Dynamic Pull-Down Circuits for Fast Bidirectional Level Shifting
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Solution Overview
Problem
Bidirectional voltage translators with static pull-down circuits consume significant area due to large resistors and dynamic pull-down circuits fail to quickly discharge output voltages, leading to prolonged high output supply currents.
Innovation Solution
The implementation of dynamic pull-down circuits at I/O ports of bidirectional voltage translators, utilizing switches and mono-shot pulse generator circuits triggered by power-on reset or output enable signals to rapidly discharge output voltages, reducing supply currents and area consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If static pull-down circuits are used, then output voltage can be pulled down, but the circuit consumes significant area due to large resistors
Solution Approach 1:
The patent transforms the static pull-down resistor into a dynamic pull-down circuit using transistors (first transistor coupled to second resistor terminal, second transistor coupled to first transistor, third transistor coupled to second transistor) that can be activated on-demand. This dynamic configuration eliminates the need for large static resistors, reducing area while maintaining effective output voltage discharge capability when needed.
Solution Approach 2:
The patent changes the resistance parameter from a fixed large value (static resistor) to a dynamically controllable value through transistor switching. The pull-down resistance is effectively changed from high (area-consuming static resistor) to low (efficient dynamic discharge path) only when discharge is required, optimizing both area and performance.
2Area of stationary object
If dynamic pull-down circuits are used, then area consumption is reduced, but output voltages are not discharged quickly enough
Solution Approach 1:
The patent incorporates a mono-shot pulse generator circuit that is triggered by power-on reset or output enable signals to generate a preliminary discharge pulse. This pulse activates the dynamic pull-down circuitry before normal operation begins, ensuring output voltages are rapidly discharged at startup without requiring continuous area-consuming pull-down resistance during operation.
Solution Approach 2:
The patent uses periodic or pulsed activation of the dynamic pull-down circuit through the mono-shot pulse generator rather than continuous activation. This approach achieves rapid voltage discharge when needed (at power-on or enable transitions) while keeping the circuit inactive otherwise, optimizing area efficiency without sacrificing discharge speed when required.
Data Source
AI summary
An example apparatus includes: an output terminal, pull-down circuitry coupled to the output terminal, the pull-down circuitry including: a resistor with a first resistor terminal and a second resistor terminal, the first resistor terminal coupled to the output terminal, a capacitor with a first capacitor terminal and a second capacitor terminal, the first capacitor terminal coupled to the output terminal, a first transistor coupled to the second resistor terminal, a second transistor coupled to the first transistor and the second resistor terminal, and a third transistor coupled to the second transistor.