ATPG Voltage Control via Adaptation Circuit
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Solution Overview
Problem
In modern automotive integrated circuits, controlling the digital supply voltage (VDD) during Automatic Test Pattern Generation (ATPG) is challenging due to the absence of a dedicated pin, leading to voltage drops and testability weaknesses, which complicates the creation of Shmoo plots and can result in false pattern failures.
Innovation Solution
The method involves using an op-amp voltage regulator with a negative feedback network, where an external test equipment applies a controlled voltage signal through an adaptation circuit to adjust the digital supply voltage, ensuring it reaches a desired target value during ATPG, thereby stabilizing the voltage and improving testability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a testmode switch is used to remap the internal supply voltage signal to an external pin, then the supply voltage can be controlled by an external source, but the switch resistance causes voltage drops during ATPG patterns leading to testability weaknesses
Solution Approach 1:
The patent introduces an adaptation circuit as an intermediary between the external test equipment and the internal voltage regulator. This circuit includes a voltage source and a coupling mechanism that can apply external voltages to the regulator's input terminals without requiring a high-resistance testmode switch, thereby mediating between external control needs and internal voltage stability requirements
Solution Approach 2:
The patent changes the operating parameters of the voltage regulator by applying external voltages that differ from normal operating conditions. During ATPG testing, external voltages are applied to the regulator's input terminals to simulate various supply voltage conditions, enabling parameter sweeps for Shmoo plot generation without being constrained by switch resistance
2Device complexity
If the internal voltage regulator is disabled and external voltage is applied directly, then supply voltage control is simplified, but voltage drops occur due to testmode switch resistance
Solution Approach 1:
The adaptation circuit serves as an intermediary that eliminates the need for a high-resistance testmode switch. It includes a voltage source coupled to the regulator's input terminals through low-resistance paths, providing accurate voltage delivery while maintaining the ability to disable the regulator during testing
Solution Approach 2:
The patent segments the voltage control function into two independent parts: the testmode switch for enabling/disabling the regulator, and the adaptation circuit for applying external voltages. This segmentation allows the voltage source to be coupled directly to the regulator inputs without passing through the testmode switch, avoiding voltage drops
3Reliability
If ATPG patterns are applied with internal voltage regulator, then normal operation is maintained, but spike currents cause voltage drops and pattern failures
Solution Approach 1:
The patent applies preliminary action by disabling the internal voltage regulator before applying ATPG patterns and pre-coupling the external voltage source to the regulator's input terminals. This preliminary configuration prevents spike currents from affecting the test supply voltage, as the external source directly controls the voltage without being influenced by internal current variations
Solution Approach 2:
The adaptation circuit acts as an intermediary that isolates the ATPG testing from the internal voltage regulator's current variations. By coupling the external voltage source directly to the regulator inputs through low-resistance paths, it mediates between the high-current ATPG patterns and the voltage control function, preventing voltage drops
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
This approach enhances the control of logic gates' supply voltage, reduces false rejections, and allows for more precise defectiveness identification, improving the stability of ATPG patterns and enabling the creation of stable Shmoo plots without being limited by switch resistance.
Implementation Method 1
an op-amp voltage regulator having its output coupled to a differential input of the op-amp and a reference voltage coupled to the other differential input
Data Source
AI summary
In an embodiment a method for testing a digital electronic circuit includes coupling an external test equipment to a digital electronic circuit in order to apply an external voltage signal to the digital electronic circuit when an automatic test pattern generation (ATPG) procedure with a given test pattern is performed, wherein a value of the external voltage signal is controlled by the external test equipment and measuring, at the external test equipment, the digital supply voltage at an output of the voltage regulator and at an input of the internal digital circuitry, wherein the external voltage signal is applied to the differential inputs of the op-amp voltage regulator through an adaptation circuit to obtain determined values of the digital supply voltage.