Systems and methods for enabling communication between an accessory charger adapter (aca) and an aca-agnostic universal serial bus controller

Abstract

A physical layer integrated circuit (PHY), including an accessory charger adapter (ACA) bridge circuit to communicate with an ACA via a universal serial bus (USB) cable having at least an ID pin and a VBUS pin. The PHY is also to communicate with an ACA-agnostic USB controller configured to act as an A-device or as a B-device. The ACA comprises a USB accessory port. The ACA bridge circuit comprises detection and control logic configured to detect, based on a resistance sensed on the ID pin, that a B-device is connected to the USB accessory port of the ACA and, as a result of such a detection, generate a signal to the USB controller that causes the USB controller to act as an A-device and ignore a VBUS drive signal from the USB controller that, if not ignored, would cause the PHY to drive the VBUS pin. The detection and control logic is also configured to detect, based on a resistance sensed on the ID pin, that an off/idle A-device or nothing is connected to the USB accessory port of the ACA and, as a result of such a detection, modify a signal to the USB controller that prevents the USB controller from being aware of a voltage on the VBUS pin.

What is claimed is: 
     
         1 . A physical layer integrated circuit (PHY), comprising:
 an accessory charger adapter (ACA) bridge circuit to communicate with an ACA via a universal serial bus (USB) cable having at least an ID pin and a VBUS pin and to communicate with an ACA-agnostic USB controller configured to act as an A-device or as a B-device, the ACA includes a USB accessory port, and the ACA bridge circuit includes detection and control logic configured to:
 detect, based on a resistance sensed on the ID pin, that a B-device is connected to the USB accessory port of the ACA and, as a result of such a detection, generate a signal to the USB controller that causes the USB controller to act as an A-device and ignore a VBUS drive signal from the USB controller that, if not ignored, would cause the PHY to drive the VBUS pin; and 
 detect, based on a resistance sensed on the ID pin, that an off/idle A-device or nothing is connected to the USB accessory port of the ACA and, as a result of such a detection, modify a signal to the USB controller that prevents the USB controller from being aware of a voltage on the VBUS pin; an RID_B resistance circuit configured to output an asserted signal when the resistance sensed on the ID pin indicates that an off/idle A-device or nothing is connected to the USB accessory port of the ACA and a USB charger is connected to a charger port of the ACA or a deasserted signal in any other case; and 
   a VBUS voltage circuit configured to output an asserted signal when the voltage sensed on the VBUS pin is above a threshold, the threshold selected to indicate that the VBUS voltage is sufficient;   the detection and control logic producing a VBUS present signal by performing a logical AND operation of the output of the VBUS voltage circuit and the inverse of the output of the RID_B resistance circuit; and   the VBUS present signal being deasserted causing the USB controller to not be aware of a voltage on the VBUS pin.   
     
     
         2 . The PHY of  claim 1  in which the detection and control logic is configured to, as a result of a detection that an off/idle A-device is connected to the USB accessory port of the ACA, mask signals from the USB controller that would otherwise cause a conflict on the VBUS pin. 
     
     
         3 . The PHY of  claim 2  in which the signals from the USB controller that would otherwise cause a conflict on the VBUS pin include signals that enable session request protocol (SRP) communication on the VBUS pin.