Melexis MLX90313 Technical data

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MLX90313

Programmable IR Sensor Interface

Features and Benefits

Dual low noise, low offset, fully programmable amplifier chain
12 bit on-chip ADC
Powerful signal conditioning and linearisation unit
Multiple output options: 12 bit digital through SPI, 8 bit resolution analog linear signal outputs or
10 bit PWM, both for ambient and object temperature.
On-chip programmable digital moving average LPF for ultimate low noise performance
ISP I/O-configuration and analog settings, accessible by SPI serial interface.
Wide supply voltage range from 4.5V-80V

Applications

Thermopile + thermistor amplification chain
Digital or analog, linear, ambient-compensated IR sensor interface
General purpose programmable sensor amplifier/ signal conditioner

Ordering Information

Part No. Temperature Suffix Package Temperature Range
MLX90313 K DF -40C to 125C Automotive

Functional Diagram Description

The MLX90313 is a versatile in-cir c uit
programmable interface, which performs signal

IR+

IR-

Tinp

Tinn

Supply Regulator

IR path

PGA

Thermistor

path

PGA

Digital Control Logic

Configuration eeprom

A/D

12Bit

A/D

12Bit

selector

output option

Linearisation unit

pwm

lin

non

lin

pwm

lin

non

lin

SPI

interface

IRout

Tempout

SPI
interface

conditioning, linearis a ti on and ambient
temperature compensation, particularly for
infrared sensors combined with a thermistor.
Other types of sensors can also be used in
various configurations. Sensors that can be used
include pressure sensors, strain gauges,
acceleration sensors etc.
The amplifier chains in MLX90313 are
programmable in very broad ranges of gain.
Both chains consist of high performance,
chopper-stabilized amplifiers, providing excellent
noise performance and low offset. The I/O
configuration as well as analo g sett ings ar e in­circuit programmable by means of the SPI-serial
interface. This serial link can also be used to
read out the output signals digitally. The circuit
can either provide linear analog or PWM (Pulse
Width Modulated) signal outputs. Additional the
circuit can perform simple control applications
using on-board comparators

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Programmable IR Sensor Interface

MLX90313 Electrical Specifications

DC Operating Parameters TA = -40oC to 125oC, VDD = 4.5V to 80V (unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit
Regulator and consumption

Supply voltage range Vin1 VDD1 7 80 V
Supply voltage range Vin VDD 4.5 5 5.5 V
Supply current Idd
Regulated supply voltage Vreg VDD, 10uF ext. cap 4.7 5 5.3 V
Regulated voltage temperature

coefficient
POR threshold voltage Vpor 1.1 1.3 1.5 V

Band-gap reference

Analog ground voltage Agnd 2.3 2.5 2.7 V
Analog ground thermal coefficient TCbg 15 50
Reference current mirror load

drive voltage

IR-chain amplifier and output driver

Common mode input range CMIR -0.1 Vdd-3 V
Common mode rejection ratio CMRR

Power supply rejection ratio PSSR
Available gain settings Air 55 5500 V/V
Gain tolerance
Amplifier offset Voff 4
Input referred white noise Vnir rms-value 25
Chopper frequency fc 8 KHz
Output voltage range IROUT 0 Vdd-

Output source current Iod IROUT 1 mA
Output sink current Ios IROUT 20
DC Output impedance, drive rod IROUT 10
DC Output impedance, sink ros IROUT 100
Capacitive load IROUT pin Cmax IROUT 50 pF
Amplifier bandwidth BW 500 Hz

Temp-chain amplifier and output driver

Common mode input range CMIR 0.1 Vdd-3VV

TCvr -2.35

Vcref 1.8 2 2.2 V

δGir

@ Ta=25°C

f ≤ 100kHz
Rsens < 60kΩ *
f ≤ 100kHz

75 dB

75 dB

-6.5 +6.5 %

55.6mA

mV/°

µV/°

µV

nV/√Hz

V

0.2

µA
Ω
Ω

Common mode rejection ratio CMRR
Power supply rejection ratio PSSR
TINP bias current Itpb bias current enabled 1/7 .1 iCref*
Available gain settings Atemp 1 40 V/V

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f ≤ 100kHz
f ≤ 100kHz

75 dB
75 dB

MLX90313

Programmable IR Sensor Interface

Parameter Symbol Test Conditions Min Typ Max Unit

Gain tolerance
Amplifier offset Voff 4
Input referred white noise Vntemp rms-value 400
Chopper frequency fc 8 kHz
Output voltage range ORtemp TEMPOUT 0 Vdd-

Output source current Iod TEMPOUT 1 mA
Output sink current Ios TEMPOUT 20 uA
DC Output impedance, drive rod TEMPOUT 10
DC Output impedance, sink ros TEMPOUT 100
Capacitive load TEMPOUT pin Cmax TEMPOUT 50 pF
Amplifier bandwidth BW 500 Hz

Rel1 open drain relay driver

High voltage protection 32 V
output impedance Ro 10

Comp1 comparator

Potentiometer input range IRirout IROUT 0 100 % of

ADC

Input stage gain 2.95 3 3.05 V/V

δGtemp

bias current enabled -6.5 +6.5 %

µV
nV/√Hz

V

0.2

Ω
Ω

Ω

Vrefp

External Reference voltage Vrefpex 1 3.3 V
Internal Reference voltage Vrefp 2.4 2.5 2.6 V
Vrefp input leakage current Ilvrefp
Resolution 12 bit
Monotonicity guaranteed by design
Differential non-linearity DNL 0.4 LSB
Integral non-linearity INL ½ LSB
Gain error full scale 1 LSB
Total input-referred noise Vref=3V 0.2 LSB

DAC

Resolution 8 bit
Monotonicity guaranteed by design
Differential non-linearity DNL ½ LSB
Integral non-linearity INL ½ LSB
*Rsens is the impedance of the sensor connected between IRINP and IRINN for the IR-chain amplifier.
**Icref is the current flowing out of pin CREF

@150°C

5uA

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MLX90313

Programmable IR Sensor Interface

General Description

The MLX90313 is a versatile in-circuit programmable interface, which performs signal conditioning,
linearisation and ambient temperature compensation, particularly for infrared sensors combined with a
thermistor. Other types of sensors can also be used in various configurations. Sensors that can be used
include pressure sensors, strain gauges, acceleration sensors etc.
The amplifier chains in MLX90313 are programmable in very broad ranges of gain, between 50 and
12000 for the IR-chain and between 1 and 120 for the Temp-chain. Both chains consist of high
performance, chopper-stabilized amplifiers, providing excellent noise performance and low offset. The I/O
configuration as well as analog settings are in-circuit programmable by means of the SPI-serial interface.
This serial link can also be used to read out the output signals digitally. The circuit can either provide
linear analog or PWM (Pulse Width Modulated) signal outputs, relative to an analog ground, or several
combinations of analog and digital comparator driven outputs. Two comparators controlled by either one
of the two linearised signals are available on chip with different possibilities for the threshold level, polarity
and switching hysteresis. One of the comparators drives the open drain output. The user can provide the
threshold for this comparator at the IROUT I/O pin with a simple potentiometer.
A bias current for the thermistor can be obtained at the TINP input by connecting an external resistor
between the CREF pin and VSS. The standard package is SOIC-20.

Unique Features

The MLX90313 integrates dual low noise programmable gain amplifier stages. Both thermistor and IR
signal path can be configured to suit a large number of components and applications. The onboard
analog to digital converter (ADC) combined with the digital linearisation unit results in linear output
signals. These output signals are available as analog or digital output signal. Applications requiring digital
temperature information can use single wire PWM output or SPI serial communication. The complete
configuration and calibration is in-system programmable through the SPI interface. Combination of all
these integrated features combined with a thermopile sensor make the MLX90313 a true high accuracy
automotive grade single-chip infrared thermometer.

Absolute Maximum Ratings

Supply Voltage, V
Supply Voltage, Vin (overvoltage) 6V
Supply Voltage, V
Supply Voltage, Vin (operating) 5.5V
Reverse Voltage Protection -5V
Supply Current, I
Output Current, I
Operating Temperature Range, T
Operating Temperature Range, T
ESD Susceptibility 2 kV
Rel1 output impedance 10 ohms

(overvoltage) 80V

in1

(operating) 16V

in1

DD
OUT

A
S

5.6 mA
3 mA

-40C to +125C

-55C to +150C

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Pin-out

MLX90313

Programmable IR Sensor Interface

VSS

1
2
3
4
5
6
7
8
9
10 11

TINP

TINN
IRINP
IRINN

REL1

IROUT

SDIN

TOUT1
TOUT2 CREF

20
19
18
17
16
15
14
13
12

TEMPOUT
CSB
SDOUT
SCLK
TSTCLK
VDD
VDD1
AGND
VREFP

Pin Symbol Description
1 TINP Temp-chain amplifier positive input
2 TINN Temp-chain amplifier negative input
3 IRINP IR-chain am plif ier positi ve in put
4 IRINN IR-chain amplifier negative input
5 VSS Supply pin
6 REL1 Open-drain relay driver output
7 IROUT IR-chain am plif ier output
8 SDIN SPI data input
9 TOUT1 Test pin/ Oscillator output
10 TOUT2 Test pin, leave open
11 CREF Bias current reference
12 VREFP Reference voltage input/output
13 AGND Analog ground, band-gap reference voltage
14 VDD1 Automotive Ignition supply pin
15 VDD Regulated supply pin
16 TSTCLK Clock for test mode; leave open
17 SCLK SPI clock input
18 SDOUT SPI data output
19 CSB SPI chip select active low
20 TEMPOUT Temp-chain amplifier output

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Programmable IR Sensor Interface

Pin Descriptions

TINP

Temperature sensor positive input pin. The pin connects to the temp-chain amplifier and the on-chip
biasing current source. The source is a mirrored version of the current running into CREF with
programmable ratio. The current source can be switched off for use of external current biasing.

TINN

Temperature sensor negative input.

IRINP - IRINN

Thermopile sensor input pins .
VSS: Supply pin

REL1

Open drain relay driver output. The typical on-resistance of this driver is <10Ω with a supply voltage of
VDD=5V. Different configurations are possible as shown below.

REL1

Vrefp

IROUT

External

potentiometer

VSS

Tambient or

Tobject

COMP

VSS

Hystere sis in

EEPROM

Tambient or

Tobject

COMP

Threshold in

EEPROM

Hystere sis in

EEPROM

REL1

VSS

The comparator is a 12 bit digital comparator. The input polarity can be inverted or not. The threshold and
hysteresis registers are 16 bit registers of which the 11 MSBs are used in the comparator circuitry.
The voltage on the IROUT pin is sampled with 8 bit ADC referred between VREFP and VSS pins.
Note. In case of potentiometer use the linearised analog output is not available. In this case the DAC is
used as 8-Bit ADC for potentiometer (or other voltage source) monitoring.

IROUT

IROUT/POTin analog/digital I/O pin. This pin can be configured as analog output of the IR sensor or as
input for an external potentiometer. (see pin description of REL1). As analog output, this pin can either be
connected to the analog amplified IR sensor signal or to the linearised object temperature by means of the
DAC. The driver can source at least 1mA and sink at least 20µA to/from an external load. If the capacitive
load on this pin exceeds 50pF, this load should be de-coupled by means of a series resistor. This pin can
be configured also as digital output to transmit the IR temperature in PWM format.
The pin is protected for over-voltage and can withstand 16V.

SDIN

Serial data input pin for the SPI. Data is accepted on the rising edge of the serial data clock (SCLK)
SDOUT

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MLX90313

Programmable IR Sensor Interface

Serial data output pin for the SPI. Data is valid on the rising edge of the serial data clock (SCLK)

SCLK

Serial data clock from the external master to be supplied to this pin. Maximum frequency = 125kHz.

CSB

Active low, chip select pin for the SPI. Communication is started on the falling edge of CS and ended on
the rising edge of CS.

TOUT1 - TOUT2:

Test pins. In normal mode, the internal clock signal of 1Mhz is present on TOUT1 and the clock of the
chopper amplifier is present on TOUT2.

CREF

Current reference output. CREF is the reference voltage output for the temperature independent current
source. The requirements for the resistor to be connected between CREF and VSS depend on the
required accuracy and range of the ambient temperature measurement. The voltage level at CREF
depends directly on the internal band-gap.

VREFP

Voltage reference I/O pin. This level is by default dependent on the on-chip band-gap reference source
and can be programmed in range 2-4.5V from eeprom . This voltage is used as reference for the DAC,
external applied potentiometer and 8-bit ADC. The chip can be configured to use an external reference
voltage instead of the on-chip reference.
The pin is protected from over-voltage and can withstand 16V

AGND

Analog ground reference pin. This voltage is derived from the on-chip band-gap and has a typical level of

2.5V for maximum output range of the amplifiers. When IROUT and/or TEMPOUT are connected directly
to the amplified analog signals, then these signals are referred to AGND. The regulator can be stopped
from the eeprom configuration register. In this case the pin can be used for external reference for the 12­bit ADC.
The pin is protected from over voltage and can withstand 16V

VDD1

High voltage supply pin. This supply pin can be connected directly to an automotive ignition supply
voltage. The internal regulator can operate with voltages between 7V and 80V.

VDD

5V regulated supply pin. The 5V regulated voltage from the on-chip regulator is available on this pin. The
internal regulator can supply up to 20mA to external circuitry. VDD can also be used to supply the chip
directly with an external 5V regulated supp ly.

TEMPOUT

TEMPOUT analog output/Comparator output pin. This pin can be configured as analog output of the

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MLX90313

Programmable IR Sensor Interface

temperature sensor or as output of the internal comparator circuit. As analog output, this pin can either be
connected to the analog amplified temperature sensor signal or to the linearised ambient temperature by
means of the DAC.
When used as comparator output, different configurations are possible as shown below.

analog options

Tam bie nt o r

Tobject

COMP

Thresho ld in

EEPROM

Hysteresis in

EEPROM

The driver can source at least 1mA and sink at least 20µA to an external load. If the capacitive load on
this pin exceeds 50pF, the load should be de-coupled by means of a series resistor. The pin is also output
for linearised Tambient in PWM mode. The pin is protected from over-voltage and can withstand 16V

Tempout

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MLX90313

Programmable IR Sensor Interface

Analog Section

Supply regulator and Power-ON Reset

The on-chip supply regulator and can be powered by an automotive ignition supply line (7V-80V). The
chip can withstand SAE standard ignition transients. The resulting voltage of the regulator is available on
VDD (5V±300mV). The VDD pin can source up to 20mA to external circuitry. The chip can also be
supplied directly with a 5V regulated supply on pin VDD.
The power-on reset (POR) circuitry is completely internal. The chip is fully operational 16ms from the time
the supply crosses 1.3V. The POR circuit will issue another POR if the supply voltage goes below 1.3V.

Band-gap, DAC and ADC references

The on-chip trimmable, curvature compensated band-gap circuitry provides a stable reference level (less
than 10ppm per °C) for several derived reference potentials used for normal operation in MLX90313.
The analog ground at the AGND pin is directly derived from this band-gap voltage. The output voltages
from both amplifier chains are relative to this potential. The AGND reference can be trimmed internally to
(2.5V±20mV). The regulator at AGND pin can be switched off to minimize the current consumption. The
pin can be also used as external input for the internal 12-bit ADC.
The reference voltages for ADC and DAC are also derived from the band-gap. The DAC reference is
available at pin VREFP. The MLX90313 DAC reference voltage can be programmed on chip to one of the
following values: 2, 2.5, 3, 3.5, 4 and 4.5 V. Depending on the customer application Melexis can program
the linearised analog outputs for object and ambient temperatures providing absolute voltage/temperature
dependence. The internal regulator for the DAC reference voltage can be switched off to minimize the
consumption (if linearised analog output is not in use) or to use externally supplied reference for DAC
reference in range 2 to 5V
The ADC reference is 2.5V typically. The chip can be also programmed to use external ADC reference
connected to pin AGND. The current reference bias voltage (present at CREF pin) is also derived from
the on-chip band-gap reference.

IR-amplifier chain

MLX90313 is available with gain settings for the IR-amplifier chain ranging from 55 to 5500. The gain can
be selected by setting the appropriate bits of the ‘Irgain1’-register (EEPROM address 00h) according to
the table below. Any gain between the abovementioned limits can be obtained within an accuracy of
±6.5%. The amplifier input-referred white noise level is below 23nVrms/√Hz. In the application with IR­sensors, with output resistance of 50kΩ typical, the total system noise will however depend mainly on the
noise of the sensor and will rise up to 45nVrms/√Hz. The offset for the chopper stabilized amplifier path
can be largely calibrated out and amounts to maximum 4µV.
The common mode input range of the amplifier is –100mV to VDD - 3V. The output range of the amplifier
is 0V to VDD-0.2V. The output of the amplifier is referred to the potential on AGND.

IR chain gain settings

GGGGG

×××=

lpabprIR

stage
contr.

bits

setting

G

pr

GCI0 GCI3 GCI2 GCI1 GCI4 GCI7 GCI6 GCI5

010

120*1112515

G

b

0XX5 0001.067
10010 0011.143
10115 0101.231
11020

G

pa

01

G

l

0111.333

1001.455

1011.600

1101.778

1112.000

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MLX90313

Programmable IR Sensor Interface

* This option is available only if ENLN=1
The pin ENLN controls both the noise level and distortion of the amplifier. If ENLN=1 the noise of the

amplifier is 23nVrms/√Hz, the gain of 20 in first stage is available but the input signal must be less than 4
mV for less than 0.05% full scale distortion.
If ENLN is 0 then the span of the input signal can be ± 40mV with distortion less than 0.1% full scale. In
this case the noise floor of the amplification chain increases 3 times.

Temp-amplifier chain

MLX90313 is available with gain settings for the Temp-amplifier ranging from 5 to 50. The gain can be
selected by setting the appropriate bits of the ‘Temp gain and current control’-register (EEPROM address
02h) according to the table below. Any gain between the abovementioned limits can be obtained within an
accuracy of ±6.5%. It is also possible to completely bypass the temperature amplifier and force the input
signal directly to the ADC. The amplifier input-referred white noise level is below 400nVrms/√Hz.
The common mode input range of the amplifier is –100mV to VDD-3V. The output range of the amplifier is
0V to VDD-0.2V. The output of the amplifier is referred to the potential on AGND.

Temp chain gain settings

MGGG

××=

lprT

stage
contr.

bits

settin
g

Note: When the current mirror is on (all settings except IRSEL[2:0] = 000b) the gain is defined as follows:

G

where Vout is the output of the analog amplifier chain, Rsens is the resistance of the sensor connected between
TINP and TINN and Icref is the current out of CREF.

G

pr

GCT2 GCT1 GCT0 GCT5 GCT4 GCT3
0001XXX
0115

100100101.2310102/7

101150111.3330113/7
11020
11125

Vout

=

T

IcrefRsens

⋅

G

l

0001.067000off

0011.1430011/7

1001.4551004/7

1011.6001015/7

1101.7781106/7

1112.0001111

M

IRSEL2 IRSEL1 IRSEL0

When the current mirror is off (IRSEL[2:0]=000b), M should be replaced by 1 and the gain is defined as follows:

Vout

G

=

T

where Vin is the voltage difference between TINP and TINN
If GCT[2:0]=0 then the temp chain will be completely off, the Timp pin will be connected directly to the ADC input,

providing Gain=1

Vin

Current Reference

The thermistor (or sensor) connected to TINP must be biased with a current source. This bias current is
mirrored from the current through the external resistor between CREF and VSS. The voltage maintained
at the CREF pin is derived from internal band-gap voltage, and thus constant. The typical value of the
voltage at CREF pin is 2V.
The current mirror ratio can be set between 1/7 and 1 according to the table for the Temp-chain gain
settings. The setting with IRSEL[2:0]=000b switches the current mirror off. In this case the thermistor
must be biased by external circuitry.

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MLX90313

Programmable IR Sensor Interface

Analog-to-Digital Converter (ADC)

MLX90313 contains a 12-bit internal analog to digital converter. Real 12 bit conversion is achieved by a
fully differential signal path of the converter. The input amplifier of the ADC has a fixed gain of 3.
Automatic calibratio n is implemented in the background, which al lo ws prec is e con vers i on in a ver y wide
temperature range. The ADC sampling rate is 7k samples/second. The reference voltage for the ADC is
normally a scaled version of the internal band-gap reference and is fixed to be 2.5V. Alternatively
MLX90313 can be configured to work with an external reference potential applied to the AGND pin. In
this case the appropriate bit in the configuration register (SELADREF bit in Confreg1) must be cleared.
Internal ADC can work with references down to 1 V keeping the 12-bit resolution.
The ADC contains an interface circuit to scale and offset the analog signals in order to make the most
efficient use of the available resolution. After amplification the IR and Temp sensor signals are referred to
AGND voltage level (typical value 2.5V). The additional offset is scaled version of the AGND.
The ADC interface circuit is given below. The output of the Temp-chain is amplified relative to the voltage
reference VrefT, which can be controlled with 2 bits (bit10 and bit9, EEPROM address 02h). The possible
values for VrefT can be calculated according to the equation:

KVAgnd

)63(4.1

VrefT

The typical values are 3.15, 3.20, 3.25 and 3.3V. If the temp path amplifier is bypassed then VrefT will be
fixed to: Agnd x 0.28 = 0.7V typical.
The output of the IR-chain is amplified relative to Refir and can be calculated according to the following
equation:

=

70

+××

, where K =0 to 3, corresponding to the value of the control bits.

KVAgnd

)34(4.1

Vrefir

The typical values (for Agnd=2.5V) are listed in the table below:
ADC interface setting

RSEL[4:0] Refir [V] RSEL[4:0] Refir [V] RSEL[4:0] Refir [V] RSEL[4:0] Refir [V]

11111b 3.25 10111b 2.85 01111b 2.45 00111b 2.05
11110b 3.20 10110b 2.80 01110b 2.40 00110b 2.00
11101b 3.15 10101b 2.75 01101b 2.35 00101b 1.95

11100b 3.10 10100b 2.70 01100b 2.30 00100b 1.90
11011b 3.05 10011b 2.65 01011b 2.25 00011b 1.85
11010b 3.00 10010b 2.60 01010b 2.20 00010b 1.80
11001b 2.95 10001b 2.55 01001b 2.15 00001b 1.75
11000b 2.90 10000b 2.50 01000b 2.10 00000b 1.70

=

70

+××

, Where K=0:31 depending on the selected value of Rsel[4:0]

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MLX90313

Programmable IR Sensor Interface

Config register 1: BYPTEMP

TINP pin

Temp-chain out

TINN pin

VReft

IR-chain out

x3 ADC

VRefir

Vrefp

12

ADCx3

-Vrefp

Linearisation

Vrefp

12

-Vrefp

Irgain register: [RSEL4:RSEL0]

Unit

ADC reference configuration

Digital-to-Analog Converter (DAC)

A 8 bit digital to analog converter can be used to output the data for the linearised Tobject- and Tambient
signals. The DAC can work with a internal programmable reference voltage, as well as with an external
one. In case the internal reference voltage is used, this voltage can be monitored on the VREFP pin. If
one wants to use his own reference voltage, this can be done by applying this voltage to the VREFP pin,
and setting the appropriate configuration bit.
The result from D/A conversion is stored on hold capacitors and buffered. The signals are available at
IROUT and TEMPOUT respectively, if the appropriate bits are set in the configuration register (EEPROM
address 04h).

The reference value for the D/A can be programmed with 3 bits: SELDR[2:0] (register Irgain2) according
to the table below:

SELDR2 SELDR1 SELDR0 ENDREFDIV VREFP

00002

00102.5
01003

01113.5
10014

10114.5

For reference voltages higher than 3V the ENDREFDIV bit must be set. In this case the ASIC will divide
internally the reference by 2 to provide proper input common mode for the output buffer amplifiers at pins
IROUT and TEMPOUT. In this case the result of the D/A conversion result will be amplified times 2 by the
output amplifiers, which will ensure the requested signal swing.
Melexis can rescale the DAC reference and eeprom table for the linearisation unit to provide absolute
analog output. This way, at maximum calibrated temperature, the voltage of IROUT or TEMPOUT pin will
always correspond to the requested D/A reference voltage.

The regulator for the VREFP voltage can be stopped and an external reference voltage can be forced and
used from the D/A. The regulator for DAC reference voltage can also be stopped (bit ENDACREF=0)
when DAC is not in use. This will save some supply current.

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SELDR(2:0)

MLX90313

Programmable IR Sensor Interface

AGND

ENDREFDIV

DAC

IRout Tout

VREFP

DACREF

IRout, Tout

ENDREFDIV

DAC configuration

Output drivers

The IROUT and TEMPOUT outputs can be connected to various signals available: The amplified analog
signals (IRINP-IRINN and TINP-TINN), the linearised object respectively ambient temperature signals, or
to the comparator circuitry. The IROUT and TEMPOUT pin drivers can source 1mA and sink 20µA and
are reverse voltage protected down to –5V relative to VSS. The available configurations are described in
table below.

Input/Output Setting

I/O pin IROUT TEMPOUT
Control

IROUTC[1:0] Configuration TOUTC[1:0] Configuration

Bits

00b IR-c hain out 00b Temp-chain out

Setting

01b Linear Tobject 01b Linear Tambient
10b Threshold Rel1 input 10b Comp1 out
11b PWM out 11b PWM out

REL1 is an open drain relay driver output controlled by the on-chip comparator circuitry. The available
configurations are described in the section on the comparator circuitry.

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MLX90313

Programmable IR Sensor Interface

Digital Section

The digital unit on board of MLX90313 realizes all functions for control, configuration, measurements and
linearisation. It contains several registers, ALU and control logic. All functions of the ASIC are hardware
fixed and controlled by different state machines, which execute in sequence all procedures necessary for
normal chip operation.

Internal registers overview

The table below contains all internal registers, their addresses for access via SPI serial interface and short
functional description. Depending on their function they can be divided in 3 groups:

• Control registers: they keep the configuration of the chip including all gain settings of the amplifiers,
analog ground level, band-gap and oscillator trimming data, etc. All this data is stored in eeprom and
after POR the system loads it in the corresponding peripheral registers.

• Data registers: they keep all data for offsets, results from measurements and linearisation of both
chains. This registers can be read vis spi in normal mode and are write accessible during test mode.

• Computation registers. These registers support the computation unit and keep all temporary data
necessary for digital low pas filtering, linearisation and comparator functions. They are not accessible
via SPI in normal mode.

Internal Register Table.

Register
IRGAIN1

IRGAIN2
TEMPGAIN
CONFREG1
CONFREG2
OSCILLATOR
BGCONTROL
LPF
ADCREG
IROUT
TOUT
IRDATA
TDATA
IROS
TOS
MAINSTM
TEST
REG TEMP
REG A
REG B
TESTCTRL 1
REG C
REG E
TESTCTRL 2

WP

Function
IR-chain settings 0 00h Test mode No

IR-chain settings 1 01h Test mode No
Temp-chain settings 2 02h Test mode No
Configuration 3 03h Test mode Always
Configuration 4 04h Test mode Always
Oscillator 5 05h Test mode No
Bandgap control 6 06h Test mode No
Low Pass Filter 7 07h Test mode No
ADC output data 8 08h Test mode Always
Tobject (lin) 9 09h Test mode Always
Tambient (lin) 10 0Ah Test mode Always
IR-chain output 11 0Bh Test mode Always
Temp-chain output 12 0Ch Test mode Always
IR-chain offset 13 0Dh Test mode Always
Temp-chain offset 14 0Eh T est m ode Alwa ys
Main state machine 15 0Fh Test mode No
Test mode control 16 10h Always No
Temporary register for test Test mode No
Accumulator A Test mode No
Accumulator B Test mode No
Test control 20 14h Test mode No
Accumulator C Test mode No
Accumulator E Testmode No
ADC test control 23 17h Test mode No

Eeprom write protect

Address Access via spi
Dec Hex Write Read

24­31

18h­1Fh

Always No

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Configuration and control registers overview and bit functions as they are read from the module

Bit functions

REGISTERH B15 B14 B13 B12 B11 B10 B9 B8
REGISTERLB7B6B5B4B3B2B1B0
IRGAIN1H ENDREFDIV ENDAC ENLN GCI7 GCI6 GCI5 GCI4 GCI3
IRGAIN1L GCI2 GCI1 GCI0
IRGAIN2H AGNDC3 AGNDC2 AGNDC1 AGNDC0 SELDR2 SELDR1 SELDR0 RSEL3
IRGAIN2L RSEL2 RSEL1 RSEL0
TEMPGAINH TRSEL1 TRSEL0 IRSEL2 IRSEL1 IRSEL0 GCT5 GCT4 GCT3
TEMPGAINL GCT2 GCT1 GCT0
CONFREG1H ERROR ENVR HVSUP SELADREF POTMET COMP1V COMP1P BYPTEMP
CONFREG1L REL1V REL1P EEWREN TESTMODE
CONFREG0H IROUTC1 IROUTC0 TOUTC1 TOUTC0 SUBINC SUBDEC NTC TIMEOS3
CONFREG0L TIMEOS2 TIMEOS1 TIMEOS0
OSCH ENAGNDB
OSCL
BGH
BGL
LPFH RSEL4 ENOSM ENTAV IROS TOS LPFIR2 LPFIR1 LPFIR0
LPFL LPFT2 LPFT1 LPFT0
TESTH1011001
TESTL
TESTCTRL1H
TESTCTRL1L
TESTCTRL 2H
TESTCTRL 2L
WPH
WPL 1100101

Register Descriptions

IRGAIN1

Read access: No. The data is accessible for read via SPI only from eeprom address 00h.
Write access: Directly to the register in test mode. To eeprom if WP-register is correctly set.

IRGAIN1 bit functions

Name POR val Function
ENDREFDIV X

1 Divide the reference for the DAC and enable output amplification by 2 of

the To and Ta outputs. Must be set for Vref=3.5V,4V,4.5V.
ENDAC X 1 Enable the DAC regulator
ENLIN X 1 Enable low noise.
GCI[7:0]

X

00000000­11111111

Control the gain of the IR amplifier chain (see ‘IR amplifier chain’)

IRGAIN2

Read access: No. The data is accessible for read via SPI only from eeprom address 01h.
Write access: Directly to internal register in test mode. To EEprom if WP-register is correctly set.

IRGAIN2 bit functions

Bit POR val Function

AGNDC [3:0]
SELDR [2:0]

X 0000-1111 Reserved
X Adjustment of the DAC reference.
X

X
X
X

000 Vref = 2V
001 Vref =2.5V
010 Vref = 3V
011 Vref = 3.5V

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IRGAIN2 bit functions

Bit POR val Function

X
X

RSEL[3:0] X

TEMPGAIN

Read access: No. The data is accessible for read via SPI only from eeprom address 02h.
Write access: Directly to internal register in test mode. To EEprom if WP-register is correctly set.

TEMPGAIN bit functions

Bit POR val Function

TRSEL[1:0]
IRSEL[2:0]

GCT[5:0]

X
X
X

100 Vref = 4V
101 Vref = 4.5V
0000-1111 Select the value of the analog ground for IR signal path.The bits are

5, RSEL4 is in LPF register (see ‘ADC’ part)

00-11 Reference voltage for Tambient measurement at ADC interface

input.

000-111 Current mirror ratio: See under M in table ‘Temp chain gain settings’

in the section on the Temp-amplifier chain (analog features)
000000­111111

Temp-gain: See table ‘Temp-chain gain settings’ in the section on

the temp-amplifier chain (analog features)

CONFREG1

Read access: Directly from internal registers or EEprom.
Write access: Directly to internal register in test mode. To EEprom if WP-register is correctly set.

CONFREG1 bit functions

Bit POR val Function

Fatal Error

X
ENVR
HVSUP 1 1 Enable the regulator for battery supply. NOTE!!! After POR this regulator will be

POTMET
COMP1V

BYPTEMP
REL1V
REL1P

EEWREN 0 1 Enables write access in EEPROM *write protect
TESTMODE 0 1 Indicates chip is in test mode *write protect

*control bits EEWREN and TESTMODE are write protected. Their values can be set only with writing the
appropriate data in ‘Test’ and ‘WP’ registers. These bits are flags which indicate the system operation

X

X

X

X

X

X

1 Flags Multiple eeprom failure. Hamming coding can detect and correct only one bit

per address. Bit will be cleared when going in test mode,disabling EEPROM
protection and returning in normal mode.( for diagnostics only)

1 Stops the internal reference for DAC (Pin VREF). The reference voltage can be

supplied externally. If ENDAC=0 then VREF is input.

always on. It can be stopped from EEPROM data.
0 External supply of ADC reference to AGND pin.SELADREF X
1 Enable the internal ADC reference (connected to AGND pin).
0 Sets threshold level for Rel1 to THRel1 in EEprom (address 75h)
1 Sets potentiometer input (pin IROUT) as threshold level
0 Sets Tobject as target voltage for comparator Comp1
1 Sets Tambient as target voltage for comparator Comp1
0 Sets polarity of Comp1: InvertingCOMP1P X
1 Sets polarity of Comp1: Non-inverting
0 Output of Temp amplifier path is connected to ADC
1 Connects TINP-TINN directly to the ADC, bypassing the Temp-chain
0 Sets Tobject as target voltage for Rel1
1 Sets Tambient as target voltage for Rel1
0 Sets polarity of Rel1: Inverting
1 Sets polarity of Rel1: Non-inverting

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mode.

CONFREG0

CONFREG0 bit functions

Bit POR val Function

IROUTC[1:0]

TOUTC[1.0]

TIMEOS[3:0]

00b IROUT pin function: IR-chain out
01b IROUT pin function: Linear Tobject
10b IROUT pin function: Threshold Rel1 input
11b IROUT pin function: PWM out
00b TEMPOUT pin function: Temp-chain out
01b TEMPOUT pin function: Linear Tambient
10b TEMPOUT pin function: Comp1 out
11b TEMPOUT pin function: PWM out
0 2nd order derivative of thermistor function is positive (used if NTC=0)SUBINC
1 2nd order derivative of thermistor function is negative (used if NTC=0)
0 2nd order derivative of thermistor function is positive (used if NTC=1)SUBDEC
1 2nd order derivative of thermistor function is negative (used if NTC=1)
0 Used thermistor is PTCNTC
1 Used thermistor is NTC
0000 Offset calibration interval: 0'00"
0001 Offset calibration interval: 0'02"
0010 Offset calibration interval: 0'17"
0011 Offset calibration interval: 0'19"
0100 Offset calibration interval: 1'07"
0101 Offset calibration interval: 1'09"
0110 Offset calibration interval: 1'24"
0111 Offset calibration interval: 1'26"
1000 Offset calibration interval: 2'14"
1001 Offset calibration interval: 2'16"
1010 Offset calibration interval: 2'31"
1011 Offset calibration interval: 2'33"
1100 Offset calibration interval: 3'21"
1101 Offset calibration interval: 3'23"
1110 Offset calibration interval: 3'38"
1111 Offset calibration interval: 3'40"

MLX90313

Programmable IR Sensor Interface

OSCCTRL

Read access: No. The data is accessible for read via SPI only from eeprom address 05h.
Write access: Only in test mode for both writing directly to internal registers and writing to Eeprom if WP
register is correctly set.

BGO: Reserved

Read access: No. The data is accessible for read via SPI only from eeprom address 06h.
Write access: Only in test mode for both writing directly to internal registers and writing to Eeprom if the
WP register is correctly set.

LPF

Read access: No. The data is accessible for read via SPI only from eeprom address 07h.

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Write access: Only in test mode for both writing directly to internal registers and writing to Eeprom if the
WP register is correctly set.

This register keeps the calibration data for the time constants of digital low pass filters of both channels
(see section Linearisation Unit).

LPF bit functions

Bit POR Val Function
RSEL4 0 Refer to ADC interface setting

0 Enable offset measurement of both IR & Temp channels.ENOSMB
1 Disable offset measurement of both IR &Temp channels.
0 Reserved for future development. Reset it for all applications.ENTAV
1 Reserved for future development. Reset it for all applications.

IROS*

LPFIR[2:0]

LPFT[2:0]

0
1 Number of averaged offset measurements for IR chain: 1024
0 Number of averaged offset measurements for Temp chain: 512TOS*
1 Number of averaged offset measurements for Temp chain: 1024
Number of averaged points for IR measurement
00b 64
01b 128
10b 256
11b 512
100b
Number of averaged points for Temp measurement
00b 64
01b 128
10b 256
11b 512
100b 1024

Number of averaged offset measurements for IR chain: 512

1024

ADCREG

Read access: Directly via SPI in all modes.
Write access: Directly to internal register in test mode.

This register keeps the result from last analog to digital conversion..

IROUT

Read access: Directly from internal register.
Write access: Directly to internal register in test mode.

This register keeps the linearised object temperature. (Tobject)
Register format:

Bit1514131211109876543210

Name D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 OVH OVL FE Res

D11..D0 : 12 bit temperature data
OVH: Overflow flag for Tambient measurement, Ta>Tamax, D[11:0] set to FFFh
OVL: Underflow flag for Tambient measurement, Ta<Tamin, D[11:0] set to 000h
FE: Fatal Error in eeprom.
Res Not used, always zero.

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Note that the last 4 bits are the status register.

TOUT

Read access: Directly from internal register.
Write access: Directly to internal register in test mode.

This register keeps the linearised ambient temperature. (Tambient)
Register format:

Bit1514131211109876543210

Name D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 OVH OVL FE Res

D11..D0 : 12 bit temperature data
OVH: Overflow flag for Tambient measurement, Ta>Tamax, D[11:0] set to FFFh
OVL: Underflow flag for Tambient measurement, Ta<Tamin, D[11:0] set to 000h
FE: Fatal Error in eeprom.
Res Not used, always zero.

Note that the last 4 bits are the status register. These bits are identical to the last 4 bits of the IROUT
register.

IRDATA

Read access: Directly from internal register.
Write access: Directly to internal register in test mode.

This register keeps the measured IR data, compensated with the current offset of the amplifier (stored in
Iros register).

TDATA

Read access: Directly from internal register.
Write access: Directly to internal register in test mode.

This register keeps the measured Temp data, compensated with the current offset of the Temp amplifier
(stored in Tos register).

IROS

Read access: Directly from internal register.
Write access: Directly to internal register in test mode.

This register keeps the offset of the IR amplifier. Each measurement from IR amplifier will be
compensated with this offset.

TOS

Read access: Directly from internal register.
Write access: Directly to internal register in test mode.

This register keeps the offset of the Temp amplifier. Each measurement from Temp amplifier will be
compensated with this offset.

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MAINSTM: Reserved

Read access: No
Write access: Directly to internal register in test mode

TEST

Read access: No.
Write access: Directly to internal register.

This register determines the chip mode. It is cleared after POR which corresponds to normal mode.
Writing the proper data in this register will put the chip in test mode which will be indicated with bit ‘Test’
from confreg0.

Test register
Bit POR val Function

B[15:9] 0000000b
B[8:0] 000000000bX

1011001b Forces chip in test mode
any other Normal mode (default)

WP

Read access: No.
Write access: Directly to internal register via SPI.

The register controls the write access to the eeprom. After POR this register is cleared and the eeprom is
protected, no write access available. Writing the proper data in this register will remove the write
protection of the eeprom and bit EEWREN (bit 1 in Confreg1) will be set.

EEprom write protect register
Bit POR val Function
B[15:9] 000000000bX

B[6:0] 0000000b

* The addresses 00-07h and 79-7Fh will be still protected. Write access here requires also ‘Test mode’.

1100101b Enables write access to Eeprom*
any other Sets EEprom write protect

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Eeprom Description

MLX90313 contains 128 x 16 EEPROM memory. The memory can be accessed through the serial
interface. The 11 most significant bits are data bits and the 5 less significant bits are control bits used for
the Error Check and Correction system (ECC). After POR the ASIC reads the full eeprom contents,
checks it and corrects the single errors (1 wrong bit per address). If higher order error is discovered then
the bit ‘fatal error’ will be set (see Confreg1 description in previous section).
The memory has two levels of protection. After POR the write access to the eeprom will be disabled. The
external unit can remove this level of protection writing proper data in WP register. In this case all
addresses in range 08-77h will be available for write access. The first and last 8 addresses will still be
disabled. The write access to these cells is available only if the write protection is removed and the chip is
in test mode.

Eeprom map overview

Address list eeprom

Register name Function
IRGAIN1 IR-chain settings 0 00h test mode**

IRGAIN2 IR-chain settings 1 01h test mode
TEMPGAIN Temp-chain settings 2 02h test mode
CONFREG1 Configuration 3 03h test mode
CONFREG2 Configuration 4 04h test mode
OSCCTRL Oscillator control 5 05h test mode
BGCTRL Bandgap control 6 06h test mode
LPF Low Pass Filter 7 07h test mode

CALIBRATION
IOS-TEMP Initial offset Temp-chain 112 70h WP

IOS-IR Initial offset IR-chain 113 71h WP
RESERVED 114 72h WP

THCOMP1
HSCOMP1
THREL1
HSREL1

RESERVED 119 77h
CHIP-ID Data 120-127 78h-7Fh test mode

*WP: Write access to EEprom is controlled by the content of the internal register WP
**Test mode: Write access controlled by the internal register WP and only available in test mode

Look up table
linearisation.

Threshold for comparator
Comp1
Hysteresis for comparator
Comp1
Threshold for comparator
of Rel1
Hysteresis for comparator
of Rel1

Address Write access
Dec Hex

8-111 08h-6Fh WP*

115 73h WP
116 74h WP
117 75h WP
118 76h WP

The last 8 addresses 0x78 to 0x7F are free to use for the user. They can hold some calibration data or
identification number. All data programmed into the eeprom must pass the error checking. Therefore, one
must add 5 hamming bits to the eeprom data, in the 5 least significant bits.

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Eeprom bit definitions

Following table gives the bit definitions for all addresses that can be modified by the user. All other
addresses contain specific calibration data and should be left unchanged.
Note that some bits marked “RES” are reserved and should never not be changed by the user. If other
bits in such an address must be changed, read original contents first to get the status of the reserved bits.

EEPROM BIT DEF ENITIONS

ADDRESS REGISTERH B15 B14 B13 B12 B11 B10 B9 B8

(HEX) REGISTERL B7B6B5B4B3B2B1B0

0x00 IRGAIN1H

IRGAIN1L GCI2 GCI1 GCI0 K H4 H3 H2 H1

0x01 IRGAIN2H AGNDC3 AGNDC2 AGNDC1 AGNDC0 SELDR2 SELDR1 SELDR0 RSEL3

IRGAIN2L RSEL2 RSEL1 RSEL0 K H4 H3 H2 H1

0x02 TEMPGAINH TRSEL1 TRSEL0 IRSEL2 IRSEL1 IRSEL0 GCT5 GCT4 GCT3

TEMPGAINL GCT2 GCT1 GCT0 K H4 H3 H2 H1

0x03 CONFREG1H ENVR HVSUP

CONFREG1L REL1P RES RES K H4 H3 H2 H1

0x04 CONFREG0H IROUTC1 IROUTC0 TOUTC1 TOUTC0 SUBINC SUBDEC NTC TIMEOS3

CONFREG0L TIMEOS2 TIMEOS1 TIMEOS0 K H4 H3 H2 H1

0x05 OSCH RES RES ENAGNDB RES RES RES RES RES

OSCL RES RES RES K H4 H3 H2 H1

0x06 BGH RES RES RES RES RES RES RES RES

BGL RES RES RES K H4 H3 H2 H1

0x07 LPFH RSEL4 ENOSM ENTAV IROS TOS LPFIR2 LPFIR1 LPFIR0

LPFL LPFT2 LPFT1 LPFT0 K H4 H3 H2 H1

0x73 THComp1 THR10

0x74 HSComp1 HST10 HST9 HST8 HST7 HST6 HST5 HST4 HST3

0x75 THRel1 THR10 THR9 THR8 THR7 THR6 THR5 THR4 THR3

0x76 HSRel1 HST10 HST9 HST8 HST7 HST6 HST5 HST4 HST3

0x78 - 0x7F USER1..7 UDATA10 UDATA9 UDATA8 UDATA7 UDATA6 UDATA5 UDATA4 UDATA3

ENDREFDIV

THR2

HST2 HST1 HST0 K H4 H3 H2 H1

THR2 THR1 THR0 K H4 H3 H2 H1

HST2 HST1 HST0 K H4 H3 H2 H1

UDATA2 UDATA1 UDATA0 K H4 H3 H2 H1

ENDAC ENLN GCI7 GCI6 GCI5 GCI4 GCI3

POTMET COMP1V COMP1P BYPTEMP REL1V

THR7

K

THR6

H4

THR5

H3

THR4

H2

THR3

H1

THR9
THR1

SELADREF

THR8
THR0

Eeprom Hamming coding

All addresses in the eeprom are coded using hamming code. Therefore, if one wants to program data into
any eeprom address, the hamming bits must be calculated first. This is not done by the
There are 11 bits + 4 hamming bits + 1 extra redundant bit in the eeprom. Data bits are numbered
D10..D0, Hamming H4..H1, the extra bit is called K.

The bit definitions in the eeprom words are:

Pos1514131211109876543210

name D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 K H4 H3 H2 H1

The hamming bits are calculated as follows:
H1 = P(D0,D1,D3,D4,D6,D8,D10)

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H2 = P(D0,D2,D3,D5,D6,D9,D10)
H3 = P(D1,D2,D3,D7,D8,D9,D10)
H4 = P(D4,D5,D6,D7,D8,D9,D10)

The extra K bit is calculated as:
K = P(D10,D9,D8,D7,D6,D5,D4,D3,D2,D1,D0,H4,H3,H2,H1)
Note :P is parity over the noted data bits. Parity is 1 if the number of ones is odd.

When reading eeprom addresses, the numerical value can be found by simply dividing the returned data
by 32.

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90313 Algorithm

The algorithm of the ASIC is divided in several operations: ECC, initialization, offset measurement, object
and ambient measurement and offset cancellation, linearisation, comparator functions. Each of this
operation is controlled from the main state machine. The sequence and control of all these state machines
is controlled from main state machine. The normal flow of the procedure is show on the diagram below.

POR

ECC

Initialization

Offset calibration

Measurement

Temp. linearisation

IR. linearisation

Comp & Relay

TRUE

Main state machine control flow

Recalibration

FALSE

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Error Check and Correction (ECC)

The ASIC starts this procedure only after Power On Reset. The state machine reads all data in the
eeprom and corrects all single errors (1 wrong bit per address) if necessary. The wrong information from
the eeprom will be refreshed with correct one. In case of double error (2 wrong bits per address) which
can only be detected, not corrected, the system will leave the data in the address and will set the flag
‘Fatal error’ (bit 1 in status register). This data is available through SPI or PWM.

Initialization

At this step the system reads its configuration from the eeprom. All data from eeprom addresses 00-07h
will be filled in the corresponding peripheral registers. After this step the ASIC is ready for normal
operation.

Offset measurement (offset drift compensation)

The offset measurement is run periodically from the main state machine. The customer can select one of
16 possible interval times for offset measurement (see ‘CONFREG0 bit functions’). Depending on the
selected values for bits IROS and TOS in LPF register (address 07h in EEPROM) the average of 512 or
1024 measurements is stored. The time this measurement takes is about 75ms or 150ms, depending on
the number of measurements taken. Note that during this time the outputs are kept on their last value
before calibration started, so the current temperature is not available during offset calibration. The
measured offset results will be stored in IROS (for IR amplifier chain) and TOS (for Temp amplifier chain)
registers.

Measurement and offset cancellation

The results from analog to digital conversion for both channels will be the mean of custom defined number
of measurements, controlled from the LPF register (address 07 in eeprom). This data will be compensated
with corresponding offsets, stored in IROS and TOS registers and final offset free data will be stored in
IRDATA (for IR amplifier chain) and TDATA (for Temp amplifier chain) registers. The number of
measurements of which the averaging is taken can vary between 64 and 1024 (see ‘LPF register bit
functions’) and can be selected independently for both channels.

Linearisation

Linearisation proceeds in two steps and can be described by the picture below. In the first step the
ambient temperature is calculated from the measured signal at TINP-TINN. The system outputs a digital
value for the ambient temperature based on the calibration data. The value is stored in a dedicated
register and from there available for the DAC and PWM (Tambient-register, address 0Ah). The register
can also be read digitally by means of the SPI.
The system is developed to support different temperature sensors. 3 bits in the configuration register
(EEprom address 03h), determine the type of characteristic. NTC defines the first derivative of the
temperature sensor (NTC-type is logical 1, PTC-type is logical 0). SUBDEC and INCDEC define the

2

second derivative of the temperature sensor (
The result of the linearisation is stored as the 12 MSB’s of the Tambient-register (or TOUT-register). The

code 000h will correspond to Tamin, FFFh will correspond to Tamax. These two limits are determined by
calibration. Accordingly the output resolution will be

VRthd

dT

).

2

TaTa

minmax

−

in K per LSB

4096

In the second step the value of the ambient temperature is combined with the measured signal at IRINP­IRINN to obtain a calculated value for the so-called object temperature, based on the calibration data. The
value is stored in a dedicated register and from there available for the DAC and PWM (Tobject-register,
address 09h). The register can also be read digitally by means of the SPI.
The result of the linearisation is stored as the 12 MSB’s of the Tobject-register (or IROUT-register). The

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code 000h will correspond to Tomin, FFFh will correspond to Tomax. These two limits are determined by

ToTo

minmax

calibration. Accordingly the output resolution will be

−

4096

in K per LSB.

Linearised output

Irout=A.To+B

To [degC]

Linearised output
Tempout=A.To+B

Irout

Vir

The rm opile C haract e r is tic

Signal [V]

The rm isto r ch arac te ris tic

Vir=f(To, Ta)

Ta

To [degC]

R=f(T a)

Irout [V]

Lin.
Unit

R

R(T)/Ro

Tempout[V]

Ta [degC]

Ta[degC]

Tempout

When reading the linearised data digitally by means of the SPI, a 16-bit word is returned. The 12 MSB’s
contain the temperature value as described above, the 4 LSB’s form a status register, which is the same
for both the IROUT address and the TOUT. The meaning of the individual bits is explained in the table
below.

Linearisation Status Register
S[3:0] Meaning

1 X X X Overflow flag for Tambient measurement, Ta>Tamax, TOUT[15:4] set to FFFh
X 1 X X Underflow flag for Tambient measurement, Ta<Tamin, TOUT[15:4] set to 000h
X X 1 X Flag for Fatal Error in eeprom *
X X X 0 Not used, al ways zero

*Fatal Error is the uncorrectable error in EEPROM (more than 2 wrong bits per address). When this error
occurs, the normal process flow does not change, but the results may go wrong.
.
The status register is particularly important when an overflow (or underflow) condition occurs for the Ta­measurement. If the overflow condition occurs IROUT register will be set to FFFh, if underflow - IROUT
wil be 000h. If the user selects to monitor the analogue output through the DAC, then care must be taken
to ensure that Tambient will never exceed the selected range, as the over- or underflow condition is not
flagged.

Comparators and relay output

MLX90313 contains two programmable 12 bit digital comparators. For each circuit the target signal, the
threshold and hysteresis can be programmed in different configurations, according to the table below. The
principle of operation is shown in the following schematics. The threshold and hysteresis values are
stored in eeprom, the control bits are part of the configuration register. The REL1 comparator threshold
can be either read from EEPROM (address 75h) or controlled by an external potentiometer connected to
IROUT. Note that the threshold and hysteresis registers in eeprom are only 11 bits wide. Therefore a zero
is added in the LSB position to the threshold and hysteresis registers, making this register also 12 bits.

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Comp1 circuitry setting

Comp1 source signal Comp1 Polarity

Control Bit COMP1V COMP1P
Setting

0 Tobject 0 Inverting
1 Tambient 1 Non-inverting

MLX90313

Programmable IR Sensor Interface

Linearised

T

ambient

Linearised

T

object

Threshold

address:73h

12

12

12 bit

2/1 MUX

COMP1V

12

COMP1P

11+1

analog

options

12 bit

digital

comparator

Hysteresis

address:74h

Comparator1 (COMP1) Configuration diagram

Note that the threshold for COMP1, is always in eeprom address 0x73.

Rel1 circuitry setting

Rel1 source signal Rel1 Threshold source Rel1 Polarity

Control Bit REL1V POTMET REL1P
Setting

0 Tobject 0 [75h] 0 Inverting
1 Tambient 1 IRDATA [03h] 1 Non-inverti ng

Tempout

12

12

12

11+1

12 bit

2/1 MUX

REL1V

12 bit

2/1 MUX

POTMET

12

REL1P

12

12 bit
digital

comparator

Hysteresis

address:76h

REL1

IROUT

ADC

4LSB 0000

8

Linearised

T

ambient

Linearised

T

object

IRDATA

register

Threshold

address:75h

Comparator2 (REL1 pin) Configuration diagram

After the temperature data is updated in TOUT and IROUT registers (the current Ta&To are calculated)
the main state machine will enable the comparator functions of the chip if one of them is enabled.
Threshold data for both outputs is stored in addresses 73h (for Comp1) and 74h (for Rel1) in eeprom.

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MLX90313

Programmable IR Sensor Interface

The threshold data can be calculated by the formula:

TTthr

min

Threshold value =

−

TT

−

where: Tthr is the target temperature for the comparator

Tmin, Tmax are the minimum and maximum temperature under calibration.

The hysteresis value can be calculated by following formula:

Hysteresis value =

Thys

TT

minmax×−

where: Thys is the desired hysteresis in deg C.

Tmin, Tmax are the minimum and maximum temperature under calibration

Both formulas are valid for ambient and IR temperatures. The data for hysteresis must be stored at
addresses 74h (for Comp1) and 76h (for Rel1) after adding the hamming bits in the 5 least significant bit
places. Refer to Hamming Coding in eeprom description section for details.

2048

×

.

minmax

2048

Pulse Width Modulation

The PWM signal has a period of 102.4ms typical consisting of 2048 clock cycles of 50µs. Every frame
starts with a leading buffer time, t

, during which the signal is always high, as shown in the figure below.

1

The leading buffer time is followed by a slot for the useful data signal, t2 and t3, where the ration t2/(t2+t3)
is the representation of the output value. t4 is a slot for signaling of special conditions, such as out of
range measurement of the sensor temperature, Tambient and the occurrence of a fatal EEprom error, i.e.
an error that can no longer be corrected automatically by the ECC circuitry of MLX90313.

Error signaling band

Condition Duty cycle nominal timing
OVH: Tambient overflow 68.75 % 70.4 ms
OVL: Tambient underflow 75 % 76.8 ms
FE: Fatal Error EEprom 81.25% 83.2 ms

t4:Error Signaling Band

Valid Data Output Band

OVH

OVL

output signal

t

1

t2+t

3

FE

t

5

time

1

T

8

5

11
16

12

T

T

16

T

8

13
16

7

T

T

8

T0

Serial Interface

Protocol

The digital interface implemented in MLX90313 is SPI compatible. It can be used to access the on-chip
EEPROM and all internal registers. The chip will always work as a slave device. The format of any

MLX90313 Programmable IR sensor Interface Page 28 Rev 1.0 21-July-2001
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MLX90313

X

A0A1A

X

Programmable IR Sensor Interface

command is always 32 bits: 8 bits for the operation code, 8 bits for the address and 16 bits of data. The
communication protocol is presented below.

CS

SCLK

SDI

SDO

write command

CS

SCLK

SDI

SDO

read command
Every write command starts with a high to low transition of CS and ends by a low to high transition of CS

after 32 periods of the serial data clock (SCLK). MLX90313 reads the data present on SDI on the rising
edge of the clock. With a delay of 8 periods of the serial clock, the SPI will repeat the opcode, address
and the first 8 bits of data on pin SDO. This allows the external master to check command and address
and terminate the operation in case of an error by forcing CS high before the end of the complete
command cycle, i.e. before the end of the 32 clock periods.
The read command is build up similarly, except that no data has to be passed of course. On SDO the
opcode will be followed direct l y by the requested data, the address is not returned in this case.

C7 C0C1C2C3C4C5C6 A7 A0A1A2A3A4A5A6 D15 D8D9D10D11D12D13D14 D7 D 0D1D2D3D4D5D6 X

C7 C0C1C2C3C4C5C 6 A7 A0A1A2A3A4A5A6 D15 D 8D9D10D11D12D13D14X X

C7 C0C1C2C3C4C5C6 A7

C7 C0C1C2C3C4C5C6 D7 D0D1D2D3D4D5D6D15 D8D9D10D11D12D13D14

2A3A4A5A6

X

The data on SDO is valid on the rising edge of the clock. In case of a read command, the SPI output will
be valid on SDO starting on the 17

th

rising edge of the clock (after CS low) as indicated in the figure

above.

Timing/speed

The bit-rate depends on the serial data clock (SCLK) supplied by the master controller and is limited to
125kb/s. The timing requirements are given in the figure and table below

tsclktcls tsch

CS

SCLK

tsu thd

SDI

tdv

SDO

SPI timing requirements
Symbol Parameter Value Unit
tsclk Sclk pe riod min 8

µs
tcls CS low to SCLK high min 50 ns
tsch SCLK low to CS high min 50 ns
tsu data in setup tim e min 200 ns
thd data in hold time min 200 ns

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MLX90313

Programmable IR Sensor Interface

tdv data out vali d min 1

operation codes

The operation code is the first series of 8bits in a command, C[7:0] in the figure on the protocol above.
Below table summarizes the operations available in MLX90313.

Operation Codes
mnem. C[7:0] Command
WR
RD
WEPR
ER
REPR
BLWR
BLER

X101X0XX
X10010XX

0001XXXX
001XXXXX
X0001XXX
1001XXXX
101XXXXX

Write internal register
Read internal register
Write Eeprom
Erase EEprom
Read Eeprom
Block Write Eeprom
Block erase Eeprom

µs

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Applications Information

MLX90313

Programmable IR Sensor Interface

IR sensor

Thermisto

MLX9024

r

high prec.

Rbias
100k

IR+

IR-

Rsens

VSS

10u

IRINP

IRINN

TINP

TINN

AGND

CREF

VDD
VSS

OPA

OPA

A/D

Digital

A/D D/A

Control and Support Blocks

D/A

Ta

12

MLX90313

To

COMP12

Ta

COMP

SPI

TEMPOUT

IROUT

REL1

VREFP
VDD1

Micro-controller I/O-port

SW1

SW2

Vref

Typical application diagram

In the above application diagram, a simple thermometer with alarm function is depicted. As external
components there are only a thermopile (like the MLX90247x) and a current setting resistor is used.
Because the current needs to be constant over temperature and time, it is advised to use a precision
resistor. The tempout pin is the output of a comparator which compares the measured object temperature
with the threshold set by the external potentiometer. The second comparator operates the relay. It
compares the ambient temperature with a fixed threshold programmed in eeprom. Both ambient and
object temperatures can be read continously by the microprocessor using the SPI interface.

For more application examples, take a look at our MLX90601 Infrared thermometer module, which
incorporates a MLX90247 thermopile sensor and the MLX90313 IR sensor interface.

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MLX90313

Programmable IR Sensor Interface

Support Tools

In a short time Melexis will provide a demo board which can demonstrate all MLX90313’s features. This
will come with software which allows easy configuration of the MLX90313. Please have a look at

www.melexis.com for latest info.

ESD Precautions

Electronic semiconductor products are sensitive to Electro Static Discharge (ESD).
Always observe Electro Static Discharge control procedures whenever handling semiconductor products.

FAQ

Q: When is the MLX90313 available ?
A: Currently Melexis only delivers the MLX90313 as part of the MLX90601x Infrared Thermometer
module. Please refer to MLX90601 datasheet for details. Samples can be obtained Q3/2001, full
production starts Q4/2001.

Glossary of Terms

ADC Analog-to-digital converter
Ambient
Compensation

ASIC application specific integrated circuit
Band-gap Circuit to generate accurate absolute voltages. Usually they are independent of

Chopper
compensated
amplifier
DAC Digital-to-analog converter
Differential
nonlinearity (DNL)
ECC Error Checking and Correction
Eeprom

Hamming coding By giving a message a extra number of bits (= so called hamming bits), one can

Integral nonlinearity
(INL)
IR Infrared. Every object emits infrared radiation in relation to its temperature. This

Linearisation The signal from a thermopile is not linear with the object temperature. MLX90313

LSB,MSB Least Significant Bit, Most Significant Bit
NTC See Thermistor.
PGA Programmable gain amplifier.

The IR signal captured by a thermopile sensor is not only dependent on the
temperature of the object (Tobject) but also on the temperature of the sensor
itself. Therefore the IR signal is compensated for this effect by means of the
measured sensor temperature (Tambient). This rather complex calculation is
performed in the linearisation unit of MLX90313.

temperature and supply voltage, like the one used in the MLX90313
Special amplifier configuration aimed at ultra low offset

The deviation of any code from an ideal 1 LSB step

non-volatile memory that can be electrically erased and rewritten. This
type of memory is used to store configuration and calibration data needed
by the MLX90313.

not only detect, but also correct a error that occurs in the stored data or the
hamming bits. The eeprom memory of the MLX90313 uses hamming coding to do
a error check and correction if needed and possible.
This is the maximum deviation from the ideal output curve and the actual output

effect can be used to measure this temperature without the need for physical
contact.

is therefore equipped with a digital calculation unit that produces an output that is
linear with the object temperature.

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MLX90313

Programmable IR Sensor Interface

POR power –on reset: reset circuit that starts the digital system in a known state

whenever the supply voltage is cycled

PSSR Power Supply Rejection Ratio: Measure for an amplifier’s immunity to

disturbances on the supply connections.
PTC See Thermistor.
SPI Serial Peripheral Interface. Commonly used 4 wire serial link to connect different

circuits over a short distance.
Ta, Tamb ient,
ambient temperature
Thermistor

Tobject, To and
Target Temperature

The temperature of the IR sensor.

Temperature dependant resistor. Basically there are 2 types. The types

that increase their resistance with rising temperature are PTC (positive

thermal coefficient) type. The ones that decrease their resistance with

rising temperature we call NTC (negative thermal coefficient) type. The

MLX90313 can work with both types.

commonly used terms in infrared thermometry. It refers to the temperature of the

target, at which the IR sensor is “looking”

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MLX90313

Programmable IR Sensor Interface

Disclaimer

Melexis reserves the right to periodically make modifications to product specifications. The information
included herein is believed to be accurate and reliable. However, Melexis assumes no responsibility for
its use; nor for any infringements of patents or other rights of third parties which may result from its use.

MLX90313 Programmable IR sensor Interface Page 34 Rev 1.0 21-July-2001
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Physical Characteristics

0.50

0.33

12.99

12.70

MLX90313

Programmable IR Sensor Interface

0.32

0.23

7.60

1.27

7.40

Notes:

1. All dimensions in millimeters.

10.45

10.15

0o to

8

1.04

0.60

o

2.66

2.45

0.290

0.127

For the latest version of this document, go to our website at:

www.melexis.com

Or for additional information contact Melexis Direct:

Europe and Japan: All other locations:

Phone: [phone] Phone: [phone]

E-mail: [e-mail] E-mail: [e-mail]

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