Voltage Switching Regulator Circuit for Jitter-Free Clock Stability
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Solution Overview
Problem
In electronic circuits requiring smooth switching between core and regulated supply voltages, existing technologies face challenges such as frequency jitter and large settling times due to variations in SoC current, leading to unstable oscillator performance.
Innovation Solution
A system and method involving a regulator circuit with a unity gain buffer and a low pass filter, where the first supply voltage is applied to both the load and the regulator circuit's input node, followed by a gradual transition to the second regulated supply voltage, using a sink current equal to the load current and a reference voltage from a bandgap reference circuit, to minimize overshoot and undershoot during the switch-over.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the supply voltage is switched directly from core supply to regulated supply, then the switching speed is fast, but frequency jitter and instability occur
Solution Approach 1:
The regulator circuit is activated in advance before the actual supply switching occurs. The input node of the regulator is connected to the core supply voltage beforehand, allowing the regulator to pre-establish its output voltage and be ready for smooth transition when the switching occurs, thereby avoiding frequency jitter while maintaining fast switching.
2Reliability
If a conventional bandgap driven regulator system is used, then power supply rejection ratio is improved, but bandwidth is restricted resulting in large settling time
Solution Approach 1:
The regulator circuit with unity gain buffer is activated in advance during the preparation phase, before the actual supply switching occurs. This preliminary activation allows the regulator to establish its output voltage and be ready for smooth transition, reducing the settling time while maintaining high power supply rejection ratio.
3Loss of time
If the supply voltage switches suddenly from one value to another, then the transition is quick, but overshoot and undershoot occur causing jitter
Solution Approach 1:
The regulator circuit acts as an intermediary between the core supply and the load. By connecting the regulator's input node to the core supply and its output to the load, it mediates the voltage transition, preventing sudden changes and eliminating overshoot and undershoot while maintaining quick transition.
Solution Approach 2:
The regulator circuit is activated in advance before the actual supply switching occurs. The input node of the regulator is connected to the core supply voltage beforehand, allowing the regulator to pre-establish its output voltage and be ready for smooth transition when the switching occurs, thereby avoiding frequency jitter while maintaining fast switching.
Data Source
AI summary
A system switches between application of a first supply voltage and a second supply voltage to a load. The second supply voltage is a regulated voltage that is generated from the first supply voltage, or is alternatively generated from a reference voltage, such as bandgap. When the load is supplied from the first supply voltage, the regulated voltage is also generated from the first supply voltage. At or after switching the load to the second supply voltage, the regulated voltage is generated instead from the reference voltage. The load is a clock circuit, such as an oscillator. The controlled switching of the supply voltage for the load in the manner described addresses concerns over introducing errors in the output clock signal when the clock circuit's supply voltage is changed.