Microchip MCP2551-E/SN High-Speed CAN Transceiver: Datasheet Essentials and Application Circuit Design

The Microchip MCP2551-E/SN is a highly reliable high-speed CAN (Controller Area Network) transceiver serving as a critical interface between a CAN protocol controller and the physical differential bus. Complying with the ISO-11898 standard, it is designed for high-speed (up to 1 Mb/s) automotive and industrial applications, providing robust communication in electrically harsh environments.

A primary function of the MCP2551 is to convert the digital signals from a CAN controller into differential signals for transmission over the CAN bus, and vice versa for reception. Its differential receiver provides exceptional noise immunity, allowing it to reject common-mode noise, which is crucial in environments with significant electromagnetic interference (EMI). The device features transient protection up to ±25 kV on the CANH and CANL bus pins (using IEC 61000-4-2), safeguarding the sensitive CAN controller from damaging voltage spikes commonly found in automotive systems.

The slope control feature, managed via the Rs pin, is a key aspect highlighted in the datasheet. By connecting a resistor to ground, the slew rate of the transmitted data signals can be reduced. This allows designers to minimize electromagnetic emissions (EME) and tune the network for optimal performance in applications where the full 1 Mb/s data rate is not required, trading off speed for signal integrity over longer distances.

Typical Application Circuit Design

A standard application circuit for the MCP2551-E/SN is straightforward, facilitating easy integration. The core design involves connecting the transceiver between a microcontroller's CAN module (e.g., an MCU with an integrated CAN controller) and the physical two-wire CAN bus.

1. Microcontroller Interface:

TXD: Connects directly to the transmit pin of the CAN controller.

RXD: Connects directly to the receive pin of the CAN controller.

VDD: Powered by a stable +5V supply, decoupled with a 100 nF capacitor close to the pin.

VSS: Connected to ground.

2. Bus Interface:

CANH and CANL: Connect to the high and low lines of the CAN bus, respectively. A 120-ohm termination resistor must be placed at each end of the bus to prevent signal reflections.

3. Slope Control (Rs Pin):

For high-speed mode, the Rs pin is directly connected to ground.

For slope-control mode to reduce EME, a resistor (typically between 10 kΩ and 100 kΩ) is connected from the Rs pin to ground. The exact value is chosen based on the desired slew rate and network length.

4. Protection and Robustness:

The datasheet recommends series resistors on the CANH and CANL lines (e.g., 10-22 Ω) to limit current during transients.

Using common-mode chokes and TVS diode arrays on the bus lines is considered best practice for enhanced EMC and ESD protection beyond the integrated capabilities.

ICGOODFIND Summary

The MCP2551-E/SN stands as a robust, industry-proven solution for implementing physical layer CAN communication. Its integrated protection features, configurable slew rate control, and compliance with international standards make it an excellent choice for designers building reliable networks for automotive and industrial control systems. Its simple application circuit allows for rapid deployment, solidifying its position as a fundamental component in any CAN-based design.

Keywords:

1. CAN Transceiver

2. High-Speed

3. ISO-11898

4. Slope Control

5. Differential Signaling