MLX16305 Datasheet, PDF (25/29 Pages) Melexis Microelectronic Systems – Interlock switch sensor interface IC

MLX16305
Interlock switch sensor interface IC
Î VMEASout (OFF) = [ 0.477, 1.552 ] V
In a similar way the corner values for the ON condition can be calculated to be
Î Vmeasout (ON)
= [ 1. 076 , 2.507 ] V
Therefore all Vmeasout values are within [0.05, Vref]
STEP 2:
The actual measurement value is the subtraction of Vmeasout (Isense) - Vmeasout (Ioffset).
In voltage that would correspond to
Î V (OFF) = VMEASout (OFF) - VMEASout (Ioffset) = [ 0.430, 0.607 ] V
Î V (ON) = VMEASout (ON) - VMEASout (Ioffset) = [ 1.028, 1.562 ] V
Therefore the 2 states can be clearly distinguished.
Furthermore depending on the definition of an ‘open wire’ or a ‘short to ground’ similar values can be
calculated to further distinguish failure mode conditions.
16.2. Resistive Switches
Resistive switches are essentially also acting like current modulated switches. Therefore diagnostics are
done in the same manner.
The MLX16305 can supply plenty of cleaning current to allow the use of low cost switches.
Nevertheless, aging may cause drift of the contact resistance values over life. The high accuracy of the
MLX16305 allows tracking of such a case and early triggering of eminent failures.
16.3. 2-wire analog sensors
Industrial sensors and sensor interfaces like the MLX90308 have a 4 to 20 mA current range. The
MLX16305 can be used to sequentially read them out.
The offset and any non-linearity induced by the 16305 in current mode can be calibrated together with the
sensor in production such that a VMEASOUT value is directly related to the sensor output.
3901016305
Rev. 005
Page 25 of 29
Data Sheet
Oct/06