CAN Bus Interconnection Circuit for 60 Ω Load Matching
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Solution Overview
Problem
Interconnecting two independent CAN bus systems with pre-defined termination resistors can result in communication failures due to a drop in bus load below the nominal 60 Ω requirement.
Innovation Solution
A circuit comprising a first and second CAN transceiver, and a pair of transistors and six resistors electrically interconnecting them, is used to interconnect the two CAN bus systems without causing communication failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two independent CAN bus systems with pre-defined termination resistors are electrically coupled together with simple conductors, then the interconnection between the CAN systems is achieved, but the bus load drops below the nominal 60 Ω requirement resulting in communication failures
Solution Approach 1:
The patent introduces an intermediary circuit between the two CAN bus systems that includes transistors and resistors. This intermediary circuit acts as a mediator to match the impedance and maintain the bus load at the required 60 Ω nominal value, preventing communication failures while enabling interconnection between the independently terminated CAN systems.
Solution Approach 2:
The patent changes the electrical parameters of the interconnection circuit by incorporating specific resistor values and transistor configurations. This modifies the effective bus load seen by the CAN transceivers, transforming the combined load of two 60 Ω systems into an equivalent 60 Ω presentation to maintain communication reliability across the interconnection.
2Adaptability or versatility
If two CAN systems independently operate at the 60 Ω nominal load, then each system maintains reliable communication, but interconnecting them with simple conductors drops the bus load to 30 Ω
Solution Approach 1:
Rather than directly connecting the two CAN systems with simple conductors, the patent introduces an intermediary circuit containing transistors and resistors. This intermediary structure enables system interconnectability while actively managing the bus load to prevent the 30 Ω drop that would occur with direct connection.
3Reliability
If termination resistors are pre-defined in each CAN system, then each system meets the 60 Ω nominal load requirement independently, but connecting them together causes the bus load to fall below the required threshold
Solution Approach 1:
The patent applies parameter changes by introducing specific resistor values and transistor configurations in the interconnection circuit. This transforms the combined electrical characteristics of two independently terminated systems into an equivalent presentation that maintains the required bus load parameters, enabling reliable interconnection.
Data Source
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AI summary
A circuit for interconnecting a first controller area network (CAN) bus with a second CAN bus includes a first CAN transceiver, a second CAN transceiver, and a pair of transistors and six resistors electrically interconnecting the first and second CAN transceivers. The first CAN bus is included in a first device, such a bed to support a person or occupant, and the second CAN bus is included in a second device, such as a mattress supported by the bed. The circuit for interconnecting the first and second CAN busses is situated in an interior region of the mattress.