Diodes Incorporated BZX84B39Q-7-F

Overview

BZX84B39Q-7-F from Diodes Incorporated is an AEC-Q101-qualified surface-mount precision Zener diode with nominal 39 V zener voltage (38.2–39.8 V range), ±2% tolerance, 350 mW power dissipation, and 130 Ω dynamic impedance at 2 mA test current. It operates across –65 °C to +150 °C and is used for voltage regulation and overvoltage protection in automotive body control modules.

For engineers reviewing the BZX84B39Q-7-F datasheet, BZX84B39Q-7-F pinout, BZX84B39Q-7-F application, or BZX84B39Q-7-F equivalent, key selection criteria include its automotive qualification, tight 2% V_Z tolerance, low 0.1 µA reverse leakage at 27.3 V, and SOT23 package compatibility with high-volume automated assembly.

Technical Context

This Zener diode functions as a two-terminal voltage reference device, operating in reverse breakdown mode with a specified test current of 2 mA. Its temperature coefficient is +33.4 mV/°C, indicating positive drift above 25 °C, and it exhibits 350 mW maximum power dissipation under ambient-temperature terminal conditions.

The device uses alloy 42 leadframe with matte tin plating and green molding compound compliant with UL 94V-0. Its thermal resistance junction-to-ambient is 357 °C/W when terminals are held at ambient temperature, enabling stable operation in compact automotive PCB layouts.

Key Specifications

Pinout & Package

Package: SOT23 - three-terminal plastic-molded case with gull-wing leads; polarity marked by cathode band on top surface; weight ≈ 0.008 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMSZ4702T1G and BZX84-C39-7-F, BZX84B39Q-7-F uniquely delivers automotive-grade reliability, tighter 2% V_Z tolerance, and halogen-free construction-critical for Tier 1 ECU suppliers requiring full PPAP documentation and material compliance.

Availability

BZX84B39Q-7-F is available at Aetrix Electronics and suitable for automotive lighting control, engine control unit (ECU) power monitoring, and body control module (BCM) I/O protection requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for BZX84B39Q-7-F 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability components for automotive, industrial, and computing markets.

The BZX84 series belongs to Diodes' precision Zener diode product line, engineered specifically for voltage regulation and transient suppression in space-constrained, high-volume automotive electronics.

FAQ

What is the maximum reverse voltage this Zener can withstand before breakdown?

The BZX84B39Q-7-F has a nominal zener voltage of 39 V with a guaranteed range of 38.2 V to 39.8 V at 2 mA test current. Its absolute maximum reverse voltage is defined by the breakdown characteristic-not a fixed "withstand" rating-and begins conducting significantly above 38.2 V. The device is rated for 350 mW dissipation, limiting practical reverse voltage under load based on current.

Is this part suitable for use in a 42 V automotive system?

Yes-BZX84B39Q-7-F is designed for 36 V nominal automotive systems and supports transient conditions up to 41.2 V (V_R = 41.2 V at I_R = 0.1 µA). Its AEC-Q101 qualification and 350 mW rating make it appropriate for 42 V architectures where clamping near 39 V protects downstream 5 V or 3.3 V regulators during load dump events.

Does the SOT23 package have a thermal pad or exposed metal slug?

No-the SOT23 package used for BZX84B39Q-7-F has no thermal pad or exposed metal slug. Thermal performance relies entirely on the copper traces connected to pins 1 and 2, with a junction-to-ambient thermal resistance of 357 °C/W when terminals are held at ambient temperature per datasheet Note 6.

How does the +33.4 mV/°C temperature coefficient affect circuit accuracy?

The +33.4 mV/°C coefficient means V_Z increases by approximately 33.4 mV per degree Celsius rise above 25 °C. Over a –40 °C to +125 °C range, this results in ~5.0 V total drift. Designers must account for this in precision references-e.g., by selecting complementary tempcos elsewhere in the signal chain or using temperature-compensated bias networks.