PLL Oscillator Voltage Regulation for PVT-Stable Frequency
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Solution Overview
Problem
Phase locked loops (PLLs), particularly in RF systems, face reduced operational reliability due to sensitivity to process-voltage-temperature (PVT) variations, which affect the stability of oscillation voltage and frequency, leading to reduced reliability in digital signal transmission and communication systems.
Innovation Solution
An integrated circuit design that includes an oscillator, a voltage regulator, and a current injection circuit, where the voltage regulator uses an operational amplifier and a reference voltage generator to maintain a constant output voltage and current, and the current injection circuit provides oscillation current to the oscillator, thereby stabilizing the oscillation voltage and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an oscillator in a time-digital converter is used to convert phase difference into a digital signal, then the PLL can operate with logic circuits only, but the operational reliability is reduced due to sensitivity to PVT variations
Solution Approach 1:
The patent implements a feedback mechanism where the oscillation voltage from the ring oscillator is fed back to the voltage regulator. The voltage regulator continuously monitors the oscillation voltage and adjusts its output to maintain a constant voltage level, compensating for PVT variations. This feedback loop ensures that the oscillator operates reliably despite process, voltage, and temperature changes while maintaining all-digital operation.
Solution Approach 2:
The voltage regulator automatically adjusts its output voltage based on the actual oscillation voltage level without external intervention. The system uses the oscillator's own output voltage as the reference for regulation, creating a self-correcting mechanism that maintains stable oscillation conditions despite PVT variations, thereby improving operational reliability while keeping the system fully digital.
2Stability of the object's composition
If the voltage regulator provides constant output voltage to the oscillator, then the oscillation frequency stability is improved, but the circuit complexity increases due to additional regulation components
Solution Approach 1:
The patent combines the voltage regulator and the oscillator into a tightly coupled system where the regulator directly supports the oscillator core. The voltage regulator is designed to work specifically with the ring oscillator, merging the voltage control function with the oscillation generation function. This integration achieves frequency stability through constant voltage supply while minimizing additional circuit complexity by making the regulator an inherent part of the oscillator system rather than a separate external component.
3Stability of the object's composition
If the current injection circuit provides oscillation current to the oscillator, then the oscillation voltage constantness is improved, but the device complexity increases due to additional current injection components
Solution Approach 1:
The current injection circuit pre-charges or pre-discharges specific nodes in the ring oscillator at predetermined times during the oscillation cycle. By injecting current in advance to compensate for expected voltage drops or fluctuations, the circuit maintains more constant oscillation voltage levels. This preliminary action approach improves voltage constantness while minimizing complexity by using simple current switches rather than continuous regulation circuits.
Data Source
AI summary
An integrated circuit including: an oscillator configured to generate an oscillating voltage with a predetermined oscillation frequency in an oscillation period; a voltage regulator configured to generate an output voltage for driving the oscillator and provide the output voltage to the oscillator; and a current injection circuit configured to provide an oscillation current to the oscillator, in response to an oscillation enable signal in the oscillation period.