Level Shifter Floating Protection for Fixed Sleep-Mode Output
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Solution Overview
Problem
In semiconductor devices, level shifters face challenges in maintaining a fixed output level when the input voltage is interrupted, leading to unreliable operation during sleep modes or initial voltage supply states, as they fail to prevent floating inputs and ensure consistent signal transmission across blocks with different operation voltages.
Innovation Solution
The input/output device incorporates a level shifter with a floating protection circuit and an output driver, using resistors and NMOS transistors to generate a predetermined output level when the input voltage is interrupted, ensuring a stable output even when the input is floated, by utilizing a second operation voltage to maintain the level shifter's functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the level shifter is supplied with only the second voltage (input/output device operation voltage) when the first voltage (CPU operation voltage) is interrupted, then the level shifter can maintain operation during sleep mode or initial voltage supply states, but the input of the level shifter becomes floated and the output is set to an incorrect value
Solution Approach 1:
A floating protection circuit is introduced as an intermediary component between the input circuit and the level shifting circuit. This circuit includes a first resistor connected to the second voltage source and a second resistor connected to ground, which work together to prevent the input node from floating when the first voltage is interrupted. The intermediary circuit ensures that the level shifter receives a valid input signal even during sleep mode or initial voltage supply states, thereby maintaining both operational reliability and output signal accuracy.
2Loss of energy
If the CPU is turned off to interrupt power supply during sleep mode, then power consumption is reduced, but the input/output device cannot maintain a fixed output level for external interface
Solution Approach 1:
The power supply system is segmented into two independent voltage sources: the first voltage (VDD1) for the CPU and input circuit, and the second voltage (VDD2) for the level shifter and output driver. This segmentation allows the CPU to be turned off during sleep mode to reduce power consumption, while the level shifter and output driver continue to operate using the second voltage, maintaining stable output signals for external interfaces.
Solution Approach 2:
The floating protection circuit acts as a mediator that bridges the gap between the interrupted first voltage and the continuously operating level shifter. It ensures that the level shifter receives a valid input signal even when the CPU is off, enabling the system to achieve both low power consumption and reliable output signal stability during sleep mode.
3Adaptability or versatility
If the level shifter converts signals between different voltage levels, then signal transmission between blocks with different operation voltages is enabled, but leakage currents occur from the input/output device to the CPU
Solution Approach 1:
The level shifter serves as an intermediary device between blocks with different voltage levels. It converts signals from the first voltage level (CPU) to the second voltage level (input/output device) and vice versa, enabling signal transmission while preventing direct voltage level conflicts that would cause leakage currents. The floating protection circuit further enhances this by ensuring proper signal levels are maintained even when the CPU is off.
Data Source
AI summary
An input/output device includes: a level shifter configured to convert an input signal of a first voltage into an output signal of a second voltage; and an output driver configured to operate in response to the output signal. The level shifter is configured to generate the output signal with a predetermined level when the first voltage is interrupted to supply.