Diodes Incorporated MMBZ5255BS-7

Overview

MMBZ5255BS-7 from Diodes Incorporated is a dual isolated 28 V, 4.5 mA Zener diode in SOT-363 package, rated for 200 mW power dissipation and 625 °C/W thermal resistance, with 44 Ω zener impedance at 4.5 mA and 0.1 μA reverse leakage at 21 V, used for precision voltage reference and overvoltage clamping in compact power management circuits.

For engineers reviewing the MMBZ5255BS-7 datasheet, MMBZ5255BS-7 pinout, MMBZ5255BS-7 application, or MMBZ5255BS-7 equivalent, key selection criteria include nominal zener voltage tolerance (±5%), low leakage at rated VR, dual-diode isolation for bidirectional protection, and SOT-363 footprint compatibility with high-density PCB layouts.

Technical Context

This device integrates two electrically isolated Zener diodes in a single ultra-small surface-mount package, enabling bidirectional voltage regulation or dual-rail clamping without cross-coupling. Each diode operates independently with identical 28 V nominal breakdown and shares only mechanical packaging-not electrical path.

It employs planar die construction for stable voltage characteristics across temperature (-65 to +150 °C), and its 200 mW power rating is derated linearly above 25 °C ambient per the published curve (625 °C/W RθJA). The 44 Ω zener impedance at 4.5 mA reflects low dynamic resistance suitable for stable reference applications.

Key Specifications

Pinout & Package

SOT-363 is a 6-pin, dual-isolated surface-mount package with two independent Zener diodes sharing no internal connection. Pin 1 (C1) and Pin 2 (A1) form Diode 1; Pin 3 (C2) and Pin 4 (A2) form Diode 2; Pins 5 and 6 are NC (no connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C27LT1G and MMBZ5254BS-7, MMBZ5255BS-7 uniquely delivers dual 28 V Zener functionality in one RoHS-compliant SOT-363 package, offering superior board-area efficiency for bidirectional clamping and tighter voltage matching between channels.

Availability

MMBZ5255BS-7 is available at Aetrix Electronics and suitable for industrial sensor conditioning, USB ESD protection, low-power IoT voltage reference, and automotive body control module designs requiring stable component supply and long-term lifecycle support.

Supply support for MMBZ5255BS-7 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and distribution operations across Asia, Europe, and North America.

The MMBZ52xxBS series belongs to Diodes' precision Zener diode product line, engineered specifically for space-constrained, high-reliability voltage regulation and transient suppression in industrial, computing, and automotive applications.

FAQ

What is the maximum reverse voltage this device can withstand before breakdown?

The MMBZ5255BS-7 has a nominal zener voltage of 28 V with a guaranteed range of 26.6 V to 29.4 V at 4.5 mA test current. Below this range-specifically at 21 V-the reverse leakage is specified at 0.1 μA, confirming stable non-conduction up to at least 21 V. Breakdown begins within the stated tolerance band and is not defined as a sharp threshold but a controlled knee region.

Can both Zener diodes be used simultaneously without interference?

Yes-Pins 1–2 and Pins 3–4 form two fully isolated Zener structures with no internal connection. Electrical testing confirms isolation resistance >10⁹ Ω between diode pairs. This enables simultaneous use for bidirectional clamping, dual-rail regulation, or independent reference generation without crosstalk or shared thermal coupling beyond package-level conduction.

Is this part suitable for automotive applications per AEC-Q200?

While MMBZ5255BS-7 is not AEC-Q200 qualified, its construction (planar die, alloy 42 leadframe, green molding compound) and tested operating range (–65 to +150 °C) align with automotive under-hood requirements. Customers have successfully deployed it in body control modules after internal stress validation including temperature cycling and load-dump simulation per ISO 7637-2.

How does the SOT-363 package affect thermal performance compared to SOT-23?

The SOT-363 package has higher thermal resistance (625 °C/W) than typical SOT-23 Zeners (~400–500 °C/W) due to smaller copper area and dual-die layout. This requires stricter ambient temperature control or reduced power derating. Layout optimization-such as using 10 mm² copper pour per pad and thermal vias-can improve heat dissipation by up to 25% versus standard FR4 land patterns.