Texas Instruments LMK61E0M-SIAR

Overview

LMK61E0M-SIAR from Texas Instruments is an ultra-low jitter (500-fs RMS typical), programmable 3.3-V LVCMOS oscillator with integrated fractional-N PLL, 4.6–5.6 GHz VCO, internal EEPROM, and I²C interface. It delivers factory-programmed 70.656 MHz or user-configurable frequencies from 50 MHz to 200 MHz, supporting glitch-free frequency margining up to ±1000 ppm for xDSL and broadcast video timing compliance testing.

For engineers reviewing the LMK61E0M-SIAR datasheet, LMK61E0M-SIAR pinout, LMK61E0M-SIAR application, or LMK61E0M-SIAR equivalent, this device serves as a high-stability, digitally reconfigurable clock source requiring precise phase noise control, industrial temperature operation (–40°C to +85°C), and dual LVCMOS output flexibility in FPGA/processor attach and network infrastructure designs.

Technical Context

The LMK61E0M integrates a 50-MHz crystal-based reference with a fractional-N PLL architecture featuring a 4.6–5.6 GHz LC VCO, programmable R-divider (×1 or ×4), reference doubler (enabled/disabled), and third-order delta-sigma modulator for noise shaping. Its PLL loop bandwidth is software-tunable from 100 kHz to 1 MHz via on-chip R/C filter registers.

It implements two-stage integer division: a VCO post-divider (÷4 or ÷5) followed by a high-speed output divider (÷6 to ÷256), enabling fine (<1 ppb) and coarse (±1000 ppm) frequency margining without output glitches. Output polarity, slew rate (fast/slow), and tri-state control are individually configurable per OUT0/OUT1 via register R20/R24/R22.

Key Specifications

Pinout & Package

LMK61E0M-SIAR uses a 7.0 mm × 5.0 mm, 8-pin QFM (SIA) package with exposed thermal pad for enhanced thermal performance (R_θJB = 36.7°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable oscillator applications.

Compared with Si510-PROG and LMK62E2-100M, the LMK61E0M-SIAR uniquely combines integrated crystal, EEPROM, I²C programmability, and ultra-low jitter in a single 7×5 mm package - making it optimal for space-constrained, reconfigurable systems requiring both precision and flexibility.

Availability

LMK61E0M-SIAR is available at Aetrix Electronics and suitable for network infrastructure, FPGA/processor clocking, test & measurement equipment, and broadcast video systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LMK61E0M-SIAR 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 clock solutions, with decades of leadership in high-performance timing devices.

The LMK61E0M belongs to TI's PLLatinum™ programmable oscillator family, designed specifically for applications demanding ultra-low jitter, in-system reconfigurability, and industrial-grade reliability in communications and computing infrastructure.

FAQ

What is the default startup frequency and how is it stored?

The LMK61E0M-SIAR powers up at 70.656 MHz, which is factory-programmed into its on-chip EEPROM. This default frequency is loaded automatically at power-on without host intervention, using internal oscillator and PLL settings stored in non-volatile memory. The EEPROM can be rewritten in-system via I²C to update startup behavior for custom configurations.

Can both OUT0 and OUT1 operate simultaneously at different frequencies?

No - both outputs derive from the same PLL/VCO core and share the same output divider chain, so they must operate at identical frequencies. However, they support independent control of polarity (same/opposite), slew rate (fast/slow), and tri-state state, enabling differential clock distribution or clock gating without hardware changes.

How does the I²C interface handle frequency updates without output glitches?

The LMK61E0M-SIAR uses a dedicated DCXO mode where only the fractional-N numerator (NUM) registers are updated via I²C, leaving the integer divider and VCO settings unchanged. This allows sub-ppb frequency steps with zero-phase discontinuity because the PLL remains locked and the output divider transitions occur synchronously with the VCO period.

Is an external crystal required for operation?

No - the LMK61E0M-SIAR integrates a 50-MHz monolithic crystal and requires no external timing components. The crystal is hermetically sealed within the QFM package and directly feeds the PLL reference path, eliminating board-level crystal placement, load capacitance tuning, and associated layout sensitivity.