What this PLL frequency synthesizer does
The Texas Instruments LMX2354SLBX is a PLLatinum™ PLL frequency synthesizer with a bypass mode, handling dual-band synthesis up to 2.5 GHz on the RF path and 550 MHz on the IF path. It accepts CMOS or TTL inputs and delivers CMOS outputs, with a 3:3 input-to-output ratio and an integrated divider and multiplier. The single-circuit device runs from a 2.7 V to 5.5 V supply and operates across the industrial temperature range of -40°C to 85°C, making it suitable for base station local oscillators, satellite receivers, and test equipment where a clean, programmable clock source is needed.
The 2.5 GHz RF maximum covers most cellular and ISM-band local oscillator requirements, while the 550 MHz IF maximum handles the downconverted intermediate frequency in a superheterodyne receiver. The differential RF input (Yes/No for input/output) helps reject common-mode noise on the reference path, though the output is single-ended CMOS — plan for a balun or external filtering if driving a differential mixer. The bypass mode lets you feed through an external VCO when the internal PLL is not needed, saving power and board space in multi-mode designs.
Package and footprint details
Housed in a 24-TFQFN CSP (4.5 mm x 3.5 mm body), this is a fine-pitch surface-mount device. The supplier device package is 24-CSP (4.5x3.5). The 'SLBX' suffix indicates the CSP package variant — the 'SLB' variant (same die, different package) is not footprint-compatible, so verify your board layout against the 24-CSP land pattern before ordering a replacement.