Single-Ended to Differential Buffer Using Shared Switched Capacitors

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Solution Overview

Problem

Existing single-ended to differential buffer circuits require a differential amplifier to be in the ON state during sampling, leading to increased area occupation when handling multiple input signals, as seen in U.S. Pat. No. 7,397,287, which necessitates replicating the circuit for each signal.

Innovation Solution

A single-ended to differential buffer circuit utilizing switched capacitors to sample and convert single-ended input signals to differential signals without requiring the differential amplifier to be in the power ON state during sampling, allowing multiple input signals to be coupled to a shared output section, thereby reducing area occupation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a differential amplifier is used in each input section to convert single-ended signals to differential signals, then the conversion accuracy is improved, but the area occupation increases significantly when handling multiple input signals

Engineering Contradiction:

Improveconversion accuracyVSAvoidarea occupation

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

Multiple input sections that previously each required a dedicated differential amplifier are merged to share a single differential amplifier. The patent reconfigures the circuit so that multiple switched capacitor input sections can sequentially or concurrently share the same differential amplifier resource, dramatically reducing the total area occupation while maintaining conversion accuracy for multiple input signals.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The differential amplifier is designed to serve multiple functions by handling multiple input signals through different input sections. The same differential amplifier can process signals from different input channels at different times or in a multiplexed manner, making it a universal component that replaces multiple specialized amplifiers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If the differential amplifier is kept in the ON state during sampling to maintain signal integrity, then the signal accuracy is improved, but the power consumption increases

Engineering Contradiction:

Improvesignal accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The differential amplifier operates in periodic cycles rather than continuously. It alternates between ON and OFF states, being activated only during specific phases when signal processing is required and remaining OFF during other phases. This periodic operation maintains signal integrity when needed while significantly reducing average power consumption compared to continuous operation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The differential amplifier transitions from a static ON state to a dynamic state where it can be switched between ON and OFF. The circuit incorporates switching mechanisms that dynamically control the amplifier's operation based on the sampling phase, allowing it to be powered ON only when required for signal conversion and powered OFF during non-critical phases.

Inventive Principle:

Principle #15Dynamics

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 achieves high input impedance and efficient conversion of single-ended signals to differential signals without the need for multiple differential amplifiers, maintaining accuracy and reducing area usage, especially suitable for applications with multiple low-frequency input signals like mobile terminals.

Implementation Method 1

a first and a second switched capacitor, each adapted to sample the input analog signal and having a first side and a second side, the first sides of the first and second switched capacitors being controllably connectable/disconnectable to/from said first and second outputs respectively

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

an output section comprising a differential amplifier having a first and a second input, a first and a second output

Methodology Applied

Scientific EffectElectrical amplification:

Data Source

PatentUS8947278B2Single-ended to differential buffer circuit and method for coupling at least a single-ended input analog signal to a receiving circuit with differential inputs

Publication Date: 2015.02.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A single-ended to differential buffer circuit is disclosed, adapted to couple at least an input analog signal to a receiving circuit. The buffer circuit comprises an output section comprising a differential amplifier having a first and a second input, a first and a second output. The buffer circuit further comprises an input section comprising a first and a second switched capacitor, each adapted to sample said input analog signal and having a first side and a second side, the first sides of the first and second switched capacitors being controllably connectable/disconnectable to/from said first and second outputs respectively. In the buffer circuit the second sides of said first and second switched capacitors are controllably connectable/disconnectable to/from said first and second inputs of the differential amplifier respectively. Moreover, in the buffer circuit the second sides of the first and second switched capacitors are controllably connectable/disconnectable to/from said second output and said first output respectively. A method for coupling at least a single-ended input analog signal to a receiving circuit with differential inputs is also disclosed.