Switchable Termination Resistance Circuit for EMI-Robust Transceivers
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Solution Overview
Problem
In communication systems with transceivers connected by a transmission line, the power consumption of transmitters increases when termination resistance is connected, and designing a switchable termination resistance is complex due to high electromagnetic interference and limited gate voltage of MOSFETs, especially in applications like automotive systems.
Innovation Solution
A switchable termination resistance circuit using NMOS termination resistance switches, Zener diodes, and a driving circuit with PMOS and NMOS switches to control the connection of termination resistance dynamically, allowing for reduced power consumption and operation under high electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If termination resistance is connected at the transmitter side, then signal transmission quality is improved, but transmitter power consumption increases
Solution Approach 1:
The termination resistance is made dynamically switchable through NMOS switches controlled by a control circuit. The resistance can be connected or disconnected based on the transmission phase, allowing the system to adapt its impedance characteristics dynamically rather than being fixed. This resolves the contradiction by enabling the termination resistance to be present only when needed for signal quality while being disconnected during transmission phases to reduce power consumption.
2Use of energy by moving object
If MOSFETs are used for switching termination resistance, then power consumption is reduced, but the design becomes complex due to limited gate voltage and electromagnetic interference
Solution Approach 1:
A control circuit acts as an intermediary between the power supply and the NMOS switches. This control circuit generates appropriate gate control signals that account for the limited gate voltage requirements of MOSFETs while providing robust switching capability. The intermediary control circuit simplifies the overall design by handling the complexity of MOSFET gate drive requirements, allowing the switches to operate reliably despite electromagnetic interference and voltage constraints.
Solution Approach 2:
The control circuit is designed to preemptively protect against electromagnetic interference by implementing shielding and filtering measures before the interference can affect the MOSFET gate signals. The gate control signals are conditioned in advance to ensure they meet the voltage requirements despite noisy environmental conditions, preventing switching errors before they occur.
3Use of energy by moving object
If termination resistance is disconnected during transmission, then power consumption is reduced, but signal transmission reliability may be compromised
Solution Approach 1:
The termination resistance is switched periodically according to the transmission protocol phases. During data transmission phases (first and second phases), the termination resistance is disconnected to reduce power consumption. During idle or reception phases (third phase), the termination resistance is connected to maintain signal integrity and reduce reflections. This periodic switching aligned with the transmission protocol resolves the contradiction by ensuring the termination resistance is present only when it benefits signal reliability.
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 reduces transmitter power consumption by disconnecting termination resistance during signal transmission phases, effectively managing electromagnetic interference and maintaining reliable signal transmission.
Implementation Method 1
A Zener diode is connected with its cathode to the input node and its anode to the midpoint node
Data Source
AI summary
The disclosure relates to a switchable termination resistance circuit for a transceiver physical layer interface. Example embodiments include a switchable termination resistance circuit (301) for a transmission line transceiver (801), the switchable termination resistance circuit (301) comprising: first and second terminals (TXP, TXN) for connection to a transmission line (103); first and second NMOS termination resistance switches (Mnsw1, Mnsw2) having source connections connected together at a midpoint node (303) and gate connections connected to an input node (304); a first resistor (R1) connected between the first terminal (TXP) and a drain connection of the first NMOS termination resistance switch (Mnsw1); a second resistor (R2) connected between the second terminal (TXN) and a drain connection of the second NMOS termination resistance switch (Mnsw2); and a Zener diode (Dz1) having a cathode side connected to the input node (304) and an anode side connected to the midpoint node (303).