mlx90313 ETC-unknow, mlx90313 Datasheet - Page 25

• Manufacturer Part Number: mlx90313
• Description: Programmable Ir Sensor Interface
• Manufacturer: ETC-unknow

Error Check and Correction (ECC)
eeprom and corrects all single errors (1 wrong bit per address) if necessary. The wrong information from
the eeprom will be refreshed with correct one. In case of double error (2 wrong bits per address) which
can only be detected, not corrected, the system will leave the data in the address and will set the flag
‘Fatal error’ (bit 1 in status register). This data is available through SPI or PWM.
Initialization
At this step the system reads its configuration from the eeprom. All data from eeprom addresses 00-07h
will be filled in the corresponding peripheral registers. After this step the ASIC is ready for normal
operation.
Offset measurement (offset drift compensation)
The offset measurement is run periodically from the main state machine. The customer can select one of
16 possible interval times for offset measurement (see ‘CONFREG0 bit functions’). Depending on the
selected values for bits IROS and TOS in LPF register (address 07h in EEPROM) the average of 512 or
1024 measurements is stored. The time this measurement takes is about 75ms or 150ms, depending on
the number of measurements taken. Note that during this time the outputs are kept on their last value
before calibration started, so the current temperature is not available during offset calibration. The
measured offset results will be stored in IROS (for IR amplifier chain) and TOS (for Temp amplifier chain)
registers.
Measurement and offset cancellation
The results from analog to digital conversion for both channels will be the mean of custom defined number
of measurements, controlled from the LPF register (address 07 in eeprom). This data will be compensated
with corresponding offsets, stored in IROS and TOS registers and final offset free data will be stored in
IRDATA (for IR amplifier chain) and TDATA (for Temp amplifier chain) registers. The number of
measurements of which the averaging is taken can vary between 64 and 1024 (see ‘LPF register bit
functions’) and can be selected independently for both channels.
Linearisation
Linearisation proceeds in two steps and can be described by the picture below. In the first step the
ambient temperature is calculated from the measured signal at TINP-TINN. The system outputs a digital
value for the ambient temperature based on the calibration data. The value is stored in a dedicated
register and from there available for the DAC and PWM (Tambient-register, address 0Ah). The register
can also be read digitally by means of the SPI.
The system is developed to support different temperature sensors. 3 bits in the configuration register
(EEprom address 03h), determine the type of characteristic. NTC defines the first derivative of the
temperature sensor (NTC-type is logical 1, PTC-type is logical 0). SUBDEC and INCDEC define the
second derivative of the temperature sensor (
The result of the linearisation is stored as the 12 MSB’s of the Tambient-register (or TOUT-register). The
code 000h will correspond to Tamin, FFFh will correspond to Tamax. These two limits are determined by
calibration. Accordingly the output resolution will be
In the second step the value of the ambient temperature is combined with the measured signal at IRINP-
IRINN to obtain a calculated value for the so-called object temperature, based on the calibration data. The
value is stored in a dedicated register and from there available for the DAC and PWM (Tobject-register,
address 09h). The register can also be read digitally by means of the SPI.
The result of the linearisation is stored as the 12 MSB’s of the Tobject-register (or IROUT-register). The
MLX90313 Programmable IR sensor Interface
3901090313
The ASIC starts this procedure only after Power On Reset. The state machine reads all data in the
d
2
dT
Page 25
VRth
2
Ta
Programmable IR Sensor Interface
).
max Ta
4096
min
in K per LSB
MLX90313
Rev 1.0 21-July-2001