LED Backlight Support in CapSense – KBA221413

Version: **

 

Question: Does capsense support LED backlighting ?

 

Answer:


CapSense works well with LED backlighting. A hole can be made in the sensor pad. LEDs are available in a surface mount package that are designed for backlighting (LED shines light on to board). LED traces should be kept to the bottom side of the board. If more than one LED is mounted behind each button, ensure that the active sensing area of the button has not been negatively impacted by multiple backlight holes punched out of the board.

 

http://www.cypress.com/documentation/development-kitsboards/cy3280-mbr3-capsense-mbr3-evaluation-kit

 

There is a problem of Cross-Talk between LED traces and CapSense sensors when the LED traces are running parallel to the CapSense traces. It is recommended to have 4mm parallel distance in between the CapSense sensor traces and LED traces with hatched ground in between them. Also, we recommend you to put 1nF capacitor in parallel with LED to reduce the rise time of the LED that avoids cross talk. Please refer "Cross-talk solutions" section in the application note "Getting started with CapSense".

 

Related resources:

1. Getting started design guide

2. Backlight fading code examples