onsemi MMBZ5255ELT1

Overview

MMBZ5255ELT1 from onsemi is a 225 mW surface-mount Zener diode in SOT-23 package, rated for 28 V nominal reverse breakdown voltage at 4.5 mA test current, with 44 Ω dynamic impedance and 0.25 μA leakage current at 21 V reverse bias. It serves as a precision voltage reference or overvoltage clamp in low-power portable electronics.

For engineers reviewing the MMBZ5255ELT1 datasheet, pinout, applications, or equivalent options, this part delivers stable 28 V regulation in space-constrained designs requiring Class 3 ESD immunity (>16 kV HBM), high-density PCB layout compatibility, and AEC-Q101 readiness for automotive-grade reliability validation.

Technical Context

This device operates as a two-terminal voltage reference using avalanche breakdown in silicon PN junction. Its 225 mW power rating on FR-5 board and 556 °C/W thermal resistance define its steady-state dissipation limits under ambient conditions. The 28 V nominal Zener voltage places it in the medium-voltage range where temperature coefficient crosses zero near room temperature.

Pin configuration is strictly anode–no connection–cathode (1–2–3), with cathode identified by band marking. The NC terminal (Pin 2) is internally unconnected and must remain floating-no external tie to ground or bias is permitted per design intent.

Key Specifications

Pinout & Package

SOT-23 (TO-236) package, 2.90 mm × 1.30 mm × 1.00 mm body size, Pb-free, void-free thermosetting plastic case with corrosion-resistant finish. Cathode indicated by polarity band.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5255ELT1, BZX84-C27LT1G offers lower impedance but lacks automotive qualification, while SZMMBZ5255ELT1G provides identical performance with certified automotive process controls-enabling drop-in replacement only when qualification scope matches system requirements.

Availability

MMBZ5255ELT1 is available at Aetrix Electronics and suitable for USB power management, Li-ion battery protection, industrial sensor conditioning, and automotive CAN interface circuits requiring stable component supply across production lifecycles.

Supply support for MMBZ5255ELT1 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 is a global semiconductor supplier delivering energy-efficient power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MMBZ52xxELT1G series targets space-constrained, low-power voltage regulation needs in portable and automotive electronics-designed specifically for high-density PCB assembly and robust electrostatic discharge resilience.

FAQ

What is the nominal Zener voltage of MMBZ5255ELT1 and how is it tested?

The nominal Zener voltage of MMBZ5255ELT1 is 28 V, measured at a test current (I_ZT) of 4.5 mA with pulse conditions to avoid self-heating. The actual device exhibits a guaranteed range of 26.6 V (min) to 29.4 V (max) at this condition, as specified in the Electrical Characteristics table on page 3 of the onsemi datasheet. This value defines the primary regulation point for MMBZ5255ELT1 in voltage-reference and overvoltage-clamp applications.

Does MMBZ5255ELT1 have a functional third pin, and what happens if Pin 2 is connected?

No, MMBZ5255ELT1 has only two active terminals: Pin 1 (Anode) and Pin 3 (Cathode). Pin 2 is explicitly designated "No Connection" in the datasheet and is internally unconnected. Connecting Pin 2 to any net-including ground-may introduce parasitic capacitance, leakage paths, or mechanical stress, potentially degrading MMBZ5255ELT1 performance or reliability. The recommended layout keeps Pin 2 floating per onsemi's mechanical and electrical specifications.

Can MMBZ5255ELT1 be used in automotive applications, and what qualification does it hold?

The base MMBZ5255ELT1 is not AEC-Q101 qualified; however, its automotive-grade counterpart SZMMBZ5255ELT1G shares identical electrical parameters and adds AEC-Q101 qualification, PPAP capability, and enhanced process traceability. For automotive use, designers must specify the SZ-prefix version. MMBZ5255ELT1 itself meets general industrial reliability standards and supports automotive-adjacent applications like infotainment accessories where full qualification is not mandated.

What is the maximum peak pulse power MMBZ5255ELT1 can handle, and under what waveform?

MMBZ5255ELT1 is rated for 225 W peak pulse power under an 8 × 20 µs double-exponential waveform (per Figure 9 in the datasheet), representing standardized surge testing per IEC 61000-4-5. This rating applies only to non-repetitive pulses and assumes proper PCB thermal design. Continuous operation above 225 mW will exceed thermal limits and cause permanent degradation of MMBZ5255ELT1 performance.

How does the ESD rating of MMBZ5255ELT1 impact system-level protection design?

MMBZ5255ELT1 features Class 3 Human Body Model ESD immunity (>16 kV), meaning it can withstand direct electrostatic discharges up to that level without parametric shift or failure. This allows MMBZ5255ELT1 to serve as a first-line defense in exposed interfaces-reducing or eliminating the need for additional TVS diodes in cost-sensitive, space-limited designs such as smartphone accessory ports or wearable sensor nodes.