onsemi MMSZ5250B

Overview

MMSZ5250B from Fairchild Semiconductor is a 5% tolerance, 20 V nominal Zener diode in SOD-123 package, rated for 500 mW power dissipation at 25°C, with 25 Ω typical dynamic impedance at 5 mA test current and 0.1 µA maximum reverse leakage at 15.2 V. It provides precise voltage regulation in low-power biasing and reference circuits.

For engineers reviewing the MMSZ5250B datasheet, pinout, applications, or equivalent options, key selection factors include its 20 V ±5% Zener voltage tolerance, 25 Ω Zener impedance at I_Z = 5 mA, thermal resistance of 340°C/W, and suitability for space-constrained PCBs using SOD-123 footprint.

Technical Context

The MMSZ5250B operates as a two-terminal voltage reference device relying on controlled reverse-breakdown conduction. Its Zener voltage is specified at 20 V (min 19 V, typ 20 V, max 21 V) with 5% tolerance, and it maintains stable regulation across -55°C to +150°C junction temperature range.

It exhibits 600 Ω maximum Zener impedance at knee current (I_ZK = 0.25 mA), 0.1 µA maximum reverse leakage at 15.2 V, and forward voltage ≤0.9 V at 10 mA - enabling bidirectional protection and low-loss forward conduction where needed.

Key Specifications

Pinout & Package

SOD-123 package: 2-pin surface-mount plastic case with cathode band marking; dimensions 2.7 × 1.5 × 1.0 mm (L × W × H); designed for reflow soldering per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX584C20 and 1N4746A, the MMSZ5250B offers optimal balance of SMD manufacturability, 500 mW capability, and 25 Ω impedance - making it preferred for production-scale consumer electronics and space-limited embedded systems requiring stable 20 V reference.

Availability

MMSZ5250B is available at Aetrix Electronics and suitable for voltage reference, overvoltage protection, and current-source bias applications requiring stable component supply, consistent parametric performance, and long-term sourcing continuity.

Supply support for MMSZ5250B 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 MMSZ52xxB series was developed for general-purpose, low-power voltage regulation in space-constrained consumer, computing, and industrial electronics - emphasizing tight tolerance, stable temperature coefficient, and SOD-123 manufacturability.

FAQ

What is the Zener voltage tolerance of MMSZ5250B?

The MMSZ5250B has a nominal Zener voltage of 20 V with a ±5% tolerance, meaning its actual breakdown voltage falls between 19 V and 21 V when tested at 5 mA. This tolerance is guaranteed across the full operating temperature range and is verified per Fairchild's Rev. E datasheet. The MMSZ5250B maintains this specification without requiring binning or external calibration.

Can MMSZ5250B be used in bidirectional clamping applications?

Yes, the MMSZ5250B supports bidirectional clamping: its reverse breakdown regulates at ~20 V, and its forward voltage is ≤0.9 V at 10 mA. This allows it to protect sensitive nodes from both positive overvoltage transients and negative-going excursions. The MMSZ5250B is commonly deployed in I/O line protection where fast response and low forward drop are required.

What is the maximum power dissipation of MMSZ5250B at 70°C ambient?

At 70°C ambient, the MMSZ5250B's power dissipation must be derated linearly from 500 mW at 25°C using its 340°C/W thermal resistance. Derating begins at 25°C, so at 70°C the allowable power is 500 mW × (1 − (70−25)/125) = 320 mW. This value ensures junction temperature stays within the 150°C limit. The MMSZ5250B datasheet specifies this derating curve explicitly in Absolute Maximum Ratings.

Is MMSZ5250B compatible with lead-free reflow soldering profiles?

Yes, the MMSZ5250B's SOD-123 package is qualified for lead-free reflow per JEDEC J-STD-020, supporting peak temperatures up to 260°C for 10 seconds. Its plastic body and matte tin-plated terminations ensure reliable wetting and intermetallic formation. The MMSZ5250B has been widely deployed in RoHS-compliant manufacturing lines since its introduction.

How does the Zener impedance of MMSZ5250B affect regulation accuracy?

The MMSZ5250B has a typical Zener impedance of 25 Ω at 5 mA, meaning a 1 mA change in Zener current causes ~25 mV output variation. This directly impacts regulation accuracy in variable-load applications. For example, in a 20 V reference supplying 1–6 mA, the MMSZ5250B contributes ±125 mV total deviation. Designers mitigate this by adding bypass capacitance or using the MMSZ5250B in low-dynamic-current roles.