Si4122 Bt

The Si4122-BT is a legacy high-performance RF frequency synthesizer IC originally manufactured by Silicon Labs (now Skyworks). While it was once a staple in digital cellular handsets and wireless data systems, it is currently obsolete (End of Life) and has been largely phased out in favor of more integrated solutions. AvaqSkyworksinc

Product Overview & Specifications

The Si4122-BT is a dual-band RF synthesizer that integrates voltage-controlled oscillators (VCOs) and phase-locked loops (PLLs) to minimize external components. AvaqAlibaba

• Frequency Support: Dual-band synthesis ranging from 900 MHz to 2.0 GHz (RF1) and 62.5 MHz to 1000 MHz (IF). AlldatasheetEbay
• Key Features: Features a self-tuning architecture to compensate for temperature drift and a 3-wire serial interface for programmable control. Avaq
• Package: The "BT" suffix denotes the TSSOP-24 package, which is primarily found today in the secondary/surplus market for maintenance of legacy equipment. LovechipAlibaba

Market Availability & Sourcing

As of late 2026, finding new-old-stock (NOS) for the Si4122-BT is difficult through primary channels. The Si4122-D-GM (QFN package) remains the closest functional equivalent but is also considered legacy (Not Recommended for New Designs). Skyworksinc

• Legacy Support: Sourcing is concentrated among specialized B2B electronics distributors in China and Hong Kong. AlibabaAlibaba
• Pricing: Available units are priced between $4.24 and $28.29 per piece, depending on quantity and supplier. Alibaba

2026 Market Trends & Insights

The RF synthesizer market in 2026 is undergoing a paradigm shift driven by 5G-Advanced and IoT maturation.

1. 1Transition to SoCs: Discrete synthesizers like the Si4122 are being rapidly replaced by Integrated RF-SoCs to reduce bill-of-materials (BOM) costs and physical footprint. Techinsights
2. 25G-Advanced & 6G Prototyping: Modern designs now demand synthesizers capable of sub-THz frequencies and ultra-low phase noise to support massive MIMO and beamforming. Techinsights
3. 3Power Efficiency: Mirroring trends in power semiconductors, there is a heavy focus on ultra-low power consumption for battery-operated IoT devices, a requirement the Si4122 struggle to meet compared to modern 2026 standards. KbvresearchTechinsights
4. 4Modern Alternatives: For new designs, industry-standard modular replacements include the Analog Devices ADF4351 (covering 35 MHz to 4.4 GHz) or fully integrated transceivers from the ADRV series. Alibaba

For maintenance or repair of systems using the Si4122-BT, you should prioritize suppliers with verified stock, as these components are increasingly scarce. Alibaba