Input Buffer Circuit for Floating Pad Tolerance and Low Loading
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Solution Overview
Problem
Integrated circuits face issues with power consumption and loading when using resistive pull-up or pull-down circuitry for input/output pads, as these circuits consume significant power when driven to opposite voltage levels and create current paths that impact output transient times.
Innovation Solution
The implementation of an input buffer circuit with a pass transistor and latch that pre-charges the pad to a reference voltage during initialization and decouples it when driven by internal or external drivers, minimizing power consumption and reducing loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive pull-up or pull-down circuitry is used for input/output pads, then floating voltages are prevented and known states are ensured, but power consumption increases significantly when pads are driven to opposite voltage levels
Solution Approach 1:
The patent implements dynamic control of the pull-up transistor, switching it between active and inactive states based on operational conditions. During initialization, the transistor is active to establish known voltage states. During normal operation, the transistor is deactivated to eliminate continuous power consumption, thus dynamically adapting the circuit behavior to different operational phases.
Solution Approach 2:
The patent employs feedback mechanisms through detection circuitry that monitors pad voltage levels and controls the gate of the pull-up transistor accordingly. When the pad voltage indicates normal operation, the feedback signal deactivates the transistor. When floating conditions are detected, the feedback reactivates the transistor, creating a closed-loop control system that optimizes power consumption while maintaining reliability.
2Reliability
If resistive pull-up or pull-down circuitry is used for input/output pads, then floating voltages are prevented, but loading effects increase and output transient times are impacted
Solution Approach 1:
The patent dynamically switches the pull-up transistor between active and inactive states. During initialization, the transistor provides strong pull-up capability to quickly establish known voltage states. During normal operation, the transistor is deactivated to eliminate loading effects on the pad, thereby improving output transient times and signal transition speeds without compromising the ability to prevent floating voltages when needed.
3Use of energy by moving object
If the pad is left floating without pull-up or pull-down circuitry, then power consumption is minimized, but the input buffer circuitry operates unpredictably and may be damaged
Solution Approach 1:
The patent applies preliminary action by activating the pull-up transistor during an initialization phase before normal operation begins. This preliminary activation establishes known voltage states on the pad and ensures the input buffer circuitry is in a defined state before any signal processing occurs, preventing unpredictable operation and potential damage while minimizing power consumption during subsequent normal operation.
Data Source
AI summary
An integrated circuit device includes a pad adapted to receive a signal from an internal or external driver, and an input buffer circuit including an input terminal coupled to the pad. The input buffer circuit includes a pass transistor having a control terminal, a first conduction terminal connected to the pad, and a second conduction terminal connected to a first voltage. The input buffer circuit also includes a latch having a terminal electrically coupled to the control terminal of the pass transistor. The input buffer circuit further includes circuitry coupled to the latch, the circuitry including a feedback transistor having a control terminal electrically coupled to the pad, a first conduction terminal electrically coupled to a second voltage, and a second conduction terminal coupled to the latch.