VBUS Bypass Capacitor Recommendation for Type-C Cable and Type-C to Legacy Cable/Adapter Assemblies – KBA97270

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Question: What is the recommendation for bypass capacitors on VBUS pins for Type-C Cables and Type-C to legacy cable/adapter assemblies?

 

Answer:

Follow these to place the bypass capacitors on VBUS pins while designing the Type-C cables and Type-C to legacy cable/adapter:

  •   For USB Full featured Type-C cables, according to USB Type-C Specification, all VBUS pins (A4, A9, B4, B9 pins of the Type-C plug) should be connected together within the Type-C connector. A 10 nF bypass capacitor (minimum voltage rating of 30 V for cable assemblies supporting USB PD) must be connected between the VBUS pin and the ground pin in the USB Type-C plug end of the cable. The bypass capacitor should be placed close to the power supply pad. Note that the bypass capacitors need to be placed at both ends of the Type-C plug. The VBUS bypass capacitance for Type-C plug can range from 9nF to 500nF. Cypress cable designs use 22nF capacitors on VBUS pins as shown in the below figure.
     
       Figure
  •   For USB2.0 Type-C cable, bypass capacitors are not required on VBUS pins. Note that all VBUS pins must be connected together within the USB Type-C plug. This recommendation is applicable for USB Type-C cable to USB2.0 Standard-A cable, USB Type-C to USB2.0 Standard-B cable, USB Type-C to USB2.0 Mini-B cable, USB Type-C to USB2.0 Micro-B cable, and USB Type-C to USB2.0 Micro-B Receptacle Adapter.
  •   For USB Type-C to USB3.1 Standard-A cable, all VBUS pins must be connected together within the USB Type-C plug, and bypass capacitors are required between the VBUS and ground pins at the USB Type-C plug side of the cable. The bypass capacitor shall be 10nF ± 20% in cables, which incorporate a USB Standard-A plug. The bypass capacitor shall be 100pF ± 20% (minimum voltage rating of 30V) in cables, which incorporate a USBPD Standard-A plug. The bypass capacitor must be placed close to the power supply pad. This recommendation is applicable for USB Type-C to USB3.1 Standard-B cable and USB Type-C to USB3.1 Micro-B cable.
  •   For USB Type-C to USB3.1 Standard-A Receptacle Adapter, all VBUS pins must be connected together within the USB Type-C plug, and a 10 nF bypass capacitor is required for the VBUS pin at the USB Type-C plug end of the cable. The bypass capacitor must be placed close to the power supply pad. A bypass capacitor is not required for the VBUS pin in the Standard-A Receptacle. This recommendation is applicable for USB Type-C to USB3.1 Standard-B Receptacle Adapter.