Texas Instruments LMK61E2BAA-SIAT

Overview

LMK61E2BAA-SIAT from Texas Instruments is an ultra-low jitter (90 fs RMS typical at >100 MHz), programmable oscillator with integrated fractional-N PLL, 4.6–5.6 GHz VCO, and factory-configured 156.25 MHz LVDS output. It features on-chip EEPROM for self-startup, I²C programmability, ±50 ppm total frequency tolerance, and operates from a single 3.3 V supply across –40°C to +85°C in a 7 mm × 5 mm QFM-8 package. It serves as a high-stability clock source for FPGA/processor reference timing in network infrastructure.

For engineers reviewing the LMK61E2BAA-SIAT datasheet, LMK61E2BAA-SIAT pinout, LMK61E2BAA-SIAT application, or LMK61E2BAA-SIAT equivalent, key selection criteria include differential output format compatibility (LVDS up to 900 MHz), PSRR (–70 dBc), fine/coarse frequency margining capability, and EEPROM-based default configuration persistence after power cycle.

Technical Context

The LMK61E2BAA-SIAT implements a fractional-N PLL architecture with a 4.6–5.6 GHz integrated VCO, supporting both integer and fractional synthesis modes. Its output divider (5–511) and configurable feedback path enable precise generation of common reference frequencies including 156.25 MHz and 161.1328125 MHz.

It integrates dual power conditioning: dedicated LDOs isolate analog PLL supplies from digital I²C/EEPROM domains, achieving –70 dBc PSRR from 50 kHz to 1 MHz. The device supports three differential output formats-LVDS (≤900 MHz), LVPECL (≤1 GHz), and HCSL (≤400 MHz)-with user-selectable configuration via I²C registers and persistent EEPROM storage.

Key Specifications

Pinout & Package

LMK61E2BAA-SIAT uses a 7 mm × 5 mm, 8-pin QFM (SIA) package with exposed thermal pad. Pin 1 is ADD, pin 2 is OUTN, pin 3 is GND, pin 4 is VDD, pin 5 is OE, 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 Si5338A-D-GM, LMK61E2BAA-SIAT trades 15 fs jitter advantage for integrated crystal and EEPROM simplicity; versus LMK61E0M-SIAT, it adds full in-system programmability and margining at modest cost premium - making it optimal for prototyping and multi-scheme production.

Availability

LMK61E2BAA-SIAT is available at Aetrix Electronics and suitable for 100G Ethernet line cards, FPGA reference clocking, medical ultrasound imaging, and 5G baseband units requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LMK61E2BAA-SIAT 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 focused on analog and embedded processing technologies, with decades of expertise in precision timing, clock synthesis, and high-reliability signal integrity solutions.

The LMK61E2 series belongs to TI's PLLatinum™ programmable oscillator product line, designed specifically for high-performance communications, computing, and test equipment demanding ultra-low jitter, flexible output formats, and robust power supply immunity.

FAQ

What is the default output frequency and format for LMK61E2BAA-SIAT?

The LMK61E2BAA-SIAT ships with factory-programmed EEPROM settings that configure it for 156.25 MHz LVDS output at power-up. This default is retained across power cycles and does not require host I²C initialization. The device supports reprogramming to other frequencies and formats (LVPECL, HCSL) via its I²C interface.

Can LMK61E2BAA-SIAT operate without an external crystal?

Yes. The LMK61E2BAA-SIAT integrates a 50 MHz crystal within the package and uses it as the reference for its fractional-N PLL - no external crystal, oscillator, or clock source is needed. This monolithic construction eliminates board-level crystal matching, layout sensitivity, and start-up timing uncertainty.

How is frequency margining implemented on this device?

Frequency margining is implemented through two independent I²C-accessible controls: coarse margining adjusts the VCO frequency via the feedback divider (±1%), while fine margining tunes the output divider (±100 ppm). Both are supported in real time without disrupting output, enabling system-level timing margin validation per IEEE 802.3 and O-RAN specifications.

What thermal considerations apply to the SIA package?

The SIA (QFM-8) package features an exposed thermal pad that must be soldered to a solid GND plane with ≥3 thermal vias (0.3 mm diameter) for effective heat dissipation. At 85°C ambient, junction temperature remains ≤125°C under typical LVDS load (196 mA), provided RθJB is maintained at ≤36.7°C/W per JEDEC 4-layer board guidelines.