1 Reply Latest reply on Mar 12, 2015 3:55 PM by user_78878863

    PCB schematic for sensor controlling application

    mengxuan.ma

       Hi all, 

         

      Greetings,

         

      I'm using PSoC 5LP to implement a sensor controlling application. The system was tested on Development kit and I recently want to make my own board.  

         

      Basically, the functions are

         

      1) getting 32 sensors outputs (32 GPIOs are needed)

         

      2) communication with PC using USB

         

      3) programming using Miniprog

         

      4) 5V power.

         

      I've designed my system and schematic is attached here. However, I feel confused about power supply. From my understanding, I need to support 3 domains' power: analog, digital and I/O pins.  

         

      My questions are

         

      a.Is that corret in my schematic using one 5 volt power supply for all domains?  

         

      b. Can I just use 0 ohm resisters to seperate them as Development kit does? How does it work?

         

      c. Can I connect GND , Vssa, Vssd together?

         

      Also, I'll really appreciate any suggestions from you about this schematic. 

         

      Thanks,

        • 1. Re: PCB schematic for sensor controlling application
          user_78878863

          There is a nice application note: PSoC5LP hardware design considerations: http://www.cypress.com/?docID=49353

             

          It should probably answer your questions. Make sure you also read the PSoC5LP Architecture TRM (technical reference manual) and the family data sheet for your device - they answer most of th questions you have.

             

          In short form: yes, powering everything by 5V is OK. If youcare about analog performance, separate analog and digital ground planes (and look at AN57821: http://www.cypress.com/?rid=39677 ). decouple the analog and digital voltage rails with ferrite beads. And make sure each supply pin pair has its own decoupling capü.

             

          I'm not sure how good the LM340 is for analog applications, maybe you can use a separate regulator for the analog voltage (one with low noise floor).

             

          Looking at the schematic I cannot see any glaring mistakes so far.