CapSense sensitivity difference

[JulB]

In a design with PSOC4 chip with 4 different sensors that are routed in a similar way (trying to respect as much as possible the recommendation rules), we are experiencing differences between sensors sensitivity. Trying to solve this issue, we did not reach good enough results  using the tuning process that appears in the guidelines.

However, we have noticed that the default sensitivity value (normally too high by default in our case) can be reduced adding a pull up resistor closed to the sensor (between the sensor and the recommended serial resistor).

We are wondering if anybody in the community has experienced such sensititvity problems than cannot be adjusted by tuning process ? and if somebody has an electrical reason why this pull-up resistor is lowering the default sensitivity level of a sensor?

Any help on this will be appreciated.

[Arpit_S]

Hi

Please let me know what do you mean by sensitivity here? is it the case that under No Touch condition you're observing difference count? or Simply the noise seen in the raw counts is high?
please guide which development environment are you using? 

Also,  Are you using IDAC Sourcing Mode or IDAC Sinking Mode?

Thanks and Regards

Arpit Srivastav

[Arpit_S · Accepted solution]

Hi,

We do not recommend using pull-up resistors with CapSense Sensors.

For more details on Manual Tuning, you can refer to https://github.com/Infineon/mtb-example-psoc4-capsense-csd-button-tuning

In order get a head-start in Manual Tuning of CapSense. You can always first enable Smart Sense which is CapSense auto-tuning algorithm and can get the values of different parameters. Then you can switch back to Manual tuning and fine tune the CapSense sensors as per you requirement. Auto Calibration of IDAC could also be used by you while using Manual Tuning

In order to reduce the sensitivity of the CapSense Sensors, You can reduce the Scan resolution and Also, you can reduce the gain of the IDAC (When Auto IDAC Calibration is not enabled). For more information refer https://github.com/Infineon/mtb-example-psoc4-capsense-csd-button-tuning

Thanks & Regards
Arpit Srivastav