onsemi MMBZ5250B

Overview

MMBZ5250B from Fairchild Semiconductor is a 20 V ±5% surface-mount Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 25 Ω dynamic impedance at 5 mA test current and 0.1 µA reverse leakage at 15 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5250B datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance, impedance vs. current behavior, thermal stability across –55°C to +150°C, and compatibility with automated SMT assembly in space-constrained PCBs.

Technical Context

The MMBZ5250B operates as a silicon planar epitaxial Zener diode optimized for stable voltage reference and clamping in DC bias networks. Its 20 V nominal breakdown is specified at I_Z = 5 mA with 5% tolerance, and it maintains <0.1 µA reverse leakage at VR = 15 V - critical for low-quiescent-current sensing nodes.

Thermal performance is defined by a maximum junction temperature of +150°C and storage range from –55°C to +150°C. The device exhibits predictable V_Z drift versus temperature (typical ±0.07%/°C), enabling use in industrial-grade voltage monitors without external compensation.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; pin 1 (anode), pin 2 (cathode), pin 3 (NC - not connected). Cathode marked by band on top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C20 and MMBZ5250BS, the MMBZ5250B offers optimal balance of low leakage, tight tolerance, and standard MSL 3 handling - making it preferred for cost-sensitive industrial and consumer designs where 0.1 µA I_R and SOT-23 footprint are decisive.

Availability

MMBZ5250B is available at Aetrix Electronics and suitable for industrial sensor conditioning, USB port protection, and low-power IoT voltage reference applications requiring stable component supply and full traceability.

Supply support for MMBZ5250B 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 designer of high-performance analog and discrete semiconductors, acquired by ON Semiconductor in 2016; its legacy Zener portfolio remains widely deployed in industrial and automotive systems.

The MMBZ52xxB series was engineered specifically for surface-mount voltage regulation in space-constrained, thermally demanding environments - emphasizing tight tolerance, low leakage, and robust SMT manufacturability.

FAQ

What is the zener voltage tolerance of the MMBZ5250B?

The MMBZ5250B has a nominal zener voltage of 20 V with a tolerance of ±5%, meaning its actual breakdown voltage falls between 19.0 V and 21.0 V when tested at I_Z = 5 mA and T_A = 25°C. This tolerance is guaranteed per the Fairchild MMBZ5221B–MMBZ5257B datasheet Rev. A2 and applies to every unit shipped. The MMBZ5250B achieves this consistency through tight process control in Fairchild's planar epitaxial Zener fabrication line.

Does the MMBZ5250B have a specified forward voltage?

Yes, the MMBZ5250B has a maximum forward voltage (V_F) of 0.9 V at forward current (I_F) = 10 mA, as stated in the "VF Forward Voltage" note across all MMBZ5200 series devices. This specification confirms its usability in bidirectional protection configurations and validates its silicon diode construction. The MMBZ5250B's V_F remains stable across –55°C to +125°C, supporting reliable operation in wide-temperature applications.

What is the maximum power dissipation rating for the MMBZ5250B?

The MMBZ5250B is rated for 350 mW power dissipation at an ambient temperature of 25°C, per the Absolute Maximum Ratings table. Derating is required above 25°C - approximately 2.33 mW/°C - down to zero at +150°C junction temperature. This rating directly governs safe continuous clamping current: at 20 V, the MMBZ5250B supports up to 17.5 mA average current without exceeding thermal limits. The MMBZ5250B's SOT-23 package enables this rating through optimized thermal resistance to ambient (R_θJA ≈ 357°C/W).

Is the MMBZ5250B RoHS compliant?

Yes, the MMBZ5250B manufactured under Fairchild's Rev. A2 specification is RoHS compliant, meeting EU Directive 2011/65/EU requirements for restriction of hazardous substances. Lead-free solderability is confirmed for reflow profiles up to 260°C peak, and the device carries the "Pb-Free" marking on its top-side laser etch. All current Aetrix Electronics stock of MMBZ5250B conforms to this standard, with full material declarations available upon request. The MMBZ5250B's compliance is documented in Fairchild's official product change notices and material content reports.

What does the 'B' suffix in MMBZ5250B indicate?

The 'B' suffix in MMBZ5250B denotes the device's tolerance grade and packaging configuration: it specifies ±5% zener voltage tolerance and indicates tape-and-reel packaging per EIA-481 standard. This distinguishes it from earlier revisions (e.g., non-B variants) that may carry wider tolerances or bulk packaging. The MMBZ5250B's 'B' designation is consistent across the full MMBZ5221B–MMBZ5257B family and is referenced in Fairchild's ordering information tables. No functional or electrical differences exist between 'B' and non-'B' versions beyond tolerance and packaging.