Texas Instruments LMK61E2-156M25SIAT

Overview

LMK61E2-156M25SIAT from Texas Instruments is an ultra-low-jitter LVPECL-output programmable oscillator generating a precise 156.25 MHz reference clock with ±50 ppm total frequency tolerance, 90 fs RMS phase jitter (12 kHz–20 MHz), and robust –70 dBc PSRR. It operates from a single 3.3 V supply across –40°C to +85°C and is pre-programmed for immediate use in high-speed serial data interfaces.

For engineers reviewing the LMK61E2-156M25SIAT datasheet, LMK61E2-156M25SIAT pinout, LMK61E2-156M25SIAT application, or LMK61E2-156M25SIAT equivalent, key selection criteria include differential output compatibility (LVPECL/LVDS/HCSL), industrial temperature stability, 7 mm × 5 mm QFM package footprint, and factory-trimmed frequency accuracy without external programming.

Technical Context

The LMK61E2-156M25SIAT integrates a high-performance PLL-based oscillator core with internal power conditioning to suppress supply noise, enabling stable clock generation without external loop filters or voltage regulators. Its architecture supports fixed-frequency operation at 156.25 MHz with LVPECL output swing of 700–1200 mV and differential rise/fall times under 200 ps.

It features an LVCMOS-compatible OE (output enable) input with internal pull-up, allowing hardware-controlled output disable into high-impedance state within 50 µs. The device uses a 6-pin QFM package with dedicated GND and VDD pins optimized for low-inductance power delivery and thermal dissipation via the exposed pad.

Key Specifications

Pinout & Package

The LMK61E2-156M25SIAT is housed in a 7 mm × 5 mm, 6-pin QFM (SIA) package with exposed thermal pad, pin-compatible with industry-standard 7050 XO footprints and optimized for minimal board area and thermal resistance (R_θJB = 37.7°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-jitter oscillator applications.

Compared with LMK61E0-156M25SIAT, the LMK61E2-156M25SIAT trades long-term stability for lower cost and broader industrial qualification; versus Si5338A-D-GM, it offers simpler integration and guaranteed jitter performance without configuration overhead.

Availability

LMK61E2-156M25SIAT is available at Aetrix Electronics and suitable for 10G/25G Ethernet switches, PCIe Gen4/Gen5 root complexes, and FPGA-based test equipment requiring stable component supply, full traceability, and lifecycle continuity.

Supply support for LMK61E2-156M25SIAT 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 delivering analog, embedded processing, and connectivity solutions with deep expertise in precision timing and high-speed signal integrity.

The LMK61XX product line was designed specifically for replacing quartz oscillators in high-performance networking, computing, and communications infrastructure where ultra-low jitter and supply noise immunity are critical.

FAQ

What output format does LMK61E2-156M25SIAT support?

This device is factory-programmed for LVPECL output only. Although the underlying LMK61XX platform supports LVDS and HCSL, the -E2 suffix and SIAT ordering code confirm LVPECL configuration at 156.25 MHz. No external programming or I²C interface is available on this variant.

Can OE pin be left floating?

No - OE has an internal pull-up, but leaving it floating risks noise-induced toggling that may cause intermittent output disable. TI specifies connecting OE to VDD (for always-enabled operation) or to a clean GPIO. A 10-kΩ pull-up to VDD is recommended if no active control is used.

Is the 7 mm × 5 mm package RoHS-compliant and lead-free?

Yes - the SIA QFM package is RoHS-compliant and lead-free, qualified to JEDEC J-STD-020 moisture sensitivity level 3 (MSL3), and rated for standard SnPb or Pb-free reflow profiles per J-STD-020. The datasheet confirms halogen-free construction and IPC/JEDEC Class 3 reliability testing.

How does its jitter compare to crystal-based oscillators?

At 156.25 MHz, LMK61E2-156M25SIAT achieves 90 fs RMS jitter - significantly lower than typical fundamental-mode quartz oscillators (200–500 fs) and competitive with high-end OCXOs. This results from integrated PLL noise filtering and proprietary VCO design, not quartz resonator quality.