STMicroelectronics SM6T24CA

Overview

SM6T24CA from STMicroelectronics is a bidirectional transient voltage suppression (TVS) diode in SMB package, designed for IEC 61000-4-2 ESD protection (30 kV air/contact) and IEC 61000-4-4 surge immunity (4 kV level 4). It features 24 V standoff voltage (V_RWM), 33.2 V clamping voltage (V_CL) at 18 A peak pulse current, and 600 W peak pulse power (10/1000 µs) at 25 °C - deployed on signal lines and DC power rails in industrial PLCs, automotive body control modules, and telecom interface circuits.

For engineers reviewing the SM6T24CA datasheet, SM6T24CA pinout, SM6T24CA application, or SM6T24CA equivalent, key selection criteria include bidirectional clamping behavior, low leakage (<0.2 µA at 25 °C), high junction temperature rating (150 °C), and compliance with UL497B (E136224) for isolated loop protection - all critical for robust overvoltage design in harsh environments.

Technical Context

The SM6T24CA operates as a voltage-clamped shunt protector: when transient voltage exceeds its reverse standoff rating (24 V), it avalanches into low-impedance conduction to divert surge current away from downstream ICs. Its planar silicon junction enables stable leakage performance across temperature (0.2 µA at 25 °C, 1 µA at 85 °C) and supports continuous operation up to T_j = 150 °C.

Clamping response is defined by dynamic resistance (R_D = 0.444 Ω at 10/1000 µs), enabling precise V_CL = V_BR(max) + R_D × I_PP calculation. Bidirectional symmetry ensures identical protection for positive and negative transients - essential for AC-coupled or floating signal paths such as RS-485, CAN bus interfaces, and sensor bridges.

Key Specifications

Pinout & Package

SM6T24CA is housed in an SMB (DO-214AA) surface-mount package with two terminals: Cathode (K) and Anode (A). The bidirectional configuration means both terminals are symmetrical - no polarity marking required for mounting; device functions identically regardless of orientation across the protected line.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional TVS diode applications.

Compared with SMBJ24CA and P6SMB24CA, SM6T24CA delivers superior temperature-stable leakage (<0.2 µA), UL497B certification for isolated loops, and tighter V_CL tolerance - making it the optimal choice for high-reliability industrial analog I/O and safety-rated telecom interfaces.

Availability

SM6T24CA is available at Aetrix Electronics and suitable for industrial PLC analog inputs, automotive body control modules, telecom RS-485 transceiver ports, and smart meter power line communication systems requiring stable component supply and long-term lifecycle support.

Supply support for SM6T24CA includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power devices, sensors, and protection components for industrial, automotive, and consumer markets.

The SM6T series belongs to ST's high-reliability TVS portfolio, engineered specifically for robust electrostatic and surge protection in mission-critical analog signal chains and isolated loop interfaces - emphasizing low leakage, high-temperature stability, and regulatory compliance.

FAQ

What is the maximum clamping voltage of SM6T24CA under a 10/1000 µs surge?

The maximum clamping voltage (V_CL) of SM6T24CA is 33.2 V when subjected to an 18 A peak pulse current with a 10/1000 µs waveform at 25 °C. This value increases with junction temperature per the coefficient α_T = 9.4 × 10⁻⁴/°C, reaching approximately 35.1 V at T_j = 125 °C using the formula V_CL(T_j) = V_CL(25 °C) × [1 + α_T × (T_j − 25)].

Does SM6T24CA require orientation-specific placement on PCB?

No - SM6T24CA is a bidirectional TVS diode, meaning its electrical behavior is identical regardless of terminal orientation. The SMB package has no polarity marking, and the device clamps symmetrically for both positive and negative transients. It may be mounted in either direction across the protected line without affecting performance or reliability.

How does SM6T24CA differ from unidirectional SM6T24A in practical use?

SM6T24CA provides symmetrical clamping for both polarities, making it ideal for AC-coupled, floating, or differential signal lines (e.g., RS-485, CAN, audio). SM6T24A clamps only in reverse bias and conducts forward like a rectifier - requiring correct polarity alignment and unsuitable for bidirectional transients. Their V_RWM, V_CL, and P_PP ratings are otherwise identical.

Is SM6T24CA compliant with lead-free soldering standards?

Yes - SM6T24CA features matte tin-plated leads qualified to J-STD-002, JESD 22-B102 E3, and MIL-STD-750 Method 2026. It supports lead-free reflow per ST's recommended profile (peak 240–245 °C, 60–90 sec above 217 °C), and is rated MSL Level 1 with unlimited floor life when stored per J-STD-020 guidelines.