Programmable I/O Clamp Circuit for Hot-Swappable Interfaces
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Solution Overview
Problem
Existing input/output (I/O) interfaces face challenges in conforming to both hot-swappability and over-voltage clamp requirements, as they must be conductive during over-voltage conditions to clamp voltages but non-conductive for hot-swappable operations, conflicting with different I/O standards such as PCI33/PCI66 and USB specifications.
Innovation Solution
A method and apparatus for an I/O interface that allows configuration for hot-swappability and over-voltage protection by using a control block with a bias control circuit to manage current conduction based on mode signals, enabling or disabling current paths depending on operational modes, and employing a pre-driver and output driver to limit external voltage to the operational power signal magnitude during over-voltage events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the I/O interface is configured to be conductive during over-voltage conditions to clamp voltage magnitude to VCCO (per PCI33/PCI66 specification), then over-voltage protection is improved, but hot-swappability deteriorates because the interface cannot remain non-conductive for safe hot-swapping operations
Solution Approach 1:
The patent implements dynamic configuration of the I/O interface by using a control block with a bias control circuit that can switch between different operational modes (hot-swap mode and over-voltage clamp mode) based on external mode signals. This allows the interface to adapt its conduction state dynamically: remaining non-conductive during hot-swapping operations while transitioning to conductive state for over-voltage clamping when required, thus resolving the contradiction between these two opposing requirements
Solution Approach 2:
The patent changes the electrical conduction parameter of the I/O interface based on operational mode. By controlling the bias circuit to adjust the conduction state of the output driver, the interface can modify its electrical characteristics to match different I/O standards - maintaining high impedance (non-conductive) for hot-swapping safety while enabling low impedance (conductive) path for over-voltage protection, thereby satisfying both conflicting specifications
2Adaptability or versatility
If the I/O interface eliminates current paths into output pins during non-operational modes to enable hot-swappability (per USB specification), then hot-swappability is improved, but over-voltage protection deteriorates because the interface cannot clamp over-voltage conditions
Solution Approach 1:
The control block dynamically adjusts the conduction state based on the operational mode signal. During normal hot-swapping operations, the interface maintains eliminated current paths for safety. However, when an over-voltage condition is detected or clamp mode is activated, the bias control circuit dynamically enables the current path to clamp the voltage, thus providing both hot-swappability and over-voltage protection at different times as needed
3Reliability
If the I/O interface maintains conduction paths for over-voltage clamping, then over-voltage protection is improved, but device complexity increases due to the need for additional control circuits and mode management
Solution Approach 1:
The patent merges the over-voltage protection function with the existing hot-swapping control infrastructure by integrating a bias control circuit into the control block that already manages the output driver. This unified approach allows a single control structure to handle both hot-swapping mode and over-voltage clamp mode, reducing overall device complexity compared to having separate independent protection circuits
Data Source
AI summary
A method and apparatus is provided for a configurable input/output (I/O) interface within an integrated circuit to support a plurality of I/O standards. The configurable I/O interface exhibits a default operation that facilitates hot-swappability, which eliminates current paths within the I/O interface that may be created during plug-and-play operation of the I/O interface. The current paths are eliminated within the I/O interface even while the I/O interface is not receiving operational power, or while the I/O interface is in a power-on reset condition. A programmable option of the configurable I/O interface, on the other hand, alleviates over-voltage conditions while the I/O interface is tri-stated by activating shunt circuitry to conduct a clamp current during the over-voltage condition. The over-voltage condition is further alleviated by passively establishing current paths through existing circuitry within the I/O interface for the duration of the over-voltage condition.