Test Apparatus Feedforward Control for Semiconductor DUT Voltage Stability
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Solution Overview
Problem
Existing power supply circuits for testing semiconductor devices struggle to maintain a constant voltage due to fluctuations in load current, leading to increased power consumption and reduced test accuracy, especially when emulating actual operating environments with non-negligible output impedance and slower response speeds.
Innovation Solution
A test apparatus with a main power supply and a power supply control unit that employs feedforward control to adjust the power supply voltage according to the operating current, using a compensation circuit to generate correction currents and reduce power consumption by minimizing the need for large compensation currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a main power supply with feedback control is used to maintain constant voltage, then voltage stability is improved, but response speed deteriorates due to non-negligible output impedance
Solution Approach 1:
The feedforward control unit calculates the operating current of the DUT in advance based on the test pattern, and generates a compensation current waveform before the voltage fluctuation occurs. This preliminary action allows the compensation current to be applied proactively, counteracting the voltage drop caused by load changes before it affects the power supply voltage, thus improving response speed without sacrificing stability
2Stability of the object's composition
If compensation current is increased to maintain voltage during load fluctuations, then voltage stability is improved, but power consumption increases
Solution Approach 1:
The compensation current waveform is calculated to provide exactly the amount of current needed to counteract voltage fluctuations, rather than continuously supplying maximum compensation current. The feedforward control unit adjusts the compensation current dynamically based on the predicted operating current, applying partial compensation only when and where needed, thus maintaining voltage stability while minimizing unnecessary power consumption
3Device complexity
If a power supply circuit with non-negligible output impedance is used, then device complexity is reduced, but test accuracy deteriorates due to voltage fluctuation
Solution Approach 1:
The feedforward control unit acts as an intermediary between the test pattern and the main power supply. It calculates the operating current from the test pattern, generates an appropriate compensation current waveform, and superimposes it on the main power supply output. This intermediary control mechanism compensates for the voltage fluctuations caused by the power supply's output impedance, maintaining test accuracy without requiring a complete redesign of the power supply circuit
Data Source
AI summary
A main power supply is arranged such that its output terminal Po is connected to a power supply terminal of a DUT via a power supply line, and is configured to feedback control an output voltage VOUT output from the output terminal such that a detection value VDD′ that corresponds to a power supply voltage VDD at the power supply terminal approaches a target value VREF′. When a test pattern is supplied to the DUT, a power supply control unit is configured to feedforward control the main power supply such that the power supply voltage VDD approaches a predetermined target waveform VTGT.