Texas Instruments LMK61E2BBA-SIAR

Overview

LMK61E2BBA-SIAR from Texas Instruments is an ultra-low jitter (90 fs RMS typical >100 MHz), programmable oscillator with integrated fractional-N PLL, 4.6–5.6 GHz VCO, and factory-configured 125 MHz LVDS output in a 7 mm × 5 mm QFM-8 package. It features on-chip EEPROM for self-startup, I²C programmability, ±50 ppm total frequency tolerance, and robust –70 dBc PSRR - deployed in FPGA clocking, baseband units, and high-speed serial interface timing.

For engineers reviewing the LMK61E2BBA-SIAR datasheet, LMK61E2BBA-SIAR pinout, LMK61E2BBA-SIAR application, or LMK61E2BBA-SIAR equivalent, key selection criteria include differential output format support (LVDS up to 900 MHz), fine/coarse frequency margining capability, industrial temperature range (–40°C to +85°C), 3.3 V single-supply operation, and EEPROM-based default configuration persistence after power cycle.

Technical Context

The LMK61E2BBA-SIAR implements a fractional-N PLL architecture with integrated 50 MHz crystal reference and VCO spanning 4.6–5.6 GHz, enabling precise synthesis of 125 MHz LVDS output via programmable integer output divider (5–511). Its dual-stage internal LDO regulation isolates analog PLL circuitry from digital noise, achieving –70 dBc PSRR across 50 kHz–1 MHz supply ripple frequencies.

Configuration is performed via I²C interface (100–400 kHz) with open-drain SCL/SDA pins, supporting runtime reprogramming and EEPROM write-back of custom settings. The device supports three differential output formats (LVPECL/LVDS/HCSL), with LVDS mode delivering 300–480 mV differential swing and 45–55% duty cycle at 125 MHz.

Key Specifications

Pinout & Package

LMK61E2BBA-SIAR uses a 7 mm × 5 mm, 8-pin QFM (SIA) package with exposed thermal pad connected to GND. Pin 1 is ADD, pin 2 is OUTN, pin 3 is GND, pin 4 is OE, pin 5 is VDD, pin 6 is OUTP, pin 7 is SCL, and pin 8 is SDA - all pins are LVCMOS-compatible except differential outputs (OUTP/OUTN).

Key Features

Applications

Equivalent & Alternatives

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

Compared with Si510-125.000M and LMK61E0M-125M00, LMK61E2BBA-SIAR uniquely balances programmability, margining, and ultra-low jitter - making it optimal for development-phase systems requiring iterative clock tuning and production-phase designs needing field-upgradable timing.

Availability

LMK61E2BBA-SIAR is available at Aetrix Electronics and suitable for FPGA reference timing, 5G baseband unit synchronization, and high-speed data acquisition systems requiring stable component supply, long-lifecycle availability, and traceable sourcing.

Supply support for LMK61E2BBA-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 over 50 years of leadership in precision timing and power management ICs.

The LMK61E2 series belongs to TI's high-performance programmable oscillator product line, designed specifically for applications demanding ultra-low jitter, flexible output formats, and EEPROM-based configuration persistence in telecom, computing, and test equipment.

FAQ

What is the factory-default output configuration for LMK61E2BBA-SIAR?

The LMK61E2BBA-SIAR ships with factory-programmed EEPROM settings generating 125 MHz LVDS output. This configuration powers up automatically without host intervention, using internal 50 MHz crystal reference and fractional-N PLL with integer output divider set to 40. The device remains in LVDS mode until reconfigured via I²C.

Can LMK61E2BBA-SIAR be used in LVPECL mode, and what are the layout requirements?

Yes - LMK61E2BBA-SIAR supports LVPECL mode up to 1 GHz via I²C register configuration. Layout requires 150 Ω AC-coupled termination to VCC–2 V on each output (OUTP/OUTN), strict 100 Ω differential impedance routing, and separation from noisy digital traces. The 7 mm × 5 mm QFM package's exposed thermal pad must be soldered to a solid GND plane with ≥3 thermal vias.

How does the frequency margining function work, and what is its resolution?

Frequency margining operates in two modes: coarse margining adjusts the output divider value (±1% step size), while fine margining tunes the fractional-N feedback divider numerator (±100 ppm resolution). Both are controlled via dedicated I²C registers and retain settings in EEPROM. Margining is used during DVT for timing closure verification and standards compliance testing.

Is external crystal required for LMK61E2BBA-SIAR operation?

No - the LMK61E2BBA-SIAR integrates a 50 MHz fundamental-mode quartz crystal within the package. This eliminates external crystal placement, matching network design, and associated layout sensitivity, reducing bill-of-materials and improving startup reliability across temperature and vibration conditions.