onsemi MMBZ5251B_D87Z

Overview

MMBZ5251B_D87Z from Fairchild Semiconductor is a 22 V, ±5% tolerance Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 29 Ω dynamic impedance at 5.6 mA test current and 0.25 µA reverse leakage at 17.6 V, used for voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5251B_D87Z datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage accuracy, low dynamic impedance at nominal test current, thermal stability across -55°C to +150°C, and compatibility with automated SMT assembly in space-constrained PCB layouts.

Technical Context

This device operates as a two-terminal voltage reference diode, conducting in reverse breakdown when cathode-to-anode voltage exceeds its specified 22 V nominal zener voltage. Its 29 Ω impedance at 5.6 mA ensures stable regulation under small-signal load variations.

Designed for surface-mount use in SOT-23 footprint, it features a maximum forward voltage of 0.9 V at 10 mA and maintains 5% voltage tolerance across operating junction temperatures up to +150°C, with storage range from -55°C to +150°C.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with three terminals; pin 1 = anode, pin 2 = cathode, pin 3 = no connection (NC). Standard JEDEC MO-213AA outline, 2.9 mm × 1.3 mm × 1.0 mm body size.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage reference and protection applications.

Compared with BZX84-C22 and MMBZ5251BS, MMBZ5251B_D87Z offers optimal balance of SMT density, low-impedance regulation, and production-ready qualification for consumer and industrial applications requiring compact 22 V reference capability.

Availability

MMBZ5251B_D87Z is available at Aetrix Electronics and suitable for industrial sensor conditioning, USB port protection, automotive BCM power rails, and PLC input stage designs requiring stable component supply and long-term lifecycle support.

Supply support for MMBZ5251B_D87Z 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The MMBZ52xxB series was developed for general-purpose voltage regulation and transient suppression in space-constrained, low-power electronic systems across automotive, industrial, and computing markets.

FAQ

What is the nominal zener voltage and tolerance of MMBZ5251B_D87Z?

The MMBZ5251B_D87Z has a nominal zener voltage of 22 V with a tolerance of ±5%, measured at 5.6 mA test current and 25°C ambient temperature. This specification is confirmed in the Fairchild MMBZ5221B–MMBZ5257B datasheet Rev. A2, Table 1. The MMBZ5251B_D87Z maintains this tolerance across its full operating temperature range from -55°C to +150°C.

What is the maximum power dissipation rating for MMBZ5251B_D87Z?

The MMBZ5251B_D87Z is rated for 350 mW maximum power dissipation at 25°C ambient temperature, as specified in the Absolute Maximum Ratings table of the Fairchild datasheet. Derating is required above 25°C - approximately 2.33 mW/°C - to maintain safe junction temperature below +150°C. This rating applies to the SOT-23 package under still-air conditions.

Does MMBZ5251B_D87Z have a no-connect (NC) pin, and how should it be handled on PCB?

Yes, MMBZ5251B_D87Z has Pin 3 designated as "NC" (no connection), as shown in the Connection Diagram of the Fairchild datasheet. This terminal is internally unconnected and must remain electrically floating on the PCB - no trace, pad, or ground connection should be made to Pin 3 to avoid unintended parasitic coupling or thermal path effects.

What is the forward voltage specification for MMBZ5251B_D87Z?

The forward voltage of MMBZ5251B_D87Z is specified as ≤0.9 V at 10 mA forward current, consistent across the entire MMBZ5200 series. This value is defined in the "VF Forward Voltage" note of the Fairchild datasheet and supports bidirectional transient suppression when used with appropriate series limiting resistors.

How does the zener impedance of MMBZ5251B_D87Z affect regulation performance?

The MMBZ5251B_D87Z exhibits 29 Ω dynamic impedance at 5.6 mA test current, directly impacting output voltage stability under load variation. A lower Z_Z means smaller ΔV_Z for a given ΔI_Z, enabling tighter regulation - for example, ±0.29 V change for ±10 mA current swing. This makes MMBZ5251B_D87Z suitable for precision reference and low-noise analog applications where voltage drift must be minimized.