MCP2562-E/MF CAN Transceiver: Design Considerations and Application Circuit Implementation

The MCP2562-E/MF is a highly integrated CAN transceiver serving as a critical interface between a Controller Area Network (CAN) protocol controller and the physical differential bus. As a second-generation high-speed transceiver from Microchip Technology, it is designed for robust performance in harsh automotive and industrial environments. Successful implementation hinges on careful attention to several key design considerations and a well-executed application circuit.

A primary design focus is ensuring robust Electromagnetic Compatibility (EMC) and minimizing Electromagnetic Interference (EMI). The MCP2562-E/MF incorporates features such as excellent ESD protection (up to ±8 kV per IEC 61000-4-2 on the CAN bus pins) and common-mode choke compatibility. To optimize EMC performance, the physical layout is paramount. It is crucial to place the transceiver as close as possible to the network connection point to minimize the length of the differential CAN trace pair (CANH and CANL). These traces must be routed as a matched-length, differential pair with a controlled impedance of approximately 120Ω, keeping them away from noisy signal lines or power supplies.

Another critical consideration is fault protection and bus health. The device is designed to withstand negative bus voltages down to -27V and positive DC voltages up to +40V, making it resilient to common automotive electrical transients. The integrated thermal protection feature safeguards the device from short-circuit conditions. Furthermore, the slope control feature, managed via the Rs pin, allows the designer to adjust the slew rate of the output drivers. This is essential for tuning the network for lower EMI emissions, especially in applications where data rate requirements are below the maximum 1 Mb/s.

Power supply integrity is fundamental. The VDD pin must be properly decoupled using a ceramic capacitor (typically 100 nF to 1 μF) placed as close as possible to the pin and the device's GND. For applications in electrically noisy environments, additional filtering, such as an LC filter or a ferrite bead on the VDD line, is highly recommended to prevent noise from coupling onto the power supply.

Implementing a Standard Application Circuit

A typical application circuit for the MCP2562-E/MF is straightforward but must be followed precisely. The core implementation involves:

1. Microcontroller Interface: The TXD pin is connected to the CAN controller's transmit output, while the RXD pin is connected to the controller's receive input. A series resistor (e.g., 470Ω) on the TXD input can help dampen any ringing.

2. Mode Selection: The STBY (Standby) pin allows for entering a low-power mode when pulled high. For normal operation, it is tied directly to ground.

3. Slope Resistance: The Rs pin is used to select the mode of operation. Connecting it directly to GND enables high-speed mode with maximum slew rate. For slope control, a resistor (e.g., 10 kΩ to 100 kΩ) is connected from Rs to GND to reduce the slew rate and lower EMI.

4. Bus Interface: The CANH and CANL pins connect to the physical bus through a common-mode choke for enhanced noise immunity. A 120Ω termination resistor must be present at each end of the CAN bus network to prevent signal reflections.

5. Protection Circuitry: Although the device has robust internal protection, adding external Transient Voltage Suppression (TVS) diodes across the CAN bus lines is considered a best practice for handling high-energy transients beyond the IEC rating.

ICGOODFIND: The MCP2562-E/MF is a cornerstone for building reliable CAN networks. Its successful deployment is not just about connecting pins; it demands meticulous attention to PCB layout for signal integrity, strategic use of external protection components, and careful configuration of its slope control feature to achieve an optimal balance between data integrity and low electromagnetic emissions. By adhering to these design principles, engineers can leverage the full potential of this transceiver in creating robust and compliant communication systems.

Keywords:

CAN Transceiver

EMC/EMI Optimization

Slope Control

Fault Protection

Application Circuit