Oscillator Clock Calibration by Transition Counting Under Aliased Sampling
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Solution Overview
Problem
Existing oscillator calibration techniques face challenges in achieving accuracy, simplicity, and low overhead, particularly in low power consumption devices and environments where PVT variations cause synchronization issues.
Innovation Solution
A novel calibration method using sampling theory, where the oscillator frequency is sampled at a reference clock frequency, and the samples are compared to a threshold to count transitions, allowing for the determination and correction of the oscillator frequency to compensate for PVT variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PLL-based calibration techniques are used, then frequency accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential calibration function from complex PLL circuits by using a simple counter to count oscillator cycles during a predetermined time period. This removes unnecessary PLL components while retaining the core frequency calibration capability, directly resolving the contradiction between accuracy and complexity.
Solution Approach 2:
The patent replaces expensive, complex PLL calibration circuits with a simple, low-cost counter-based approach. The counter is a minimalistic component that provides sufficient calibration accuracy without the overhead of PLL circuitry, effectively using a 'cheap' solution to replace a 'expensive' one.
2Device complexity
If integer counting based calibration is used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary action by establishing a predetermined time period for counting oscillator cycles. This fixed time window is set in advance to ensure consistent and accurate frequency measurements, improving precision without adding circuit complexity. The predetermined period acts as a preparatory measure that guarantees measurement accuracy.
3Device complexity
If manual calibration is used, then device complexity is reduced, but productivity deteriorates
Solution Approach 1:
The patent implements self-service by enabling the system to automatically perform frequency calibration without human intervention. The microcontroller automatically counts oscillator cycles, compares the count to a reference value, and adjusts the oscillator frequency accordingly. This automated self-calibration process dramatically improves productivity while maintaining low device complexity.
Data Source
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Figure 3~4(c)
Figure 5(a)~6(d)
AI summary
Method for calibrating an oscillator frequency fosc of an oscillator signal in an electronic system functioning at a reference clock with a frequency fclock, comprising: a) sampling of fosc at fclock; b) comparing the samples to a threshold value and obtaining a binary comparison signal; c) counting the number of transitions from zero to one and/or from one to zero in the comparison signal during a number of cycles Ntrans-calib of the reference clock; d) in case fclock ≥ 2 fosc-id where fosc-id is the ideal oscillator frequency, determining the real oscillator frequency: fosc−real=fosc−idNtrans−realNtrans−id Ntrans-real is the counted number of transitions and Ntrans-id is the ideal number of transitions that should occur during Ntrans-calib; in case fclock < 2 * fosc-id, determining the real perceived oscillator frequency fperceived−real=fperceived−idNtrans−realNtrans−id fperceived-id is the ideal perceived oscillator frequency fperceived−id=fosc−id−fclock⋅fosc−idfclock the represents the rounding function; e) correcting the oscillator frequency until Ntrans-real = Ntrans-id