MBR3 device can detect (tested) up to 30 cm distance with the ALP filter enabled.
If you want to detect up to 30 cm, then you need to have a minimum of 15 cm loop diagonal with the ALP filter enabled.
The Cp of the sensor needs to be between 5 to 45 pF.
Can you measure the Cp of the sensor using ez-click and check if it between the range 5 to 45 pF?
It may not be possible to detect 50 cm using CapSense devices. (Not validated)
The proximity distance increases if the Cp of the sensor decreases. Therefore it is recommended to use make sure that there is no conductive floating objects near the proximity sensor. There should not be any ground near the sensor (except a ground ring around the sensor for noise immunity). It is recommended to drive shield for the hatch pattern (if any) to reduce Cp of the sensor.
Since MBR3 uses SmartSense, you may not be able to use this device, if the Cp is greater than 45 pF.
We highly recommend using latest gen CapSense devices such PSoC 4000S, 4100S and 4100S plus, that supports upto 200 pF parasitic capacitance. Since ALP filter support is available only for older capsense components (v2.0), so you have to use this for higher distances.
The MBR3 device will set the no touch raw counts (called baselines) to 85 % of the max raw count 0.85 * 2^16 (~55705 +/- 10%). If you do not observe this, then it means the auto-calibration has failed. This could mean the sensor Cp is too high.