onsemi SZMMBZ5257ELT1G

Overview

SZMMBZ5257ELT1G from onsemi is a 33 V ±5% Zener voltage regulator diode in SOT-23 package, rated for 225 mW power dissipation at 25°C on FR-5 board, with 58 Ω dynamic impedance at 3.8 mA test current and 0.1 μA leakage at 25 V reverse bias - used for precision voltage reference and overvoltage protection in portable power rails.

For engineers reviewing the SZMMBZ5257ELT1G datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage tolerance (±5%), thermal resistance (556 °C/W), AEC-Q101 qualification, ESD robustness (>16 kV HBM), and NC pin configuration in compact SOT-23 footprint.

Technical Context

This device operates as a two-terminal shunt regulator with cathode-anode polarity, where regulation occurs when reverse-biased above its nominal 33 V Zener voltage. It features a non-connected (NC) terminal (Pin 2), enabling simplified layout while maintaining mechanical stability in high-density PCBs.

Designed for automotive-grade reliability, SZMMBZ5257ELT1G meets AEC-Q101 stress testing requirements and supports operation across −65°C to +150°C junction temperature range. Its 700 Ω maximum impedance at knee current (IZK) and 0.25 A peak surge capability support transient suppression in low-power supply monitoring circuits.

Key Specifications

Pinout & Package

SOT-23 (TO-236) surface-mount plastic package, 2.90 × 1.30 × 1.00 mm, void-free thermosetting case with UL 94 V-0 flammability rating and Pb-free finish. Cathode indicated by polarity band.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C33LT1G and MMSZ5257ET1G, SZMMBZ5257ELT1G uniquely combines AEC-Q101 qualification, 16 kV HBM ESD rating, and precise 33 V ±5% tolerance in a 225 mW footprint - making it the only choice for safety-critical automotive voltage supervision where regulatory auditability and transient immunity are mandatory.

Availability

SZMMBZ5257ELT1G is available at Aetrix Electronics and suitable for automotive body control modules, USB-C power delivery monitors, and industrial IoT sensor nodes requiring stable component supply with full AEC-Q101 traceability and PPAP documentation.

Supply support for SZMMBZ5257ELT1G 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

onsemi is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

SZMMBZ5257ELT1G belongs to the SZMMBZ52xxELT1G series - engineered specifically for automotive-grade voltage regulation and transient suppression in space-constrained, high-reliability electronic control units.

FAQ

What is the Zener voltage tolerance of SZMMBZ5257ELT1G?

The SZMMBZ5257ELT1G has a Zener voltage specification of 31.35 V (min), 33 V (nominal), and 34.65 V (max) at I_ZT = 3.8 mA, corresponding to a ±5% tolerance. This tight tolerance ensures predictable clamping behavior in precision voltage reference circuits, especially critical in automotive applications where supply rail margins are tightly defined per OEM specifications. The value is measured under pulsed conditions at 25°C ambient.

Is SZMMBZ5257ELT1G pin-compatible with standard MMBZ5257ELT1G?

Yes, SZMMBZ5257ELT1G shares identical pinout (Pin 1: Anode, Pin 2: NC, Pin 3: Cathode), package dimensions (SOT-23), and electrical specifications with MMBZ5257ELT1G. The "SZ" prefix denotes automotive-specific manufacturing controls, AEC-Q101 qualification, and PPAP capability - not a physical or functional change. Layout reuse is fully supported without modification.

What does the "NC" pin (Pin 2) mean for SZMMBZ5257ELT1G?

Pin 2 of SZMMBZ5257ELT1G is internally not connected (NC), serving only as a mechanical anchor in the SOT-23 package. It must remain unconnected in PCB layout - no routing or grounding is required. This design simplifies routing in dense layouts and avoids unintended parasitic paths that could affect regulation accuracy or ESD performance.

Does SZMMBZ5257ELT1G support high-temperature operation?

Yes, SZMMBZ5257ELT1G is rated for junction temperatures from −65°C to +150°C and is qualified per AEC-Q101 for automotive under-hood environments. Its thermal resistance of 556 °C/W (Junction-to-Ambient on FR-5) allows reliable operation at 85°C ambient when power dissipation remains ≤150 mW - verified through accelerated life testing per JEDEC standards.

How does the ESD rating of SZMMBZ5257ELT1G compare to generic Zener diodes?

SZMMBZ5257ELT1G achieves Class 3 Human Body Model ESD rating (>16 kV), exceeding typical Zener diodes rated at <8 kV. This is achieved via optimized junction design and passivation - enabling direct placement on exposed I/O lines in handheld medical and consumer devices without additional ESD protection components, reducing BOM count and board area.