MLX90320 Datasheet, PDF (16/32 Pages) Melexis Microelectronic Systems – Automotive small sensor interface

MLX90320
Automotive small sensor interface
The FLT pin voltage is compared with the DA-converted value of CLAMPLOWdig and CLAMPHIGHdig. If the FLT
pin voltage is greater than the DA-converted value of CLAMPHIGHdig, then this last voltage is used as input of the
output stage. If the FLT pin voltage is smaller than the DA-converted value of CLAMPLOWdig, then this last
voltage is used as input of the output stage. The transition from in range mode to clamping mode and vice versa
takes place without overshoot.
The output pin low clamping level can be calculated by the formula :
Equation 6
( ) Vout_lowclamp = Low_clamp + Clamplow_dig × 0.013 × V_DD
Explanation of parameters used in equation 6:
Vout_lowclamp is the output pin low clamping voltage.
Low_clamp is the lowest clamp level and has a typical value of 4% +/-1% variation from sample to sample.
Clamplow_dig is the decimal value (range of 0 to 7) of the low clamp level stored in EEPROM at the
address 19.
The output pin high clamp level can be calculated by the formula:
Equation 7
( ( ) ) Vout_highclamp = High_clamp + Clamphigh_dig − 7 × 0.013 ×V_DD
Explanation of parameters used in equation 7:
Vout_highclamp is the output pin high clamping voltage.
High_clamp is the highest clamp level and has a typical value of 96% +/-1% variation from sample to
sample.
Clamphigh_dig is the decimal value (range of 0 to 7) of the high clamp level stored in EEPROM at the
address 19 and 23.
6.4.4 The Faults detection
As mentioned before, a reliable memory is obtained by storing each bit three times in the EEPROM and
by using parity check to detect data corruption and majority voting when accessing the data. Thanks to the setting
of output clamping levels, the MLX90320 output voltage goes to the fault bands to point out that a fault occurred
and that the output signal is unreliable. The MLX90320 contains circuitry which detects and diagnoses the
following faults with the loads as described and specified in and under the conditions of paragraph 5:
Internal faults
Fault detection of INP and INM have the levels at 1.5 and 3.5 Volt (with 5 Volt supply).
• INP and/or INM open
• Sensing element supply open
• Short-circuit of INP and/or INM with VDD
• Short-circuit of INP and/or INM with GND
• Short-circuit of FLT with VDD or GND
3901090320
Rev 004
Page 16 of 32
Data Sheet
Mar/05