MTCH101 - metal housing / button sensitivity
In my solution the MTCH101 is used as a main button (only one button for device). The device is powered by Li-Ion cell. The MTCH-101 is supplied by 2,8 V with capacitors 100 nF and 10 uF placed near to the chip.
The pad sensor on PCB has a round shape of 7 mm diameter. According to the datasheet the pad sensor on PCB is divide for two similar pieces. One pieces is connected to the MTCH and the second is connected to the ground. Around the sensor the pcb is free from the gnd.
The PCB is placed in the metal housing (aluminium). The distance between housing and the pad sensor on PCB is 0.2 mm. The MTCH should detect bending of the metal housing.
The metal housing is connected to the ground (gnd from cell).
I have got problem with low sensitivity of the button. Especially if the button is pushed for few seconds. If the housing is pressed then MTCH detect this but if the housing is pressed for longer time then the MTCH will lost the signal.
What is the reason of this situation? In addition I have detected that if the housing and gnd on the pcb is connected to the gnd from power supplier or usb cable the sensitivity of the MTCH works much better.