Robust cable-type detection for usb power delivery

Abstract

A system and method for detecting a USB cable-type. A USB PD device configured at a near end of a USB cable is configured to (i) receive and process a signal from a device at a far end of the USB cable to determine a power rating of the USB cable and (ii) adjustably establish power delivered by the first device to the USB cable as a function of the determined USB cable power rating.

What is claimed is: 
     
         1 . A system comprising:
 a universal serial bus (USB) cable having a near end and a far end and including a Vbus wire;   a first device having a receptacle configured to be coupled to the near end of the USB cable; and   a second device configured to be coupled to the far end of the USB cable, the second device configured to generate a signal on the Vbus wire;   wherein the first device is configured to determine a power rating of the USB cable by receiving and processing the signal from the second device through the receptacle.   
     
     
         2 . The system as specified in  claim 1 , wherein:
 the receptacle has an ID pin and a Vbus pin; and   the first device is configured to detect a presence of a capacitor coupled between the ID pin and the Vbus pin as a function of the signal received from the second device.   
     
     
         3 . The system as specified in  claim 1 , wherein:
 the receptacle has an ID pin and a ground pin; and   the first device is configured to detect a presence of a capacitor coupled between the ID pin and the ground pin as a function of the signal received from the second device.   
     
     
         4 . The system as specified in  claim 1 , wherein the first device is configured to deliver power to the USB cable while simultaneously detecting a presence of the signal from the second device. 
     
     
         5 . The system as specified in  claim 1 , wherein the first device is configured to adjustably establish the power delivered by the first device to the USB cable as a function of a presence of the signal and not a content of the signal. 
     
     
         6 . The system as specified in  claim 1 , wherein the first device is configured to establish the amount of power delivered by the first device to the USB cable as a function of the determined power rating of the USB cable. 
     
     
         7 . The system as specified in  claim 1 , wherein the signal comprises one of: a GoodCRC control message, a Ping control message, a HardReset packet, a Get_sink_cap control message, a Get_source_cap control message, a BitStream message, and a Capabilities message. 
     
     
         8 . The system as specified in  claim 1 , wherein the second device is configured to limit the amount of power delivered by the first device to the USB cable as a function of the determined power rating of the USB cable. 
     
     
         9 . A method of determining a power rating of a Universal Serial Bus (USB) cable extending between a first device coupled to a near end of the USB cable and a second device coupled to a far end of the USB cable, the method comprising the steps of:
 receiving a signal from the second device at the first device; and   determining the power rating of the USB cable using the signal.   
     
     
         10 . The method as specified in  claim 9 , wherein:
 the first device comprises a receptacle having an ID pin and a Vbus pin; and   determining the power rating of the USB cable comprises detecting a presence of a capacitor coupled between the ID pin and the Vbus pin as a function of the signal received from the second device.   
     
     
         11 . The method as specified in  claim 9 , wherein:
 the first device comprises a receptacle having an ID pin and a ground pin; and   determining the power rating of the USB cable comprises detecting a presence of a capacitor coupled between the ID pin and the ground pin as a function of the signal received from the second device.   
     
     
         12 . The method as specified in  claim 9 , wherein the first device delivers power to the USB cable while simultaneously detecting a presence of the signal from the second device. 
     
     
         13 . The method as specified in  claim 9 , wherein the first device adjustably establishes the power delivered by the first device to the USB cable as a function of a presence of the signal and not a content of the signal. 
     
     
         14 . The method as specified in  claim 9 , wherein the signal comprises one of: a GoodCRC control message, a HardReset packet, a Get_sink cap control message, a Get_source_cap control message, a BitStream message, a Ping message, and a Capabilities message. 
     
     
         15 . The method as specified in  claim 9 , wherein the first device adjusts the power it delivers to the USB cable as a function of the determined power rating. 
     
     
         16 . The method as specified in  claim 9 , wherein the second device limits the power delivered to the USB cable by the first device as a function of the determined power rating. 
     
     
         17 . An apparatus comprising:
 a controller configured to receive a signal sent to a first device coupled at a near end of a Universal Serial Bus (USB) cable from a second device coupled at a far end of the USB cable;   the controller configured to determine a power rating of the USB cable based on the received signal.   
     
     
         18 . The apparatus as specified in  claim 17 , wherein the controller is configured to adjust the amount of power delivered by the first device to the USB cable as a function of the determined power rating 
     
     
         19 . The apparatus as specified in  claim 17 , wherein the controller is configured to limit the amount of power delivered by the second device to the USB cable as a function of the determined power rating. 
     
     
         20 . The apparatus as specified in  claim 17 , wherein:
 the first device comprises a receptacle having an ID pin and a Vbus pin; and   the controller is configured to determine the power rating of the USB cable by detecting a presence of a capacitor coupled between the ID pin and the Vbus pin as a function of the signal received from the second device.   
     
     
         21 . The apparatus as specified in  claim 17 , wherein:
 the first device comprises a receptacle having an ID pin and a ground pin; and   the controller is configured to determine the power rating of the USB cable by detecting a presence of a capacitor coupled between the ID pin and the ground pin as a function of the signal received from the second device.   
     
     
         22 . The apparatus as specified in  claim 17 , wherein the controller is configured to adjustably establish the power delivered by the first device to the USB cable as a function of a presence of the signal and not a content of the signal. 
     
     
         23 . The apparatus as specified in  claim 17 , wherein the signal comprises one of: a GoodCRC control message, a HardReset packet, a Get_sink_cap control message, a Get_source_cap control message, a BitStream message, a Ping control message, and a Capabilities message.