PLL-VCO Partitioning With Interface Calibration for Low Spurious Tones
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Solution Overview
Problem
Oscillator circuits employing phase locked loops (PLLs) face issues with spurious tones due to low isolation between PLL and voltage-controlled oscillator (VCO) circuitry, which limits performance and cannot always be filtered effectively.
Innovation Solution
An integrated circuit design that spatially isolates PLL and VCO circuitry by implementing two instances of the integrated circuit, where one instance handles PLL functionality and the other VCO functionality, with a single interface for control and calibration, reducing cross-coupling and spurious tones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PLL and VCO circuitry are integrated on the same chip, then device complexity is reduced and integration is improved, but spurious tones increase due to low isolation between circuit blocks
Solution Approach 1:
The patent divides the oscillator system into two separate integrated circuit devices: one dedicated to PLL functionality and the other to VCO functionality. This segmentation physically separates the circuit blocks that generate spurious tones, allowing each device to be optimized independently while reducing cross-coupling and interference between the PLL and VCO circuitry.
2Object-generated harmful factors
If two separate integrated circuits are used for PLL and VCO functionality, then spurious tones are reduced through improved isolation, but device complexity and interconnection requirements increase
Solution Approach 1:
The patent introduces interface circuitry as an intermediary component that manages communication between the PLL device and VCO device. This interface includes calibration circuitry and control signal pathways that simplify the interconnection requirements, allowing the two separate devices to work together as a coordinated system without requiring complex external routing or additional components.
3Object-generated harmful factors
If PLL and VCO circuitry are separated spatially, then isolation is improved and spurious tones are reduced, but calibration and control complexity increases
Solution Approach 1:
The patent combines the calibration and control functions into a unified interface system that manages both PLL and VCO devices. The calibration circuitry is designed to work across device boundaries, allowing centralized control and calibration procedures that simplify the user interface while maintaining the physical separation needed for low spurious tone operation.
Data Source
AI summary
An integrated circuit includes phase locked loop (PLL) circuitry, voltage controlled oscillator (VCO) circuitry, and interface circuitry. The PLL circuitry includes a reference signal input terminal, a reference frequency divider circuit, a reference signal output terminal, a switch, a phase detector, a charge pump, and a control voltage output terminal. The reference frequency divider circuit is coupled to the reference signal input terminal. The switch is coupled to the reference frequency divider circuit and to the reference signal output terminal. The switch is configured to switchably connect the reference frequency divider circuit to the reference signal output terminal. The VCO circuitry includes a control voltage input terminal, a VCO, calibration circuitry, and a calibration input/output (I/O) terminal. The VCO is coupled to the control voltage input terminal. The calibration circuitry is coupled to the VCO. The calibration I/O terminal is coupled to the calibration circuitry.