2 Replies Latest reply on Mar 2, 2020 7:28 AM by AdBi_4635021

    CYPD3177 Safe_PWR_EN Requirement

    AdBi_4635021

      Hello,

       

      I am designing in a CYPD3177 for a 30W (12V @ 2.5A max.) USB PD solution integrating with the BQ25703A Charge controller.  I have set up the BCR to accept 5V as VBUS minimum, and I wanted to know if the Safe_PWR_En is required if I am OK with 5V on VBUS as a primary voltage or can I leave the pin disconnected? If the Safe_PWR is required, what is the intended method to effectively merge the two power lines then to deliver power to my system and battery if I do use this line? Is safe power only intended to alert or indicate a problem? I haven't seen much in the datasheets or evaluation guides that talk about this, from the schematic of the evaluation kit the safe 5V does not go to main system power.   Any guidance you can offer to this would be much appreciated.

        • 1. Re: CYPD3177 Safe_PWR_EN Requirement
          ShifangZ_26

          Hi ,

           

          The Safe_PWR_EN will enable to LOW (open the FET on the path) with three conditions:

          1. Only Safe5V.

          2. Cap_mismatch bit is asserted in RDO.

          3. Voltage on VBUS mismatch sink PDO's voltage operation range. Or Current on VBUS mismatch sink PDO's current operation range.

           

          If your design is not take care above three conditions, you can let is floating.

           

          Best Regards,

          Lisa

          • 2. Re: CYPD3177 Safe_PWR_EN Requirement
            AdBi_4635021

            HI Lisa,

             

            When you mention the current mismatch, I can set the maximum current limit via the coarse and fine resistor dividers, but if I can accept 5V as my minimum bus voltage and I connect a charger that is not capable of PD will I still get the 5V @ 500mA standard coming off a USB port or will I get a shutoff of the system where onyl 5V is available.  Really what I'm asking is can I use non PD chargers with standard 5V output only as long as my VBus minimum is 5V?