On-Chip Oscillator Calibration During SPI Control Messages
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Solution Overview
Problem
Existing RF front-end chips, such as mmWave beamformer chips, require an accurate on-chip oscillator but cannot justify the use of expensive precision oscillators, leading to inaccuracies due to process and temperature variations, and current solutions like dummy SPI commands or additional control lines are inefficient and space-consuming.
Innovation Solution
An adjustable oscillator is integrated into the IC, calibrated during standard control protocol messages using a precise clock frequency, enabling accurate operation without dummy commands or additional control lines, and is periodically re-calibrated during SPI or other serial control protocol commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an expensive precision oscillator is used, then oscillator accuracy is improved, but cost increases
Solution Approach 1:
The patent uses a low-cost, integrated ring oscillator instead of an expensive precision oscillator. The ring oscillator is calibrated periodically using measurement circuitry and control logic to maintain adequate accuracy for non-critical RFFE operations, accepting that it requires periodic recalibration rather than being permanently precise.
Solution Approach 2:
The patent changes the operating parameters of the ring oscillator through calibration. Measurement circuitry measures the oscillator's actual frequency, and control logic adjusts calibration parameters to compensate for process and temperature variations, transforming a low-cost oscillator into one with improved effective accuracy.
2Measurement precision
If dummy SPI commands or additional control lines are used for calibration, then oscillator accuracy is improved, but device complexity and space consumption increase
Solution Approach 1:
The patent merges the oscillator calibration function with existing SPI control protocol messages. The measurement circuitry and control logic use standard SPI commands that are already present in the system, eliminating the need for separate dummy commands or additional control lines. The calibration data is transmitted through the existing SPI interface.
Solution Approach 2:
The control logic and measurement circuitry serve multiple functions: they calibrate the oscillator during normal SPI operations and also provide frequency measurement capabilities. This multi-functionality eliminates the need for dedicated calibration-only control mechanisms.
3Measurement precision
If continuous calibration is performed, then oscillator accuracy is maintained, but power consumption increases
Solution Approach 1:
The patent implements periodic calibration instead of continuous calibration. The control logic periodically initiates calibration sequences based on temperature changes, time intervals, or specific SPI message triggers. This maintains oscillator accuracy when needed while allowing the measurement circuitry and calibration functions to remain inactive during stable operating conditions, reducing power consumption.
Data Source
AI summary
A wireless communication device can include an oscillator circuit. The oscillator circuit can include an oscillator and measurement circuitry coupled to the oscillator. The measurement circuitry can receive an output signal of the oscillator and measure oscillator error by comparing the output signal of the oscillator to a nominal frequency for an amount of time. The oscillator circuit can further include adjustment circuitry to adjust an oscillator frequency of the oscillator based on the measured oscillator error.