MLX90621

16x4 IR array

Datasheet

39001090621

Page 9 of 44

Datasheet IR16x4

Rev 3.0

15 September 2016

Principle of operation

7.

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

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)

Read measurement data (PTAT + desired IR data)

(see 7.2.1, 7.2.2, 8.2.1, 9.4.2)

Tambient calculation

Pixel offset cancelling

Pixel to pixel normalization

Object emissivity compensation

Object temperature calculation

Image processing and correction

POR/Brown Out flag cleared?

(see 8.2.2.1)

No

Yes

Calcullations (see 7.3)

Thermal Gradient Compensation