onsemi BZX84C56LT1

Overview

BZX84C56LT1 from onsemi is a 56 V, ±5% tolerance Zener diode in SOT-23 package, rated for 225 mW power dissipation at 25°C on FR-5 board, with 200 Ω dynamic impedance at 5 mA test current and 110 µA reverse leakage at 42.8 V, used for voltage regulation and overvoltage protection in portable electronics and high-density PCBs.

For engineers reviewing the BZX84C56LT1 datasheet, pinout, applications, or equivalent options, key selection criteria include nominal Zener voltage (56 V), tolerance (±5%), power rating (225 mW), dynamic impedance (200 Ω @ 5 mA), and thermal resistance (556 °C/W) - all critical for precision clamping and stable reference design.

Technical Context

This device operates as a two-terminal voltage reference using avalanche breakdown in silicon PN junction, with cathode-anode polarity marked by band. Its 56 V nominal Zener voltage falls in the positive temperature coefficient region (+39.2 mV/°C), requiring thermal compensation in precision circuits.

The SOT-23 package features pin 1 (anode), pin 2 (no connection), and pin 3 (cathode), supporting automated placement and reflow soldering up to 260°C for 10 seconds. It delivers ESD robustness of Class 3 (>16 kV HBM) and meets UL 94 V-0 flammability rating.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package (Case 318, Style 8), void-free thermosetting body with corrosion-resistant finish, 2.80–3.04 mm length, 1.20–1.40 mm width, 0.99–1.26 mm height, cathode indicated by band.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5267BLT1, BZX84C56LT1 offers lower dynamic impedance (200 Ω vs. 250 Ω) and reduced capacitance (40 pF vs. 100 pF), improving regulation fidelity and high-frequency performance; compared with BZX84C56LT1G, it shares identical electrical behavior but uses standard SnPb termination - suitable for legacy assembly lines not yet migrated to Pb-free processes.

Availability

BZX84C56LT1 is available at Aetrix Electronics and suitable for smartphone power rail clamping, USB port overvoltage protection, and industrial sensor reference stability requiring stable component supply across production lifecycles.

Supply support for BZX84C56LT1 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

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

The BZX84C56LT1 belongs to the BZX84CxxxLT1 series of standard-tolerance Zener diodes designed specifically for compact, cost-sensitive voltage regulation in space-constrained portable and high-density electronic systems.

FAQ

What is the maximum power dissipation of the BZX84C56LT1 on an FR-5 board?

The BZX84C56LT1 has a maximum power dissipation of 225 mW at 25°C ambient temperature on FR-5 board. This rating decreases linearly with rising temperature at 1.8 mW/°C above 25°C, corresponding to a thermal resistance of 556 °C/W. Engineers must verify board layout, copper area, and airflow to ensure actual junction temperature remains below +150°C under worst-case load conditions. The BZX84C56LT1 datasheet specifies this limit in the Maximum Ratings table.

Does the BZX84C56LT1 have a no-connect pin, and how should it be handled on the PCB?

Yes, the BZX84C56LT1 has pin 2 designated as "No Connection" per its SOT-23 pinout (pin 1 = anode, pin 2 = NC, pin 3 = cathode). This terminal is internally unconnected and must remain electrically floating - no PCB trace, pad, or solder mask opening should be assigned to it. Including a pad for pin 2 may cause solder bridging or unintended thermal coupling; recommended land pattern follows onsemi's SOT-23 footprint with only two active pads. The BZX84C56LT1 mechanical drawings confirm pin 2 is non-functional.

What is the Zener voltage tolerance and test condition for the BZX84C56LT1?

The BZX84C56LT1 has a Zener voltage tolerance of ±5%, specified as 52 V minimum to 60 V maximum at a test current (IZT) of 5 mA and ambient temperature of 25°C. This tolerance applies to the nominal 56 V rating and is confirmed in the Electrical Characteristics table on page 3 of the official datasheet. The BZX84C56LT1 achieves this tolerance via process-controlled doping and post-trim testing, making it suitable for general-purpose regulation where tight initial accuracy is not required.

How does the temperature coefficient of the BZX84C56LT1 affect its regulation performance?

The BZX84C56LT1 exhibits a positive temperature coefficient of +39.2 mV/°C at 56 V, meaning its Zener voltage increases approximately 39.2 mV for every 1°C rise in junction temperature. This behavior is typical for Zeners above ~5.6 V and must be accounted for in precision references - for example, a 50°C junction rise adds ~2 V to the clamping threshold. The BZX84C56LT1 datasheet provides typical TC curves (Figure 1) and confirms this value in the Electrical Characteristics table.

Is there a Pb-free version of the BZX84C56LT1, and how does it differ electrically?

Yes, the BZX84C56LT1G is the Pb-free variant of the BZX84C56LT1, featuring SnAgCu (SAC305) termination instead of SnPb. Electrically, the BZX84C56LT1G is identical to the BZX84C56LT1 - same Zener voltage range (52–60 V), same 225 mW power rating, same 200 Ω dynamic impedance, and same temperature coefficient. The only differences are environmental compliance (RoHS/REACH) and soldering profile compatibility. The BZX84C56LT1G is documented in the same datasheet as a drop-in replacement for lead-free manufacturing.