Bootstrap Circuit Precharge for Parasitic Capacitance in ADCs

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Solution Overview

Problem

Conventional bootstrap circuits fail to generate a booting voltage effectively due to parasitic capacitance at output nodes, which affects the operation of subsequent circuits.

Innovation Solution

A bootstrap circuit comprising a receiving circuit, a switched capacitor module, and a booting circuit is designed to apply an initial voltage to the control signal, enabling the transistor and increasing the voltage level, thereby reducing the influence of parasitic capacitance and improving signal quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional bootstrap circuit uses a switched capacitor to generate booting voltage, then the circuit structure is simple, but parasitic capacitance at output nodes prevents the booting voltage from reaching the target level

Engineering Contradiction:

Improvebooting voltage generation accuracyVSAvoidcircuit structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The bootstrap circuit is divided into multiple functional modules: a receiving circuit with transistor and gate, a switched capacitor module with separate control, and a booting circuit with initial voltage source. This segmentation allows each module to be optimized independently, with the booting circuit specifically addressing the parasitic capacitance issue without redesigning the entire system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The booting circuit applies an initial voltage to the gate of the receiving circuit before the switched capacitor module operates. This preliminary action ensures that the gate is pre-charged to the required voltage level, compensating for the voltage loss caused by parasitic capacitance and ensuring accurate booting voltage generation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If parasitic capacitance is present at output nodes, then the circuit implementation is straightforward, but the booting voltage cannot reach the target level and subsequent circuit operations are affected

Engineering Contradiction:

Improvesignal qualityVSAvoidparasitic capacitance influence

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The booting circuit provides an initial voltage that counteracts the harmful effect of parasitic capacitance before it can degrade the signal quality. By pre-charging the gate to the appropriate voltage level, the circuit compensates for the voltage drop that would otherwise occur due to parasitic capacitance, thereby maintaining signal integrity.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The booting circuit acts as an intermediary between the power supply and the receiving circuit, providing a buffered initial voltage that isolates the receiving circuit from the direct impact of parasitic capacitance. This intermediary stage ensures that the control signal maintains its intended voltage level despite the presence of parasitic elements.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If the control signal voltage level is insufficient, then the transistor cannot be properly enabled, but increasing the voltage level requires additional circuit components

Engineering Contradiction:

Improvetransistor switching capabilityVSAvoidvoltage level adjustment circuit

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The booting circuit is merged with the receiving circuit by directly coupling the initial voltage source to the gate. This integration allows the voltage level adjustment to be achieved without adding separate, standalone voltage boosting equipment, thereby improving transistor switching capability while minimizing the increase in overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

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

The solution enhances the linearity and quality of the output signal, making it more suitable for subsequent circuits by effectively overcoming the limitations imposed by parasitic capacitance.

Implementation Method 1

The switched capacitor module comprises a capacitor and a plurality of switches coupled to the capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the booting voltage may not reach the goal due to parasitic capacitance at output nodes of the switched capacitor

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Data Source

PatentUS10601435B2Initial booting bootstrap circuit and associated analog-to-digital converter

Publication Date: 2020.03.24 MEDIATEK INC

AI summary

A bootstrap circuit including a receiving circuit, a switched capacitor module and a booting circuit is provided. The receiving circuit receives an input signal to selectively output an output signal according to a control signal. The switched capacitor module is coupled to the input signal, and is arranged for generating the control signal according to the input signal. The booting circuit is coupled to the receiving circuit, and is arranged for applying an initial voltage when the control signal starts to enable the transistor, to increase a voltage level of the control signal.