Open Pin Detection Circuit Using Selective Inverter Thresholds
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Solution Overview
Problem
Existing techniques for detecting open integrated circuit pins using internal pull-up or pull-down resistors can adversely affect the operation of internal and external circuits, and are often complex and resource-intensive.
Innovation Solution
A two-phase open detect circuit that selectively couples a pull-up resistor during a pull-up phase and a pull-down resistor during a pull-down phase to an input pin, using inverters with specific width-to-length ratios for MOSFETs to determine if the pin is open without disrupting normal circuit operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pull-up or pull-down resistor is coupled to an input pin to detect open pins, then open pin detection is enabled, but the performance of internal cells and voltage levels of input signals are adversely affected
Solution Approach 1:
The patent applies preliminary action by performing open pin detection before the input pin is used for its intended function. The detection circuit activates the pull-up or pull-down resistor only during the detection phase, determining the pin's open/closed state before normal operation begins. This ensures detection capability is achieved without the resistor interfering with subsequent circuit performance or signal levels during normal operation.
Solution Approach 2:
The patent implements periodic action by enabling the pull-up or pull-down resistor only during specific detection time intervals rather than continuously. The detection circuit activates the resistor during designated detection periods and deactivates it during normal operation periods. This periodic activation allows open pin detection to be performed while preventing the resistor from adversely affecting internal cell performance and input signal voltage levels during normal circuit operation.
2Measurement precision
If a complex open bond detection circuit is used to verify continuity through bonding wires, then detection accuracy is improved, but die area and current requirements increase
Solution Approach 1:
The patent applies universality by designing a detection circuit that can handle multiple input pins using a single shared detection circuit rather than requiring separate circuits for each pin. The detection circuit selectively activates pull-up or pull-down resistors for different pins as needed, allowing one circuit structure to serve multiple detection functions. This multi-functional approach maintains detection accuracy while significantly reducing die area and circuit complexity compared to dedicated circuits for each pin.
Solution Approach 2:
The patent utilizes parameter changes by dynamically switching the resistance values and connectivity configurations within the detection circuit. The circuit changes parameters such as which pull-up or pull-down resistor is active, and which pins are connected to the detection network, based on which pin is being tested. This dynamic parameter adjustment allows accurate detection of individual pin states while using a compact, low-complexity circuit structure that shares resources across multiple pins.
3Reliability
If a pull-up resistor is continuously coupled to an input pin, then open pin detection is maintained, but current consumption increases
Solution Approach 1:
The patent implements periodic action by activating the pull-up or pull-down resistor only during specific detection time intervals rather than maintaining continuous coupling. The detection circuit controls the activation timing, enabling the resistor during detection phases and disabling it during normal operation phases. This periodic activation maintains open pin detection capability while significantly reducing average current consumption compared to continuous resistor coupling.
Solution Approach 2:
The patent applies dynamics by making the pull-up or pull-down resistor configuration dynamic rather than static. The detection circuit dynamically controls which resistor is active and when it is active, adapting the resistor coupling state based on detection requirements. This dynamic configuration allows the circuit to maintain detection capability only when needed, reducing current consumption during periods when detection is not required, while still providing reliable open pin detection when activated.
Data Source
AI summary
A technique of detecting an open integrated circuit (IC) pin includes selectively coupling a first open detect circuit, which includes a first inverter having a first threshold, to the IC pin. Next, a first logic state at an output of the first inverter is determined. Then, based upon the first logic state, it is determined whether the IC pin is open or whether it is indeterminate as to whether the IC pin is open. When it is indeterminate as to whether the IC pin is open, based on the first logic state, a second open detect circuit is selectively coupled to the IC pin. The second open detect circuit includes a second inverter having a second threshold (the first threshold is greater than the second threshold). A second logic state at an output of the second inverter is then determined. Finally, based upon the first and second logic states, it is determined whether the IC pin is open.