MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614
Page 11 of 40
Data Sheet
Rev 003
03/Oct/2007
8.3 Block description
8.3.1 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.
8.3.2 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.
8.3.3 EEPROM
A limited number of addresses in the EEPROM memory can be changed by the customer. The whole
EEPROM can be read via SMBus interface.
EEPROM (32X16)
Name
Address
Write acces
Tomax
000h
Yes
Tomin
001h
Yes
PWMCTRL
002h
Yes
Ta range
003h
Yes
Emissivity correction coefficient
004h
Yes
Config Register1
005h
Yes
Melexis reserved
006h
No
…
…
…
Melexis reserved
00Dh
No
SMBus address
00Eh
Yes
Melexis reserved
00Fh
Yes
Melexis reserved
010h
No
…
…
…
Melexis reserved
018
No
Melexis reserved
019h
Yes
Melexis reserved
01Ah
No
Melexis reserved
01Bh
No
ID number
01Ch
No
ID number
01Dh
No
ID number
01Eh
No
ID number
01Fh
No
The addresses Tomax, Tomin and Ta range are for customer dependent object and ambient temperature
ranges. For details see point 8.5.3 below in this document
The address
Emissivity contains the object em sivity (factory default 1.0 = 0xFFFF), 16 bit.
is
Emissivity = dec2hex[ round( 65535 x
ε) ]
where dec2hex[ round( X ) ] represents decimal to hexadecimal conversion with round-off to nearest value
(not truncation). In this case the physical emissivity values are
ε = 0.1…1.0.