MLX90320_12 Datasheet, PDF (11/33 Pages) Melexis Microelectronic Systems – Automotive sensor interface

MLX90320
Automotive sensor interface
Figure 2: Two typical MLX90320 output characteristics obtained after calibration
Besides the coarse gain and offset adjustment, the MLX90320 can accurately adjust the output span and offset to
the desired values by calibrating a fine gain and a fine offset 10 bits DAC. This fine calibration allows also
compensating second order temperature drifts of the sensor sensitivity and offset. An accurate temperature chain
gives the information needed to compensate this temperature drift. The user has the possibility of selecting
between an internal or external temperature sensor by setting one bit in EEPROM.
What follows is the description of the different features of the MLX90320. For each feature the different calibration
parameters associated will be explained and their address in the EEPROM will be given. Only typical values are
used in this section.
6.1 EEPROM
The EEPROM is a 64 x 5 bits memory. A detailed description of the EEPROM memory address map is given in
the paragraph 9. So each EEPROM address contains 4 calibration bits and one parity bit. The sum of the '1''s of
the five bits must be '1'. That means that when data is '0000' the parity must be '1' (other examples:'0100' parity is
'0'; '1100' parity is '1'; '1111' parity is '1').
6.2 The programmable clock.
The CLKADJ[3:0] bits are stored in address 3 of the EEPROM. These bits are used to program the oscillator. If
CLKADJ[3:0] = 1111, the oscillator runs at the highest frequency. If CLKADJ[3:0] = 0000, the oscillator runs at the
slowest frequency. This calibration is required to calibrate the 4 MHz oscillator within +/-15% accuracy. A bad
oscillator calibration may cause malfunction of the communication protocol thus it is only factory set.
3901090320
Rev 007
Page 11 of 33
Data Sheet
Feb/12