Taiwan Semiconductor Corporation 1SMB5948

Overview

1SMB5948 from Taiwan Semiconductor is a 3 W, 91 V nominal surface-mount Zener diode in DO-214AA (SMB) package, featuring 5% voltage tolerance, 4.1 Ω dynamic impedance at 200 mA test current, and 150 °C maximum junction temperature. It serves as a precision voltage reference or overvoltage clamp in DC/DC converters and power supply regulation circuits.

For engineers reviewing the 1SMB5948 datasheet, 1SMB5948 pinout, 1SMB5948 application, or 1SMB5948 equivalent, key selection criteria include its 91 V Zener voltage with ±5% tolerance, low 4.1 Ω Zener impedance at I_ZT = 200 mA, 3 W steady-state power rating, and SMB package thermal performance (R_θJA = 226 °C/W).

Technical Context

The 1SMB5948 operates as a single-die, glass-passivated Zener diode optimized for stable voltage regulation under DC bias conditions. Its electrical behavior is defined by a nominal V_Z of 91 V at I_ZT = 200 mA, with Zener impedance measured at 4.1 Ω and leakage current limited to 0.25 μA at 69.2 V.

Thermal design relies on its DO-214AA package with R_θJL = 25 °C/W and R_θJA = 226 °C/W, supporting operation from –55 °C to +150 °C. The cathode band polarity marking and matte tin-plated leads comply with J-STD-002 solderability and JESD 201 Class 2 whisker resistance requirements.

Key Specifications

Pinout & Package

DO-214AA (SMB) surface-mount package with cathode indicated by a visible band; two-terminal device with no internal connections beyond anode and cathode.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5365B and BZX84-C91, the 1SMB5948 uniquely balances 3 W power handling, 4.1 Ω low-impedance regulation, and compact SMB packaging-making it optimal for mid-power SMPS and DC/DC converter protection where thermal and space constraints coexist.

Availability

1SMB5948 is available at Aetrix Electronics and suitable for switching mode power supplies, on-board DC/DC converters, and lighting applications requiring stable component supply with full traceability and RoHS/halogen-free compliance.

Supply support for 1SMB5948 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

Taiwan Semiconductor Corporation (TSC) is a vertically integrated semiconductor manufacturer specializing in discrete power devices, analog ICs, and ESD protection solutions for industrial, computing, and consumer markets.

The 1SMB59xx series is part of TSC's high-reliability Zener diode portfolio designed specifically for stable voltage reference and transient clamping in power conversion systems operating across –55 °C to +150 °C.

FAQ

What is the nominal Zener voltage and tolerance of the 1SMB5948?

The 1SMB5948 has a nominal Zener voltage of 91 V with a ±5% tolerance, meaning its actual breakdown voltage falls between 86.45 V and 95.55 V when tested at 200 mA. This specification is verified per the manufacturer's electrical characteristics table and applies under standard 25 °C ambient conditions. The 1SMB5948 maintains this tolerance across its qualified operating temperature range, making it suitable for precision regulation tasks where predictable voltage clamping is required.

What is the maximum continuous power dissipation for the 1SMB5948?

The 1SMB5948 is rated for 3 W maximum continuous power dissipation at lead temperature (T_L) of 75 °C, with linear derating of 40 mW/°C above that point. At 25 °C ambient, its power rating drops to 550 mW due to higher thermal resistance to ambient (R_θJA = 226 °C/W). This dual-rating reflects real-world mounting conditions: the 3 W rating assumes direct heat sinking via copper pads, while the 550 mW rating applies to standard PCB layouts without enhanced thermal relief. The 1SMB5948 must be applied within these limits to avoid exceeding its 150 °C maximum junction temperature.

Does the 1SMB5948 have RoHS and halogen-free compliance?

Yes, the 1SMB5948 meets RoHS Directive 2011/65/EU requirements and is halogen-free per IEC 61249-2-21. Its molding compound contains no brominated or chlorinated flame retardants, and all plating and substrate materials comply with restricted substance thresholds. This compliance is confirmed in the product's mechanical data section and supported by Taiwan Semiconductor's material declarations. The 1SMB5948 is suitable for export to EU, China, and other jurisdictions enforcing strict environmental regulations-no additional qualification testing is required for RoHS/halogen-free conformance.

What is the Zener impedance of the 1SMB5948 and why does it matter?

The 1SMB5948 exhibits a Zener impedance (Z_ZT) of 4.1 Ω when measured at its specified test current of 200 mA. This low impedance value indicates minimal change in Zener voltage under varying load currents-a critical factor for stable voltage reference and accurate overvoltage clamping. In practical terms, a 100 mA load shift causes only ~0.41 V deviation in output voltage, enabling tighter regulation than higher-impedance alternatives. The 1SMB5948's 4.1 Ω Z_ZT directly supports its use in feedback networks and precision clamp circuits where voltage stability under dynamic conditions is essential.

How is polarity identified on the 1SMB5948 package?

Polarity on the 1SMB5948 is indicated by a distinct cathode band marked on the body of the DO-214AA (SMB) package. This band identifies the cathode terminal, which must be connected to the higher-potential node in reverse-bias Zener operation. The anode is the unmarked end. This marking complies with industry-standard diode polarity conventions and is visible under standard optical inspection. Correct orientation is essential: reversing the 1SMB5948 in-circuit results in forward conduction (≈0.7 V drop) instead of Zener breakdown, compromising regulation or protection functionality.