Reference-Less Frequency Detector for One-Cycle Threshold Sensing
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Solution Overview
Problem
Conventional frequency detectors require a reference clock, which is not available in certain applications, and are slow in comparing input clock frequencies with a threshold, making them unsuitable for fast-response frequency detection.
Innovation Solution
A fast-response reference-less frequency detector is implemented using two pulse-shaping circuits in series, which generate a control signal based on the waveform of the input clock signal, determining if it is higher or lower than a threshold frequency without the need for an external reference clock, allowing for frequency detection within one cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional frequency detectors use two separate counters to count edges of input clock and reference clock, then frequency comparison can be performed, but the comparison speed is slow and requires a reference clock that may not be available
Solution Approach 1:
The patent extracts the reference clock requirement from the frequency detection system by using the input clock signal itself as the timing reference. Instead of requiring an external reference clock and two separate counters, the invention uses a single counter that counts input clock edges within a fixed number of input clock cycles, eliminating the need for a reference clock and reducing system complexity while maintaining frequency comparison capability
Solution Approach 2:
The patent merges the functions of reference clock generation and frequency counting into a single counter operation. The same counter that counts input clock edges also implicitly measures frequency by counting within a fixed time window defined by a predetermined number of input clock cycles, combining multiple functions into one operation to reduce device complexity
2Measurement precision
If conventional frequency detectors compare frequencies after a certain number of reference cycles, then accurate comparison is achieved, but the response time is slow
Solution Approach 1:
The patent performs preliminary action by pre-defining the counting window in terms of a fixed number of input clock cycles before the actual frequency measurement begins. This predetermined window ensures that the comparison is always made over a consistent, adequate time period sufficient for accurate frequency determination, while the fast counter operation ensures rapid completion within each window
Solution Approach 2:
The patent implements periodic action by repeatedly performing frequency measurements in fixed intervals defined by a predetermined number of input clock cycles. Each period consists of counting input clock edges within one window, then comparing the count to a threshold, and repeating the process in the next window, providing both accuracy through consistent measurement intervals and fast response through regular periodic updates
Data Source
AI summary
An apparatus includes a first circuit and a second circuit. The first circuit may be configured to generate a waveform in response to a frequency of an input clock signal and a threshold frequency. The second circuit may be configured to generate a control signal in response to a type of the waveform. The type of the waveform may comprise at least one of pulses and a steady state. The control signal may have a first state when the type of the waveform is the pulses and a second state when the type of the waveform is the steady state. A width of the pulses may be based on the threshold frequency.