Taiwan Semiconductor Corporation BZX85C51

Overview

BZX85C51 from Taiwan Semiconductor is a 1.3W, ±5% tolerance Zener diode with nominal breakdown voltage of 51V, designed for precision voltage regulation and reference in low-power DC circuits; it operates across -65°C to +200°C junction temperature range and features hermetically sealed DO-41 glass package.

For engineers reviewing the BZX85C51 datasheet, BZX85C51 pinout, BZX85C51 application, or BZX85C51 equivalent, key selection criteria include its 51V nominal Zener voltage (48–54V min–max), 115Ω dynamic impedance at 4mA test current, 0.25µA leakage at 36V reverse bias, and suitability for voltage stabilization in adapters, lighting drivers, and on-board DC/DC converters.

Technical Context

The BZX85C51 functions as a single-die, silicon planar Zener diode operating in reverse breakdown mode, with specified Zener voltage tested under 10ms pulse conditions and thermal resistance of 130°C/W junction-to-ambient.

Its electrical behavior is defined by two key test points: 4mA Zener test current (IZT) yielding 51V nominal VZ and 115Ω impedance, and 0.5mA knee test current (IZK) where impedance rises to 1500Ω - indicating stable regulation onset above threshold conduction.

Key Specifications

Pinout & Package

DO-41 glass axial package with cathode indicated by a single black band; leads are pure tin plated and solderable per J-STD-002; weight ≈242 mg.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5257B and MMBZ5257BS, the BZX85C51 provides 2.6× higher power dissipation in a through-hole DO-41 package, making it suitable for applications requiring robust voltage clamping or regulation under sustained load without forced cooling.

Availability

BZX85C51 is available at Aetrix Electronics and suitable for low-voltage stabilizers, adapters, lighting applications, and on-board DC/DC converters requiring stable component supply and long-term manufacturability.

Supply support for BZX85C51 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 analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, serving industrial, consumer, and computing markets since 1979.

The BZX85C series belongs to TSC's general-purpose Zener diode product line, engineered for reliable voltage reference and regulation in cost-sensitive, thermally demanding applications across power supplies and embedded systems.

FAQ

What is the nominal Zener voltage and tolerance of the BZX85C51?

The BZX85C51 has a nominal Zener voltage of 51 V with a standard tolerance of ±5%, meaning its actual breakdown voltage falls between 48 V and 54 V at 4 mA test current under pulse conditions. This tolerance is confirmed in the Electrical Specifications table and applies across the full operating temperature range.

What is the maximum power dissipation rating for the BZX85C51?

The BZX85C51 is rated for a maximum power dissipation of 1.3 W at 25°C ambient temperature. Its thermal resistance is 130°C/W junction-to-ambient, so derating is required above 25°C - for example, at 75°C ambient, maximum allowable power drops to approximately 0.95 W to maintain TJ ≤ 200°C.

How is polarity marked on the BZX85C51 DO-41 package?

The BZX85C51 uses a single black cathode band on the glass body to indicate the cathode terminal; the unmarked end is the anode. This marking aligns with JEDEC DO-41 standards and is visible during manual or automated visual inspection prior to soldering.

What is the Zener impedance of the BZX85C51 and why does it matter?

The BZX85C51 exhibits a Zener impedance (ZZT) of 115 Ω at its 4 mA test current (IZT). This value quantifies how much the output voltage changes per unit change in current - lower impedance yields tighter regulation, especially critical in feedback networks where stability and accuracy depend on minimal VZ drift under varying load.

Is the BZX85C51 RoHS compliant and what does that mean for my design?

Yes, the BZX85C51 is RoHS compliant per EU Directive 2011/65/EU, meaning it contains no lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE) above threshold limits. This enables unrestricted sale in EU markets and simplifies compliance documentation for end equipment.