Data Sheet

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 11 of 42 Data Sheet
Rev 004 30/Jul2008
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 V
POR
(note that this level is
different for MLX90614Axx and MLX90614Bxx). During the time POR is active, the POR signal is available as
an open drain (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
To
max
000h Yes
To
min
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 018h 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 To
max
, To
min
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.
Erase (write 0) must take place before write of desired data is made.