Latch-Based Floating Pin Detection for Stable Logic Levels
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Solution Overview
Problem
Floating terminals in digital circuits can cause operational problems, including unknown states and unintended current paths that may damage components or discharge the power source, as they are not driven to valid logic voltages.
Innovation Solution
A float detector circuit comprising latches, a control circuit, pull-up, and pull-down circuits that determine if an input terminal is floating by providing drive signals and detecting latch output signals, ensuring the terminal is at a valid logic level and preventing damage by drawing or sourcing current as necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a float detector is implemented to detect floating terminals, then reliability is improved, but device complexity increases
Solution Approach 1:
The float detector is divided into multiple functional blocks: a first latch for sampling input signals, a control circuit for generating drive signals, pull-up and pull-down circuits for forcing logic levels, and a second latch for detecting transitions. This segmentation allows each component to perform a specific function, improving reliability while keeping individual components simple.
Solution Approach 2:
The control circuit proactively generates drive signals to force the input terminal to known logic levels (high or low) before detection. This preliminary action ensures that the terminal is in a defined state, preventing floating conditions from causing unreliable operation. The system prepares the terminal in advance rather than reacting to floating states after they cause problems.
2Reliability
If continuous monitoring of input terminals is implemented, then reliability is improved, but energy consumption increases
Solution Approach 1:
The float detector operates periodically rather than continuously. The control circuit generates drive signals at specific intervals, forcing the input terminal to logic levels and sampling the results at discrete moments. This periodic operation maintains detection reliability while allowing the circuit to consume minimal quiescent current between measurement cycles, significantly reducing overall energy consumption.
3Measurement precision
If multiple latches and control circuits are used to detect floating states, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses feedback through latch outputs to control subsequent drive signals. The first latch samples the input terminal state, and its output feeds the control circuit, which uses this information to generate appropriate drive signals. This feedback mechanism ensures accurate detection by continuously monitoring and responding to the terminal state, improving measurement precision while using simple, well-defined feedback paths.
Solution Approach 2:
The control circuit applies drive signals that may be stronger or more frequent than strictly necessary, ensuring that the input terminal is reliably forced to known logic levels. This excessive action guarantees accurate detection of floating states by overwhelming any weak or ambiguous signals, improving measurement precision while the simple latch logic keeps the overall circuit complexity manageable.
Data Source
AI summary
A float detector includes a latch and a float detection circuit. The latch includes a latch output and an input/output (I/O) terminal. The I/O terminal is coupled to an input terminal. The float detection circuit includes a detection input, a drive output, and a float detection circuit. The detection input is coupled to the latch output. The drive output is coupled to the I/O terminal. The float detector is configured to provide a drive signal at the drive output, and determine that the input terminal is floating based on a latch output signal received at the detection input responsive to the drive signal.