EVB90620 Datasheet, PDF (9/39 Pages) Melexis Microelectronic Systems – High precision non-contact temperature measurements

MLX90620
16x4 IR array
7 Principle of operation
The output of all IR sensors and absolute temperature sensors is scanned according to the
programmed refresh rate. Using their output data as well as calibration constants written in EEPROM the
absolute chip temperature and object temperature, ‘seen’ by each pixel can be calculated. For this goal
several sequential calculations must be done according to the Figure 3 Operation block diagram
POR (see 8.3)
Wait 5ms
Read the EEPROM table (see 8.2.3, 9.5)
Store the calibration coefficients in the MCU RAM for fast access
Write the oscillator trim value into the IO at address 0x93 (see 7.1, 8.2.2.2, 9.4.4)
Write the configuration value (IO address 0x92) (see 8.2.2.1, 9.4.3)
The value is either read from the EEPROM or hard coded externally
Set the POR/ Brown Out flag to “1” (bit 10 at address 0x92)
Yes
POR/Brown Out flag cleared?
(see 8.2.2.1)
No
Read measurement data (PTAT + desired IR data)
(see 7.2.1, 7.2.2, 8.2.1, 9.4.2)
Calcullations (see 7.3)
Tambient calculation
Pixel offset cancelling
Pixel to pixel normalization
Object emissivity compensation
Object temperature calculation
Image processing and correction
Figure 3 Operation block diagram
3001090620
Rev 4.0
Page 9 of 40
Datasheet IR16x4
19 September 2012