onsemi BZX84C27

Overview

BZX84C27 from ON Semiconductor (formerly Fairchild) is a 27 V ±5% tolerance surface-mount Zener diode in SOT-23 package, rated for 250 mW power dissipation at 25°C ambient, with typical zener impedance of 45 Ω at 20 mA and reverse leakage current ≤50 nA at 18.9 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the BZX84C27 datasheet, pinout, applications, or equivalent options, key selection criteria include its 27 V nominal zener voltage, 5% tolerance, 45 Ω dynamic impedance at 20 mA, thermal resistance of 465°C/W (junction-to-ambient), and SOT-23 footprint compatibility with automated PCB assembly.

Technical Context

The BZX84C27 operates as a silicon planar epitaxial Zener diode optimized for stable voltage reference and clamping in space-constrained designs. It exhibits a negative temperature coefficient below 5 V and transitions to positive above ~5 V; at 27 V, its temperature coefficient is +21.4 mV/°C, enabling predictable drift compensation in bias networks.

Its electrical behavior is defined under three test currents (1 mA, 5 mA, 20 mA), with specified min/max V_Z and Z_Z values confirming tight parametric control across production lots. The device supports operation from –55°C to +150°C junction temperature and maintains <0.05 µA leakage up to 18.9 V reverse bias.

Key Specifications

Pinout & Package

Package: SOT-23 (TO-236AB), 3-terminal plastic surface-mount package with cathode-marked lead. Standard JEDEC MO-213AA outline, 1.3 mm × 2.9 mm × 1.1 mm body size, compatible with reflow soldering per IPC/JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5256BS-7-F and 1N4750A, the BZX84C27 offers optimal balance of SMT compatibility, 250 mW capability, and JEDEC-standardized marking-making it preferred for volume production of compact, thermally constrained PCBs requiring 27 V regulation.

Availability

BZX84C27 is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, automotive ECU voltage reference, and portable medical instrument power management requiring stable component supply and full traceability.

Supply support for BZX84C27 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BZX84 series belongs to ON Semiconductor's precision Zener diode product line, engineered for stable voltage reference and overvoltage protection in space-constrained, high-reliability electronic systems.

FAQ

What is the nominal zener voltage and tolerance of the BZX84C27?

The BZX84C27 has a nominal zener voltage of 27 V with a tolerance of ±5%, meaning its actual breakdown voltage falls between 25.1 V and 28.9 V when tested at 5 mA zener current. This tolerance is marked as 'C' on the device and conforms to JEDEC standards for commercial-grade Zener diodes. The BZX84C27 maintains this specification across its full operating temperature range.

What is the maximum power dissipation rating for the BZX84C27?

The BZX84C27 is rated for 250 mW power dissipation at an ambient temperature of 25°C when mounted on a standard FR-4 PCB (76.2 mm × 114.3 mm). Its junction-to-ambient thermal resistance is 465°C/W, so power must be derated linearly above 25°C-reducing to zero at approximately 150°C ambient. The BZX84C27 also supports 550 mW when referenced to lead temperature at 25°C.

What is the zener impedance of the BZX84C27 and why does it matter?

The BZX84C27 exhibits a maximum zener impedance of 45 Ω at 20 mA test current, which quantifies how tightly it regulates voltage under varying load conditions. Lower Z_Z means smaller output voltage deviation for a given current change-critical in feedback loops and reference supplies. The BZX84C27's 45 Ω value ensures <1% regulation error for ±1 mA load steps, making it suitable for precision analog circuits.

How does temperature affect the BZX84C27's zener voltage?

The BZX84C27 has a positive temperature coefficient of +21.4 mV/°C at 5 mA, meaning its zener voltage increases predictably with rising temperature. This behavior is inherent to higher-voltage Zeners (>5 V) and enables stable bias point design when combined with complementary TC components. The BZX84C27 remains functional from –55°C to +150°C junction temperature, with voltage drift fully characterized in its datasheet.

Is the BZX84C27 compatible with automated SMT assembly processes?

Yes, the BZX84C27 uses the industry-standard SOT-23 package (JEDEC MO-213AA), designed explicitly for pick-and-place and reflow soldering. Its 1.3 mm × 2.9 mm footprint, coplanar leads, and matte tin finish meet IPC/JEDEC J-STD-020 moisture sensitivity and thermal profile requirements. The BZX84C27 is qualified for volume manufacturing and supports high-yield assembly without special tooling or process adjustments.