Microchip Technology UM4902C

Overview

UM4902C from Microsemi is a high-power RF PIN diode designed for low-distortion switching and attenuation in HF–S-band systems. It features 400 V reverse voltage rating, 37.5 W power dissipation (at 25°C stud temperature), 0.5 Ω typical series resistance at 100 MHz, >5 µs carrier lifetime, and 3 pF capacitance at 100 V reverse bias. It is used in UHF phase shifters and megawatt peak-power duplexers.

For engineers reviewing the UM4902C datasheet, UM4902C pinout, UM4902C application, or UM4902C equivalent, key selection criteria include thermal path efficiency, RF voltage handling beyond reverse bias, low capacitance at 0 V, carrier lifetime-dependent linearity, and compatibility with automatic insertion equipment in high-reliability RF subsystems.

Technical Context

The UM4902C employs a non-cavity, thermally matched PIN structure with a thick intrinsic region optimized for high RF power control. Its long carrier lifetime (>5 µs) enables efficient RF signal modulation with low DC bias current while maintaining low distortion across HF to S-band frequencies.

It delivers stable parallel resistance (>10 kΩ at 100 MHz, 100 V reverse bias) and low series resistance (0.3–0.5 Ω), supporting high dynamic range in switched filter networks and antenna couplers where precise impedance control and minimal insertion loss are critical.

Key Specifications

Pinout & Package

UM4902C is housed in Style "C" isolated stud package: metal stud cathode, insulated anode terminal, hermetically sealed ceramic/metal construction rated for high-voltage, high-power RF operation. Thermal path from chip to stud is optimized for lower junction-to-case thermal resistance versus UM4000 series.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-power RF PIN diode applications.

Compared with UM4002C and UMX4902C, the UM4902C offers superior thermal performance for high-duty-cycle RF switching, while UMX4902C provides identical RF behavior with compliant finish-making UM4902C the baseline for legacy Sn/Pb processes and UMX4902C the default for new RoHS-compliant production.

Availability

UM4902C is available at Aetrix Electronics and suitable for UHF phase shifters, megawatt peak-power duplexers, antenna coupler networks, and switched filter banks requiring stable component supply across military, aerospace, and industrial radar programs.

Supply support for UM4902C 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, RF, and timing solutions for defense, aerospace, and industrial markets.

The UM4900 series was developed specifically for high-power RF switching applications demanding robust thermal performance, low distortion, and proven field reliability in mission-critical radar and communications infrastructure.

FAQ

What is the maximum reverse voltage rating for UM4902C?

The UM4902C has a reverse voltage rating of 400 V at 10 µA leakage current. This rating allows it to safely handle RF peak voltages significantly exceeding the applied DC reverse bias in high-power duplexers and phase shifters, as confirmed in Microsemi's qualification testing across thousands of operational hours.

How does UM4902C differ from UM4002C in thermal performance?

The UM4902C achieves 37.5 W power dissipation at 25°C stud temperature due to its shorter thermal path, whereas UM4002C is rated for 25 W under the same condition. The UM4902C's thermal resistance is 4°C/W versus 6°C/W for UM4002C-enabling higher RF power handling without thermal derating in compact layouts.

Is UM4902C compatible with automated PCB assembly processes?

Yes, UM4902C is compatible with automatic insertion equipment. Its Style "C" package features standardized mechanical dimensions and robust terminal geometry, and the RoHS-compliant UMX4902C variant uses matte tin plating optimized for consistent solder wetting and reflow compatibility in high-volume manufacturing.

What is the typical carrier lifetime of UM4902C and why does it matter?

The UM4902C has a carrier lifetime greater than 5 µs, measured at 10 mA forward current. This long lifetime enables high RF power control with low bias current and reduces intermodulation distortion-critical for maintaining signal fidelity in radar phase shifters and broadband attenuators where linearity directly impacts system dynamic range.

Does UM4902C require heatsinking, and what is its thermal mounting requirement?

Yes, UM4902C requires direct thermal coupling to a heatsink via its isolated stud cathode. The stud must be mounted to a thermally conductive surface maintained at ≤25°C for full 37.5 W rating; thermal interface material with low bondline thickness and high conductivity is recommended to minimize junction-to-sink thermal resistance in high-reliability RF assemblies.