onsemi BZX55C4V3_T50R

Overview

BZX55C4V3_T50R from Fairchild Semiconductor is a 4.3 V, ±5% tolerance Zener diode in DO-35 glass package, rated for 500 mW power dissipation at 75°C with 75 Ω dynamic impedance at 5 mA test current and 1 μA reverse leakage at 1 V reverse voltage. It provides precise voltage regulation in low-power reference and protection circuits.

For engineers reviewing the BZX55C4V3_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage accuracy, thermal derating behavior, DO-35 mechanical compatibility, and low-leakage performance under bias conditions typical of sensor biasing and overvoltage clamping.

Technical Context

The BZX55C4V3_T50R operates as a silicon planar Zener diode optimized for stable voltage reference generation and transient voltage suppression in DC-biased circuits. Its 4.3 V nominal breakdown voltage is specified at 5 mA test current with ±5% tolerance, and it maintains regulation across -65°C to +200°C operating temperature range.

Thermal design requires attention to lead length (3/8″) and ambient temperature: power dissipation derates linearly at 4.0 mW/°C above 75°C, and maximum zener current IZM is 90 mA at 25°C, decreasing with rising junction temperature per the derating curve.

Key Specifications

Pinout & Package

DO-35 glass axial package with cathode band marking; two-terminal device requiring no PCB footprint adaptation beyond standard 0.3–0.4 inch lead spacing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4730A and BZX55C4V3 (ON Semi), the BZX55C4V3_T50R offers identical regulation performance in the compact DO-35 form factor, enabling direct replacement where thermal constraints limit power dissipation to 500 mW and legacy through-hole layout must be preserved.

Availability

BZX55C4V3_T50R is available at Aetrix Electronics and suitable for power supply reference, sensor biasing, overvoltage clamp, and microcontroller I/O protection requiring stable component supply and long-term manufacturability.

Supply support for BZX55C4V3_T50R 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, signal conditioning, and discrete components before its acquisition by ON Semiconductor in 2016.

The BZX55 series was developed as a general-purpose, cost-optimized Zener diode family targeting industrial control, instrumentation, and consumer electronics where stable, low-power voltage reference and clamping were required.

FAQ

What is the exact Zener voltage range for BZX55C4V3_T50R at 25°C?

The BZX55C4V3_T50R has a guaranteed Zener voltage range of 4.0 V to 4.6 V at 5 mA test current and 25°C ambient temperature, reflecting its ±5% tolerance specification. This range is measured under thermal equilibrium conditions with 3/8″ lead length and defines the usable regulation window for circuit design. The BZX55C4V3_T50R's voltage stability across temperature is supported by its -65°C to +200°C operating range.

Does BZX55C4V3_T50R have a cathode marking, and how is it identified?

Yes, the BZX55C4V3_T50R features a visible cathode band on the DO-35 glass body, consistent with industry-standard polarity marking. The cathode is the end marked with a distinct color band (typically black or dark stripe), and this terminal must be connected to the higher-potential side of the circuit for proper Zener operation. The BZX55C4V3_T50R's top marking also includes "5C" on the second line and "4V3" on the third line per Fairchild's marking convention.

What is the maximum reverse leakage current for BZX55C4V3_T50R, and at what voltage is it specified?

The BZX55C4V3_T50R exhibits a maximum reverse leakage current of 1 μA at 1 V reverse voltage and 25°C, as specified in the Fairchild datasheet. This low leakage supports energy-efficient operation in always-on circuits such as sensor bias networks. The BZX55C4V3_T50R maintains this performance across its full -65°C to +200°C operating temperature range, with leakage increasing predictably at elevated temperatures.

Can BZX55C4V3_T50R be used in place of BZX55C4V7 or BZX55C3V9 in a circuit?

No - the BZX55C4V3_T50R is not interchangeable with BZX55C4V7 or BZX55C3V9 due to differing nominal Zener voltages (4.3 V vs. 4.7 V vs. 3.9 V) and corresponding regulation windows. Substituting would shift reference or clamp thresholds by ±0.4 V minimum, potentially causing system-level errors. The BZX55C4V3_T50R must be selected specifically for 4.3 V applications; voltage-specific variants are not functionally substitutable without circuit revalidation.

What is the power derating behavior of BZX55C4V3_T50R above 75°C?

The BZX55C4V3_T50R derates linearly at 4.0 mW/°C above a lead temperature of 75°C, reducing its maximum allowable power dissipation from 500 mW. At 100°C lead temperature, its usable power drops to 400 mW; at 125°C, it falls to 300 mW. This derating applies regardless of ambient temperature and must be calculated using actual measured lead temperature, not board temperature. The BZX55C4V3_T50R's thermal performance is validated for 3/8″ lead length per JEDEC standards.