Output Buffer Voltage Shifting for Low-Power I/O Reliability
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Solution Overview
Problem
The reduction of internal supply voltage in CMOS processes to lower power consumption in integrated circuits has led to high power consumption in input/output buffers and potential damage due to voltage differences, with leakage currents and hot carrier injection posing risks to buffer transistors.
Innovation Solution
An operating method and circuit for an output buffer that generates sourcing and sinking control signals based on indication signals and output data, using level-shifting and internal voltage selection to manage voltage levels and apply operating voltages effectively, thereby reducing power consumption and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If internal supply voltage is reduced to lower power consumption, then power consumption of integrated circuits is reduced, but input/output buffer power consumption remains high and transistors may be damaged
Solution Approach 1:
The patent implements dynamic voltage adjustment by generating different sourcing control signals (first and second sourcing control signals) based on indication signals that represent different operating voltage levels. The output buffer dynamically switches between different voltage levels (e.g., 1.8V, 2.5V, 3.3V) rather than operating at a fixed voltage, allowing the system to optimize power consumption while maintaining transistor reliability through appropriate voltage selection.
Solution Approach 2:
The patent changes the voltage parameter of the output buffer by using indication signals to select from multiple internal voltage levels. The sourcing control circuit generates control signals that adjust the output voltage based on the indication signals, enabling the buffer to operate at different voltage levels (1.8V, 2.5V, 3.3V) to balance power consumption and reliability requirements.
2Adaptability or versatility
If different supply voltages are applied to input/output buffers in different ICs, then interfacing between ICs is enabled, but leakage current paths form and buffers may be damaged
Solution Approach 1:
The patent applies preliminary action by generating the first sourcing control signal in advance based on the indication signals before the actual data transmission occurs. The sourcing control circuit prepares the appropriate voltage level and control signals (swinging between operating voltage and reference voltage) to prevent leakage current paths and voltage damage before they can occur, ensuring safe interfacing between ICs with different voltage levels.
Solution Approach 2:
The patent uses an intermediary approach by introducing indication signals that carry voltage level information and using these to generate appropriate sourcing control signals. The sourcing control circuit acts as an intermediary that translates indication signals into the correct voltage levels, enabling safe communication between ICs with different supply voltages without direct exposure to harmful voltage differences.
3Power
If voltage difference greater than rated voltage is applied across buffer transistor terminals, then higher operating voltage is achieved, but gate oxide layer is destroyed and transistors are damaged
Solution Approach 1:
The patent implements feedback by using indication signals that provide information about the desired operating voltage level. The sourcing control circuit receives these indication signals and generates appropriate sourcing control signals (first and second) that feedback control the output voltage, ensuring it never exceeds the rated voltage difference that would damage the gate oxide layer while still achieving the desired operating voltage level.
Data Source
AI summary
A method of buffering data from core circuitry includes generating a first sourcing control signal responsive to indication signals indicating an operating voltage and output data, generating a second sourcing control signal responsive to the indication signals, and applying the operating voltage to an output terminal in response to the first sourcing control signal and the second sourcing control signal. The first sourcing control signal swings between the operating voltage and a reference voltage. The reference voltage is a signal selected from among a plurality of internal voltages in response to selection signals generated as a result of decoding the indication signals.