Switchable Termination Resistance Circuit for EMI-Stable Transceivers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing switchable termination resistance circuits in transceivers face challenges in high electromagnetic interference environments, particularly in automotive applications, leading to complex designs and increased power consumption due to varying resistance values and interference-induced voltage fluctuations.
Innovation Solution
A switchable termination resistance circuit using NMOS and PMOS switches with a Zener diode to maintain stable gate-source voltage, coupled with a driving circuit for level shifting, allowing the termination resistance to be switched on and off dynamically to manage interference and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the termination resistance is connected at the transmitter side during transmission phases, then the signal transmission quality is improved, but the transmitter power consumption increases
Solution Approach 1:
The termination resistance is made dynamically switchable between connected and disconnected states based on the transmission phase. During transmission phases (first and second phases), the termination resistance is disconnected to reduce power consumption. During receive phases (third phase), the termination resistance is connected to improve signal reception quality. This dynamic switching resolves the contradiction by adapting the termination resistance connection state to the operational requirements of each phase.
2Use of energy by moving object
If the termination resistance is switched off during transmission phases, then the power consumption is reduced, but the signal transmission quality deteriorates
Solution Approach 1:
The termination resistance is periodically connected and disconnected according to the transmission protocol phases. It is disconnected during transmission phases (when quality is less critical) and connected during receive phases (when quality is critical). This periodic switching pattern allows the system to accept temporary quality degradation during transmission in exchange for significant power savings, while maintaining quality when it matters most for reception.
3Reliability
If the termination resistance circuit is designed for high voltage operation under electromagnetic interference, then the reliability in automotive applications is improved, but the device complexity increases
Solution Approach 1:
A driving circuit is introduced as an intermediary between the control logic and the termination resistance switches. This driving circuit performs level shifting to generate appropriate gate voltages for the MOSFET switches, isolating the high-voltage EMI-prone termination resistance circuit from the low-voltage control logic. The driving circuit absorbs the complexity of high-voltage operation, allowing the main termination resistance circuit to be designed for reliability under EMI while keeping the overall system manageable.
4Ease of operation
If the MOSFET gate voltage is limited to low values, then the ease of operation is improved, but the ability to switch termination resistance under high common mode voltages deteriorates
Solution Approach 1:
The driving circuit acts as a level-shifting intermediary that translates low-voltage control signals into high-voltage gate drive signals suitable for MOSFET operation under high common mode voltages. This allows the control logic to operate at safe low voltages while the termination resistance switches can handle high voltage conditions, resolving the contradiction between ease of operation and adaptability to high voltage environments.
Solution Approach 2:
The driving circuit dynamically adjusts the gate voltage parameters based on the operating conditions. It applies appropriate voltage levels to the MOSFET gates to ensure proper switching behavior under varying common mode voltage conditions, while keeping the control signals within safe voltage limits. This parameter adaptation allows the system to maintain ease of operation while achieving versatility in high voltage operation.
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 circuit effectively maintains stable resistance under high electromagnetic interference, reducing power consumption by half and ensuring accurate signal transmission by dynamically controlling the termination resistance.
Implementation Method 1
a first Zener diode Dz1 having an anode connected to a midpoint node 303 of the switchable termination resistance circuit 301 and a cathode connected to an input node 304 of the driving circuit 302
Implementation Method 2
First and second NMOS termination resistance switches Mnsw1, Mnsw2 are connected in series between the first and second resistors R1, R2
Data Source
Figure 1
Figure 2
Figure 3
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).