Ring VCO Startup Helper Circuit for Midpoint Biasing
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Solution Overview
Problem
Traditional ring voltage controlled oscillators (VCOs) face challenges in startup due to large inverter size ratios, leading to increased loading and power consumption, and may get stuck in a latched condition if auxiliary inverters are not properly sized, disrupting differential operation and oscillation.
Innovation Solution
The implementation of a ring VCO circuit with a startup helper circuit, featuring a series of stages with parallel inverters and biasing resistors connected to inputs and outputs, providing a resisting bias to help internal nodes converge to a midpoint around half the supply voltage, maintaining differential operation and aiding in startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large inverter size ratio is used between main inverter and auxiliary inverter, then startup is ensured, but loading and power consumption increase
Solution Approach 1:
The biasing resistor is connected to provide a preliminary voltage bias at the input node before the VCO startup process begins. This preliminary action sets the initial voltage condition that facilitates reliable startup without requiring oversized inverters, thereby reducing power consumption while ensuring startup reliability.
Solution Approach 2:
The biasing resistor acts as an intermediary element that mediates the voltage distribution at the inverter input node. It provides a controlled voltage bias that enables the auxiliary inverter to function properly during startup without requiring a large size ratio, thus resolving the contradiction between startup reliability and power consumption.
2Use of energy by moving object
If auxiliary inverter size is reduced to decrease loading and power consumption, then power efficiency improves, but latched conditions may occur disrupting differential operation
Solution Approach 1:
The biasing resistor provides a preliminary voltage bias that ensures the auxiliary inverter operates in the correct region during startup. This preliminary voltage setting allows the auxiliary inverter to be sized smaller without risking latched conditions, maintaining differential operation reliability while reducing power consumption.
Solution Approach 2:
The biasing resistor changes the voltage parameter at the inverter input node, establishing an optimal operating point that enables smaller auxiliary inverter sizing. This parameter change ensures that even with reduced auxiliary inverter size, the differential operation remains reliable and latched conditions are prevented.
3Area of moving object
If inverter size ratio is optimized for compact layout, then area reduction is achieved, but startup may fail due to insufficient driving capability
Solution Approach 1:
The biasing resistor provides a preliminary voltage bias that compensates for the reduced driving capability of smaller inverters in compact layouts. This preliminary action ensures that even with optimized (smaller) inverter sizes for area efficiency, reliable startup is still achieved.
Solution Approach 2:
The biasing resistor serves as an intermediary that bridges the gap between compact inverter sizing and sufficient driving capability. It provides the necessary voltage bias to ensure proper operation of smaller inverters, enabling area reduction without sacrificing startup reliability.
Data Source
AI summary
A ring voltage controlled oscillator (VCO) circuit is herein provided. According to one embodiment, a ring VCO circuit includes a plurality of stages connected in series, wherein each stage includes a first inverter, a second inverter, a third inverter and a fourth inverter, the first inverter connected in parallel with the third and fourth inverters and the second inverter connected in parallel with the third and fourth inverters, and a first biasing resistor connected to a first node and coupled to an input of the first inverter. The first biasing resistor includes a first switch configured to set the first biasing resistor to about zero voltage.