Differential Resistor Level Formatter for High Speed DC Precision
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Solution Overview
Problem
Existing level formatters in the automated test equipment (ATE) industry face challenges in achieving both high speed and stringent DC precision, with open-loop formatters being fast but inaccurate due to temperature-dependent Shottky diode leakage, and closed-loop formatters being slow.
Innovation Solution
A programmable level formatter using a bipolar transistor bridge with closed-loop current sources and biasing elements, which switches reference voltages based on differential voltage control signals, providing both speed and precision by replicating input voltages at output buffers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If open-loop formatters using unguarded shottky diode bridges are used, then speed is improved, but DC precision deteriorates due to temperature-dependent Shottky diode leakage
Solution Approach 1:
The patent implements a closed-loop feedback mechanism using operational amplifiers that continuously monitor the output voltage and adjust the Shottky diode bridge configuration to maintain precise DC levels. The feedback loop compensates for temperature-dependent leakage by dynamically balancing the circuit, achieving both high speed and stringent DC precision (better than 1 mV) simultaneously
Solution Approach 2:
The patent changes the operating parameters of the Shottky diode bridge by introducing controlled biasing voltages and using programmable gain amplifiers to adjust the feedback gain. This allows the system to maintain optimal performance across varying temperature conditions while preserving fast switching speeds through controlled parameter adjustment rather than fixed configurations
2Measurement precision
If closed-loop formatters are used, then DC precision is improved, but speed deteriorates
Solution Approach 1:
The patent introduces dynamic elements to the closed-loop formatter by using programmable gain amplifiers and digitally controllable switch networks that can adjust the feedback loop characteristics in real-time. This allows the system to switch between high-precision modes and high-speed modes dynamically, achieving both DC precision better than 1 mV and rise/fall times of 140 psec or less depending on operational requirements
3Device complexity
If fixed voltage ranges are used in level formatters, then device complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The patent implements a universal level formatter design where a single circuit architecture can handle multiple voltage ranges and logic levels through programmable control. The Shottky diode bridge is configured with programmable gain amplifiers and digitally controllable switches that allow the same hardware to adapt to different voltage specifications (e.g., 5V, 3.3V, 2.5V, 1.8V standards) without requiring separate dedicated circuits for each voltage range, thus achieving both simplicity and versatility
Data Source
AI summary
A level formatter is provided that has differentially coupled closed loop current sources, each configured to precisely establish a current proportional to a reference voltage. A bridge circuit is differentially coupled to two supplementary current sources and controlled to rapidly switch the current from the supplementary current sources to produce output voltages at respective outputs that are approximately equal to respective one of two reference voltages.