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CAPSENSE™ & MagSense Forum Discussions

Ashwatthama
Level 1
Level 1
First like given First question asked Welcome!

I have designed a keypad PCB but due to space constraint I have doubts regarding Proximity sensor affecting Buttons or vice versa.

Also I have doubt regarding Ground / Shield flood, I want shield flood on front side for detecting false touch but I am confused, if I should flood the backside with shield or ground ?

Chip in use = CY8CMBR3116

PCB dimensions = 80mm (h) * 58mm (w)

Button to button distance (center to center) = 18mm

Proximity sensor track to button (border to border) = 0.6 to 1mm

Proximity and ground ring around it have values as specified in design toolbox

Please comment if there is something wrong.

Since I am a novice any tips to improve the design will be appreciated.

Thank you in advance.

keypad.PNG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

@PandaS @Hari 

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1 Reply
Srivastav
Moderator
Moderator
Moderator
100 replies posted 25 likes received 100 sign-ins

Hi @Ashwatthama ,

Please refer to below mentioned tips/guidelines:

We would recommend you to check the Cp of the CapSense sensors. It must be in the supported range. Please refer to https://www.infineon.com/dgdl/Infineon-AN85951_PSoC_4_and_PSoC_6_MCU_CapSense_Design_Guide-Applicati...  Table 2 for more details.
To calculate the Cp of the sensor use the Built-in Self-Test (BIST) APIs documented in the Component
datasheet. These functions allow you to read out an estimate of the sensor parasitic capacitance. You can
also confirm this reading independently with an LCR meter.

You can also refer to https://github.com/Infineon/mtb-example-psoc4-msc-capsense-csd-button-tuning/blob/master/main.c 

We would recommend not to have any solid GND pour close or beneath the CapSense Sensors.

We would recommend you to have Ground Hatch of 25% on the top layer (7 mil line, 45 mil spacing) 17% on the bottom layer (7 mil line, 70 mil spacing). For more details refer to https://www.infineon.com/dgdl/Infineon-AN85951_PSoC_4_and_PSoC_6_MCU_CapSense_Design_Guide-Applicati... Hatch GND has to be in top layer as well as pointed by the design guide.

Also please follow all the recommendations given in CapSense MBR design guide https://www.infineon.com/dgdl/Infineon-AN90071_CY8CMBR3xxx_CapSense(R)_Design_Guide-ApplicationNotes... as well as CapSense Design guide https://www.infineon.com/dgdl/Infineon-AN85951_PSoC_4_and_PSoC_6_MCU_CapSense_Design_Guide-Applicati... 

 

Please note that Proximity sensor Parasitic Capacitance (CP) range is between 8pF - 45pF. Please refer to https://www.infineon.com/dgdl/Infineon-AN90071_CY8CMBR3xxx_CapSense(R)_Design_Guide-ApplicationNotes... Page Number 30.

 

You can also make use of  SNS_CP_HIGH register and DEBUG_CP. Please refer to https://www.infineon.com/dgdl/Infineon-CY8CMBR3xxx_CapSense_Express_Controllers_Registers_TRM-Additi... Page No. 121, 161 respectively

Thanks!
Kind regards

Arpit Srivastav