Serdes Pin Sharing with T-Coil Impedance Matching
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Solution Overview
Problem
High-speed data communication between cellular transceivers and modems requires numerous wires, which are difficult to manage and route due to their large number, necessitating a more efficient method to reduce wire count while maintaining signal integrity and impedance matching.
Innovation Solution
A transceiver design that shares transmit and receive pins using a common T-coil circuit with adjustable termination impedance and a controller to manage operational modes, allowing for calibration and impedance matching without affecting input impedance, enabling bidirectional communication with reduced pin count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a parallel interface is used to achieve high-speed data communication, then data transmission speed can be maintained, but the number of wires required increases significantly making routing difficult
Solution Approach 1:
The patent merges transmit and receive functions into a single bidirectional pin, allowing the same physical pin to carry both transmitted and received signals through time-division multiplexing. This reduces the number of wires required while maintaining high-speed data communication capability through the use of SERDES (Serializer/Deserializer) blocks that convert parallel data to serial data for transmission over fewer channels.
Solution Approach 2:
The patent employs dynamic switching mechanisms including transmit/receive enable signals and calibration switches that dynamically reconfigure the circuit state based on operational mode. The T-coil circuit and termination impedance are dynamically adjusted during calibration to maintain proper input impedance matching when switching between transmit and receive modes, enabling flexible pin sharing without compromising signal integrity.
2Device complexity
If transmit and receive pins are shared to reduce wire count, then the number of wires is reduced, but maintaining proper input impedance and signal integrity becomes difficult
Solution Approach 1:
The patent implements a calibration mode that is executed before normal transmit/receive operations to pre-adjust the termination impedance and T-coil circuit parameters. This preliminary calibration ensures that when the circuit switches between transmit and receive modes, the input impedance remains properly matched to the transmission line, preventing signal reflections and maintaining signal integrity without requiring complex real-time adjustments.
Solution Approach 2:
The patent dynamically changes the termination impedance parameter based on operational mode. During receive mode, the termination impedance is set to match the transmission line characteristic impedance (e.g., 50 ohms) to minimize reflections. During transmit mode, the impedance is adjusted to present a high impedance to prevent signal leakage into the receiver. This parameter switching is controlled by transmit/receive enable signals and calibration switches.
3Measurement precision
If calibration is performed to improve signal integrity, then input matching and return loss are improved, but the amplifier may be affected by external signals during calibration
Solution Approach 1:
The patent applies preliminary anti-action by using a calibration switch to isolate the amplifier from the T-coil circuit and transmission line before calibration measurements are taken. This isolation prevents external signals from the transmission line from interfering with the calibration process. The calibration switch is controlled to ensure the amplifier is properly isolated during calibration mode, eliminating the harmful effect of external signal interference while still allowing accurate input matching and return loss measurements.
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 allows for high-speed bidirectional communication with reduced pin count, improved input matching, and minimized return loss, effectively addressing the challenge of managing numerous wires in data communication systems.
Implementation Method 1
a first common T-coil circuit coupled to a first input-output pin of the transceiver; a termination impedance coupled to the first common T-coil circuit
Implementation Method 2
a termination impedance coupled to the first common T-coil circuit and configured to match an impedance of a transmission line coupled to the first common T-coil circuit
Implementation Method 3
an amplifier configured to receive an input signal from the first input-output pin through the first common T-coil circuit
Data Source
AI summary
A transceiver includes a first common T-coil circuit coupled to a first input-output pin of the transceiver, a termination impedance coupled to the first common T-coil circuit and configured to match an impedance of a transmission line coupled to the first common T-coil circuit, an amplifier configured to receive an input signal from the first input-output pin through the first common T-coil circuit based on a receive enable signal, and a first transmission buffer configured to transmit an output signal to the first input-output pin through the first common T-coil circuit based on a transmit enable signal.