3 Replies Latest reply on Aug 2, 2019 9:02 AM by ShifangZ_26

    TCPM-managed VBUS voltage

    ArYi_4340101

      Hi, hopefully this is a fairly straightforward question. Reading through the TCPCI spec, I have come across this section:

       

      The TCPM shall issue COMMAND.SourceVbusHighVoltage to enable the TCPC to transition the VBUS

      source to a higher voltage level. VBUS_HV_TARGET is an optional register declared in

      DEVICE_CAPABILITIES_1 register. The target voltage for COMMAND.SourceVbusHighVoltage can be

      set in the VBUS_HV_TARGET register. Alternatively, the target voltage level for

      COMMAND.SourceVbusHighVoltage is set in a vendor defined manner.

       

      From this, we can conclude that the TCPC is expected to handle voltage transitions, and not the TCPM. My question is, since the TCPM is ultimately the one which is issuing the capabilities (system policy manager) and setting the VBUS_HV_TARGET register in the TCPC, is there any violation of the specification if it also performs the voltage transition? I'm asking because my implementation is a multi-port one, where any one of the ports may deliver PD voltages, but only a maximum of one may do so at any given point. That is, if one port is operating in HV (>5V), all remaining ports are restricted to 5V. I want to have the master configure the voltage, as I plan to use a single adjustable regulator to supply HV_VBUS, and the master directs this VBUS to the TCPC which is requesting it. The 5V rail on the other hand is a shared resource. I would naturally rather not put a dedicated regulator on every port as this adds unnecessary cost.

       

      Thanks in advance.

        • 1. Re: TCPM-managed VBUS voltage
          ShifangZ_26

          Hi ,

           

          The USB Type-C Port Controller Interface, TCPCI, is the interface between a USB Type-C Port Manager and a USB Type-C Port Controller. The goal of the USB Type-C Port Controller Interface (TCPCI) is to provide a defined interface between a TCPC and a TCPM in order to standardize and simplify USB Type-C Port Manager implementations.

           

          This is defines some registers for TCPM and TCPC, and it is more easy to use multiple TCPC with limit regulator. You are correct that it can be support to one regulator sever multiple TCPC and controlled by TCPM.

           

          Best Regards,

          Lisa

          • 2. Re: TCPM-managed VBUS voltage
            ArYi_4340101

            Hi Lisa,

             

            Thank you for your prompt response! So just to make absolutely clear what it is I'm trying to achieve, I've done a very oversimplified block diagram of the power interconnect.

             

            USB_C_TCPCI.png

            The TCPCI connections aren't shown to keep things from getting messy, but each TCPC is connected to the TCPM via a dedicated TCPCI. My aim is to have the TCPM in full control of transitioning the adjustable regulator's output voltage and steering the power to the intended TCPC via the HV_EN_x lines. When a TCPC requests a PDO, the TCPM writes the approved voltage to the TCPC's VBUS_HV_TARGET register and subsequently transitions the adjustable regulator voltage and directs it to the correct TCPC. The TCPC has no control over the voltage. Is there anything in the TCPCI or PD specs that prohibits an architecture like this?

             

            Thank you again in advance.

            • 3. Re: TCPM-managed VBUS voltage
              ShifangZ_26

              Hi ,

               

              You could try to follow this architecture, please kindly notice that CCGx from Cypress is not implement TCPCI spec in the SDK firmware currently.

               

              Best Regards,

              Lisa