Nexperia USA Inc. BZX84W-B39X

Overview

BZX84W-B39X from Nexperia is a ±2% tolerance Zener voltage regulator diode in SOT323 (SC-70) package, rated for 39 V nominal Zener voltage at 5 mA, 350 Ω differential resistance, and 36.4 mV/K temperature coefficient. It delivers stable reference voltage in low-power analog circuits, power supply feedback loops, and overvoltage protection nodes.

For engineers reviewing the BZX84W-B39X datasheet, BZX84W-B39X pinout, BZX84W-B39X application, or BZX84W-B39X equivalent, key selection criteria include Zener voltage tolerance, thermal coefficient stability at operating current, junction-to-ambient thermal resistance, and non-repetitive surge capability under transient conditions.

Technical Context

This device operates as a reverse-biased silicon Zener diode with sharp breakdown knee at 39 V, designed for precision voltage regulation in low-current (<20 mA) DC biasing and clamping functions. Its ±2% tolerance ensures tight output voltage control without trimming circuitry.

The 350 Ω differential resistance at I_Z = 5 mA and 36.4 mV/K temperature coefficient at I_Z = 2 mA define its dynamic impedance and thermal drift behavior-critical for maintaining reference accuracy across ambient temperature shifts from −55 °C to +150 °C.

Key Specifications

Pinout & Package

SOT323 (SC-70) leadless surface-mount plastic package with 3 terminals, optimized for high-density PCB layouts and reflow/wave soldering per IPC-7095 guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84W-B39X, BZX84W-C39 trades voltage precision for slightly lower impedance and lower cost, while MMSZ4702T1G offers greater power headroom at the expense of board space-making BZX84W-B39X optimal for compact, precision-critical regulation where ±2% tolerance is mandatory.

Availability

BZX84W-B39X is available at Aetrix Electronics and suitable for power supply feedback loops, overvoltage clamp circuits, and low-power sensor biasing requiring stable component supply across industrial, consumer, and test equipment programs.

Supply support for BZX84W-B39X 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

Nexperia is a global semiconductor expert focused on high-volume, high-reliability discrete and logic devices, headquartered in Nijmegen, Netherlands.

The BZX84W series belongs to Nexperia's general-purpose Zener diode product line, engineered for stable voltage regulation in space-constrained, cost-sensitive applications across consumer, industrial, and communications markets.

FAQ

What is the maximum continuous reverse current the BZX84W-B39X can sustain without degradation?

The BZX84W-B39X is rated for 275 mW total power dissipation at 25 °C ambient on a standard FR4 PCB. At its 39 V Zener voltage, this corresponds to a maximum continuous reverse current of approximately 7.05 mA (275 mW ÷ 39 V). Exceeding this value risks thermal runaway and permanent parametric shift.

Can BZX84W-B39X be used in place of a 39 V Zener with ±5% tolerance?

Yes, but only if the application requires tighter regulation: BZX84W-B39X provides ±2% tolerance (38.2–39.8 V) versus ±5% (37.0–41.0 V) for the C-series. Substitution improves accuracy but may increase cost; verify that downstream circuitry does not rely on the wider tolerance band for margin or redundancy.

Is Pin 2 internally connected, and what happens if it is soldered to ground?

No-Pin 2 is explicitly marked "n.c." (not connected) in the datasheet and has no internal bond wire or die connection. Soldering it to ground creates an unintended short path that may disrupt PCB layout integrity, cause solder bridging, or induce measurement errors during ICT testing; it must remain electrically floating and unconnected.

How does the 36.4 mV/K temperature coefficient affect performance at 85 °C ambient?

At 85 °C ambient, assuming typical thermal resistance (R_th(j-a) = 455 K/W) and 5 mA bias (195 mW dissipation), junction temperature reaches ~175 °C-beyond absolute maximum (150 °C). In practice, derated operation at ≤3 mA keeps T_j < 150 °C, limiting total drift to ≤2.2 V (36.4 mV/K × 60 K ΔT), well within ±2% band.