4 Replies Latest reply on Jan 22, 2020 2:59 AM by OlEr_1999891

    UVP when CYPD3120 is powered via VCONN?

    OlEr_1999891

      Hi!

       

      We are making a "USB-C to DC" adapter that should support up to 20V. We don't want to power the CYPD3120 thru VBUS since we feel that using the internal LDO generates too much heat when going from 20V VBUS. Instead, we planned to power the CCG3 thru VCONN, that's why we used the CYPD3120.

       

      We had a discussion on the design here: Force VCONN continuously on

       

      We have the sample up and running now and it sources power via VCONN correctly, but we have the following problem:

       

      1. When powering the chip normally thru VBUS power and connected to VBUS_C Pin 31 everything works well, but again, this is not the setup we want.

      2. When powering the chip from VCONN (5V) to VBUS_C Pin 31, everything works but when the higher voltage is provided the chip resets with a HARD RESET. We believe this is because the VBUS level stays at 5V instead of the 20V that was expected and an UV condition is triggered.

      3. When we power the chip from VCONN (5V) to VSYS (Pin 20), the chip starts (LED blinking), but USB-FS subsystem and CC signalling doesn't start. We are guessing the might have something todo with that VDDD/VDDIO is now 5V instead of 3.3 as it is when system is powered vi VBUS (Pin 31) and the internal LDO. Or?

       

      For 2, we have disabled VBUS_UVP_ENABLE and VBUS_OVP_ENABLE

       

      Have attached schematics and the log from point 2 above.

       

      Cheers

      Olof

        • 1. Re: UVP when CYPD3120 is powered via VCONN?
          ShifangZ_26

          Hi Olof,

           

          1. You are using CCG3 for PD negotiation, but you are not feed VBUS voltage to CCG3 for VBUS monitor.

          2. The UVP is not because the thread of UVP is 5V, the root cause is: the PD contract is 20V already (The PS_RDY was sent by Type-C power source.) on VBUS, and CCG3 have acked with GOODCRC, but, the VBUS MONITOR cannot monitor the VBUS voltage timely.

          3. CCG3 can support internal VBUS monitor and external VBUS monitor, the firmware use internal monitor by default. You need wire VBUS of Type-C to VBUS of CCG3 to achieve internal VBUS monitor. Otherwise, you need select external VBUS monitor with GPIO for CCG3.

           

          Best Regards,

          Lisa

          • 2. Re: UVP when CYPD3120 is powered via VCONN?
            OlEr_1999891

            Hi Lisa!

             

            So, if I understand this correctly. if we want to power the chip via VCONN at 5V instead of Type-C VBUS at 20V (which we rather not), while still be able to negotate VBUS up to 20V, we need to use an external VBUS monitor (similar to the CCG4 design I guess)? Even if we disable OVP/UVP in the firmware?

             

            Want I don't understand is why CCG3 doesn't work correctly when powered via 5V via VSYS (no USB device or CC-signalling).

             

            If it had worked to power via VSYS, would we still need to use the external voltage monitor for VBUS?

             

            What happens if VBUS (up to 20V) is connected to Pin 31 and VCONN (5V) is connected to VSYS at the same time? How does the internal power switch function work in the CCG3?

             

            Cheers

            Olof

            • 3. Re: UVP when CYPD3120 is powered via VCONN?
              ShifangZ_26

              Hi Olof,

               

              The root cause of your case is:

              You are not feed VBUS voltage to CCG3 for VBUS monitor.

               

              The way to fix is:

              One way, you can use CCG3 internal monitor for VBUS, you just need wire VBUS of Type-C interface to VBUS of CCG3. This hardware will helps you can use the default firmware.

              The other way, you need select external VBUS monitor with GPIO for CCG3.

               

              For your questions:

              1. if we want to power the chip via VCONN at 5V instead of Type-C VBUS at 20V (which we rather not), while still be able to negotate VBUS up to 20V, we need to use an external VBUS monitor (similar to the CCG4 design I guess)?

              Lisa>> You need VBUS monitor whatever it is internal VBUS monitor or external VBUS monitor.

               

              Even if we disable OVP/UVP in the firmware?

              Lisa>> Yes.

               

              2. Want I don't understand is why CCG3 doesn't work correctly when powered via 5V via VSYS (no USB device or CC-signalling).

              >> If you only powered VSYS, it shall be working. We have confirmed with CY4531 board. The VBUS or VCONN shall be wire to Type-C interface, since the attach and detach event is replied on this.

               

              3. If it had worked to power via VSYS, would we still need to use the external voltage monitor for VBUS?

              >> You need VBUS monitor whatever it is internal VBUS monitor or external VBUS monitor.

               

              4. What happens if VBUS (up to 20V) is connected to Pin 31 and VCONN (5V) is connected to VSYS at the same time? How does the internal power switch function work in the CCG3?

              >> The CCG3 will disable VBUS regulator with slightly delay, since the VSYS threshold is 3.0V. 

               

              Best Regards,

              Lisa

              • 4. Re: UVP when CYPD3120 is powered via VCONN?
                OlEr_1999891

                Hi Lisa!

                 

                Thanks for all the answers. Seems like the best solution is to attach both VCONN to VSYS and VBUS to VBUS on CCG3. Then we use the internal voltage monitor for VBUS but once the VCONN power is on, the chip will source power from VCONN and disable the VBUS regulator and we remove the heat problem.

                 

                Kind Regards

                Olof