The following procedure should be followed for determining the sensor characteristics:
- Determine the diameter of coil (dcoil), which should be 3 times larger than the desired switching distance (dswitch)
- Determine the desired frequency (ƒSENSOR) which should be between 300 kHz and 19 MHz
- Calculate the range of allowable inductance from the following equation:
Equation 7. where:
- LSENSOR is the inductance of the LSENSE coil or LREF coil
- ISENSOR_MAX is given in the electrical table
- Calculate the externally placed sensor capacitor:
Equation 8. where:
- CBOARD is the parasitic capacitance introduced by the board layout (~4 pF for good layout)
- CIN_COM is the parasitic pin capacitance of LCOM specified as 12 pF in the electrical table