Dual-Function IC Pin for Current Limiting and Fault Output
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Solution Overview
Problem
Low voltage current limited power switches, such as USB power switches, often require multiple pins for current limiting and fault output functions, which can be costly and inefficient in low pin count packages, lacking a unified solution for current limiting and open-drain output capabilities.
Innovation Solution
An integrated circuit pin is configured to serve both as a current limiting input and an open-drain output by using an application resistor to set a current limiting set point, allowing the resistor to function as an open-drain output after startup, enabling dual functionality in a standard 8-pin package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pins are used for current limiting input and open-drain output, then functional reliability is improved, but device complexity and pin count increase
Solution Approach 1:
The patent combines the current limiting input function and open-drain output function into a single integrated circuit pin. The pin can operate in different modes: as a current limiting input during normal operation, and as an open-drain output during fault conditions. This merging eliminates the need for separate pins while maintaining functional reliability through mode switching.
Solution Approach 2:
The integrated circuit pin is designed with multi-functionality, serving dual purposes as both a current limiting input and an open-drain output. The pin can be configured to perform different functions based on operational requirements, reducing the overall pin count while maintaining all necessary functionalities for reliable operation.
2Device complexity
If a single pin is used for both current limiting input and open-drain output, then device complexity is reduced, but functional reliability may deteriorate
Solution Approach 1:
The patent implements dynamic functionality where the pin can switch between different operational modes. The pin dynamically changes its function based on the operational state: serving as a current limiting input during normal operation and switching to open-drain output mode during fault conditions. This dynamic switching maintains functional reliability while using a single pin.
Solution Approach 2:
The integrated circuit internally manages the pin's function switching without requiring external control. The circuit automatically configures the pin for current limiting or open-drain output based on internal fault detection and operational state, eliminating the need for additional control pins or complex external circuitry while maintaining reliability.
3Adaptability or versatility
If multiple pins are used for power switch functions, then functional capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple power switch functions (current limiting input and open-drain output) into a single pin, reducing the total pin count. This reduction in pin count directly lowers manufacturing costs for low pin count packages while maintaining full functional capability through the pin's multi-functional design and mode switching.
Data Source
AI summary
An integrated circuit comprises at least one pin and has at least one resistor connected between a reference voltage and the at least one pin. Current measurement circuitry applies a voltage across the at least one resistor and measures a current at the at least one pin responsive to the applied voltage in a first mode of operation. The measured current enables determination of a current limit set point for the integrated circuit. In a second mode of operation, the at least one resistor comprises a pull up resistor and the at least one pin that is connected to the at least one resistor comprises an open-drain output.