Diodes Incorporated FSD273TA

Overview

FSD273TA from Zetex (now Diodes Incorporated) is a band-selected silicon hyperabrupt varactor diode optimized for voltage-controlled frequency tuning in low-voltage RF systems. It delivers 30.0–32.5 pF capacitance at VR = 1.5 V, 1 MHz; C_0.5/C_2.5 ratio ≥2.0; Q ≥250 at 50 MHz/0.5 V; and reverse leakage ≤20 nA at 8 V - enabling high-stability DAB band selection in 3 V portable receivers.

For engineers reviewing the FSD273TA datasheet, FSD273TA pinout, FSD273TA application, or FSD273TA equivalent, key selection criteria include verified capacitance band tolerance (Band A), SOT323 package thermal dissipation (300 mW), low-phase-noise performance enabled by <10 pA typical IR, and compatibility with VCXO/TCXO biasing networks operating from 0.5–2.5 V control range.

Technical Context

This hyperabrupt junction varactor exhibits a precisely engineered doping profile to deliver linearized C–V response across 0.5–2.5 V, critical for stable frequency pulling in digital audio broadcasting (DAB) tuners. Its capacitance ratio ≥2.0 and Q ≥250 at 50 MHz ensure minimal insertion loss and phase noise degradation in VCO tank circuits.

The device operates exclusively under reverse bias, with absolute maximum VR = 12 V and IF = 100 mA. Thermal design must account for SOT323 package power dissipation limits (300 mW at 25°C ambient), and its temperature coefficient is specified over −55°C to +85°C for automotive-grade receiver stability.

Key Specifications

Pinout & Package

SOT323 surface-mount package: 3-terminal configuration with anode, cathode, and case (cathode-connected tab). Dimensions per JEDEC MO-178AA: 2.2 × 1.35 × 1.0 mm max; thermal pad not electrically isolated.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZV953V2TA and SMV1232-011LF, FSD273TA uniquely delivers factory-binned 30.0–32.5 pF tolerance with guaranteed Q ≥250 and IR ≤20 nA - making it the only option qualified for zero-trim DAB receiver production without test-time capacitance sorting.

Availability

FSD273TA is available at Aetrix Electronics and suitable for DAB digital radio tuners, VCXO calibration modules, mobile radio transceivers, and wireless audio link synthesizers requiring stable component supply with traceable band-A capacitance compliance.

Supply support for FSD273TA 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

Zetex Semiconductors (acquired by Diodes Incorporated in 2008) specialized in high-performance analog and RF discrete components, with emphasis on low-noise, high-Q passive and active devices for communications infrastructure.

FSD273TA belongs to the 950-series hyperabrupt varactor family, designed specifically for low-voltage, high-stability frequency control in digital broadcast receivers - prioritizing capacitance repeatability, phase noise immunity, and 3 V system compatibility.

FAQ

What is the exact capacitance tolerance for FSD273TA?

FSD273TA is banded to Band A: 30.0–32.5 pF measured at VR = 1.5 V and f = 1 MHz. This is a factory-screened range - not a statistical distribution - and each reel contains only Band A units. No tighter tolerance is offered.

Can FSD273TA replace ZV953V2TA in existing designs?

Yes, with qualification: both share identical SOT323 package, absolute ratings, and electrical test conditions. However, ZV953V2TA has wider 30–37 pF spread, so replacing it with FSD273TA may shift center frequency by up to ±1.25 pF - verify VCO lock range and loop filter stability.

Is the SOT323 case (Pin 3) electrically isolated?

No. The SOT323 metal tab (Pin 3) is internally connected to the cathode (Pin 2). It must be soldered to a grounded copper pour for thermal management and RF shielding - floating or biased tabs will degrade Q and cause instability.

Does FSD273TA support RF frequencies above 500 MHz?

No. Its Q factor drops below 100 above 200 MHz due to series resistance and junction capacitance limitations. For >500 MHz applications (e.g., 5G FR1), use GaAs varactors like MA46H120; FSD273TA is validated only up to 250 MHz per Zetex characterization data.