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USB TPD4S214 VBUS Detection

Other Parts Discussed in Thread: TPD4S214

Dear Sirs,

I am looking for using an A-type connector w/o ID pin for both host and peripheral operation modes.

I need to have the CPU aware of the VBUS direction, as follows:

1. If the external VBUS is active, the CPU shall get the external VBUS and realize that a host is connected, and that it shall operate as peripheral

2. If the ext VBUS is not active, the CPU shall drive it in preparation for a hypothetical slave to be attached.

Can the TPD4S214 operate in such mode?

How shall I connect it in the system?

Thanks,

 Avishai

  • Moving to ESD e2e Forum
  • Avishai,

    It is not clear to me how you plan to determine if the VBUS Pin is active or not. Please let me know.

    Regards,
  • Hi

    I planned to use the chip to replace the  pin so that it will sense if the vbus comes from outside or not and the cpu will turn onor off the internal 5v supply according ly.

    Avishai

  • Avishai,

    Can you provide a schematic please?

    Thanks,
  • Please see attached

    What I am trying to do is to notify the CPU if VBUS is active from the bus side, regardless of the ID state so that the CPU can deactivate the 5V_PS accordingly.

    I would like to build a state machine as follows:

    1. 5V_PS is always active, and the CPU is in host mode, wating for a peripheral to be connected.

    2. If a host is attached on the USB side, the CPU will get an indication that there is an external VBUS present. 

         The TPD4S214 -CPU can perform one of the following actions:

           A. The TPD4S214 will  open the external_VBUS to VOTG_IN switch, and the CPU will realize that it should act as peripheral

           B. The CPU will shut down the 5V_PS, the TPD4S214 will keep the external_VBUS to VOTG_IN switch in closed position, and the CPU will act as peripheral.

    3. Once the external_VBUS is detached, the TPD4S214 will notify the CPU and the system will switch to state one.

    I am looking for the following answers, please:

    1. Can this state machine be implemented (note: the ID pin is not connected. What should I use for default value for the TPD4S214)

    2. What is the control logic of the CPU in order to realize this functionality, based on FLT# and DET pins?

    3. Can 2-A  path be used? as if I use 2-B, the CPU response time may be too long even if interrupt is used.

    I hope it is understood.

    Thanks,

     Avishai

  • Hi,

    I think its more of USB (or power) than ESD issue.
    Thanks,
    Avishai
  • Elias,

    TPD4S214 only provides ESD protection to the ID pin, it is not used for any logic in the TPD4S214. The problem with trying to implement the TPD4S214's /FLT and DET pins for determining whether a host or peripheral is attached to VBUS can be shown thus:

    • With TPD4S214 Enabled:
      • With 5V_PS on, nothing attached:
        • /FLT = H
        • DET = H
      • With 5V_PS on, 5V attached:
        • /FLT = H
        • DET = H

    There is no way to distinguish between having a host attached or not to disable the 5V_PS. The DET pin only provides a detection scheme while the device is disabled. You need to have a way to enable/disable the device determined by a device being attached, this needs to be done without using TPD4S214 logic, usually by monitoring ID pin. By design, if ID indicates to CPU an attachment, DET can be used to determine if it is a host or peripheral. Without having some way to detect an attachment (TPD4S214 can only DET an attachment of a HOST but not a peripheral, and only when TPD4S214 is disabled) of a peripheral, your scenario will not work.

    Regards,