use the following procedures to calculate thresholds to program to the TIC12400-Q1 for proper switch detection:

1. Calculate the equivalent resistance values at different switch states, taking into account R_DIRT and the 8% resistance variation.
2. Estimate the voltage established when wetting current flows through the switch by utilizing the relationship V_INX = R_{SW_EQU} × I_{WETT_ACT}, where R_{SW_EQU} is the equivalent switch resistance value and I_{WETT_ACT} is the actual wetting current flowing through the switch. The 5 mA wetting current setting is selected in this design, because it best uses the dynamic range of the ADC (from 0 to 6 V). The wetting current, however, can vary depending on manufacturing process variation and operating temperature, and needs to be taken into account. Referring to the electrical table of the TIC12400-Q1 and assuming enough headroom for the current source (CSO) to operate, the 5 mA wetting current setting produces current ranging between 4.5 mA and 5.5 mA (for V_S – IN_X ≥ 3 V condition). The voltage established on the TIC12400-Q1 input pin (V_INX) can be calculated accordingly.

3. Take the ground shift non-ideality into account. As defined in Section 9.3.1, the ground shift can vary between ±1 V. Therefore, effectively, the actual voltage seen at the TIC12400-Q1 can also vary up to ±1 V.
4. Convert the voltage established on the INx pin into equivalent ADC code. The full-scale range of the 10-bit ADC is from 0 V to 6 V, with 6 V corresponding to the max code of 1023. Therefore, the ADC code spread for each of the 3 different switch states can be calculated accordingly.
5. After the ADC code spread for each switch state is calculated, the detection threshold can be chosen to be the mid-point between the upper and lower codes of two neighboring states to give best margin for detection.