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Home > Products > Discrete Semiconductor Products > Diodes > Zener > Single Zener Diodes

Taiwan Semiconductor Corporation 1SMB5951

Name: 1SMB5951
Brand: Taiwan Semiconductor Corporation
SKU: 1SMB5951
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1SMB5951

Manufacturer:: Taiwan Semiconductor Corporation

Category:: Single Zener Diodes

Package:: DO-214AA, SMB

Datasheet:: 1SMB5951.pdf

Description:: DIODE ZENER 120V 3W DO214AA

Quantity:: RFQ Add To RFQ list

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Inventory:9,566

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Product details

Overview

1SMB5951 from Taiwan Semiconductor is a 3 W, 120 V nominal Zener diode in DO-214AA (SMB) surface-mount package, featuring glass-passivated junction, 3.1 mA test current (IZT), 4500 Ω maximum Zener impedance at IZK, and 12 mA maximum DC Zener current (IZM). It operates across –55°C to +150°C junction temperature range and is used for voltage regulation and overvoltage protection in DC/DC converters.

For engineers reviewing the 1SMB5951 datasheet, 1SMB5951 pinout, 1SMB5951 application, or 1SMB5951 equivalent, key selection criteria include its 120 V nominal Zener voltage with ±5% tolerance, low-inductance SMB package, moisture sensitivity level 1 rating, RoHS/halogen-free compliance, and thermal resistance of 226°C/W (junction-to-ambient).

Technical Context

The 1SMB5951 is a single-die, unidirectional Zener diode optimized for stable voltage reference and transient clamping in high-voltage power rails. Its 120 V nominal breakdown voltage is specified at 3.1 mA test current, with dynamic impedance rising to 4500 Ω at knee current (IZK = 1 mA), indicating controlled low-current regulation behavior.

Thermally, it supports 3 W dissipation at lead temperature TL = 75°C (derated at 40 mW/°C above), and 550 mW at ambient TA = 25°C (derated at 4.4 mW/°C above). Its junction-to-lead thermal resistance is 25°C/W, enabling effective heat transfer to PCB copper pads per JESD51-5 guidelines.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	114.0–126.0 V @ I_ZT = 3.1 mA - defines precise clamping threshold for 120 V rail protection
Power Dissipation (P_TOT)	3 W at T_L = 75°C - supports sustained regulation under moderate thermal load on 5 mm × 5 mm Cu pad
Zener Impedance (Z_ZK)	4500 Ω @ I_ZK = 1 mA - indicates higher dynamic resistance near knee, suitable for coarse reference not precision sensing
Junction Temperature Range	–55°C to +150°C - enables operation in industrial and automotive under-hood environments
Package	DO-214AA (SMB) - surface-mount, 0.100 g weight, matte tin-plated leads, UL 94V-0 molding compound
Leakage Current	0.25 μA @ V_R = 91.2 V - ensures minimal standby power loss below rated Zener voltage

Pinout & Package

DO-214AA (SMB) package: molded plastic case with cathode band marking polarity; leads are matte tin-plated, solderable per J-STD-002; meets JESD201 Class 2 whisker resistance.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Current entry terminal during forward bias; connected to lower-potential node in Zener configuration	Provides conduction path when reverse-biased voltage exceeds 120 V; must be routed to ground or return path in clamp topology
Cathode	Current exit terminal during reverse breakdown; marked by band on package body	Connected to protected node (e.g., DC/DC output); absorbs surge energy by shunting excess current to ground

Key Features

Feature	Design Value
Glass-passivated chip junction	Enhances long-term stability and reliability under thermal cycling and humidity exposure
Low inductance construction	Minimizes voltage overshoot during fast transients, critical for SMPS output rail clamping
Moisture sensitivity level 1	Eliminates need for dry-pack or bake-out prior to reflow, reducing manufacturing overhead
RoHS and halogen-free compliance	Meets IEC 61249-2-21 and global environmental directives for industrial and consumer end equipment

Applications

Switching Mode Power Supply (SMPS)	On-board DC/DC Converter
Use Scenario: Clamping flyback transformer leakage spikes in 100–150 V output SMPS designs. IC Role / Device Role / Timing Role: Passive voltage clamp protecting primary-side MOSFET and secondary rectifier. Use Value: Limits peak drain voltage to ≤126 V, preventing avalanche failure while operating within 3 W thermal envelope.	Use Scenario: Regulating auxiliary bias supply in isolated 48 V to 12 V DC/DC modules. IC Role / Device Role / Timing Role: Zener reference for optocoupler feedback loop or linear post-regulator. Use Value: Provides stable 120 V reference with ±5% tolerance and <0.25 μA leakage at 91.2 V, minimizing quiescent loss.
Lighting Application	Adapter Protection
Use Scenario: Overvoltage protection in constant-current LED drivers with 100+ V bus. IC Role / Device Role / Timing Role: Crowbar element triggered during open-load or short-circuit fault conditions. Use Value: Activates at 114–126 V to divert >12 mA surge current, safeguarding driver ICs without requiring active control.	Use Scenario: Input-stage transient suppression in universal-input AC/DC adapters. IC Role / Device Role / Timing Role: Secondary-side clamp absorbing line-induced surges reflected through transformer. Use Value: Withstands 8/20 μs pulses up to 1000 W (per Fig.10), maintaining regulation after repeated 120 V transients.

Switching Mode Power Supply (SMPS)

On-board DC/DC Converter

Use Scenario: Clamping flyback transformer leakage spikes in 100–150 V output SMPS designs.

IC Role / Device Role / Timing Role: Passive voltage clamp protecting primary-side MOSFET and secondary rectifier.

Use Value: Limits peak drain voltage to ≤126 V, preventing avalanche failure while operating within 3 W thermal envelope.

Use Scenario: Regulating auxiliary bias supply in isolated 48 V to 12 V DC/DC modules.

IC Role / Device Role / Timing Role: Zener reference for optocoupler feedback loop or linear post-regulator.

Use Value: Provides stable 120 V reference with ±5% tolerance and <0.25 μA leakage at 91.2 V, minimizing quiescent loss.

Lighting Application

Adapter Protection

Use Scenario: Overvoltage protection in constant-current LED drivers with 100+ V bus.

IC Role / Device Role / Timing Role: Crowbar element triggered during open-load or short-circuit fault conditions.

Use Value: Activates at 114–126 V to divert >12 mA surge current, safeguarding driver ICs without requiring active control.

Use Scenario: Input-stage transient suppression in universal-input AC/DC adapters.

IC Role / Device Role / Timing Role: Secondary-side clamp absorbing line-induced surges reflected through transformer.

Use Value: Withstands 8/20 μs pulses up to 1000 W (per Fig.10), maintaining regulation after repeated 120 V transients.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N5951B (ON Semiconductor)	Same 120 V nominal V_Z, but 1.5 W rating, DO-41 package, higher Z_ZT (1500 Ω)	Lower power handling limits use to non-sustained clamping; axial lead requires manual or wave soldering	Select when legacy through-hole layout or lower-cost qualification is prioritized over SMT automation
SMBJ120A (Littelfuse)	TVS diode, 120 V standoff, 133 V breakdown, 600 W peak pulse power, DO-214AA package	Designed for fast transient suppression (ns response), not DC regulation; higher leakage (~1 μA)	Choose for surge-only protection where clamping speed matters more than stable DC reference accuracy

Compared with 1SMB5951, 1N5951B offers lower cost and legacy compatibility but sacrifices SMT efficiency and thermal performance; SMBJ120A delivers superior transient immunity but lacks tight DC regulation and exhibits higher leakage-making 1SMB5951 optimal for combined regulation + moderate-clamp roles in space-constrained SMB layouts.

Availability

1SMB5951 is available at Aetrix Electronics and suitable for switching mode power supplies, on-board DC/DC converters, and lighting applications requiring stable component supply, RoHS-compliant sourcing, and moisture-insensitive SMT placement.

Supply support for 1SMB5951 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 components for industrial and consumer markets.

The 1SMB59xx series is part of TSC's surface-mount Zener diode product line, engineered for high-reliability voltage regulation and transient suppression in compact, automated assembly environments.

FAQ

What is the nominal Zener voltage and tolerance of the 1SMB5951?

The 1SMB5951 has a nominal Zener voltage of 120 V with a tolerance of ±5%, meaning its actual breakdown voltage falls between 114.0 V and 126.0 V when measured at 3.1 mA test current (I_ZT) and 25°C ambient temperature. This tolerance is confirmed in the Electrical Specifications table of the official TSC datasheet (Version M2102), and applies strictly to the 1SMB5951 variant-not the full 1SMB5926–1SMB5956 family.

What is the maximum DC Zener current (I_ZM) for the 1SMB5951?

The maximum DC Zener current (I_ZM) for the 1SMB5951 is 12 mA, as specified in the Electrical Specifications table under "Maximum DC Zener Current" for device marking code 951B. This value represents the highest continuous current the 1SMB5951 can safely conduct in reverse breakdown while remaining within its 3 W power limit and thermal derating constraints.

Does the 1SMB5951 have a defined Zener impedance at the test current?

Yes-the 1SMB5951 has a Zener impedance (Z_ZT) of 5.5 Ω at its 3.1 mA test current (I_ZT), per the Electrical Specifications table. This low dynamic impedance at nominal operating current supports stable regulation under moderate load variations, distinguishing it from higher-impedance variants like 1SMB5956 (1.9 Ω at 1.9 mA).

What is the junction-to-ambient thermal resistance (R_θJA) of the 1SMB5951?

The junction-to-ambient thermal resistance (R_θJA) of the 1SMB5951 is 226°C/W, measured under standard JEDEC conditions (single-layer PCB, no copper pour). This value is documented in the Thermal Performance section of the TSC datasheet and determines allowable power dissipation at elevated ambient temperatures-e.g., limiting 1SMB5951 to ~1.2 W at 70°C ambient.

Is the 1SMB5951 compatible with lead-free reflow soldering processes?

Yes-the 1SMB5951 uses matte tin-plated leads qualified per J-STD-002 and is rated for lead-free reflow soldering. Its DO-214AA (SMB) package carries moisture sensitivity level 1 (per J-STD-020), meaning it may be stored indefinitely at ≤30°C/60% RH and placed directly into reflow without baking, supporting high-yield automated assembly.

1SMB5951 Specifications

Product attributes: Attribute value

Manufacturer:: Taiwan Semiconductor Corporation

Series:: -

Package/Case:: DO-214AA, SMB

Packaging:: Tape & Reel (TR)

Product Status:: Active

Voltage - Zener (Nom) (Vz):: 120 V

Tolerance:: ±5%

Power - Max:: 3 W

Impedance (Max) (Zzt):: 360 Ohms

Current - Reverse Leakage @ Vr:: 1 µA @ 91.2 V

Voltage - Forward (Vf) (Max) @ If:: -

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DO-214AA (SMB)

1SMB5951 FAQ

1.How can I place an order for 1SMB5951 through Aetrix?

Please submit a Request for Quotation (RFQ) for 1SMB5951 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for 1SMB5951 reliable?

The price and inventory of 1SMB5951 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMB5951 is usually 5 days.

3.What payment methods are accepted for 1SMB5951?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMB5951 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1SMB5951?

1SMB5951 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1SMB5951 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for 1SMB5951?

For technical support, including 1SMB5951 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMB5951 requirements.

6.How does Aetrix verify that 1SMB5951 is sourced from the original manufacturer or authorized distributors?

All 1SMB5951 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 1SMB5951 meets industry standards.

7.What is the process for return or replacement of 1SMB5951?

All 1SMB5951 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMB5951, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The 1SMB5951 part is unused and in its original packaging.

Return procedure for 1SMB5951:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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