Microchip Technology 1N3649R

Overview

1N3649R from Microsemi is a high-reliability glass-passivated power rectifier diode rated for 800 V peak repetitive reverse voltage (V_RWM), 3.3 A average forward current (I_F), and 25 A non-repetitive surge current (I_FSM). It features glass-to-metal seal construction and operates from –65°C to +150°C, used in military-grade DC power supplies and high-stress industrial rectification circuits.

For engineers reviewing the 1N3649R datasheet, 1N3649R pinout, 1N3649R application, or 1N3649R equivalent, key selection criteria include its MIL-PRF-19500/260 qualification, DO-203AA (DO-4) stud-mount package, 2.2 V forward voltage at 10 A, 5 µA max reverse leakage at 800 V/25°C, and thermal resistance of 2.0°C/W junction-to-case.

Technical Context

This axial-leaded, stud-mounted rectifier uses a glass-passivated silicon die sealed in a hermetic glass-to-metal package, enabling stable operation under extreme thermal cycling and humidity. Its design supports high-surge tolerance (25 A, 8.3 ms half-sine) and low thermal resistance (2.0°C/W) for efficient heat transfer to heatsinks.

The device exhibits tightly controlled reverse leakage-5 µA maximum at 800 V and 25°C, rising to 200 µA at 800 V and 150°C-making it suitable for high-temperature, low-leakage DC bus conditioning where reliability outweighs cost sensitivity.

Key Specifications

Pinout & Package

1N3649R uses the DO-203AA (formerly DO-4) package: a hermetically sealed, glass-to-metal, stud-mounted metal case with axial leads. The case serves as the cathode terminal; the axial lead is the anode. Mounting requires torque-controlled fastening per MIL specifications (15 in-lb max on 10-32NF-2B nut).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-reliability power rectifier applications.

Compared with 1N3649R, the base 1N3649 requires inverted mechanical integration, while VMI 1N3649R offers identical form-fit-function with assured lifecycle support-making it the recommended alternative for both legacy refresh and new high-reliability deployments.

Availability

1N3649R is available at Aetrix Electronics and suitable for avionics power supplies, military radar modulators, and industrial welding controls requiring stable component supply, MIL-qualified traceability, and long-term obsolescence management.

Supply support for 1N3649R 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 Corporation (now part of Microchip Technology) specialized in high-reliability analog and mixed-signal semiconductors for aerospace, defense, and industrial markets.

The 1N3649R belongs to Microsemi's MIL-PRF-19500/260-qualified power rectifier family, engineered for mission-critical DC power conversion where parameter stability, hermeticity, and surge resilience are non-negotiable.

FAQ

What does the 'R' suffix in 1N3649R signify?

The 'R' suffix in 1N3649R indicates reversed polarity: the metal case (stud) is the cathode, and the axial lead is the anode. This configuration enables direct cathode-to-heatsink mounting while maintaining circuit isolation. The 1N3649R must not be substituted with the non-R version without verifying mechanical and electrical compatibility in the target layout.

Is 1N3649R compliant with MIL-PRF-19500/260?

Yes, 1N3649R is explicitly qualified per MIL-PRF-19500/260, Class B, as confirmed in the official Microsemi T4-LDS-0135 datasheet. This includes rigorous environmental testing, lot traceability, and screening for high-reliability applications such as aerospace and defense systems.

What is the thermal resistance of 1N3649R, and how does it impact heatsink design?

The 1N3649R has a junction-to-case thermal resistance (R_θJC) of 2.0°C/W. When dissipating 7.3 W (e.g., at 3.3 A × 2.2 V), this results in a 14.6°C temperature rise from case to junction. To maintain T_j ≤ 150°C at T_C = 150°C, the heatsink must limit total thermal resistance (case-to-ambient) to avoid exceeding junction limits under worst-case conditions.

Can 1N3649R be used in place of 1N3650R?

No-1N3650R is rated for 1000 V V_RWM, whereas 1N3649R is rated for 800 V. Substituting 1N3649R in a 1000 V application risks reverse breakdown and catastrophic failure. Voltage derating rules do not justify this substitution; the 1N3649R must only be used where maximum applied reverse voltage remains ≤ 800 V.

What is the maximum reverse leakage current for 1N3649R at elevated temperature?

At 800 V reverse voltage and junction temperature of 150°C, the 1N3649R exhibits a maximum reverse leakage current (I_R) of 200 µA, as specified in the Microsemi T4-LDS-0135 datasheet. This value is critical for high-impedance bias networks and low-power standby circuits operating in hot environments.