MLX90320_12 Datasheet, PDF (17/33 Pages) Melexis Microelectronic Systems – Automotive sensor interface

MLX90320
Automotive sensor interface
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.
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%Vdd.
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%Vdd.
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
The MLX90320 will detect a Fault condition when INP and/or INM have a level outside of the 1.5 to 3.5 Volt range
(with 5 Volt supply).The MLX90320 will also detect the following faults:
• INP and/or INM open
• Sensing element supply open
3901090320
Rev 007
Page 17 of 33
Data Sheet
Feb/12