Self-Calibrating PLL Oscillator Trimming Without Factory Testing
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Solution Overview
Problem
Conventional phase-locked loop (PLL) circuits require factory testing and permanent trimming of voltage-controlled oscillators (VCOs), limiting their frequency range and increasing manufacturing costs, while self-calibrating designs often necessitate additional components or longer calibration times.
Innovation Solution
A phase-locked loop circuit with a self-calibration mechanism that uses the phase/frequency detector's error signals to automatically trim the oscillator to the appropriate operating curve upon power-up, eliminating the need for factory trimming and additional components, and allowing reuse across different applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If factory testing and permanent trimming of VCOs is performed, then manufacturing precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies preliminary action by performing VCO trimming automatically during the first normal operation state upon power-up, rather than requiring factory testing. The microcontroller unit automatically adjusts the VCO trim value based on frequency measurements taken during initial operation, eliminating the need for complex factory testing equipment and processes while achieving the same frequency accuracy.
2Manufacturing precision
If permanent trimming is applied to VCOs, then manufacturing precision is improved, but adaptability deteriorates
Solution Approach 1:
The patent implements dynamics by making the VCO trim value adjustable and reconfigurable rather than permanent. The microcontroller unit can modify the trim value stored in non-volatile memory based on actual frequency measurements and environmental conditions, allowing the VCO to adapt to different frequency requirements and operating conditions while maintaining accurate frequency control.
3Adaptability or versatility
If self-calibration is implemented using additional components, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the microcontroller unit perform multiple functions: it controls the oscillator, measures frequency, determines trim values, and manages calibration operations. This multi-functional approach eliminates the need for separate dedicated calibration circuits, state machines, or additional counters, achieving self-calibration capability while minimizing additional hardware complexity.
4Adaptability or versatility
If calibration circuits with state machines are used, then adaptability is improved, but productivity deteriorates due to longer calibration time
Solution Approach 1:
The patent applies skipping by implementing a streamlined calibration process that quickly transitions through necessary steps. The microcontroller unit performs frequency measurement and trim value determination in a rapid sequence during the first normal operation state, avoiding lengthy calibration routines. The system rushes through the essential calibration steps without unnecessary delays, achieving fast automatic trimming.
Data Source
AI summary
A phase-locked loop circuit comprises an oscillator having a plurality of operating curves and being suitable for generating an output signal. In a calibration state the oscillator is trimmed to an operating curve for use in a normal operation state. The phase-locked loop circuit further comprises a phase/frequency detector being suitable for generating at least one error signal based on an input signal and a feedback signal generated on the basis of the output signal. The phase-locked loop circuit further comprises a loop filter being suitable for generating a loop-filter signal based on the at least one error signal, the loop-filter signal being applied to the oscillator in the normal operation state. The phase-locked loop circuit further comprises a calibration circuit being suitable for trimming the oscillator to the operating curve for use in the normal operation state on the basis of the at least one error signal.