Diodes Incorporated MMBZ5257BW-7-F

Overview

MMBZ5257BW-7-F from Diodes Incorporated is a 33 V, 200 mW surface-mount Zener diode in SOT323 package, rated for ±3% voltage tolerance at 3.8 mA test current, with 58 Ω dynamic impedance and 0.1 μA reverse leakage at 25 V, used for precision voltage regulation and overvoltage protection in low-power analog sensor interfaces.

For engineers reviewing the MMBZ5257BW-7-F datasheet, MMBZ5257BW-7-F pinout, MMBZ5257BW-7-F application, or MMBZ5257BW-7-F equivalent, key selection criteria include nominal Zener voltage accuracy, low leakage at derated reverse voltage, thermal resistance (625 °C/W), AEC-Q101 qualification, and compatibility with automated SMT assembly on FR4 PCBs.

Technical Context

This Zener diode operates in reverse breakdown to maintain stable reference voltage under varying load and temperature conditions. Its 33 V nominal Zener voltage is specified at 3.8 mA test current, with dynamic impedance measured at 1 kHz and maximum 700 Ω at knee current (0.25 mA).

The device uses alloy-42 leadframe with matte tin plating, conforms to J-STD-020D Level 1 moisture sensitivity, and features green molding compound compliant with halogen- and antimony-free requirements (<900 ppm Br/Cl, <1000 ppm Sb).

Key Specifications

Pinout & Package

Package: SOT323 - three-terminal plastic surface-mount case with cathode-marked top-side marking (KM2), 0.3 mm typical lead thickness, UL 94V-0 flammability rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C33-7-F and MMSZ5257T1G, MMBZ5257BW-7-F uniquely balances AEC-Q101 compliance, compact SOT323 size, and verified 0.1 μA leakage at 25 V-making it optimal for space-constrained automotive and portable medical applications demanding long-term voltage stability.

Availability

MMBZ5257BW-7-F is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, automotive cabin control modules, and medical wearable battery monitors requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MMBZ5257BW-7-F 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 ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The MMBZ52xxBW series belongs to Diodes' AEC-Q101-qualified Zener diode product line, engineered specifically for precision voltage reference and overvoltage protection in automotive and high-reliability industrial systems.

FAQ

What is the maximum reverse voltage this Zener can withstand without breakdown?

The MMBZ5257BW-7-F exhibits sharp reverse breakdown at its nominal 33 V Zener voltage, with guaranteed operation up to 34.65 V (max V_Z). Below 31.35 V (min V_Z), it remains in high-impedance reverse blocking mode with ≤0.1 μA leakage at 25 V. It is not rated for sustained operation above 34.65 V.

Is this part suitable for use in a 125°C ambient environment?

Yes - the device supports T_A = –65°C to +150°C, but power must be derated per Fig. 1: at 125°C ambient, maximum allowable P_D drops to ~80 mW (40% of 200 mW), limiting safe Zener current to ~2.4 mA at 33 V on standard FR4.

Does the SOT323 package have an exposed thermal pad?

No - the SOT323 package for MMBZ5257BW-7-F has no exposed thermal pad. Thermal performance relies solely on the two signal leads and molded body; recommended pad layout per AP02001 uses 0.65 mm pitch, 0.3 mm wide traces with 0.8 mm solder mask opening.

How does the 58 Ω Zener impedance affect regulation accuracy under load variation?

At 3.8 mA test current, 58 Ω Z_ZT means a 1 mA change in Zener current causes ~58 mV shift in output voltage. For example, if load draws 2 mA from a 33 V rail via series resistor, regulation error increases by ~116 mV versus no-load condition - critical for sub-0.1% reference designs.