onsemi BZX55C24_T50R

Overview

BZX55C24_T50R from Fairchild Semiconductor is a 24 V ±5% Zener diode in DO-35 glass package, rated for 500 mW power dissipation at 75°C with 80 Ω dynamic impedance at 5 mA test current and 0.1 μA reverse leakage at 19.2 V. It provides precision voltage regulation in low-power reference and protection circuits.

For engineers reviewing the BZX55C24_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance, thermal derating behavior, cathode identification via color band, and compatibility with through-hole PCB layouts requiring stable 24 V clamping.

Technical Context

This device operates as a two-terminal voltage reference using avalanche breakdown in silicon PN junction. Its 24 V nominal zener voltage is specified at 5 mA test current with ±5% tolerance, and it maintains regulation across -65°C to +200°C operating temperature range.

The DO-35 package features axial leads with cathode indicated by a color band; forward voltage is ≤1.3 V at 100 mA, and maximum zener current is 18 mA at 24 V under worst-case thermal conditions.

Key Specifications

Pinout & Package

DO-35 glass axial-leaded package with cathode identified by a single color band on the body; no polarity-sensitive terminals beyond anode/cathode distinction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX55C24_T50R, 1N4749A offers double the power rating in a larger axial package, while MMSZ5249B delivers identical voltage specs in a surface-mount form factor-enabling trade-offs between manufacturability, thermal management, and layout density.

Availability

BZX55C24_T50R is available at Aetrix Electronics and suitable for industrial power supply monitoring, automotive ECU reference design, and programmable logic controller I/O protection requiring stable component supply and long-lifecycle support.

Supply support for BZX55C24_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, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The BZX55 series was designed as a general-purpose, cost-optimized Zener diode family for voltage regulation and transient suppression in industrial, automotive, and consumer electronics.

FAQ

What is the exact zener voltage range for BZX55C24_T50R at 25°C?

The BZX55C24_T50R has a guaranteed zener voltage range of 22.8 V to 25.6 V at 5 mA test current and 25°C ambient, reflecting its ±5% tolerance specification. This range remains valid under lead temperature conditions of 30°C ±1°C with 3/8" lead length, as defined in the Fairchild datasheet Rev. D1. The BZX55C24_T50R is not characterized for tighter tolerances outside this published window.

How does thermal derating affect BZX55C24_T50R's power handling above 75°C?

BZX55C24_T50R must be derated at 4.0 mW/°C above 75°C lead temperature, reducing its usable power from 500 mW to 400 mW at 100°C. This linear derating curve is defined in the Absolute Maximum Ratings table and applies regardless of airflow or PCB copper area. Engineers must verify actual lead temperature-not ambient-in thermal design, as the BZX55C24_T50R's performance depends on TL, not TJ.

Is BZX55C24_T50R suitable for use as a voltage reference in precision analog circuits?

BZX55C24_T50R provides adequate stability for non-critical references but lacks temperature-compensated characteristics found in bandgap or temperature-stabilized Zeners. Its 80 Ω dynamic impedance and ±5% initial tolerance limit accuracy in high-precision applications. For analog circuits requiring <1% total error, the BZX55C24_T50R should be paired with trimming or used only in coarse threshold detection-not as a primary reference.

What marking identifies the cathode on BZX55C24_T50R?

The cathode of BZX55C24_T50R is marked by a single color band on the glass body of the DO-35 package, consistent with industry-standard polarity indication. The top-marking format shows "F" (Fairchild logo) on line 1, "5C" on line 2, and "24" on line 3-confirming the 24 V rating and distinguishing it from other BZX55C variants. No additional symbols or text denote polarity beyond the band.

Can BZX55C24_T50R replace BZX55C22 or BZX55C27 in existing designs?

Substituting BZX55C24_T50R for BZX55C22 or BZX55C27 requires verification of system-level voltage margin, as their zener ranges (20.8–23.3 V and 25.1–28.9 V) do not overlap with BZX55C24_T50R's 22.8–25.6 V window. While all share DO-35 packaging and 500 mW rating, the BZX55C24_T50R introduces a 1.8 V shift relative to BZX55C22 and a 1.5 V shift versus BZX55C27-potentially causing incorrect trip points in protection circuits.