onsemi MURF860G Ultra-Fast Power Rectifier: Datasheet, Application Circuit, and Replacement Guide

The onsemi MURF860G is a prominent member of the Ultra-Fast Recovery Rectifier family, engineered to meet the demanding requirements of modern high-frequency power conversion circuits. This device is specifically designed for use in freewheeling, snubbing, and clamping applications, which are critical in switch-mode power supplies (SMPS), inverters, and motor drives.

Datasheet Overview and Key Specifications

The datasheet for the MURF860G reveals a component built for performance and reliability. Its key electrical characteristics define its application boundaries:

Repetitive Peak Reverse Voltage (VRRM): 800 V

Average Forward Rectified Current (IF(AV)): 8 A

Peak Forward Surge Current (IFSM): 100 A (non-repetitive)

Forward Voltage Drop (VF): 1.7 V max. (at 8 A, 25°C)

Reverse Recovery Time (trr): 50 ns (Ultra-Fast characteristic)

Package: TO-220F (FULLPAK), a fully molded, isolated package that simplifies mounting by eliminating the need for an insulating washer.

The ultra-fast recovery time is arguably its most critical feature. This parameter minimizes the period of reverse recovery current, which directly reduces switching losses in the associated transistor (like a MOSFET) and suppresses high-frequency ringing and noise. This leads to improved efficiency, reduced electromagnetic interference (EMI), and enhanced thermal performance of the overall system.

Typical Application Circuit

A classic application for the MURF860G is as a freewheeling diode in a switch-mode power supply. In a standard buck converter or power factor correction (PFC) boost converter circuit, the diode is placed in parallel with the inductive load.

When the main power switch (MOSFET) turns on, current flows through the inductor to the load. When the switch turns off, the inductor's collapsing magnetic field maintains current flow. This current now finds a path through the MURF860G, "freewheeling" around the inductor and load. The diode's fast recovery ensures it ceases conduction almost instantly when the switch turns back on, preventing short-circuiting the input supply.

Replacement and Cross-Reference Guide

When a direct replacement for the MURF860G is needed, it is crucial to match or exceed its key parameters to ensure system integrity. Potential replacements or equivalents include:

STMicroelectronics STTH8R06D (600V, 8A, Ultrafast)

Vishay UF860G (800V, 8A, Ultrafast)

Diodes Incorporated DSR8X800U (800V, 8A, Ultrafast)

When selecting a replacement, pay close attention to:

1. Voltage Rating (VRRM): Must be at least 800V.

2. Current Rating (IF(AV)): Must be 8A or higher.

3. Recovery Time (trr): Should be equal to or faster than 50ns.

4. Package: The TO-220F (isolated) package is a key feature for many designs. A standard TO-220AB would require a separate insulating kit.

ICGOODFIND: The onsemi MURF860G stands out as a robust and highly efficient ultra-fast rectifier, essential for high-frequency power management. Its excellent combination of 800V voltage blocking, 8A current handling, and an ultra-fast 50ns recovery time makes it an ideal choice for designers seeking to optimize efficiency and reliability in switching power circuits. Careful cross-referencing of its core specifications is vital for a successful replacement.

Keywords: Ultra-Fast Recovery Rectifier, Freewheeling Diode, Reverse Recovery Time, TO-220F Package, Switch-Mode Power Supply (SMPS)