Vishay General Semiconductor - Diodes Division SM6T33CA-M3/5B

Overview

SM6T33CA-M3/5B from Vishay General Semiconductor is a bidirectional transient voltage suppressor (TVS) diode in SMB (DO-214AA) package, rated for 33 V breakdown voltage (V_BR = 31.4–34.7 V at 1.0 mA), 600 W peak pulse power (10/1000 μs), and clamping voltage of 45.7 V at 13.1 A. It protects signal lines and power rails in automotive sensor units and industrial control interfaces against ESD and inductive switching transients.

For engineers reviewing the SM6T33CA-M3/5B datasheet, SM6T33CA-M3/5B pinout, SM6T33CA-M3/5B application, or SM6T33CA-M3/5B equivalent, key selection criteria include bidirectional clamping capability, AEC-Q101 qualification eligibility (via HM3 suffix), low clamping ratio (VC/VBR ≈ 1.45), and halogen-free RoHS compliance per M3 grade.

Technical Context

This bidirectional TVS operates symmetrically across both polarities, with identical V_BR, V_C, and I_PPM specifications in forward and reverse directions. Its glass-passivated junction ensures stable leakage (<1.0 μA at V_WM = 28.2 V) and robust surge handling up to 13.1 A under standardized 10/1000 μs waveform.

Thermal performance is defined by R_θJA = 100 °C/W (typ.) and R_θJL = 20 °C/W (typ.), supporting operation from –65 °C to +150 °C. The device meets J-STD-020 MSL Level 1 and JESD201 Class 2 whisker resistance, enabling lead-free reflow at 260 °C peak.

Key Specifications

Pinout & Package

Package: SMB (DO-214AA), molded plastic case with matte tin-plated leads; dimensions 4.57 mm × 3.94 mm × 2.20 mm (L × W × H); UL 94 V-0 rated; polarity unmarked for bidirectional configuration.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transient voltage suppression applications.

Compared with SMAJ33CA and 1.5KE33CA, SM6T33CA-M3/5B delivers optimal balance of SMT manufacturability, thermal performance (R_θJA = 100 °C/W), and low clamping voltage-making it preferred for new automotive and industrial PCB designs requiring AEC-Q101 readiness and halogen-free compliance.

Availability

SM6T33CA-M3/5B is available at Aetrix Electronics and suitable for automotive sensor units, industrial CAN bus interfaces, consumer power adapter inputs, and telecom line card surge protection requiring stable component supply and halogen-free compliance.

Supply support for SM6T33CA-M3/5B 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

Vishay General Semiconductor is a global leader in discrete semiconductors, specializing in diodes, rectifiers, MOSFETs, and protection devices with emphasis on reliability and automotive-grade qualification.

The SM6T Series is designed specifically for robust transient suppression in harsh environments-targeting automotive, industrial, and telecom applications where bidirectional clamping, AEC-Q101 readiness, and consistent surge performance are mandatory.

FAQ

What does the "CA" suffix indicate in SM6T33CA-M3/5B?

The "CA" suffix denotes a bidirectional configuration: SM6T33CA-M3/5B provides symmetrical transient suppression in both polarities, unlike unidirectional variants (e.g., SM6T33A). This eliminates polarity marking on the SMB package and enables use on AC-coupled or floating signal paths without orientation concerns. The device's V_BR, V_C, and I_PPM values apply identically in either direction, as confirmed in the Vishay SM6T datasheet revision 09-Jan-2024.

Is SM6T33CA-M3/5B qualified to AEC-Q101?

SM6T33CA-M3/5B itself is not AEC-Q101 qualified; however, the SM6T33CA-HM3 variant (with HM3 suffix) is explicitly listed as AEC-Q101 qualified in the Vishay datasheet. The M3 suffix indicates halogen-free and RoHS-compliant construction, but automotive qualification requires the HM3 ordering code. Engineers selecting SM6T33CA-M3/5B for automotive use must verify whether system-level qualification permits commercial-grade components or mandates HM3-grade parts.

What is the maximum clamping voltage of SM6T33CA-M3/5B under standard test conditions?

The maximum clamping voltage (V_C) of SM6T33CA-M3/5B is 45.7 V, measured at peak pulse current (I_PPM) of 13.1 A using the industry-standard 10/1000 μs double-exponential waveform. This value is guaranteed across the full operating temperature range and reflects worst-case conduction behavior during surge events. It is lower than many competing 33 V TVS diodes, contributing to enhanced downstream IC protection.

How does the SMB (DO-214AA) package of SM6T33CA-M3/5B compare thermally to SMA (DO-214AC)?

The SMB package used in SM6T33CA-M3/5B has a typical junction-to-ambient thermal resistance (R_θJA) of 100 °C/W, versus ~140 °C/W for the smaller SMA package. This 40 °C/W improvement allows SM6T33CA-M3/5B to sustain higher average power dissipation in compact layouts. The SMB's larger copper pad area (0.2" × 0.2") and lower R_θJL (20 °C/W vs. ~25 °C/W for SMA) further enhance thermal reliability in high-duty-cycle surge environments.

Can SM6T33CA-M3/5B be used in place of a unidirectional TVS like SM6T33A?

SM6T33CA-M3/5B can replace SM6T33A only in circuits where bidirectional clamping is acceptable or required-such as AC signal lines, differential buses, or floating grounds. It must not be substituted in unidirectional applications with strict polarity-dependent biasing (e.g., DC power rail with cathode-grounded configuration), as its symmetrical structure lacks defined anode/cathode marking and exhibits identical forward/reverse characteristics. Always validate circuit topology before interchange.