Texas Instruments LMX2541SQX3740E/NOPB

Overview

LMX2541SQX3740E/NOPB from Texas Instruments is an ultra-low-noise fractional-N PLL frequency synthesizer with integrated VCO, operating from 3480 MHz to 4000 MHz (VCO core), and supporting output frequencies down to 55.2 MHz via programmable divider (÷63). It delivers –225 dBc/Hz normalized PLL phase noise floor, 2.6 mRad RMS integrated phase error (100 Hz–20 MHz at 3.74 GHz), and supports up to 104-MHz phase detector frequency. It is used in high-performance RF local oscillator generation for wireless infrastructure.

For engineers reviewing the LMX2541SQX3740E/NOPB datasheet, LMX2541SQX3740E/NOPB pinout, LMX2541SQX3740E/NOPB application, or LMX2541SQX3740E/NOPB equivalent, key selection criteria include VCO frequency range (3480–4000 MHz), integrated RMS phase error, phase detector rate capability, external VCO bypass support, and WQFN-36 package compatibility with TI's PLLatinum timing architecture.

Technical Context

The LMX2541SQX3740E/NOPB implements a delta-sigma fractional-N PLL with fully integrated VCO tank circuit and programmable output divider (1–63). Its architecture enables continuous frequency coverage from 55.2 MHz to 571.4 MHz when using ÷63–÷8 division, while maintaining ultra-low phase noise through integrated low-noise LDOs and optimized charge pump design.

It supports dual-mode operation: internal VCO mode (default) and external VCO mode (via ExtVCOin pin), with programmable charge pump gain (1×–32×), FastLock mode, analog/digital lock detect, and digital FSK modulation. The device uses a 3-wire MICROWIRE interface compatible with 1.6-V logic levels and operates from 3.15 V to 3.45 V supply.

Key Specifications

Pinout & Package

LMX2541SQX3740E/NOPB is housed in a 36-pin WQFN (NJK) package with exposed thermal pad (DAP). Pin 0 is GND (DAP), and the package supports standard reflow profiles per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RF synthesizer applications.

Compared with LMX2594RHBR and ADF4355BCPZ, the LMX2541SQX3740E/NOPB offers superior integration of crystal oscillator circuitry and lower system-level BOM count for 3.5 GHz base stations, while trading off maximum frequency and absolute noise floor for proven reliability and thermal performance in industrial ambient conditions.

Availability

LMX2541SQX3740E/NOPB is available at Aetrix Electronics and suitable for wireless infrastructure (LTE/5G), test and measurement instrumentation, avionics SATCOM terminals, and FM broadcast exciters requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for LMX2541SQX3740E/NOPB 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

Texas Instruments is a global semiconductor company specializing in analog, embedded processing, and connectivity technologies, with leadership in high-performance timing and RF solutions.

The LMX2541 family was designed specifically for ultra-low-noise RF frequency synthesis in wireless infrastructure and precision instrumentation, emphasizing integrated VCO performance, phase noise optimization, and system-level power integrity.

FAQ

What is the minimum output frequency achievable with LMX2541SQX3740E/NOPB?

The LMX2541SQX3740E/NOPB achieves continuous output from 55.2 MHz to 571.4 MHz using its programmable VCO divider (÷63 to ÷8). At ÷63, the lower bound is 3480 MHz ÷ 63 = 55.2 MHz. Below this, gaps occur unless external division is added. This range covers FM broadcast, ISM bands, and IF stages in 5G RU designs.

Does LMX2541SQX3740E/NOPB support external crystal oscillators?

Yes, the LMX2541SQX3740E/NOPB supports external crystal oscillators via OSCin and OSCin* pins (Pins 21/22). It accepts crystals from 5 MHz to 20 MHz with ESR ≤100 Ω and power dissipation ≤200 µW. Internal oscillator circuitry eliminates need for external load capacitors in most cases.

How does the FastLock mode function in LMX2541SQX3740E/NOPB?

FastLock mode in the LMX2541SQX3740E/NOPB accelerates PLL lock by dynamically adjusting loop bandwidth and pre-charging the Vtune line based on target frequency. It reduces lock time by >50% during large frequency hops (e.g., 100 MHz steps) while minimizing cycle slips-critical for TDD-based 5G frame switching.

Can LMX2541SQX3740E/NOPB operate with an external VCO?

Yes, the LMX2541SQX3740E/NOPB supports external VCO mode via the ExtVCOin pin (Pin 12). When enabled, the internal VCO is bypassed, and the PLL locks to the external VCO signal (400–6000 MHz). This allows hybrid architectures using high-power GaN VCOs or temperature-stable OCXOs for ultra-low drift applications.

What is the RMS phase error specification for LMX2541SQX3740E/NOPB at 3.74 GHz?

The LMX2541SQX3740E/NOPB specifies 2.6 mRad RMS phase error integrated from 100 Hz to 20 MHz at 3.74 GHz (maximum VCO frequency). This value is measured with a 100 MHz Wenzel crystal reference in integer-N mode and optimized loop bandwidth-directly enabling <0.015° jitter for high-order QAM constellations.