MLX90320_12 Datasheet, PDF (24/33 Pages) Melexis Microelectronic Systems – Automotive sensor interface

MLX90320
Automotive sensor interface
8 Typical applications circuits
8.1 Ratio-metric mode with use of external temperature sensor.
The external temperature sensor is needed for applications where the temperature surrounding the customer
sensor is different from the temperature surrounding the MLX90320. In the ratio-metric application mode, to keep
the accuracy, the same supply should be used for the customer sensor, the MLX90320 and an ADC that makes
the digital conversion of the analog output signal.
The capacitor C1 on the output is typical 47nF. Range: 0 – 100nF.
The capacitor C2 on the FLT pin is optional. Typical value = 10nF. Range: 0 – 100nF. It is used to decrease the
noise and set the bandwidth of the system.
An estimation of the MLX90320 bandwidth versus the capacitor at the FLT pin is given by the formula:
BW_−3dB
=
2π
1
× 2kΩ × C_FLT
The decoupling capacitors C3 between the supply and the ground and C4 between output and supply have a
typical value of 47nF.
The external resistor R1 is placed between the TMP pin and the supply. It is used as an external temperature
sensor. The external temperature sensor could be of type Panasonic, ERAS15J103V (R1 = 10k +/- 5%, TCR =
1500ppm/degC +/- 200ppm/degC) for the -40ºC to 140ºC temperature range. If the ground broken wire detection
is required the load has to be a pull up resistor R2 with a typical value of 2.8kOhm that can be placed at the
90320 side or at the ECU side.
3901090320
Rev 007
Page 24 of 33
Data Sheet
Feb/12