Multiphase Low-Current Oscillator Without Comparator Bottlenecks
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Solution Overview
Problem
Conventional relaxation oscillators are limited to frequencies below 1 MHz, require high current consumption, and are not suitable for multiphase systems due to their reliance on comparators and voltage-dependent properties, making them inefficient for high-frequency applications and portable devices.
Innovation Solution
The design eliminates the need for a conventional comparator by using differential input stages with a reference stage and phase stages, incorporating transistors, current sources, capacitors, and logic blocks to provide variable current supply through negative feedback, allowing for efficient operation at high frequencies and multiphase capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional relaxation oscillators are used, then the circuit is simple and easy to manufacture, but the frequency is limited to below 1 MHz and current consumption is high
Solution Approach 1:
The patent changes the fundamental operating parameters of the oscillator by eliminating the comparator and one-shot timer, using instead a differential input stage with cross-coupled transistors and capacitors. This parameter change enables the circuit to operate at frequencies up to 50 MHz while maintaining manufacturing simplicity through standard CMOS processes.
Solution Approach 2:
The patent extracts and removes the comparator and one-shot timer components from the conventional relaxation oscillator architecture. By taking out these frequency-limiting components, the circuit achieves high-frequency operation capability while reducing the number of discrete components and overall circuit complexity.
2Device complexity
If conventional relaxation oscillators are used, then the circuit architecture is simple, but current consumption is high making them unsuitable for portable devices
Solution Approach 1:
The differential input stage with cross-coupled transistors and capacitors creates a self-sustaining oscillation mechanism that does not require external one-shot timers or complex control logic. The circuit generates its own timing signals through the inherent properties of the differential pair and feedback network, reducing overall current consumption while maintaining architectural simplicity.
3Ease of manufacture
If conventional relaxation oscillators are used, then the design is straightforward, but they are not suitable for multiphase systems due to voltage-dependent properties
Solution Approach 1:
The differential input stage architecture provides a universal foundation that can easily generate multiple phases by adding more differential pairs with appropriate phase shifts. The circuit's performance becomes independent of supply voltage variations, enabling reliable multiphase operation for applications such as phase-shifted PWM controllers and multi-phase power converters.
4Ease of manufacture
If conventional relaxation oscillators are used, then the circuit uses standard components, but frequency stability varies with supply voltage and temperature
Solution Approach 1:
The cross-coupled transistor configuration with capacitive feedback creates a regenerative effect that stabilizes the oscillation frequency. The differential input stage provides inherent compensation for supply voltage and temperature variations through its symmetric structure and feedback mechanism, maintaining frequency stability while using only standard CMOS components.
Data Source
AI summary
An oscillator includes a reference stage and multiple phase stages. The reference stage has a reference transistor having a gate coupled to a voltage reference and a drain coupled to a reference current source. Each phase stage includes a transistor, two current sources, a capacitor, switch, inverter, and latch. The transistor has a drain coupled to a first current source, a gate coupled to a node and a source coupled to the reference transistor's source. The capacitor and switch couple between the node and ground. The second current source couples to the node. The transistor's drain couples to the inverter's input. The inverter's output couples to the latch's set input. The latch's output couples to the switch. The inverter output also couples to the reset input of a subsequent phase stage's latch. The inverter output for a last stage couples to the reset input of a first stage latch.