1 Reply Latest reply on Nov 26, 2017 5:29 PM by rzzh

    CY8CMBR3108 proximity design

    ludovic.dufourg_2887926

      Hello,

       

      I want to create a pcb with CY8CMBR3108 and some proximity sensors
      I was planning in following the same design as the CY8CKIT-024, with modification, and hace some questions:

      -Is it possible to achieve the same fonctionnality as the kit when plugged on a CY8CKIT-042 with a CY8CMBR3108 connected through I2C to a microcontroller?

      -Can I have the components on the same side as the sensors, maybe with a ground fill between sensors and components, if so, what hatched ground should I use?

      -Can I place the components at the center of the PCB, with the sensors "surrounding"

      -After reading the datasheet for the 024 kit, I am not sure about the connection of the ground/shield trace, it seems to be connected to the smaller copper loop, and the hatched pattern at the bottom of the card. If I want this kind of shield, the hatched pattern must not be connected to the ground, am I right? Do I have to connect it to the hatched pattern on the side of the components & sensors?

       

      Thanks in advance

        • 1. Re: CY8CMBR3108 proximity design
          rzzh

          Hi ludovic,

           

          I want to create a pcb with CY8CMBR3108 and some proximity sensors

          -Is it possible to achieve the same fonctionnality as the kit when plugged on a CY8CKIT-042 with a CY8CMBR3108 connected through I2C to a microcontroller?

          --Yes. The proximity performance is decided by MBR3 hardware design, its software configuration and environment, not related with which MCU and communication protocol you are using(not including wireless protocol, for wireless, there is risk of EMC for capsense)

           

          -Can I have the components on the same side as the sensors, maybe with a ground fill between sensors and components, if so, what hatched ground should I use?

          -- Yes, you can. But it is recommended to keep them as far as possible away with sensors area. For proximity application, hatch ground is not recommended to use, as any ground will decrease proximity distance. Using shield or clearance is better.

           

          -Can I place the components at the center of the PCB, with the sensors "surrounding"

          -- Yes. You can, but not the best practice...Some ON/OFF, high speed digital, power circuits may 'hurt' proximity performance. If this kind of layout must be used, Sensor-clearance-Shield-clearance-GND-Other components are recommended to 'isolate' Capsense and other components.

           

          -After reading the datasheet for the 024 kit, I am not sure about the connection of the ground/shield trace, it seems to be connected to the smaller copper loop, and the hatched pattern at the bottom of the card. If I want this kind of shield, the hatched pattern must not be connected to the ground, am I right? Do I have to connect it to the hatched pattern on the side of the components & sensors?

          -- Right. Shield and GND must not be connected together.

          -- Not 'have to'. If without shield, you can get enough proximity distance, shield hatch can be removed. But GND may decrease proximity distance obviously. Either clearance or shield hatch is recommended for sensors layer(not considering other components in...).  Shield is also a special sensor. If it is too close with GND, its driver strength will be decreased. If shield is too close with some digital parts/noise source, it will be injected with more noise...Recommend to refer to CapSense Design Guide:

          AN85951 - PSoC® 4 and PSoC Analog Coprocessor CapSense® Design Guide | Cypress Semiconductor

           

           

          Thanks,

          Ryan