3 Replies Latest reply on May 16, 2020 3:33 AM by SananyaM_56

    How does the CYPD3177 EZ-PD™ BCR treat legacy and "USB-C only" charging?

    MaCa_4691661

      If I plug in a CYPD3177 to a legacy Type-A charger, using a USB-A to USB-C cable, how does the CYPD3177 behave?

       

       

      1. Does it attempt to verify current capability using something like BC 1.2 and the datalines?

       

       

      2. Or does it simply ignore the "Power Delivery" aspect of the design and simply pass the "legacy" 5 V through to the system?

       

       

      3. Does the undervoltage detection still work with legacy charging: "FAULT is driven to Logic HIGH if ... Voltage on VBUS_IN is 20% below the VBUS_MIN setting or 20% above the VBUS_MAX setting".

       

       

      The reason I ask is because I have a design where legacy Type-A 2 A chargers are sufficient to power the design. I want to know what would happen if the user was to use these kind of chargers.

       

       

      Similarly, how does the device act when connected to a USB-C only device(i.e. no PD functionality)? I similarly would like to know what would happen if the user was to use a 5 V  @ 3 A non-PD USB-C charger.

        • 1. Re: How does the CYPD3177 EZ-PD™ BCR treat legacy and "USB-C only" charging?
          SananyaM_56

          Hello,

           

          Yes, it will fall back to legacy charging and check for the current capability on the DP/DM lines. The fault detection should work based on the VBUS_MIN and VBUS_MAX setting so in this case 5V can be set.

           

          If you connect to only a Type-C capable charger, it will pass 5V and not have any PD negotiation with the device.

           

          Best Regards,
          Sananya

          • 2. Re: How does the CYPD3177 EZ-PD™ BCR treat legacy and "USB-C only" charging?
            MaRe_4701411

            Hello,

            I have a related problem with the BCR.  The system we are designing requires 20W+, so I am hoping to use the FAULT pin to detect when a user tries to use an under-powered USB charger, including type-C non-PD chargers.  I have swapped out resistors on the voltage dividers to read as follows:

            VBUS_MAX: 5k/NC (pull-up/pull-down), unchanged

            VBUS_MIN: 5k/1k (9V min)

            ISNK_COARSE: 5k/5k (3A)

            ISNK_FINE: NC/5k (0mA)

             

            Test points were read on a multimeter (text is pretty small, so I hope I'm hitting the right test points):

            TP7: 3.389V (VBUS_MAX)

            TP8: 0.557V (VBUS_MIN)

            TP6: 1.696V (ISNK_COARSE)

            TP9: 0V (ISNK_FINE)

             

            However, when I try to use a standard type-C connector, the FAULT LED does not light up, nor does the voltage on TP3 is high (3.4V).  I expected the FAULT pin to alert since my minimum voltage was set to 9V, but it does not.  I get 4.8V on DC_OUT and 0V on SAFE_5V_OUT.

             

            What am I missing?

             

            I have been able to probe the I2C addresses outline in the HPI specification.  For example, with the standard type-C adapter, the Current PDO and Current RDO (0x1010 and 0x1014) both read all zeros.

             

            When I use a PD charger, i get 15V on DC_OUT,  0V on SAFE_5V_OUT.  The current RDO reads 0x0004B12C, and the current PDO reads 0x4004B12C.

             

            Again, what am I missing?

             

            Any advice you can provide would be greatly appreciated.

             

            Regards,
            Matt

            • 3. Re: How does the CYPD3177 EZ-PD™ BCR treat legacy and "USB-C only" charging?
              SananyaM_56

              Hello Matt,

               

              Please follow up on the thread https://community.cypress.com/message/235177?et=watches.email.thread#235177 since its on the same query.

               

              Best Regards,

              Sananya