Multi-Oscillator TD Converter for Low-Noise Digital PLLs
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Solution Overview
Problem
Conventional PLL circuits face challenges in miniaturization due to the variance of analog circuit characteristics and increased leakage currents, leading to limited improvements in area, power consumption, and speed, while ADPLL circuits, which replace analog components with digital ones, offer potential solutions but struggle with quantization noise and power supply voltage fluctuations.
Innovation Solution
A TD converter with multiple oscillators operating in different modes, using a PFD circuit and computation circuit to process phase information from these oscillators, reduces quantization noise and power supply voltage fluctuations by adjusting operating frequencies based on input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If analog components are replaced with digital components in PLL circuits, then area is reduced and power consumption is lowered, but quantization noise increases
Solution Approach 1:
The patent divides the oscillation measurement function into multiple oscillators operating at different frequencies. Instead of using a single oscillator, the system employs a first oscillator and a second oscillator with different oscillation frequencies, allowing the digital circuit to measure phase differences without being affected by quantization noise at a single frequency point.
Solution Approach 2:
The patent changes the oscillation frequency parameter by using multiple oscillators with different frequencies. The digital circuit selects appropriate oscillation periods from different frequency ranges to measure the time difference, thereby avoiding the quantization noise problem that occurs when using a fixed frequency oscillator.
2Object-affected harmful factors
If multiple oscillators with different frequencies are used, then quantization noise is reduced, but device complexity increases
Solution Approach 1:
The patent designs a digital circuit that can universally handle multiple oscillation frequencies. The same digital circuit measures both the first oscillation period from the first oscillator and the second oscillation period from the second oscillator, and can flexibly select appropriate periods for time difference measurement, reducing the need for separate dedicated circuits for each frequency.
Solution Approach 2:
The patent combines the functions of multiple oscillators and a unified digital measurement circuit into a single integrated system. The digital circuit integrates the measurement of different oscillation periods and performs the time difference calculation in a unified manner, reducing overall system complexity despite using multiple oscillators.
3Device complexity
If a single oscillator is used, then device complexity is minimized, but measurement precision deteriorates due to quantization noise
Solution Approach 1:
The patent introduces dynamic frequency selection where the digital circuit can adaptively choose oscillation periods from different frequency ranges based on the measurement requirements. This dynamic approach allows the system to maintain high measurement precision by selecting appropriate oscillation periods while keeping the overall device complexity manageable through a unified digital measurement architecture.
Data Source
AI summary
Provided is a TD converter including: a plurality of oscillators which at least include a first oscillator and a second oscillator receiving control signals input thereto, respectively, and operating in operating modes with oscillation frequencies different from each other, respectively, wherein each control signal indicates a time difference between a reference clock and a target clock; and a computation circuit which calculates a digital output value depending on the time difference, by using a plurality of pieces of phase information retained according to the reference clock in the plurality of oscillators, respectively.