Prevent the change of CapSense raw value

[andycheng]

Hello, further to a question I asked (https://community.cypress.com/t5/PSoC-4-MCU/Reversing-proxmity-sensing/m-p/270896#M39101).  After weeks of testing, I found that the CapSense values are very sensitive to the voltage of the power supply.  At 3.8v the raw value could be 8000, while 3.7v could be 1000 and even lower when approaching 3.6v. 

Since my system runs off a 3.8v battery as the power supply (connected to VDD of CY8C4245 directly). Is there any way to get a stable value from CapSense even the supply voltage drop a little? Like an internal regulator or something?  

Thank you!

[Hari · Accepted solution]

Hi @andycheng 

Unfortunately, there is no way around this. You need to make sure that the supply coming to the VDDA pin of the micro is stable at 3.3V externally. CapSense supports compensating only for 50mV change in VDDA and any higher change will directly affect CapSense operation. 

You need to use a voltage regulator externally to get the supply to a stable range.

Best regards, 
Hari

[andycheng]

Hi Hari,

Thank you very much for the reply! Now putting in a regulator.

Andy