Microchip Technology 1PMT5943/TR7

Overview

1PMT5943B from Microsemi is a 56 V, ±5% tolerance surface-mount Zener diode in the Powermite® package, rated for 3.0 W DC power dissipation at TAB 1 = 60°C, with 86 Ω dynamic impedance at 6.7 mA test current and 1300 µA max reverse leakage at 42.6 V. It serves as a precision voltage reference or overvoltage clamp in DC power rails and regulator feedback networks.

For engineers reviewing the 1PMT5943B datasheet, 1PMT5943B pinout, 1PMT5943B application, or 1PMT5943B equivalent, key selection criteria include zener voltage accuracy, thermal resistance (30°C/W junction-to-TAB1), ESD rating (>16 kV HBM), low knee impedance, and compatibility with automated SMT assembly.

Technical Context

This Zener diode operates in reverse breakdown mode with a nominal zener voltage of 56 V measured at 6.7 mA (IZT) with TAB 1 held at 30°C. Its Powermite® package features a full metallic bottom and integral heat sink locking tab, enabling direct thermal conduction to the PCB pad.

The device exhibits 86 Ω dynamic impedance at IZT, 1300 µA max reverse leakage at VR = 42.6 V, and a thermal resistance of 30°C/W from junction to TAB 1 - critical for stable regulation under sustained 3.0 W power dissipation.

Key Specifications

Pinout & Package

Package: Powermite® surface-mount molded package with full metallic bottom and integral heat sink locking tab (TAB 1). Cathode is designated by TAB 1. Mounting orientation is unrestricted.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMCJ56A and BZX84-C56, the 1PMT5943B uniquely combines 3.0 W continuous Zener regulation, low-impedance precision clamping, and Powermite® thermal performance - making it irreplaceable in high-power reference or hybrid protection-regulation roles.

Availability

1PMT5943B is available at Aetrix Electronics and suitable for DC power supply regulation, overvoltage protection circuits, programmable voltage references, and temperature-stable bias networks requiring stable component supply and traceable sourcing.

Supply support for 1PMT5943B 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

Microsemi (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability analog, mixed-signal, and radiation-hardened components for aerospace, defense, and industrial markets.

The Powermite® Zener diode product line delivers high-power surface-mount voltage regulation in compact packages, engineered for thermal efficiency and manufacturability in harsh-environment power systems.

FAQ

What is the zener voltage tolerance for 1PMT5943B?

The 1PMT5943B has a standard zener voltage tolerance of ±5% at 56 V, measured at IZT = 6.7 mA with TAB 1 held at 30°C. Tighter tolerances (±2% and ±1%) are available with suffixes C and D respectively, but the base 1PMT5943B part uses ±5%. This tolerance directly impacts regulation accuracy in feedback loops and reference circuits where 1PMT5943B is deployed.

Can 1PMT5943B be used in place of a through-hole 1N5256B?

No - while both are 56 V Zeners, the 1PMT5943B is a 3.0 W surface-mount device in Powermite® packaging with 30°C/W thermal resistance, whereas the 1N5256B is a 0.5 W through-hole device in DO-35 with much higher thermal resistance. Substituting 1PMT5943B for 1N5256B requires PCB redesign to accommodate the Powermite® footprint and thermal pad; it is not a drop-in replacement. The 1PMT5943B offers superior power handling but different mechanical integration.

What is the maximum reverse voltage (VR) that guarantees IR ≤ 1300 µA for 1PMT5943B?

Per the datasheet, the 1PMT5943B guarantees IR ≤ 1300 µA at VR = 42.6 V. This value is derived from the "REVERSE VOLTAGE VR MAX" column in the Electrical Characteristics table and corresponds to the voltage below which leakage remains within specification. Operating above 42.6 V risks exceeding the specified leakage limit, affecting low-power circuit integrity - a critical consideration when using 1PMT5943B in battery-powered or energy-harvesting designs.

How does the Powermite® package improve thermal performance of 1PMT5943B?

The Powermite® package improves thermal performance of 1PMT5943B primarily through its full metallic bottom and integral heat sink locking tab (TAB 1), achieving a junction-to-TAB1 thermal resistance of 30°C/W. This allows efficient heat transfer from the silicon die directly into the PCB copper pour. Unlike plastic-bodied SMD Zeners, the metal bottom eliminates flux entrapment and ensures consistent solder joint quality - both essential for maintaining thermal reliability under continuous 3.0 W operation in 1PMT5943B applications.

Is 1PMT5943B suitable for automotive applications?

The 1PMT5943B meets operating temperature range requirements (-55°C to +150°C junction/storage) and has >16 kV HBM ESD rating, supporting many automotive subsystems. However, it is not AEC-Q200 qualified, and Microsemi's documentation does not list automotive-grade screening or PPAP support for this part. For production automotive use, 1PMT5943B should undergo system-level qualification; it is commonly used in non-safety-critical aftermarket or industrial-automotive hybrids where full AEC compliance is not mandated.