Texas Instruments LMX2531LQE1226E/NOPB

Overview

LMX2531LQE1226E/NOPB from Texas Instruments is a high-performance fractional-N delta-sigma PLL frequency synthesizer with fully integrated VCO, on-chip tank inductor, and ultra-low-noise LDOs for PLL/VCO supply regulation. It delivers 1184–1268 MHz RF output (high-band), supports 2.8–3.2 V operation, consumes 37–46 mA typical current, and achieves –142 dBc/Hz phase noise at 1-MHz offset for 1226 MHz output. It is used as a local oscillator in wireless LAN transceivers requiring stable, low-spur clock generation.

For engineers reviewing the LMX2531LQE1226E/NOPB datasheet, LMX2531LQE1226E/NOPB pinout, LMX2531LQE1226E/NOPB application, or LMX2531LQE1226E/NOPB equivalent, key selection criteria include its integrated VCO tuning range, FastLock capability, MICROWIRE serial interface timing compliance, and verified harmonic suppression performance across temperature.

Technical Context

The LMX2531LQE1226E/NOPB implements a fourth-order delta-sigma modulator for fractional-N synthesis, enabling fine frequency resolution without integer boundary spurs. Its architecture integrates a fully differential VCO with on-die inductor and adjustable third/fourth poles for loop filter optimization.

It features dual regulated supplies: VregVCO powers the VCO core with <±2% regulation, while VregPLL1 supplies the charge pump with <±4% mismatch between sink/source currents. The device uses a 36-pin WQFN package with dedicated ground pins for VCO, buffer, and digital sections to minimize coupling.

Key Specifications

Pinout & Package

LMX2531LQE1226E/NOPB is housed in a 36-pin 6 mm × 6 mm × 0.8 mm WQFN package (NJH0036D variant) with exposed thermal pad. Pin functions are validated per TI SNAS252S Rev S datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMX2531LQE1226E/NOPB, the LMX2531LQE1312E/NOPB extends upper frequency by 92 MHz while maintaining identical power, noise, and interface behavior; the LMX2531LQE1146E/NOPB trades 78 MHz of upper range for marginally better phase noise at lower offsets but shares full software and layout compatibility.

Availability

LMX2531LQE1226E/NOPB is available at Aetrix Electronics and suitable for cellular base stations, wireless LAN infrastructure, and satellite communication equipment requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LMX2531LQE1226E/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 leader specializing in analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The LMX2531 product line delivers highly integrated, low-phase-noise frequency synthesizers with on-die VCOs for wireless infrastructure, test equipment, and high-speed data converter clocking applications.

FAQ

What is the operating frequency range of the LMX2531LQE1226E/NOPB?

The LMX2531LQE1226E/NOPB operates in the high-band VCO range of 1184–1268 MHz. When the internal divider is enabled (DIV2 = 1), it delivers 592–634 MHz-matching its designated low-band specification. This dual-range capability allows flexible use in both direct-RF and IF-synthesis architectures without external dividers.

Does the LMX2531LQE1226E/NOPB require external loop filter components?

Yes, the LMX2531LQE1226E/NOPB requires an external passive loop filter between CPout (Pin 24) and Vtune (Pin 23). While third/fourth poles are integrated and adjustable, the primary RC network-including series resistor, shunt capacitor, and optional zero capacitor-must be placed externally to set loop bandwidth, phase margin, and transient response per application requirements.

What is the significance of the "E" suffix in LMX2531LQE1226E/NOPB?

The "E" in LMX2531LQE1226E/NOPB denotes the NJH0036D 36-pin WQFN package variant-specifically qualified for the LMX2531LQ1146E, LMX2531LQ1226E, LMX2531LQ1312E, LMX2531LQ1415E, LMX2531LQ1515E, LMX2531LQ2820E, and LMX2531LQ3010E versions per TI's SNAS252S datasheet.

How does the FastLock feature function in the LMX2531LQE1226E/NOPB?

The FastLock feature in the LMX2531LQE1226E/NOPB accelerates PLL lock acquisition by dynamically adjusting loop bandwidth during frequency transitions and includes a programmable timeout counter. If lock is not achieved within the timeout window, the device asserts FLout (Pin 25) and halts further attempts-preventing system hang during reference oscillator failure or configuration error.

Can the LMX2531LQE1226E/NOPB operate with a 1.8-V MICROWIRE interface?

Yes, the LMX2531LQE1226E/NOPB supports 1.8-V MICROWIRE signaling on DATA, CLK, LE, and CE pins, as explicitly stated in the "Features" section of the TI SNAS252S datasheet. Input voltage limits (VIH ≤2.75 V, VIL ≥0.4 V) and timing parameters (tCS ≥25 ns, tCWH ≥25 ns) remain valid at 1.8-V logic levels, enabling direct interfacing with low-voltage MCUs.