STMicroelectronics SM5908

Overview

SM5908 from STMicroelectronics is a unidirectional Transil™ TVS diode designed for transient overvoltage protection in power supply and interface lines. It features a 5 V stand-off voltage, 7.6 V clamping voltage at 30 A (10/1000 µs), 1500 W peak pulse power rating, and operates up to 175 °C junction temperature - deployed in industrial SMPS and automotive ECUs where low leakage and high thermal stability are critical.

For engineers reviewing the SM5908 datasheet, SM5908 pinout, SM5908 application, or SM5908 equivalent, key selection criteria include clamping performance under 10/1000 µs surges, SMC package thermal resistance (15 °C/W junction-to-leads), UL94V-0 flammability compliance, and IEC 61000-4-2 Level 4 ESD robustness (15 kV air / 8 kV contact).

Technical Context

The SM5908 uses planar junction technology to achieve low leakage current (<1 µA @ 5 V) and stable breakdown behavior across -55 °C to +175 °C operating range. Its unidirectional configuration provides asymmetric surge suppression with cathode-banded polarity marking and defined forward voltage drop (≤3.0 V @ 100 A).

Thermal design relies on SMC (DO-214AB) package characteristics: 15 °C/W junction-to-leads thermal resistance and 90 °C/W junction-to-ambient (on recommended FR4 pad layout). It meets MIL-STD-883G HBM (25 kV) and IEC 61000-4-5 surge immunity standards without derating below 125 °C.

Key Specifications

Pinout & Package

SM5908 is housed in an SMC (DO-214AB) surface-mount package per JEDEC outline, with cathode indicated by a band on the body. The two-terminal device has no internal complexity - anode and cathode are accessed via the two leads, optimized for high-current PCB trace routing and thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ5.0A and P6SMB5.0A, SM5908 delivers lower clamping (7.6 V vs ≥9.2 V), higher surge power (1500 W vs ≤600 W), and superior thermal performance (15 °C/W vs ≥25 °C/W junction-to-leads) - making it optimal for high-reliability industrial and automotive power rail protection where voltage margin and thermal headroom are constrained.

Availability

SM5908 is available at Aetrix Electronics and suitable for industrial SMPS input protection, automotive body control modules, medical patient monitor front-ends, and telecom DSL line interfaces requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for SM5908 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 silicon solutions for automotive, industrial, and power management applications.

The Transil™ TVS diode product line targets high-energy transient suppression in harsh-environment electronics, emphasizing robustness, precision clamping, and long-term parametric stability under thermal and electrical stress.

FAQ

What is the maximum allowable surge current for SM5908 under a 10/1000 µs waveform?

The SM5908 is rated for 30 A peak pulse current at 7.6 V clamping voltage under 10/1000 µs waveform per Table 3. At higher currents (e.g., 120 A), clamping rises to 8.5 V - verified in Figure 5. Exceeding 1500 W peak power (e.g., >197 A at 7.6 V) risks permanent short-circuit failure per Table 1 note 1.

Does SM5908 meet automotive qualification standards such as AEC-Q200?

No - SM5908 is not AEC-Q200 qualified. While it operates up to 175 °C and passes MIL-STD-883G HBM testing, ST does not list it in their AEC-Q200-certified portfolio. For automotive applications, it may be used at the designer's risk with full validation per vehicle-level EMC and reliability requirements.

Can SM5908 be used in bidirectional configurations?

No - SM5908 is strictly unidirectional, with cathode marked by a band. Bidirectional protection requires pairing two devices or selecting a dedicated bidirectional part like SM5908C (not offered by ST). Reverse-bias connection will block conduction and leave the circuit unprotected.

How does the SMC package affect thermal performance compared to DO-201?

The SMC package delivers 15 °C/W junction-to-leads thermal resistance versus 20 °C/W for DO-201 (Table 2), enabling higher sustained power handling. Its smaller footprint also reduces parasitic inductance - critical for maintaining clamping speed during fast-rising transients like ESD.