Differential Receiver Wake-Up Using Common-Mode Decoupling Capacitors
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Solution Overview
Problem
In computing systems, differences in power supply voltages and semiconductor process technologies between integrated circuits lead to challenges in AC coupling, particularly during power-up, where rapid application of a new DC bias is necessary to facilitate communication between integrated circuits with different DC bias levels.
Innovation Solution
A bus charging circuit that generates a current control signal based on a power-up signal to source either a rapid charge current or a trickle charge current to a capacitively coupled input/output port of an integrated circuit, with the option to select a trickle charge current after a delay period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a series capacitor is used to remove DC component and allow only high frequency signal to pass, then signal transmission quality is improved, but the time required to charge the capacitor during power-up increases, delaying communication start
Solution Approach 1:
The patent applies preliminary action by pre-charging the series capacitor through a dedicated charging circuit before normal signal transmission begins. The charging circuit activates during power-up to establish the necessary DC bias voltage on the capacitor, so that when communication starts, the capacitor is already charged and ready to pass high-frequency signals immediately, eliminating the delay that would otherwise occur while the capacitor charges through the signal path
Solution Approach 2:
The patent uses an intermediary charging circuit as a mediator between the power supply and the series capacitor. This charging circuit includes a control circuit that generates a current control signal and a charging circuit that sources current to the capacitor, acting as an intermediate structure that prepares the capacitor for operation without interfering with the main signal transmission path once charged
2Adaptability or versatility
If integrated circuits have different power supply requirements and voltage levels, then device functionality is improved, but establishing a common DC bias for communication between circuits becomes difficult
Solution Approach 1:
The series capacitor acts as an intermediary element that couples different voltage domains while blocking DC offset. By placing a capacitor in the signal path between integrated circuits with different power supply voltages, the DC components from different voltage levels are blocked, while AC signal components can pass through. This allows circuits with different power supply requirements to communicate reliably without direct DC connection
Solution Approach 2:
The patent changes the electrical parameters of the signal path by introducing a series capacitor that transforms the coupling method between circuits. The capacitor allows the system to handle varying DC voltage levels by blocking DC and passing only AC components, enabling communication between circuits with different power supply voltages while maintaining signal integrity
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 solution enables efficient and timely application of DC bias, reducing the time required for communication between integrated circuits to begin and maintaining the necessary voltage levels during operation.
Implementation Method 1
The input of the differential receiver may be coupled to the bus through common mode decoupling capacitors that block low frequency and DC signals. The blocking of low frequency and DC signals may facilitate a fast wake-up of the differential receiver.
Data Source
AI summary
Embodiments of an AC coupled bus charging system are disclosed that may allow for different charging currents. The charging system may include a charging circuit and a control circuit. The charging circuit may be operable to controllably select different charging currents dependent upon the output of the control circuit.