AcelaMicro Interface ICs

Use isolated transceivers when there is a need to break ground loops, provide safety isolation, or protect against high common-mode voltages. Isolation is essential in industrial environments with long cable runs, motor drives, or high-voltage systems. Non-isolated transceivers are suitable for short distances within the same ground domain where cost is a primary concern.

Use isolated transceivers for long distances, high voltages, or ground loop prevention.

CMTI (Common-Mode Transient Immunity) measures how well an isolated transceiver rejects fast voltage transients between its input and output sides. High CMTI (typically >25kV/μs) is essential in applications with switching power supplies, motor drives, or high-voltage inverters where fast transients can cause data errors. AcelaMicro isolated transceivers offer CMTI of 50kV/μs or higher.

Select transceivers with CMTI >25kV/μs for noisy environments with switching equipment.

RS-485 maximum cable length depends on data rate. At 100kbps, maximum length is approximately 1200 meters. At 1Mbps, maximum length reduces to about 100 meters. At 20Mbps (ACM485 maximum), maximum length is approximately 15 meters. These limits are due to signal attenuation and timing considerations. Use twisted pair cable with characteristic impedance of 120Ω. Terminate both ends of the bus with 120Ω resistors to prevent reflections. For long distances, use proper cable shielding and grounding to minimize EMI.

Use 1200m max at low speeds, 15m max at 20Mbps. Always use twisted pair with termination.

CAN bus protection requires multiple layers. Use transceivers with integrated ESD protection like ACM1050 (±8kV contact, ±15kV air). Add external TVS diodes on the CANH and CANL lines for additional surge protection. Use common mode chokes to filter high-frequency noise. Implement proper termination with split termination (two 60Ω resistors with capacitor to ground) for better EMI performance. Ensure proper shielding and grounding of the cable. For severe environments, consider isolated transceivers to protect against ground potential differences.

Use integrated ESD protection, add TVS diodes, use common mode chokes, proper termination.

RS-485 is a physical layer standard defining electrical characteristics for multi-drop communication. It supports various protocols (Modbus, Profibus) and allows master-slave or multi-master configurations. Data rates up to 20Mbps are possible. CAN bus includes both physical layer and protocol layer (CAN 2.0B), with built-in arbitration, error detection, and fault confinement. CAN is ideal for real-time control systems with deterministic latency. RS-485 is simpler and lower cost for basic multi-drop communication. CAN is more robust for critical control applications. Both use differential signaling for noise immunity.

Use RS-485 for simple multi-drop communication. Use CAN for real-time control with error detection.