Nexperia USA Inc. BZX84-B18,215

Overview

BZX84-B18,215 from Nexperia is a ±2 % tolerance Zener voltage regulator diode in SOT23 (TO-236AB) package, rated for 18 V nominal breakdown voltage at 5 mA test current, 250 mW total power dissipation, and 40 W non-repetitive peak reverse power. It serves as a precision reference or overvoltage clamp in low-power analog supply rails and signal conditioning circuits.

For engineers reviewing the BZX84-B18,215 datasheet, BZX84-B18,215 pinout, BZX84-B18,215 application, or BZX84-B18,215 equivalent, key selection criteria include Zener voltage tolerance (±2 %), thermal resistance (330 K/W junction-to-solder-point), differential resistance (225 Ω max at 5 mA), temperature coefficient (+12.6 mV/K), and SOT23-compatible reflow footprint.

Technical Context

This device operates in reverse-bias breakdown mode with a specified Zener voltage of 17.6 V to 18.4 V at I_Z = 5 mA, exhibiting a positive temperature coefficient of +12.6 mV/K - enabling stable regulation across ambient temperatures from –55 °C to +150 °C. Its differential resistance remains ≤225 Ω under nominal bias, supporting low-noise voltage reference use.

The diode features non-repetitive surge capability up to 40 W for 100 μs pulses, with maximum forward voltage of 0.9 V at 10 mA and reverse leakage <0.05 μA at VR = 15 V. Thermal design relies on its 330 K/W junction-to-solder-point resistance when mounted on standard FR4 PCBs.

Key Specifications

Pinout & Package

Package: SOT23 (TO-236AB), surface-mount plastic package with 3 leads, 1.9 mm × 1.1 mm body, 0.45 mm lead pitch, and standard reflow footprint per Figure 12.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C18,215, the BZX84-B18,215 offers tighter voltage control critical for precision analog stages; versus MMSZ5245B-7-F, it trades power headroom for miniaturization and thermal performance on fine-pitch PCBs.

Availability

BZX84-B18,215 is available at Aetrix Electronics and suitable for industrial sensor interfaces, programmable logic controller (PLC) I/O protection, medical device reference circuits, and automotive body-control module voltage supervision requiring stable component supply and long-term obsolescence management.

Supply support for BZX84-B18,215 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, with manufacturing in Europe and Asia.

The BZX84 series belongs to Nexperia's precision Zener diode product line, engineered for stable voltage reference and overvoltage protection in space-constrained, cost-sensitive industrial and consumer applications.

FAQ

What is the maximum continuous reverse current this diode can sustain at 18 V?

The BZX84-B18,215 does not specify a maximum continuous reverse current rating. Its safe operation is defined by power dissipation: at 18 V, continuous current must be limited to ≤13.9 mA to stay within the 250 mW P_tot limit at T_amb ≤ 25 °C. Derating applies above 25 °C per the 500 K/W junction-to-ambient thermal resistance.

Can this Zener diode replace a BZX84-A18 in an existing design?

Yes, but with reduced voltage accuracy: BZX84-A18 has ±1 % tolerance (17.82–18.18 V), while BZX84-B18,215 has ±2 % (17.6–18.4 V). The wider spread may increase output error in precision references. Differential resistance (225 Ω vs. 200 Ω max) and temperature coefficient (+12.6 mV/K vs. +12.4 mV/K) are nearly identical, so thermal behavior remains consistent.

Is Pin 2 truly unused, or does it serve a mechanical function?

Pin 2 is electrically unconnected (n.c.) per Nexperia's official pinning diagram and internal construction. It serves only as a mechanical lead for package integrity and pick-and-place stability - no electrical connection exists internally. PCB layout must leave it unconnected; soldering it risks mechanical stress or shorting.

How does the 330 K/W junction-to-solder-point thermal resistance impact PCB layout?

This value means each watt of dissipated power raises the junction temperature by 330 K above the cathode solder point temperature. To keep T_j ≤ 150 °C at 250 mW, the cathode pad must stay ≤ 67.5 °C. Achieving this requires ≥10 mm² of 70 µm copper connected directly to the cathode pad, with no thermal relief, per Nexperia's recommended footprint in Figure 12.