onsemi BZX84C24

Overview

BZX84C24 from ON Semiconductor is a 24 V ±5% tolerance surface-mount Zener diode in SOT-23 package, rated for 250 mW power dissipation at 25°C ambient, with nominal zener voltage of 22.8–25.6 V at 5 mA test current and dynamic impedance of 70 Ω max, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the BZX84C24 datasheet, pinout, applications, or equivalent options, key selection considerations include its 24 V nominal zener voltage, 5% tolerance, 250 mW power rating, 70 Ω max zener impedance at 5 mA, and SOT-23 package compatibility with automated PCB assembly.

Technical Context

The BZX84C24 operates as a silicon planar epitaxial Zener diode optimized for stable voltage reference and clamping in DC bias networks. It exhibits a negative temperature coefficient below 5 V and transitions to positive above ~5 V; at 24 V, its dVZ/dT is +18.4 mV/°C, enabling predictable thermal drift compensation in regulated supplies.

Designed for operation at test currents from 1 mA to 20 mA, the device maintains low leakage (IR ≤ 0.05 µA at VR = 16.8 V) and low capacitance (80 pF at 0 V, 1 MHz), supporting use in noise-sensitive signal conditioning and feedback path stabilization where parasitic reactance must be minimized.

Key Specifications

Pinout & Package

Package: SOT-23 (TO-236AB), 3-terminal plastic surface-mount package with cathode marked by band. Standard footprint compatible with JEDEC MO-215.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5249BS-7-F and 1SMA5929BT3G, the BZX84C24 offers balanced performance: 250 mW rating provides better thermal headroom than the 200 mW alternative while retaining SOT-23 footprint, and its 70 Ω Z_Z supports tighter regulation than the 100 Ω part without requiring DO-214AC board area.

Availability

BZX84C24 is available at Aetrix Electronics and suitable for power supply monitoring, overvoltage protection, reference voltage source, and feedback path stabilization requiring stable component supply across industrial, instrumentation, and embedded control programs.

Supply support for BZX84C24 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 logic solutions for automotive, industrial, and cloud power applications.

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 BZX84C24 and how is it tested?

The BZX84C24 has a nominal zener voltage of 24 V, specified as 22.8–25.6 V at a test current of 5.0 mA per the official ON Semiconductor datasheet. This range reflects its ±5% tolerance grade. The measurement is performed under controlled 25°C ambient conditions using a stabilized DC current source, and the device must be reverse-biased with cathode at higher potential than anode to enter breakdown mode. The BZX84C24 achieves this regulation behavior through controlled silicon avalanche characteristics.

Can BZX84C24 be used in place of a 22 V or 27 V Zener diode?

No, the BZX84C24 is not interchangeable with 22 V or 27 V Zener diodes due to its specific 22.8–25.6 V regulation band. Substituting it for BZX84C22 (20.8–23.4 V) would risk undershoot in overvoltage detection, while replacing BZX84C27 (25.1–28.9 V) could cause premature clamping. Each BZX84C variant is laser-trimmed for its designated voltage; the BZX84C24 must be selected only where 24 V ±5% regulation is explicitly required.

What is the maximum power dissipation of BZX84C24 and under what conditions?

The BZX84C24 has a maximum power dissipation of 250 mW at ambient temperature (T_A) of 25°C when mounted on a standard FR-4 PCB (76.2 mm × 114.3 mm). Derating is required above 25°C at 2.15 mW/°C based on its 465°C/W junction-to-ambient thermal resistance. At 85°C ambient, usable power drops to approximately 122 mW. This limit applies only under steady-state DC conditions - pulsed operation requires consultation with ON Semiconductor per Absolute Maximum Ratings Note 2.

How does the temperature coefficient affect BZX84C24 performance in real circuits?

The BZX84C24 exhibits a positive temperature coefficient of +18.4 mV/°C at 5 mA, meaning its zener voltage increases linearly with junction temperature. In a 24 V reference circuit operating from –40°C to +125°C, this results in a total shift of ~3.0 V. Designers must account for this drift in precision applications - for example, by pairing the BZX84C24 with a compensating NTC thermistor or selecting it only where ±10% overall tolerance is acceptable. The BZX84C24 datasheet confirms this value is measured and specified, not estimated.

Is BZX84C24 suitable for ESD protection in USB or I²C interfaces?

The BZX84C24 is not recommended for primary ESD protection on USB or I²C interfaces due to its relatively high clamping voltage (up to 25.6 V) and 80 pF capacitance, which exceeds typical interface requirements (<5 pF for high-speed USB, <10 pF for 400 kHz I²C). While it can serve as secondary overvoltage clamp downstream of dedicated TVS arrays, the BZX84C24 lacks the fast response and low dynamic resistance needed for direct ESD event suppression. For those roles, purpose-built low-capacitance TVS diodes such as ESD9X-24V are preferred.