Self-Calibrating Oscillator Circuit for Fast On-Chip Frequency Trimming
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Solution Overview
Problem
Integrated oscillators in power management integrated circuits (PMICs) face significant variations due to process variations, component tolerances, temperature, and voltage sensitivity, leading to frequency deviations of up to 25-50% from their intended operating frequency, which complicates calibration and increases manufacturing costs and time.
Innovation Solution
The implementation of self-calibrating oscillators that use a compact circuit with additional logic gates to autonomously measure and adjust voltage and current references, eliminating the need for external frequency measurement and reducing calibration time from milliseconds to microseconds, allowing for on-chip calibration without expensive test equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional external calibration equipment is used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The oscillator performs self-calibration by internally measuring its own output frequency using a counter and timing circuit integrated within the oscillator itself, eliminating the need for external frequency measurement equipment. The oscillator compares its output frequency against a reference and automatically adjusts its operating parameters to achieve the target frequency.
Solution Approach 2:
A time interval measurement circuit serves as an intermediary between the oscillator output and the calibration control system. This circuit measures the time interval between consecutive rising edges of the oscillator output signal, converting frequency information into a measurable time parameter that can be processed by the calibration logic.
2Manufacturing precision
If traditional calibration methods are used, then frequency accuracy is improved, but calibration time increases
Solution Approach 1:
The calibration system pre-calculates the required adjustment amount based on the measured frequency deviation. By determining the correction value in advance and applying it directly to the oscillator's control voltage or current, the system achieves rapid calibration without iterative adjustments, reducing calibration time from milliseconds to microseconds.
Solution Approach 2:
The patent replaces manual or iterative mechanical calibration processes with an automated electronic system that uses digital counting, time interval measurement, and electronic voltage/current adjustment. This substitution enables parallel processing of multiple oscillators and eliminates the time-consuming step-by-step adjustment process.
3Ease of manufacture
If untrimmed oscillators are used, then manufacturing cost is reduced, but frequency variation increases
Solution Approach 1:
The patent adjusts the oscillator's operating parameters (voltage, current, or frequency division ratio) through digital control after fabrication. By measuring the actual output frequency and calculating the required parameter change, the system compensates for manufacturing variations in passive components and transistor characteristics, achieving consistent frequency output across all oscillators without requiring precise initial trimming.
Data Source
AI summary
Integrated circuits having self-calibrating oscillators, and methods of operating the same are disclosed. A disclosed example integrated circuit includes a clock generator, a comparator having a first input connected to an output of the clock generator and a second input connected to a reference voltage, a calibration done detector having an input connected to an output of the comparator and an output communicatively coupled to a calibration code register.