Texas Instruments LMK04131SQ/NOPB

Overview

LMK04131SQ/NOPB from Texas Instruments is a dual-loop jitter-cleaning clock conditioner IC with cascaded PLL architecture, supporting 5 independent clock outputs in LVDS, LVPECL, and LVCMOS formats. It operates from 3.15 V to 3.45 V, features an internal VCO tuned to 1430–1570 MHz, delivers ≤160 fs RMS jitter (12 kHz–20 MHz) at 122.88 MHz output, and targets high-speed serial interface timing in cellular basestations and optical transport line cards.

For engineers reviewing the LMK04131SQ/NOPB datasheet, LMK04131SQ/NOPB pinout, LMK04131SQ/NOPB application, or LMK04131SQ/NOPB equivalent, key selection criteria include its dual-PLL jitter cleaning capability, programmable output format per channel (LVDS/LVPECL/LVCMOS), redundant reference inputs with loss-of-signal detection, and support for crystal or external VCXO reference sources - all in a 48-pin WQFN package.

Technical Context

The LMK04131SQ/NOPB implements two independent PLLs: PLL1 accepts dual redundant reference inputs (CLKin0/CLKin1) with automatic/manual switching and loss-of-signal detection, while PLL2 uses a dedicated OSCin/OSCin* input with optional ×2 frequency doubler and integrated VCO. Its cascaded architecture enables precise jitter attenuation by cleaning a noisy system reference before multiplication/distribution.

Each of its five output channels (CLKout0–CLKout4) includes dedicated divider blocks and configurable output format - specifically: CLKout0 and CLKout4 as LVDS, CLKout1 and CLKout3 as LVPECL, and CLKout2 as dual LVCMOS - enabling simultaneous generation of multiple standardized frequencies (e.g., 122.88 MHz, 156.25 MHz, 311.04 MHz) without external components.

Key Specifications

Pinout & Package

Package: 48-pin WQFN (7.0 × 7.0 × 0.8 mm) with exposed thermal pad (DAP), optimized for thermal dissipation in high-jitter-performance applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock jitter cleaning applications.

Compared with LMK04131SQ/NOPB, LMK04828RHAT offers lower jitter and integrated power management but requires more board space and cost; Si5341-B-GM provides superior frequency flexibility and software control but trades off deterministic jitter performance for programmability.

Availability

LMK04131SQ/NOPB is available at Aetrix Electronics and suitable for cellular infrastructure, optical transport, broadcast video, and high-speed data acquisition requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LMK04131SQ/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 high-performance timing solutions for industrial, automotive, and communications markets.

The LMK041xx family was designed specifically for jitter-critical infrastructure applications - delivering precision clock conditioning with dual-loop PLLs, low-noise VCOs, and flexible output formatting in compact packages.

FAQ

What is the maximum output frequency supported by LMK04131SQ/NOPB?

The LMK04131SQ/NOPB supports up to 1080 MHz on LVDS and LVPECL outputs (CLKout0/CLKout1/CLKout3/CLKout4), and up to 250 MHz on LVCMOS outputs (CLKout2). These limits are defined by electrical specifications under 3.3 V supply and −40 °C to +85 °C operation, with proper termination and layout. Exceeding these frequencies risks degraded jitter, increased skew, or failure to meet output voltage swing specs.

Does LMK04131SQ/NOPB support crystal oscillator input directly?

Yes, the LMK04131SQ/NOPB supports direct connection of a 6–20 MHz fundamental-mode crystal to the OSCin/OSCin* pins in crystal oscillator mode. The device integrates necessary bias circuitry and load capacitance tuning (via register configuration), eliminating the need for an external oscillator module. Crystal ESR must be ≤100 Ω, and power dissipation should remain below 200 µW for reliability.

How does the dual-reference input redundancy work on LMK04131SQ/NOPB?

The LMK04131SQ/NOPB implements hardware-based automatic reference switchover between CLKin0 and CLKin1 using loss-of-signal (LOS) detection on pins 34 and 35. When the active reference fails, the device transitions to the backup within one reference cycle (e.g., <10 ns for 100 MHz input) without glitching outputs. Manual selection is also supported via register control, allowing deterministic control during system initialization or maintenance.

Can LMK04131SQ/NOPB generate 156.25 MHz and 311.04 MHz simultaneously?

Yes, the LMK04131SQ/NOPB can generate both 156.25 MHz and 311.04 MHz simultaneously. These frequencies correspond to VCO frequencies of 1250 MHz and 1244.16 MHz respectively - both within the device's 1430–1570 MHz VCO range. Table 3 in the datasheet confirms both are supported configurations using integer-N division, and the five independent output dividers allow concurrent assignment without conflict.

What is the purpose of the SYNC* pin on LMK04131SQ/NOPB?

The SYNC* pin on LMK04131SQ/NOPB is an active-low input that triggers deterministic phase alignment across all five clock outputs. When asserted, it resets the output dividers synchronously, ensuring zero-phase offset between CLKout0–CLKout4 after release. This is essential for multi-lane SerDes systems (e.g., CPRI, eCPRI, OTN) where inter-channel skew must be minimized to maintain data eye integrity.