Reference Voltage Stabilizer Circuit for Noise Reduction
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Solution Overview
Problem
Conventional reference voltage stabilizer circuits for AD converters face challenges in maintaining stability against both disturbance noise and self-noise, particularly in high-speed and high-accuracy applications, due to limitations in capacitive elements and buffers, which often result in trade-offs that fail to ensure adequate noise reduction within the required time frames.
Innovation Solution
A reference voltage stabilizer circuit is introduced, comprising a preceding-stage capacitive path and a subsequent-stage resistive path with a transistor and bias generator circuit, which separates the signal line into an I/O pin side and an internal circuit side, allowing for effective reduction of disturbance noise by the capacitive path and self-noise by the resistive circuit, enabling rapid stabilization of the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an external bypass capacitor is provided between I/O pins outside an integrated circuit, then disturbance noise on the reference voltage is reduced, but the capacitor becomes less effective around 100 MHz or more due to parasitic inductance of the package
Solution Approach 1:
The patent divides the noise filtering function into two separate stages: an external bypass capacitor for low-frequency disturbance noise and an internal bypass capacitor for high-frequency self-noise. This segmentation allows each capacitor to operate in its optimal frequency range, overcoming the limitation of the external capacitor becoming ineffective above 100 MHz due to parasitic inductance.
Solution Approach 2:
The patent introduces an internal bypass capacitor as an intermediary element between the external bypass capacitor and the reference voltage source. This internal capacitor acts as a mediator that handles high-frequency noise that the external capacitor cannot effectively filter, thereby maintaining reference voltage stability across a broad frequency spectrum.
2Object-generated harmful factors
If the capacitance of the internal bypass capacitor is increased to compensate for the external capacitor's ineffectiveness, then self-noise is reduced, but ringing of noise occurs due to resonance with parasitic inductance
Solution Approach 1:
The patent applies partial action by using a relatively small internal bypass capacitor (e.g., 100 fF to 10 pF) rather than a large capacitor that would cause resonance. This smaller capacitance is sufficient to handle high-frequency self-noise without creating problematic resonance with the parasitic inductance, thus avoiding ringing noise while still providing effective noise filtering.
3Measurement precision
If a large capacitive element is provided inside an integrated circuit to reduce self-noise, then AD conversion accuracy is improved, but it is unrealistic to provide such a large capacitive element inside an integrated circuit
Solution Approach 1:
The patent changes the capacitance parameter to a small value (100 fF to 10 pF) that is realistic for integration while maintaining effectiveness. By combining this small internal capacitor with the external bypass capacitor, the system achieves the noise reduction performance equivalent to a large capacitor without the area penalty, thus improving AD conversion accuracy while keeping the integrated circuit compact.
4Object-affected harmful factors
If only an external bypass capacitor is used, then disturbance noise is reduced, but it cannot respond to self-noise generated by the AD converter itself
Solution Approach 1:
The patent segments the noise filtering responsibilities between external and internal components. The external bypass capacitor handles disturbance noise from power supply variations, while the internal bypass capacitor specifically addresses self-noise generated by the AD converter. This segmentation ensures both types of noise are effectively managed by the appropriate component positioned optimally.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration maintains stable reference voltages despite parasitic inductance and high-frequency noise, ensuring high AD conversion accuracy and reducing the need for large capacitive elements, thus overcoming the limitations of conventional methods.
Implementation Method 1
a preceding-stage circuit (1) including a capacitive path connected between the first and second signal lines
Implementation Method 2
a subsequent-stage circuit (2) including a resistive path connected between the first and second signal lines
Data Source
AI summary
A reference voltage is maintained stable against disturbance noise and self-noise of an internal circuit. A reference voltage stabilizer circuit for stabilizing the reference voltage to be supplied through at least one of first or second signal lines includes a preceding-stage circuit including a capacitive path connected between the first and second signal lines; and a subsequent-stage circuit including a resistive path connected between the first and second signal lines, and a resistive circuit inserted, between the capacitive path and the resistive path, into one of the first or second signal lines through which the reference voltage is supplied.