Switched-Capacitor Differential Buffer for Shared Analog Inputs
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Solution Overview
Problem
Existing buffer circuits require a differential amplifier to be in the power ON state during sampling, leading to increased area occupation when handling multiple single-ended analog signals, especially in applications like mobile terminals where high source impedances and low-frequency signals are common.
Innovation Solution
A single-ended to differential buffer circuit utilizing switched capacitors and a resettable differential amplifier, where the capacitors sample and hold the input signal without requiring the amplifier to be constantly powered, allowing for multiple inputs to share a single output section and reducing area occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential amplifier is used for each input signal to convert single-ended signals to differential signals, then the conversion accuracy and reliability are improved, but the area occupation increases significantly when handling multiple input signals
Solution Approach 1:
The patent merges multiple input signal processing paths into a single shared differential amplifier. Multiple switched capacitor networks (SC1-SC4, SC5-SC8) connect to a common differential amplifier output, allowing multiple single-ended signals to be converted to differential signals using one amplifier instead of requiring separate amplifiers for each input channel.
Solution Approach 2:
The differential amplifier is designed to serve multiple functions by accepting inputs from multiple switched capacitor networks simultaneously. The single amplifier handles conversion for multiple input signals (Vin1, Vin2, etc.) through time-multiplexed switching, making it a universal component that replaces multiple dedicated amplifiers.
2Measurement precision
If the differential amplifier is kept in power ON state during sampling, then the signal conversion accuracy is maintained, but the energy consumption increases
Solution Approach 1:
The differential amplifier operates in periodic cycles rather than continuously. It alternates between active conversion phases (when needed for signal processing) and low-power standby states. The switched capacitor networks perform sampling and holding functions during intervals when the amplifier is not actively converting signals, reducing overall energy consumption while maintaining conversion accuracy when the amplifier is active.
3Adaptability or versatility
If multiple dedicated buffer circuits are used for multiple input signals, then the signal processing capability is improved, but the device complexity increases
Solution Approach 1:
The circuit is segmented into modular switched capacitor networks (SC1-SC4 for first signal, SC5-SC8 for second signal) that can be selectively activated. Each segment handles a specific input signal through controlled switching, allowing the system to process multiple inputs without requiring permanently active complex circuitry for each channel.
Solution Approach 2:
The circuit employs dynamic switching mechanisms where the switched capacitors and amplifiers are activated only when needed for specific signal conversions. The switching network dynamically connects different input signals to the shared differential amplifier based on processing requirements, reducing static complexity while maintaining dynamic multi-input capability.
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 signals.
Implementation Method 1
an input circuit section (21) associated to said single ended input analog signal (Vin) comprising a first (CS1) and a second (CS2) switched capacitor
Data Source
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AI summary
A single-ended to differential buffer circuit is (21,22) is disclosed, adapted to couple at least an input analog signal (Vin) to a receiving circuit (24). The buffer circuit (21,22) comprises an output section (22) comprising a differential amplifier (25) having a first (31) and a second (32) input, a first (41) and a second (42) output. The buffer circuit further comprises an input section (21) comprising a first (CS1) and a second (CS2) switched capacitor, each adapted to sample said input analog signal (Vin) and having a first side (p1',p2') and a second side (p1", p2"), the first sides (p1', p2') of the first and second switched capacitors being controllably connectable / disconnectable to/from said first (41) and second (42) outputs respectively. In the buffer circuit the second sides (p1",p2") of said first (CS1) and second (CS2) switched capacitors are controllably connectable/disconnectable to/from said first (31) and second (32) inputs of the differential amplifier (25) respectively. Moreover, in the buffer circuit the second sides (p1", p2") of the first and second switched capacitors (CS1,CS2) are controllably connectable/disconnectable to/from said second output (42) and said first output (41) respectively. A method (100) for coupling at least a single-ended input analog signal (Vin) to a receiving circuit (24) with differential inputs is also disclosed.