7
1
Slave Address
1
Rd A
8
8
8
8
8
1
1
Data Byte Low
A
Data Byte High
A
PEC
A
P
………..
Figure 5: SMBus read word format
7.4.3.1.2 Write Word (depending on the command – RAM or EEPROM)
1
………..
7
1
1
8
1
Wr A
Command
A
………..
S
Slave Address
8
8
8
8
8
1
1
Data Byte Low
A
Data Byte High
A
PEC
A
P
Figure 6: SMBus write word format
7.4.4 AC specification for SMBus
7.4.4.1 Timing
The MLX90614 meets all the timing specifications of the SMBus [1]. The maximum frequency of the
MLX90614 SMBus is 100KHz and the minimum is 10KHz.
The specific timings in MLX90614’s SMBus are:
SMBus Request (tREQ ) is the time that the SCL should be forced low in order to switch MLX90614 from PWM
mode to SMBus mode;
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;
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).
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.
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).
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).
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).
3901090614
Rev 1.0
Page 15 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
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].
Timeout,L
Tsuac
Timeout,H
Thdac
SCL
PWM/SDA
Figure 7: SMBus timing
7.4.5 Bit transfer
Sampling
data
Changing
data
SCL
PWM/SDA
Figure 8: 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.
7.4.6 Commands
In application mode 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, TOBJ1 - 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 Ta). The MSB for the raw data
(e.g. IR sensor1 data) is a sign bit (sign and magnitude format).
Opcode
Command
000x xxxx*
RAM Access
001x xxxx*
EEPROM Access
1111_0000**
Read Flags
1111_1111
Enter SLEEP mode
Note*: The xxxxx are 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[15] – EEBUSY – the previous write/erase EEPROM access is still in progress. High active.
Data[14] – Unused
Data[13] - EE_DEAD – EEPROM double error has occurred. High active.
Data[12] – INIT – POR initialization routine is still ongoing. High active.
Data[11] – not implemented..
Data[10..0] – all zeros.
Flags read is a diagnostic feature. The MLX90614 can be used regardless of these flags.
3901090614
Rev 1.0
Page 16 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.4.7 Sleep Mode
MLX90614 can enter Sleep Mode via 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 (typ), 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 tDDq=13ms. 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.
7.4.7.1 Enter Sleep Mode
Sleep
command
Stop
condition
Sleep
SCL
PWM/SDA
Stop
Figure 9: Enter sleep
7.4.7.2 Exit from Sleep Mode
Sleep
Awake
Normal
SCL
PWM/SDA
tDDq
Figure 10: Exit Sleep Mode
3901090614
Rev 1.0
Page 17 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.5 PWM
The MLX90614 can be read via PWM or SMBus compatible interface. Selection of PWM output is done in
EEPROM configuration (factory default is PWM). 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]
00
01
11
10*
PWM1 data
Ta
Ta
Tobj1
Tobj2
PWM2 data
Tobj1
Tobj2
Tobj2
Undefined
Tmin,1
Tarange,L
Tarange,L
Tomin
Tomin
Tmax,1
Tarange,H
Tarange,H
Tomax
Tomax
Tmin,2
Tomin
Tomin
Tomin
N.A.
Tmax,2
Tomax
Tomax
Tomax
N.A.
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
Figure 11: PWM timing
7.5.1 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:
Tout =
2t2
* (Tmax − Tmin) + Tmin ,
T
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 Tobj1, Tobj2 or Ta according to Config Register [5:4] settings.
3901090614
Rev 1.0
Page 18 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
The different time intervals t1-t3 have the following functions:
t1: Start buffer. During this time the signal is always high. t1 = 0.125*T (T is the PWM period, refer to fig. 11).
t2: Valid Data Output Band, 0 to 1/2T. PWM output data resolution is 10 bit.
t3: Error band – information for Fatal error in EEPROM (double error detected, not correctable). t3 = 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).
Example:
Tobj1 => Config Reg[5:4] = 11’b
Tomin = 0°C
=>
Tomin [EEPROM] = 100 * (tomin + 273.15) = 6AB3h
=>
Tomax [EEPROM] = 100 * (tomax + 273.15) = 7E3Bh
Tomax = +50°C
Captured PWM high duration is 0.495*T => t2=(0.495 – 0.125)*T=0.370*T =>
measured object temperature = 2X0.370* (50°C -0°C)+0°C = +37.0°C.
7.5.2 Extended PWM format
The PWM format for extended PWM is shown in Figure 11. Note that with bits DUAL[5:1]>00h each period
will be repeated 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 12.
Figure 12: 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:
Tout1 =
2t 2
* (Tmax1 − Tmin1 ) + Tmin1
T
Tout2 =
2t 5
* (Tmax2 − Tmin2 ) + Tmin2
T
For Data 2 field the equation is:
Where Tmin1,Tmax1,Tmin2 and Tmax2 are given in Table 9, t2=thigh1-t1, and t5=thigh2-t4.
Time bands are: t1=0.125*T, t3=0.25*T and t4=1.125*T. As shown in Figure 11, 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 signalling will be 43.75% duty cycle for Data1 and 93.75% for
Data2.
Note:EEPROM error signalling is implemented in automotive grade parts only.
Example:
Configuration: Ta : Tobj1 @ Data1 : Data2 => Config Reg[5:4] = 00b,
Tamin = -5°C
=>
Tarange, L [EEPROM] = 100*(Tamin+38.2)/64 = 33h,
Tamax = +105°C =>
Tarange,H [EEPROM] = 100*(Tamax+38.2)/64 = DFh,
Tarange [EEPROM]=DF33h
Tomin = 0°C
=>
Tomin [EEPROM] = 100 * (Tomin + 273.15)/64 = 6AB3h
Tomax = +50°C
=>
Tomax [EEPROM] = 100 * (Tomax + 273.15)/64 = 7E3Bh
Captured high durations are 0.13068*(2T) and 0.7475*(2T), where 2T is each captured PWM period. Time band t4 is
provided for reliable determination between Data1 and Data2 data fields. Thus Data1 is represented by 0.13068*(2T) and
Data2 – by 0.7475*(2T), and the temperatures can be calculated as follows:
t2/T=(thigh1/T)-0.125=0.13636 => Ta=+25.0°C,
t5/T=( thigh2/T)-1.125=0.370 => Tobj1=+37.0°C.
3901090614
Rev 1.0
Page 19 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.5.3 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 (Tomin and Tomax) and one for
Ta (Tarange: the 8MSB are foreseen for Tamax and the 8LSB for Tamin).
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 2.56 °C.
The object data for PWM is rescaled according to the following equation:
TPWM obj =
TRAM − TMIN EEPROM
K PWM obj
, K PWM obj =
TMAX EEPROM − TMIN EEPROM
1023
The TRAM is the linearised Tobj, 16-bit (0000…FFFFh, 0000 for -273.15°C and FFFFh for +382.2°C) and the
result is a 10-bit word, in which 000h corresponds to ToMIN[°C], 3FFh corresponds to ToMAX[°C] and 1LSB
ToMAX − ToMIN
[°C]
1023
= TMIN ∗ 100 LSB
corresponds to
TMIN EEPORM
TMAX EEPORM = TMAX ∗ 100 LSB
The ambient data for PWM is rescaled according to the following equation:
TPWM ambient =
TRAM − TMIN EEPROM
K PWM ambient
, K PWM ambient =
TMAX EEPROM − TMIN EEPROM
1023
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
100
LSB
64
100
− (− 38.2)] ∗
LSB
64
TMAX − TMIN
[°C]
1023
TMIN EEPORM = [TMIN − (− 38.2 )] ∗
TMAX EEPORM = [TMAX
3901090614
Rev 1.0
Page 20 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.6 Switching Between PWM and SMBus communication
7.6.1 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 enabled). Note that the SCL pin needs to be kept high in order to use
PWM.
tREQ
SCL
PWM/SDA
Start
PWM
SMBus
Stop
Figure 13: Switching from PWM mode to SMBus
7.6.2 Request condition
tREQ
SCL
SMBus Request
Figure 14: 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 disabled PWM, it can be only enabled by
switching Off-On of the supply or exit from Sleep Mode. The MLX90614’s SMBus request condition requires
forcing LOW the SCL pin for period longer than the request time (tREQ). The SDA line value is ignored in this
case.
7.6.3 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.
3901090614
Rev 1.0
Page 21 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.7 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
(
)
Vir (Ta, To ) = A. To 4 − Ta 4 ,
Where To is the object temperature absolute (Kelvin) temperature, Ta is the sensor die absolute (Kelvin)
temperature, and A is the overall sensitivity.
An additional temperature sensor is needed for measuring the temperature of 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.
7.7.1 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 temperatureTa is made available in
memory.
The resolution of the calculated Ta is 0.01 ˚C. The sensor is factory calibrated for the full automotive range
(-40 to 125 ˚C). In RAM cell ,006h, 0000h corresponds to -40 ˚C and 4074h (16500d) corresponds to 125 ˚C.
The conversions from RAM contend to real Ta is easy using the following relation:
Ta[° K ] = Tareg × 0.01 Note that via SMBus Ta is read divided by 2, or Ta,SMBus[°K]=Tareg x 0.02
7.7.2 Object temperature To
The result has a resolution of 0.01 ˚C and is available in RAM. To is derived from RAM as:
To[° K ] = Toreg × 0.01 Note that via SMBus To is read divided by 2, or To,SMBus[°K]=Toreg x 0.02
7.7.3 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
sensor is selected and which temperature sensor will be used. Measurements, compensation and
linearization routines run in a closed loop afterwards.
Processing ambient temperature includes:
Offset measurement with fixed length FIR filter
Additional filtering with fixe length IIR filter. The result is stored into RAM as TOS
Temperature sensor measurement using programmable length FIR *.
Offset compensation
Additional processing with programmable length IIR **. The result is stored into RAM as TD.
Calculation of the ambient temperature. The result is stored into RAM as TA
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 IROS.
3901090614
Rev 1.0
Page 22 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
Gain measurement with fixed length FIR filter
Offset compensation
Additional gain filtering with fixed length IIR, storing the result into RAM as IRG.
Gain compensation calculation, the result is stored into RAM as KG
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 IR1D.
Calculation of the object temperature. The result is available in RAM as TOBJ1.
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 IR2D
Calculation of the object temperature. The result is available in RAM as TOBJ2.
PWM calculation:
Recalculate the data for PWM with 10 bit resolution
Load data into PWM module
3
TA Offset meas
OSTa= meas(NTos)
IR Offset meas
OSIR= meas(NIRos)
IR1 meas
IR1D= meas(NIR)
IR2 meas
IR2D= meas(NIR)
filtering
TOS= IIR(LTos,OSTa)
filtering
IROS= IIR(LIRos,OSIR)
Offset comp
IR1Dcomp= IR1D- IROS
Offset comp
IR2Dcomp= IR2D- IROS
TA meas
TDATA= meas(NTa)
Gain drift
IRGm= meas(NIRg)
Gain comp
IR1Dg= IR1Dcomp*KG
Gain comp
IR2Dg= IR2Dcomp*KG
Offset comp
TDATAcomp= TDATA-TOS
Offset comp
IRGcomp= IRGm- IROS
filtering
IR1D= IIR(LIR,IR1Dg)
filtering
IR2D= IIR(LIR,IR2Dg)
filtering
TD= IIR(LTa,TDATAcomp)
filtering
IRG= IIR(LG,IRGcomp)
TOBJ1 calculation
TA calculation
KG calculation
1
TA
TOBJ2 calculation
PWM calculation
3
2
TOBJ1
2
IR offset
1
Initialization
TOBJ2
Note*: The measurements with programmable filter length for FIR filter use the same EEPROM’s sell for N.
Note**: The IIR filter with programmable filter length uses the same EEPROM’s sell for L.
Load PWM registers
Figure 15: Software flow
3901090614
Rev 1.0
Page 23 of 35
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
7.8 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.
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
EEPORM at address 021h (Tomin) and the hysteresis at address 020h (Tomax).
The logical state of the PWM/SDA pin is as follows:
PWM/SDA pin is high if Tobj 1 ≥ threshold + hysteresis
PWM/SDA pin is low if Tobj 1 ≤ threshold − hysteresis
“1”
hysteresis
hysteresis
“0”
threshold
T
Figure 16: 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 = 6CA7h
hysteresis is 1°C => 1 * 100 = 100 = 64h
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
8 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.
It 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 is 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 and 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 temperatures measurements available via a single line (extended PWM).
A built-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).
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MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
9 Performance Graphs
9.1 Temperature accuracy of the MLX90601AAA
380
To,oC
± 4 oC
300
240
± 4 oC
± 3 oC
180
± 4 oC
± 3 oC
± 2 oC
± 2 oC
± 2 oC
± 3 oC
± 2 oC
± 1 oC
± 1 oC
± 2 oC
± 2 oC
± 1 oC
± 0.5 oC
± 1 oC
± 2 oC
± 3 oC
± 1 oC
± 1 oC
± 2 oC
± 3 oC
± 3 oC
± 3 oC
± 2 oC
± 3 oC
± 4 oC
120
60
0
-40
-70
-40
-20
0
50
100
125
Ta,oC
Figure 17: Preliminary accuracy of MLX90601AAA (Ta,To)
All accuracy specifications apply under settled isothermal conditions only.
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MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
A version of the MLX90614 with accuracy suited for medical applications is available upon request. The
accuracy in the range Ta 10ºC - 40ºC and To 32ºC - 42ºC is shown in diagram below. The accuracy for the
rest ranges is same as in previous diagram.
To,oC
45
42
39
36
32
30
± 0.2 oC
± 0.1 oC
± 0.3 oC
± 0.3 oC
± 0.2 oC
10
20
30
Ta,oC
40
Figure 18: Preliminary accuracy of MLX90601BAA (Ta,To) for medical applications.
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Single and Dual Zone
Infra Red Thermometer in TO-39
9.2 Field Of View (FOV)
Field of view is determined at 50% thermopile signal and with respect to the sensor main axis.
Parameter
MLX90614xAA
MLX90614xAB
MLX90614xBA
MLX90614xBB
Peak zone 1
±0°
±0
-25°
-30°
Width zone 1
72°
80°
70°
70°
-25°
+30°
70°
70°
Peak zone 2
Not applicable
Width zone 2
Figure 19: FOV of MLX90614xAA
1
0.5
-80o
-60o
-40o
-20o
0o
20o
40o
60o
80o
Figure 20: FOV of MLX90614xBA
1
0.5
-80o
-60o
3901090614
Rev 1.0
-40o
-20o
0o
20o
40o
60o
Page 27 of 35
80o
Figure 21: identification of zone
1&2 relative to alignment tab.
Data Sheet
14/Sep/2006
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
10 Applications Information
10.1 Use of the MLX90614 thermometer in SMBus configuration
+3.3V
R1 R2
2
PW M
SDA
3
C1 U1
0.1uF
SMBus
SCL 1
Vz
Vdd
U1
MCU
Vdd
Vss
4
SDA
SCL
GND
MLX90614Bxx
Figure 22: Connection of MLX90614 to SMBus, 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.
10.2 Use of multiple MLX90614s in SMBus configuration
+3.3V
I1
I2
Ipu1
Ipu2
R1
2
PW M
SDA
3
C1 U1
0.1uF
Vss
4 MLX90614Bxx
SMBus
Vdd
C2 U1
0.1uF
MCU
SDA
SCL
Current source or resistor
pull-ups of the bus
GND
C3
Cbus1
2
PW M
SDA
3
U1
Vdd
SCL 1
Vz
Vdd
R2
SCL 1
Vz
Cbus2
C4
Vss
4 MLX90614Bxx
SDA
SCL
Figure 23: SMBus configuration of multiple sensors.
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.
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Single and Dual Zone
Infra Red Thermometer in TO-39
10.3 Thermal alert / thermostat
+5V
+24V
+
D1
Alert dev ice
R1 R2
2
PW M
SDA
3
Vdd
C1 U1
0.1uF
R2
SCL 1
Vz
3
Vss
4 MLX90614Axx
C1 U1
0.1uF
SMBus
SCL 1
Vz
Vdd
U1
MCU
2
PW M
SDA
Vdd
2
P WM
SDA
Vss
4
SDA
3
SCL
C2
GND
MLX90614Bxx
Q1
10uF
U2
SCL 1
Vz
Vdd
C3
0.1uF
R1
U1
MLX90614Axx
-
+3.3V
Vss
4
C*
AC line
figure 24: Possible thermal relay configurations.
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
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 be also read
in this configuration.
10.4 High voltage source operation
J1
V+
PWM
GND
CON1
MLX90614Axx: V=8...16V
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.
Q1
R1
C*
Vdd
3
Q1
+12V
1 MLX90614
SCL
U1
Vz
4
PW M
Vss
2 SDA
C1
2.2uF
+5V
R1
U1
5.7V
Equivalent schematics
Figure 25: 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).
When the zener diode function of the SCL/Vz pin is used, the 2-wire SMBus function is only available if the
voltage regulator is overdriven (5V regulated power is forced to the VDD pin).
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Single and Dual Zone
Infra Red Thermometer in TO-39
11 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
that 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 trigger on inappropriate levels, resulting in
unspecified operation and is not recommended.
The MLX90614xxx is designed and calibrated to operate as a non contact thermometer in settled
conditions. Using the module in 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 with
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 it’s 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. Therefore, higher than 5V applications are likely to use PWM output or 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.
Sleep mode is available in 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 power-down mode and the pull-up on
the SCL line needs to be disabled in order to keep the overall power drain in power-down really small.
The PWM pin is not designed for direct drive of inductive loads (such as electro-magnetic relays). Some
driver needs 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 (trasformerless). 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 to use 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 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.
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Single and Dual Zone
Infra Red Thermometer in TO-39
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 LSBs error.
Check www.melexis.com for most current application notes about MLX90614.
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:
Reflow Soldering SMD’s (Surface Mount Devices)
•
•
IPC/JEDEC J-STD-020
Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices
(classification reflow profiles according to table 5-2)
EIA/JEDEC JESD22-A113
Preconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing
(reflow profiles according to table 2)
Wave Soldering SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)
•
•
EN60749-20
Resistance of plastic- encapsulated SMD’s to combined effect of moisture and soldering heat
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 SMD’s (Surface Mount Devices) and 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.
The application of Wave Soldering for SMD’s is allowed only after consulting Melexis regarding assurance of
adhesive strength between device and board.
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.asp
The MLX90614 is RoHS compliant
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Single and Dual Zone
Infra Red Thermometer in TO-39
12 ESD Precautions
Electronic semiconductor products are sensitive to Electro Static Discharge (ESD).
Always observe Electro Static Discharge control procedures whenever handling semiconductor products.
13 FAQ
When I measure aluminium and plastic parts settled at the same conditions I get significant errors on
aluminium. Why?
Different materials have different emissivity. A typical value for aluminium (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
( )
( )
q = ε 1 .α 1 . T1 .σ . A1 .Fa−b − ε 2 . T2 .σ . A2 ,
4
4
where
1 and 2 are the emissivities of the two objects,
1 is the absorptivity of the sensor (in this case),
is the Stefan-Boltzmann constant,
A1 and A2 are the surface areas involved in the radiation heat transfer,
Fa-b is the shape factor,
T1 and T2 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 aluminium) 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 is a specialised 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 aluminium 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.
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Single and Dual Zone
Infra Red Thermometer in TO-39
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
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.
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Single and Dual Zone
Infra Red Thermometer in TO-39
14 Package Information
The MLX90614 is packaged in an industry standard TO – 39 can.
Figure 26: Packaging options
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Infra Red Thermometer in TO-39
15 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.
16 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 lifesupport 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.
© 2006 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:
Phone: +32 1367 0495
E-mail: [email protected]
America:
Phone: +1 603 223 2362
E-mail: [email protected]
ISO/TS 16949 and ISO14001 Certified
3901090614
Rev 1.0
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