onsemi 1SMB5946BT3

Overview

1SMB5946BT3 from onsemi is a 3 W surface-mount Zener diode with nominal Zener voltage of 75 V (±5%), maximum Zener impedance of 5 Ω at 140 mA test current, and reverse leakage current ≤0.25 μA at 56 V. It features AEC-Q101 qualification, ESD rating >16 kV (HBM), and UL 94 V-0 flammability compliance. It serves as a precision voltage reference or overvoltage clamp in DC power regulation circuits for automotive body control modules.

For engineers reviewing the 1SMB5946BT3 datasheet, pinout, applications, or equivalent options, key selection criteria include its 75 V nominal Zener voltage, 5 Ω dynamic impedance at IZT = 140 mA, thermal resistance of 226 °C/W (junction-to-ambient), and SMB (Case 403A) package suitability for high-reliability PCB-mounted voltage stabilization.

Technical Context

This device operates as a two-terminal, unidirectional voltage regulator in reverse-biased mode, maintaining stable output voltage across varying load currents within its 3 W steady-state power limit at TL = 75°C. Its Zener breakdown mechanism provides predictable clamping behavior with temperature coefficient optimized for 75 V-class devices.

The SMB package enables top-side or bottom-side board mounting, with modified L-bend leads for enhanced solder joint reliability and flat handling surface for accurate pick-and-place placement. Thermal derating follows a linear 4.4 mW/°C reduction above TA = 25°C, supporting operation from −65°C to +150°C.

Key Specifications

Pinout & Package

Package: SMB (Case 403A), surface-mount plastic package with cathode polarity band; dimensions: 3.56 mm × 4.32 mm × 2.20 mm (L × W × H); UL 94 V-0 rated; Pb-free (G suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1SMB5946BT3, 1N5365B lacks surface-mount compatibility and automotive qualification, while SZ1SMB5946BT3G offers identical performance with formal AEC-Q101 documentation and PPAP readiness-making it the recommended upgrade path for automotive production.

Availability

1SMB5946BT3 is available at Aetrix Electronics and suitable for automotive body control modules, industrial power supply clamps, LED driver references, and telecom line interface protection requiring stable component supply and long-term lifecycle support.

Supply support for 1SMB5946BT3 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 (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The 1SMB59xxBT3 series is part of onsemi's high-reliability Zener regulator portfolio, engineered for precision voltage reference and transient suppression in harsh-environment applications demanding AEC-Q101 compliance and robust thermal performance.

FAQ

What is the Zener voltage tolerance of the 1SMB5946BT3?

The 1SMB5946BT3 has a Zener voltage tolerance of ±5%, with a nominal value of 75 V and specified range of 71.25 V to 78.75 V at I_ZT = 140 mA. This tolerance is guaranteed per device marking and applies across the full operating temperature range of −65°C to +150°C, ensuring consistent clamping performance in automotive and industrial environments where 1SMB5946BT3 is deployed.

Does the 1SMB5946BT3 require a heatsink for 3 W operation?

No, the 1SMB5946BT3 does not require an external heatsink for 3 W operation when mounted on a standard FR-4 PCB with the recommended footprint per datasheet Figure 1. Its thermal resistance junction-to-ambient is 226 °C/W, meaning at 25°C ambient it reaches ~600°C junction temperature at full 3 W - however, the rated 3 W dissipation is defined at TL = 75°C (lead temperature), not TA. For continuous 3 W use, thermal design must maintain lead temperature ≤75°C via copper pour and layout; 1SMB5946BT3 relies on PCB conduction, not heatsinks.

Is the 1SMB5946BT3 RoHS-compliant and lead-free?

Yes, the 1SMB5946BT3 is RoHS-compliant and lead-free, as confirmed by the "G" suffix in its full ordering designation (SZ/1SMB5946BT3, G) and explicit statement in the datasheet: "Pb−Free Packages are Available." The device meets JEDEC J-STD-020 moisture sensitivity level (MSL) 1 and is compatible with standard lead-free reflow profiles up to 260°C for 10 seconds, making it suitable for modern SMT assembly processes where 1SMB5946BT3 is integrated into high-reliability boards.

How does the ESD rating of the 1SMB5946BT3 benefit system design?

The 1SMB5946BT3 features Class 3 ESD rating (>16 kV per Human Body Model), which eliminates the need for additional discrete ESD protection components on the same net. This simplifies BOM, reduces PCB area, and improves signal integrity in voltage reference or clamp nodes where 1SMB5946BT3 is used - especially critical in automotive infotainment and ADAS subsystems where electrostatic discharge immunity is mandated and board space is constrained.

Can the 1SMB5946BT3 be used in place of the 1N5365B?

The 1SMB5946BT3 is not a direct drop-in replacement for the 1N5365B due to package incompatibility: 1SMB5946BT3 uses SMB (surface-mount) while 1N5365B uses DO-204AL (axial). Electrically, both share 75 V nominal Zener voltage and similar Z_ZT, but 1SMB5946BT3 offers superior thermal performance (R_JA = 226 °C/W vs. ~50 °C/W for 1N5365B), AEC-Q101 qualification, and ESD robustness. Use 1SMB5946BT3 only when redesigning for SMT and automotive-grade reliability - not as a pin-compatible swap.