Pre-Charged Voltage Level Shifter With Input Pre-Conditioning
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Solution Overview
Problem
Conventional voltage level shifter (VLS) circuits face contention issues between pre-charge and pull-down circuits during the pre-charge phase, leading to potential power consumption and area inefficiencies, especially when shifting signals between significantly different voltage domains.
Innovation Solution
Incorporating a pre-conditioning circuit that generates a pre-conditioned input signal based on a pre-condition control signal, preventing the pull-down circuit from activating during the pre-charge phase, thus avoiding the need for additional stacked transistors and maintaining the drive strength of the pull-down circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional VLS circuit is used without a pre-conditioning circuit, then the circuit structure is simpler, but contention occurs between the pre-charge circuit and pull-down circuit during the pre-charge phase, leading to increased power consumption and reduced reliability
Solution Approach 1:
The pre-conditioning circuit is activated during the pre-charge phase to pre-condition the input signal before the main VLS operation. This preliminary action ensures that the input signal is properly prepared (e.g., discharged or held at a specific voltage level) before the evaluation phase begins, preventing contention between the pre-charge and pull-down circuits while maintaining overall circuit reliability
Solution Approach 2:
The pre-conditioning circuit acts as an intermediary between the input signal and the main VLS circuitry. It conditions the input signal during the pre-charge phase and passes the conditioned signal to the pull-up and pull-down circuits during the evaluation phase, thereby mediating the interaction between different circuit components and preventing harmful contention
2Reliability
If additional stacked transistors are added to the pull-down circuit to prevent activation during pre-charge phase, then contention is avoided, but the drive strength of the pull-down circuit is reduced
Solution Approach 1:
Instead of modifying the pull-down circuit with additional stacked transistors that would reduce its drive strength, the pre-conditioning circuit performs the necessary preparation in advance during the pre-charge phase. This allows the pull-down circuit to maintain its original strong drive strength while still avoiding contention through the pre-conditioned input signal
Solution Approach 2:
The VLS circuit is segmented into distinct functional phases: a pre-charge phase where the pre-conditioning circuit operates, and an evaluation phase where the pull-up and pull-down circuits operate. This temporal segmentation allows each circuit component to perform its function optimally without interfering with others, maintaining both reliability and drive strength
3Loss of energy
If the pull-down circuit is weakened to avoid contention during pre-charge phase, then power consumption is reduced, but the circuit can no longer operate over a wider range of voltages
Solution Approach 1:
The circuit operates in periodic cycles consisting of a pre-charge phase and an evaluation phase. During the pre-charge phase, the pre-conditioning circuit prepares the input signal with minimal power consumption. During the evaluation phase, the full-strength pull-up and pull-down circuits operate to provide wide voltage adaptability. This periodic operation allows the circuit to maintain low average power consumption while preserving full voltage operating range capability when needed
4Reliability
If a pre-conditioning circuit is added to pre-condition the input signal, then contention between pre-charge and pull-down circuits is mitigated, but the device complexity increases
Solution Approach 1:
The pre-conditioning circuit is merged with the existing VLS circuit architecture, sharing control signals and timing with the pre-charge and evaluation phases. This integration minimizes the additional complexity introduced by the pre-conditioning functionality while achieving reliable contention mitigation through coordinated operation with the existing circuit components
Data Source
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AI summary
Voltage level shifter (VLS) circuits (302) employing a pre-conditioning circuit (320) for pre-conditioning an input signal (IN) to be voltage level shifted in response to a pre-charge phase (CTRLh) are disclosed. A VLS circuit (302) is configured to voltage level shift an input signal (IN) in a lower voltage domain (VDI) on an output node (306B) in a higher voltage domain (VDh). The VLS circuit includes a pre-charge circuit (312) configured to pre-charge the output node (306B) in a pre- charge phase. The VLS circuit also includes a pull-up circuit (314U) and a pull-down circuit (334) that are configured to pull-up and pull- down the pre-charge phase of the output node, respectively, in an evaluation phase (CTRLh= 1) based on a logic state of the input signal (IN) to generate the output signal. To mitigate or avoid contention between the pull-up and pull-down circuits in the evaluation phase, the input signal is pre-conditioned (CTRLI) such that the pull-down circuit is deactivated in response to the pre-charge phase.