MLX90320LFRLFR MELEXIS [Melexis Microelectronic Systems], MLX90320LFRLFR Datasheet - Page 15

• Manufacturer Part Number: MLX90320LFRLFR
• Description: Automotive small sensor interface
• Manufacturer: MELEXIS [Melexis Microelectronic Systems]

Equation 4
Explanation of parameters used in equation 4:
The
The fine offset calibration allows also a second order compensation of the temperature drift of the sensor offset.
The value of the fine offset is given by the formula:
Equation 5
Explanation of parameters used in equation 5:
The ALU computes the equation 5 with 12 bits but the result is truncated to 10 bits because the Offset DAC is a
10 bit DAC. When the MLX90320 is not able to compensate for the sensor offset drift with temperature, the fine
offset calibration parameters stored in EEPROM will lead to a FNOff
the MLX90320 output voltage will go into a fault band to indicate that the output voltage is not reliable anymore.
The MLX90320 also offers the possibility to set clamping levels to the output voltage. This allows creating fault
bands necessary to detect external and internal faults.
6.4.3 The output clamping levels
The output voltage is in application mode limited by a 3-bit programmable low and 3-bit programmable high
clamping-level. In order to set the clamping level in a high impedance node, the clamping is done at the FLT pin.
3901090320
Rev 004
FNOff
FNOff
V
5
DD
real
ana
log
FNOff
FNOff
T
temperature chain outputs 10 bits but 12 bits are stored (address 0 to 2 of the EEPROM). The MSB
must always be 0 and the other 11 bits are obtained from an averaging from the previous temperature
readings. This gives more accuracy to the output of the temperature chain. The T1 value used in
equation 5 is in the [0..1] range with an 11 bit resolution.
O
accurately the sensor offset at room temperature. 12 bits are stored (address 28 to 30 of the EEPROM)
but only the 10 first are used. The two MSB must be 0. The O
range with a 10 bit resolution.
O
12 bits are stored (address 24 to 26 of the EEPROM). The MSB is the sign bit (two’s complement): If
O1[11] = 1 then O1 is negative, if O1[11] = 0 then O1 is positive. The O1 value used in equation 5 is in
the [-2..2] range with an 11 bit resolution.
O
temperature. 12 bits are stored (address 20 to 22 of the EEPROM). The MSB is the sign bit (two’s
complement): If O2[11] = 1 then O2 is negative, if O2[11] = 0 then O2 is positive. The O2 value used in
equation 5 is in the [-2..2] range with an 11 bit resolution.
term of equation 3 and 4 are due to the ratio-metric behaviour of the fine and coarse offset DACs.
1
0
1
2
is the output of the temperature chain corresponding to the room temperature. The ADC of the
O
is the zero order fine offset coefficient (independent from the temperature) used to compensate
is the first order fine offset coefficient used to compensate the sensor offset drift with temperature.
is the second order fine offset coefficient used to compensate the sensor offset drift with
0
. 1
analog
real
136
O
is the value of the fine offset in the [0..1] range with a 10 bit resolution.
1
is the voltage at the output of the fine offset DAC.
FNOff
T
T
1
real
O
2
. 1
59
T
. 1
T
136
1
Page 15 of 32
2
V
5
DD
Automotive small sensor interface
real
0
value out of the [0..1] range. In this case
value used in equation 5 is in the [0..1]
MLX90320
Data Sheet
Mar/05