Microchip Technology UM4301B

Overview

UM4301B from Microsemi is a high-power PIN diode designed for RF switching and linear attenuator applications in HF–1 GHz systems. It features 100 V reverse voltage rating, ≤2.2 pF capacitance at 100 V/1 MHz, ≤1.5 Ω series resistance at 100 mA/100 MHz, ≥200 kΩ parallel resistance at 100 V/100 MHz, and 250 µm I-region width - enabling low-distortion signal control in broadband RF front-ends.

For engineers reviewing the UM4301B datasheet, UM4301B pinout, UM4301B application, or UM4301B equivalent, key selection criteria include its 100 V blocking capability, thermal resistance of 7.5 °C/W (Package A), 20 W power dissipation at 25 °C stud temperature, and suitability for low-distortion RF attenuators requiring transit-time-limited operation below 5 MHz.

Technical Context

The UM4301B employs a thick intrinsic (I) region (≥250 µm) to achieve carrier lifetimes ≥6.0 µs, enabling low intermodulation distortion in analog RF attenuation paths. Its non-cavity, thermally matched construction supports stable DC biasing and high RF voltage hold-off under low reverse bias.

Designed for linear-mode operation, it delivers predictable resistance modulation (RS = 1.5 Ω min at 100 mA, RS = 1000 Ω max at 10 µA) across HF to 1 GHz, with capacitance tightly controlled to ≤2.2 pF - critical for maintaining impedance integrity in broadband switch/attenuator topologies.

Key Specifications

Pinout & Package

UM4301B is supplied in Style 'B' package: axial-lead, non-isolated, stud-mounted metal-can configuration with two terminals - anode and cathode - mounted on opposite ends of the cylindrical metal body. Thermal path is optimized through the stud base.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RF PIN diode switching and attenuation applications.

Compared with UM4301C and UM7301B, UM4301B offers the optimal balance of high power (20 W), moderate capacitance (2.2 pF), and grounded-stud thermal efficiency - making it the default choice for grounded-bias, high-linearity HF–VHF RF control where thermal management is via pin conduction.

Availability

UM4301B is available at Aetrix Electronics and suitable for RF transmitter attenuators, radar T/R switching, automated test equipment signal routing, and EMI pre-compliance attenuation requiring stable component supply across industrial, defense, and communications programs.

Supply support for UM4301B 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 RF, analog, and radiation-hardened components for aerospace, defense, and industrial markets.

The UM4300 series was developed specifically for high-linearity, high-power RF switching and analog attenuation in mission-critical communication and radar systems where distortion, thermal stability, and voltage hold-off are paramount.

FAQ

What is the maximum reverse voltage rating for UM4301B?

The UM4301B has a reverse voltage rating of 100 V at 10 µA leakage current. This rating is verified per Microsemi's published absolute maximum ratings table and applies under DC or low-frequency reverse bias conditions. The device can hold off significantly higher RF peak voltages in switching applications due to its low capacitance and thick I-region, but sustained DC reverse bias must remain ≤100 V to avoid degradation. UM4301B maintains this rating across its specified operating temperature range.

Does UM4301B require a heatsink for 20 W operation?

Yes - UM4301B achieves its 20 W power dissipation rating only when mounted with thermal interface to a heatsink or cold plate, per Package A specifications (25 °C pin temperature). Its thermal resistance is 7.5 °C/W, meaning a 150 °C junction-to-ambient rise would occur without heatsinking at full power. For reliable continuous operation, a heatsink maintaining pin temperature ≤25 °C is required. Derating is necessary above 25 °C ambient.

How does UM4301B differ from UM4301C?

UM4301B and UM4301C share identical die characteristics (100 V rating, 2.2 pF, 1.5 Ω RS), but differ in package isolation: UM4301B has a non-isolated stud (cathode electrically connected to mount), while UM4301C provides cathode-to-stud isolation. This makes UM4301C suitable for floating-bias circuits like certain T/R switches, whereas UM4301B is optimized for grounded-stud thermal paths. Both offer 20 W dissipation and 7.5 °C/W θ.

Is UM4301B RoHS compliant?

The standard UM4301B is not RoHS compliant. Microsemi offers RoHS-compliant versions under the UMX4301B designation, which uses lead-free terminations and compliant packaging materials. UMX4301B retains identical electrical and thermal specifications but requires explicit ordering with the "UMX" prefix. Legacy UM4301B remains available for legacy or exempt applications.

What is the typical carrier lifetime of UM4301B and why does it matter?

The UM4301B has a minimum carrier lifetime (τ) of 6.0 µs, measured at 10 mA forward current. This long lifetime directly enables low intermodulation distortion in linear attenuator applications by ensuring transit-time-limited operation below 5 MHz - preventing harmonic generation and spectral regrowth. It also defines the upper frequency limit for effective resistance modulation, making UM4301B ideal for HF–VHF analog control where signal purity is critical.