4 Replies Latest reply on Jul 15, 2020 7:12 AM by JeHi_4734781

    CY4533 EZ-PD BCR Evaluation Kit 800 Hz Sawtooth Wave

    JeHi_4734781

      Hello,

       

      I am using the CY4533 EZ-PD BCR Evaluation Kit for a work project exploring the use of USB C power in place of more common power supplies. While using the CY4533 (set to 5V), I measured the power output and noticed a sawtooth wave with a frequency of around 800 Hz. I am trying to identify the cause of that specific wave, which is too slow to be caused by the switching frequency of the USB C power supply that I am using to power the CY4533 kit. Is this 800 Hz sawtooth wave a product of the CY4533 EZ-PD BCR Evaluation Kit or is it coming from somewhere else? If it is not coming from the CY4533, where could it be coming from? Thanks!

        • 1. Re: CY4533 EZ-PD BCR Evaluation Kit 800 Hz Sawtooth Wave
          SananyaM_56

          Hello,

           

          Could you please let us know how you are providing VBUS from your source and at what voltage? Please also attach a snippet of the waveform you are seeing at the DC output of the kit.

           

          Best Regards,
          Sananya

          • 2. Re: CY4533 EZ-PD BCR Evaluation Kit 800 Hz Sawtooth Wave
            JeHi_4734781

            I have a RAVPOWER PD Pioneer 90W GaN Tech Type C Wall Charger plugged into the outlet. That power supply can provide 5, 9, 12, 15, or 20 volts. That power supply is connected via a USB C cable to the CY4533 chip. The chip is set to 5 V, and I have the chip connected to a resistor and LED in series to act as my load. When I measure the output signal with an oscilloscope, this is what I see.

             

            IMG_20200710_133952304.jpg

            DS1Z_QuickPrint19.png

            DS1Z_QuickPrint20.png

            This sawtooth wave is a little less than 800 Hz. From what I know, power supplies like the one I am using operate at a couple of hundred kHz, so I am not sure what is causing the output to look like it does. Is it because of the CY4533 kit or is it actually coming from my power supply?

            • 3. Re: CY4533 EZ-PD BCR Evaluation Kit 800 Hz Sawtooth Wave
              SananyaM_56

              Hello,

               

              Thanks for the details. From the waveform, I couldnt understand if you have an offset of 5V on Vout, could you please measure the DC voltage level on the kit using a multimeter? If yes, could you please try setting the BCR to any other voltage such as 9V and confirm if you see the same waveform?

              As you mentioned, and from the FFT waveform, it doesnt seem like the power supply is causing this. But to confirm, can you please use the same charger with other sink devices and check the waveform?

               

              Best Regards,

              Sananya

              • 4. Re: CY4533 EZ-PD BCR Evaluation Kit 800 Hz Sawtooth Wave
                JeHi_4734781

                I have been doing some more research on USB-C and I was able to take a USB-C cable, cut it in half, and use a pull-up resistor to allow power output through the cable even though it wasn't connected to a load (CY4533 kit). With that cable that was only connected to my power supply, I measured the voltage output and saw the same waveform, which leads me to believe that it is in fact my power supply giving of the waveform that I described earlier. Thank you for your responses, and I think that I have the answer I need.