Nexperia USA Inc. BZX384-B51-QX

Overview

BZX384-B51-QX from Nexperia is a ±2 % tolerance Zener voltage regulator diode in SOD323 (SC-76) package, rated for 51 V nominal breakdown voltage at 2 mA, 300 mW total power dissipation, and qualified to AEC-Q101 for automotive voltage reference and overvoltage protection circuits.

For engineers reviewing the BZX384-B51-QX datasheet, BZX384-B51-QX pinout, BZX384-B51-QX application, or BZX384-B51-QX equivalent, key selection criteria include its 51 V ±2 % Zener voltage tolerance, low thermal resistance (110 K/W junction-to-solder-point), 40 W non-repetitive peak reverse power capability, and automotive-grade reliability under -65 °C to +150 °C ambient conditions.

Technical Context

This device operates as a precision shunt voltage reference in reverse-biased mode, with differential resistance of 400 Ω at I_Z = 2 mA and temperature coefficient of +0.05 mV/K - indicating near-zero drift across operating temperature. Its low 150 pF capacitance at 1 MHz supports stable regulation in high-frequency feedback paths.

The diode's AEC-Q101 qualification confirms robustness against mechanical shock, temperature cycling, and humidity exposure, while its 150 °C maximum junction temperature enables use in engine control units and powertrain modules where thermal margin is constrained.

Key Specifications

Pinout & Package

Package: SOD323 (SC-76), surface-mount plastic package with 2 leads, 2.3 mm × 1.35 mm footprint, 0.45 mm height, and cathode marked by bar on top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX384-B51-QX, the BZX384-B51-Q offers identical performance in a standard reel format, while MMSZ5257B-TP trades automotive reliability and tighter tolerance for higher power rating and lower cost - making it unsuitable for safety-critical or temperature-stable reference roles.

Availability

BZX384-B51-QX is available at Aetrix Electronics and suitable for automotive engine control units, industrial programmable logic controllers, medical infusion pump power monitors, and body control module wake-up detection circuits requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for BZX384-B51-QX 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 essential efficiency technologies, delivering high-performance, reliable discrete and logic devices for automotive, industrial, and consumer markets.

The BZX384-Q series belongs to Nexperia's automotive-qualified Zener diode product line, engineered specifically for precision voltage reference and overvoltage protection in harsh-environment electronic control modules.

FAQ

What is the maximum reverse voltage this diode can withstand continuously?

The BZX384-B51-QX is rated for continuous reverse operation at its nominal Zener voltage of 51 V. Its absolute maximum limiting value is defined by the 300 mW total power dissipation limit - meaning sustained reverse voltage must be paired with current below 5.88 mA (300 mW ÷ 51 V) to avoid thermal runaway at 25 °C ambient. Derating applies above 25 °C per the 110 K/W junction-to-solder-point thermal resistance.

How does the ±2 % tolerance affect accuracy in a 51 V reference application?

The ±2 % tolerance means the actual Zener voltage falls between 49.98 V and 52.02 V at 2 mA test current. In a typical 51 V reference design, this translates to ±1.02 V worst-case deviation - sufficient for applications like overvoltage lockout (e.g., disable at >53 V) but insufficient for high-precision ADC references without calibration. The +0.05 mV/K temperature coefficient adds only ±1.2 mV over a 25 °C to 125 °C range, preserving most of the initial tolerance budget.

Can this diode replace a 1N4733A in an existing design?

No - the 1N4733A is a 5.1 V, 1 W through-hole Zener, whereas BZX384-B51-QX is a 51 V, 300 mW SMD device. Voltage, power, package, and thermal characteristics differ fundamentally. A direct replacement would require redesigning the bias network, PCB layout, and thermal management. For 5.1 V equivalents, consider BZX384-B5V1-Q (5.1 V, ±2 %, SOD323).

Is the cathode marking consistent across all BZX384-Q series variants?

Yes - all BZX384-Q series diodes use identical SOD323 package marking: a single bar on the top surface adjacent to pin 1, which is always the cathode. This matches the pinning diagram in Table 2 of the datasheet and is verified across all 111 types in the series, including BZX384-B51-QX with its "N5" top-side marking.