Integrated Circuit Test Circuitry for External Resistance Measurement
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Solution Overview
Problem
The increasing complexity and density of printed circuit assemblies, combined with the compact size of surface mount passive devices, make it challenging and costly to test all nodes effectively, especially when physical access is limited, leading to incomplete verification and uncertainty about the circuit's operation.
Innovation Solution
A system and method that utilize an integrated circuit (IC) with integrated test circuitry to observe and determine target resistance values in external circuits by applying varying reference voltages and output voltages, allowing for the determination of electrical characteristics without the need for expensive test equipment, even when nodes are obscured or difficult to access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the density and number of parts per circuit board increases, then the performance and functionality of the circuit assembly is improved, but the number of interconnected nodes to be tested rises exponentially while physical access to those nodes decreases
Solution Approach 1:
The patent introduces an intermediary measurement system that uses easily accessible nodes (such as voltage taps or test points) as mediators to indirectly measure the electrical characteristics of difficult-to-access nodes. This intermediary approach allows test equipment to probe accessible points while deriving information about obscured nodes through mathematical relationships and circuit analysis, resolving the contradiction between increased node density and decreased physical accessibility.
Solution Approach 2:
The patent replaces direct mechanical probing of obscured nodes with an electrical measurement system that uses voltage dividers, current measurements, and computational analysis. Instead of physically accessing each node with a probe, the system uses electrical signals and mathematical models to determine resistance, continuity, and other characteristics of difficult-to-reach nodes, thereby substituting mechanical access with electrical-field-based measurement.
2Ease of operation
If indirect access methods are used to test obscured nodes, then testing can be performed without physical access, but test times increase and resolution is less than ideal
Solution Approach 1:
The patent implements preliminary action by pre-configuring the circuit board with embedded test points, voltage taps, and measurement circuitry during the manufacturing process. These preliminary structures are built into the design, allowing rapid indirect measurement of obscured nodes without requiring complex probing setups or extended test procedures, thereby reducing test time while maintaining accessibility to difficult-to-reach nodes.
3Reliability
If complete test verification of all circuit assembly nodes is performed, then uncertainty regarding circuit operation is reduced, but the cost of testing increases significantly
Solution Approach 1:
The patent applies partial action by selectively measuring a subset of key nodes and using mathematical propagation to infer the state of other nodes. Rather than directly probing every single node, the system measures critical points and uses circuit theory to calculate characteristics of inaccessible nodes, achieving comprehensive verification without the excessive hardware complexity and cost of direct universal access to all nodes.
4Area of stationary object
If surface mount passive devices with compact size are used, then the density of the circuit board is improved, but the devices are difficult to place and solder correctly
Solution Approach 1:
The patent implements self-service by incorporating self-test and self-verification capabilities directly into the circuit board design. The measurement system automatically detects placement errors, soldering defects, and component failures without requiring manual inspection or complex external testing equipment. This self-service approach compensates for the increased manufacturing difficulty of compact surface mount devices by providing automated verification that catches errors immediately after assembly.
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 efficient and effective testing of circuit assemblies by verifying and quantifying target resistances, reducing uncertainty about the circuit's performance and meeting expectations, while avoiding the need for expensive test equipment and indirect access methods.
Implementation Method 1
The test circuitry applies a reference voltage that varies over time and first and second output voltages that are different from each other
Implementation Method 2
The logic determines first and second values associated with an electrical characteristic of the external circuit responsive to the first and second reference voltages
Data Source
AI summary
A test system includes a circuit assembly having an IC and an external circuit. The IC includes test circuitry used to observe data indicative of target resistances in the external circuit. The test system evaluates the data to determine target resistance values. A first embodiment measures two output voltages responsive to a time varying reference voltage. The two output voltages can be used to determine resistance values in the external circuit. A second embodiment enables logic contention on the IC, controllably fixes a pull-down element on the IC, and controllably sweeps a pull-up element on the IC until the voltage at a node between the pull-down and pull-up elements and coupled to an external circuit exceeds a reference voltage.