ACA Bridge Circuit for USB ID Pin Resistance Detection

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Solution Overview

Problem

Legacy USB controllers are ACA-agnostic and misinterpret signals from Accessory Charger Adapters (ACAs), leading to improper behavior and potential short circuits when interacting with USB devices and chargers, as they do not understand additional resistance values on the ID pin indicating different configurations.

Innovation Solution

A Physical Layer Integrated Circuit (PHY) with an ACA bridge circuit and detection/control logic that senses resistance on the ID pin to adjust the USB controller's behavior, ensuring it acts as an A-device or B-device correctly and ignores or modifies VBUS drive signals to prevent contention, and detects the presence of B-devices or off/idle A-devices to manage VBUS awareness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If legacy USB controllers are used, then device compatibility is maintained, but proper communication with ACAs cannot be achieved leading to misinterpretation of signals

Engineering Contradiction:

Improvecommunication compatibility with ACAsVSAvoidsignal interpretation accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces an intermediary translation layer between the legacy USB controller and the ACA device. This intermediary translates the resistance-based ID pin signals from the ACA into standardized USB OTG signals that the legacy controller can properly interpret, enabling reliable communication without requiring controller replacement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transforms the resistance values present on the ID pin into standardized voltage levels or digital signals that the legacy USB controller can recognize. By changing the parameter representation from resistance to voltage/digital form, the legacy controller can correctly interpret ACA device states without understanding the original resistance encoding.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If legacy USB controllers interact with ACAs, then device connectivity is maintained, but short circuits may occur due to improper signal handling

Engineering Contradiction:

Improvedevice connectivityVSAvoidshort circuit risk

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary detection and correction of signal states before they reach the legacy USB controller. By preemptively translating and conditioning the ID pin signals, the system prevents the legacy controller from making incorrect decisions that could lead to short circuits, while still maintaining full device connectivity.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If USB controllers are designed to support ACA behavior, then proper ACA communication is achieved, but hardware cost increases

Engineering Contradiction:

ImproveACA signal interpretationVSAvoidhardware cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent places the ACA translation functionality in an intermediary component rather than requiring it to be built into expensive legacy USB controllers. This intermediary can be a separate chip or module that adds ACA support capability without replacing the entire controller, thereby reducing hardware costs while achieving reliable ACA communication.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables proper communication and behavior between ACA-agnostic USB controllers and ACAs, preventing short circuits and ensuring correct device configuration, even when legacy hardware interacts with ACAs and chargers, without the need for costly hardware replacements.

Implementation Method 1

detection and control logic configured to detect, based on a resistance sensed on the ID pin

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentUS10430360B2USB bridge circuitry and of RID A, RID GND inputs, IDGND output

Publication Date: 2019.10.01 TEXAS INSTRUMENTS INC

AI summary

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.