Vishay General Semiconductor - Diodes Division SM6T30CA-M3/5B

Overview

SM6T30CA-M3/5B from Vishay General Semiconductor is a bidirectional transient voltage suppressor (TVS) diode in SMB (DO-214AA) package, designed for clamping ESD and surge transients on signal/power lines. It features 30 V standoff voltage (VWM), 33.2 V minimum breakdown (VBR), 600 W peak pulse power (10/1000 μs), and 49.9 V maximum clamping voltage at 14.5 A IPPM - used to protect automotive sensor interfaces, industrial I/O ports, and USB/RS-485 data lines.

For engineers reviewing the SM6T30CA-M3/5B datasheet, SM6T30CA-M3/5B pinout, SM6T30CA-M3/5B application, or SM6T30CA-M3/5B equivalent, key selection criteria include bidirectional clamping capability, 150 °C junction temperature rating, halogen-free RoHS compliance (M3 suffix), and compatibility with automated SMT placement on 0.2" × 0.2" copper pads.

Technical Context

This bidirectional TVS operates symmetrically across both polarities, enabling protection of AC-coupled or differential signal paths without polarity constraints. Its glass-passivated junction ensures stable breakdown behavior and low leakage (<1 μA at VWM), while low-inductance SMB packaging supports fast response to sub-microsecond transients.

The device meets J-STD-020 MSL Level 1 (260 °C reflow peak) and is rated for non-repetitive 10/1000 μs surges up to 600 W. Thermal resistance (RθJA = 100 °C/W) and junction-to-lead (RθJL = 20 °C/W) values define its derating profile above 25 °C ambient, per Figure 2 in the datasheet.

Key Specifications

Pinout & Package

Package: SMB (DO-214AA), bidirectional - no polarity marking; symmetrical terminals with cathode/anode roles interchangeable depending on transient direction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ30CA and SMCJ33CA, the SM6T30CA-M3/5B delivers optimal balance of 600 W surge capacity, 49.9 V clamping, and compact SMB footprint - making it ideal for space-constrained automotive and industrial modules where thermal management is limited.

Availability

SM6T30CA-M3/5B is available at Aetrix Electronics and suitable for automotive sensor interfaces, industrial RS-485 networks, and USB 2.0 data line protection requiring stable component supply and halogen-free compliance.

Supply support for SM6T30CA-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, MOSFETs, optoelectronics, and passive components with emphasis on reliability and automotive-grade qualification.

The SM6T Series is engineered for high-reliability transient suppression in harsh environments - targeting automotive, industrial, and telecom applications where AEC-Q101 qualification, low leakage, and repeatable clamping performance are critical.

FAQ

What is the clamping voltage of SM6T30CA-M3/5B at its rated peak pulse current?

The SM6T30CA-M3/5B has a maximum clamping voltage (VC) of 49.9 V at 14.5 A peak pulse current (IPPM), measured under the standard 10/1000 μs waveform. This value is guaranteed across the full operating temperature range and defines the upper voltage limit imposed on protected circuits during surge events. The SM6T30CA-M3/5B maintains this clamping performance due to its glass-passivated junction and low-inductance SMB package.

Is SM6T30CA-M3/5B suitable for automotive applications?

Yes, SM6T30CA-M3/5B is qualified to AEC-Q101 when ordered with HM3 suffix (e.g., SM6T30CAHM3_B/I); the M3 suffix indicates halogen-free RoHS compliance but not automotive qualification. For automotive use, specify the HM3 variant. The SM6T30CA-M3/5B itself is rated for -65 °C to +150 °C junction temperature and meets MSL Level 1, supporting reflow assembly in automotive PCB manufacturing.

How does the bidirectional design of SM6T30CA-M3/5B affect its circuit implementation?

The bidirectional design of SM6T30CA-M3/5B eliminates polarity concerns during layout - it can be placed symmetrically across any two nodes (e.g., differential pair or line-to-ground) without orientation checks. Unlike unidirectional TVS diodes, the SM6T30CA-M3/5B clamps both positive and negative transients equally, making it ideal for AC-coupled or floating signal paths such as RS-485, CAN, or audio lines.

What is the thermal resistance of SM6T30CA-M3/5B, and how does it impact power derating?

SM6T30CA-M3/5B has a typical junction-to-ambient thermal resistance (RθJA) of 100 °C/W and junction-to-lead (RθJL) of 20 °C/W. At ambient temperatures above 25 °C, its peak pulse power must be linearly derated per Figure 2 in the datasheet - e.g., at 75 °C ambient, usable PPPM drops to ~400 W. Proper copper pad sizing (0.2" × 0.2" per terminal) is required to achieve these thermal ratings. The SM6T30CA-M3/5B relies on PCB copper for heat dissipation during repetitive surge events.

Does SM6T30CA-M3/5B require additional series impedance for effective transient suppression?

No, SM6T30CA-M3/5B functions as a shunt protector and does not require series impedance to operate, but adding a small series resistor (e.g., 1–10 Ω) or ferrite bead upstream improves energy distribution and reduces ringing during fast transients. The SM6T30CA-M3/5B's low clamping voltage (49.9 V) and fast response (<1 ns) make it effective even without external impedance - however, system-level IEC testing may necessitate coordinated filtering to meet immunity thresholds.