RF synthesizer with integrated VCO — band reach and board-space trade-off
The LMX2541SQ3320E/NOPB is a PLL frequency synthesizer (RF) with an on-chip VCO, covering output frequencies up to 3.6 GHz. That range spans ISM bands at 2.4 GHz, cellular infrastructure, and test-equipment local oscillators — no external multiplier needed for most sub-4 GHz designs. Integrating the PLL and VCO in a single 36-WQFN (6x6 mm) package shrinks the footprint compared to a discrete PLL + VCO pair, but the exposed thermal pad demands a solid ground-plane via array for heat sinking — the datasheet's recommended layout is worth following closely.
The supply range is 3.15 V to 3.45 V — a tight 300 mV window that rules out shared 3.3 V rails with heavy ripple. A dedicated low-noise LDO for the VCO supply is typical; the phase-noise plot degrades noticeably if the supply noise exceeds the PSRR budget at the loop bandwidth. The 36-WQFN package with exposed pad helps keep the VCO junction temperature below the 125°C absolute max even at 85°C ambient, provided the PCB thermal design is adequate.
Procurement can commit to this part for new designs without a near-term obsolescence watch. The ROHS3 compliance covers current global environmental regulations. CT works for prototype or low-volume builds. Surface-mount only; no through-hole variant exists.