onsemi BZX84C33

Overview

BZX84C33 from ON Semiconductor (formerly Fairchild) is a 33 V, ±5% tolerance Zener diode in SOT-23 package, rated for 250 mW power dissipation at 25°C ambient, with typical zener impedance of 55 Ω at 20 mA and reverse leakage current ≤0.05 µA at 23.1 V, used for voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the BZX84C33 datasheet, pinout, applications, or equivalent options, key selection considerations include its 33 V nominal zener voltage, 5% tolerance, 250 mW power rating, 55 Ω dynamic impedance at 20 mA, and SOT-23 surface-mount package compatibility with space-constrained PCB layouts.

Technical Context

The BZX84C33 operates as a silicon planar epitaxial Zener diode optimized for stable voltage reference and clamping functions in DC bias networks. Its design targets low-current regulation (1–20 mA), with specified zener voltage range 31.0–35.4 V across test currents and temperature-dependent voltage drift of +27.4 mV/°C at 5 mA.

Thermal performance is defined by junction-to-ambient resistance of 465 °C/W on FR-4 PCB (76.2 mm × 114.3 mm), limiting continuous power handling at elevated ambient temperatures; maximum operating junction temperature is 150 °C, with storage range spanning −55 to +150 °C.

Key Specifications

Pinout & Package

Package: SOT-23 (TO-236AB), 3-terminal surface-mount plastic package with standard cathode marking (band). Dimensions: 2.9 mm × 1.3 mm × 1.0 mm (L × W × H).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5265BLT1G and 1N4748A, the BZX84C33 offers optimal balance of SOT-23 miniaturization, 250 mW power handling, and 55 Ω impedance-making it ideal for production-volume, space-constrained, low-to-moderate current regulation tasks where automated assembly is required.

Availability

BZX84C33 is available at Aetrix Electronics and suitable for industrial sensor interfaces, USB port protection circuits, PLC input modules, and DC-DC feedback networks requiring stable component supply and long-term manufacturability.

Supply support for BZX84C33 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 manufacturer specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The BZX84 series belongs to ON Semiconductor's general-purpose Zener diode product line, engineered for reliable voltage regulation and transient suppression in cost-sensitive, high-volume consumer and industrial electronics.

FAQ

What is the nominal zener voltage of the BZX84C33 and how tightly is it specified?

The BZX84C33 has a nominal zener voltage of 33 V, with a guaranteed range of 31.0 V to 35.4 V at 20 mA test current. Its ±5% tolerance (denoted by the "C" suffix) means the actual measured V_Z falls within that band under standard conditions, making it suitable for non-critical regulation where moderate precision suffices. This specification is verified per ON Semiconductor's BZX84C3V3–BZX84C33 Rev. 1.10 datasheet.

Can the BZX84C33 be used in place of a 33 V Zener diode with tighter tolerance?

No-the BZX84C33 is specifically rated at ±5% tolerance and cannot substitute for tighter-tolerance devices like ±1% or ±2% Zeners without risking out-of-spec operation. Its 31.0–35.4 V range may cause unacceptable variation in feedback loops or reference circuits requiring higher precision. For such cases, consider alternatives like the BZX84C33LT1G with tighter binning or a shunt reference IC. Always verify with the BZX84C33 datasheet before substitution.

What is the maximum continuous power dissipation for the BZX84C33 at 70°C ambient temperature?

At 70°C ambient, the BZX84C33's power dissipation must be derated from its 250 mW rating at 25°C using its 465 °C/W junction-to-ambient thermal resistance. The allowable power drops to approximately 137 mW (calculated as 250 mW × [1 − (70−25)/465]). Exceeding this risks exceeding the 150°C max junction temperature. Derating curves are provided in the BZX84C33 datasheet Figure 5.

Does the BZX84C33 have a specified capacitance value, and is it suitable for RF decoupling?

The BZX84C33 has a typical junction capacitance of 70 pF at 0 V reverse bias and 1 MHz, per the BZX84C3V3–BZX84C33 Rev. 1.10 datasheet. While usable for low-frequency filtering, this capacitance is too high and poorly controlled for RF decoupling above ~10 MHz. It is not characterized for RF performance, and dedicated RF capacitors or TVS diodes with specified C_J and f_r should be used instead of the BZX84C33 in RF signal paths.

How is the cathode identified on the BZX84C33 SOT-23 package?

The cathode of the BZX84C33 is marked by a visible band or dot adjacent to Pin 2 on the SOT-23 package body. Pin 1 is the anode, Pin 2 is the cathode, and Pin 3 is internally unconnected. Correct orientation is critical-reverse installation prevents proper zener breakdown and may cause open-circuit behavior. The BZX84C33 datasheet confirms this pinout in Section 1, Package Outline Drawing.