CAN Bus Driver Accelerated State Transitions
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Solution Overview
Problem
Current CAN bus drivers face limitations in transitioning from a dominant to a recessive data bus state due to high output resistance, leading to longer decay times and reduced data transmission speeds, which can result in unreliable data sampling and increased network latency.
Innovation Solution
The introduction of an additional driver with adjustable strength to accelerate the transition from a dominant to a recessive data bus state, utilizing an acceleration logic to reduce the decay time and ensure correct differential voltage levels, thereby improving noise-to-signal ratio and data transmission speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output resistance of the bus driver is kept high in the recessive data bus phase to allow overwriting by other drivers, then the ability to overwrite values without short circuit is improved, but the decay time for transitioning from dominant to recessive state increases
Solution Approach 1:
The driver is segmented into a main driver and an additional driver that operate independently. The main driver maintains high output resistance for reliable overwriting, while the additional driver provides accelerated discharge capability during state transitions, resolving the contradiction between overwriting reliability and transition speed.
Solution Approach 2:
The additional driver acts as an intermediary element that mediates between the main driver's high impedance state and the need for fast discharge. It provides a controlled discharge path that doesn't interfere with the main driver's overwriting function while accelerating the transition to recessive state.
2Productivity
If the decay time is reduced to increase data transmission speed, then the data transmission speed is improved, but the output resistance must be reduced which compromises the overwriting capability
Solution Approach 1:
The driver functionality is segmented into two independent drivers: the main driver maintains high output resistance for overwriting reliability, while the additional driver provides fast discharge capability for high data transmission speed, allowing both requirements to be satisfied simultaneously.
Solution Approach 2:
The additional driver is dynamically activated only during state transitions to accelerate discharge, and deactivated during normal operation to maintain high output resistance. This dynamic control allows the system to achieve fast transitions without permanently compromising overwriting capability.
3Loss of time
If an additional driver is introduced to accelerate the transition, then the decay time is reduced, but the device complexity increases
Solution Approach 1:
The additional driver and main driver are merged into a single integrated CAN transceiver unit with shared control logic and common output stage. This integration minimizes the increase in device complexity while providing the benefits of accelerated state transitions.
Solution Approach 2:
The additional driver is designed with multi-functionality: it accelerates discharge during transitions, can be dynamically controlled to maintain high impedance when not needed, and works in conjunction with the main driver's overwriting function. This universal design justifies the added complexity by providing multiple benefits from a single component.
Data Source
AI summary
A bus driver for driving a differential data bus can be in a dominant data bus state and in a recessive data bus state. In the dominant data bus state, the bus driver connects the first and second single-wire data bus lines to a first and second electrical potential and temporarily does not drive the first and second single-wire data bus lines in the recessive data bus state. In the recessive data bus state after a change from the dominant data bus state to the recessive data bus state, bus driver connects the first and second single-wire data bus lines to a fourth electrical potential for an active time.