Texas Instruments LMK03328RHST

Overview

LMK03328RHST from Texas Instruments is an ultra-low-jitter clock generator with two independent fractional-N PLLs, eight programmable outputs (AC-LVPECL/LVDS/CML/HCSL/LVCMOS), integrated EEPROM for startup configuration, and dual reference inputs (crystal or external). It delivers 100 fs RMS jitter (FOUT > 100 MHz), –80 dBc PSNR, and operates across –40°C to 85°C for PCIe Gen5/Gen6 timing in high-speed serial infrastructure.

For engineers reviewing the LMK03328RHST datasheet, LMK03328RHST pinout, LMK03328RHST application, or LMK03328RHST equivalent, this device supports critical timing requirements in multi-gigabit switch fabric, telecom line cards, and server clock trees where phase noise floor (–164 dBc/Hz at 156.25 MHz), VCO range (4.8–5.4 GHz), and fine frequency margining (±50 ppm) directly impact BER and system synchronization stability.

Technical Context

The LMK03328RHST integrates two fully independent fractional-N synthesizers with on-chip VCOs (4.8–5.4 GHz), each supporting configurable R/M/N dividers, loop bandwidth tuning (up to 400 kHz), and charge pump current (6.4 mA typical). Its Smart MUX enables automatic or manual selection between primary (1–300 MHz) and secondary (10–52 MHz crystal or 1–300 MHz external) references.

Output distribution includes eight differential/LVCMOS channels with per-channel supply domains (1.8/2.5/3.3 V), programmable fan-out modes, and glitchless coarse margining via output dividers. The on-chip EEPROM stores up to 71 pin-selectable default configurations, eliminating boot-time I²C initialization in ROM mode.

Key Specifications

Pinout & Package

LMK03328RHST uses a 7 mm × 7 mm, 48-pin WQFN package (RHS) with exposed thermal pad (DAP) requiring 6×6 via pattern to PCB ground for optimal thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with Si5341-B-GM and ICS8430I-01T, the LMK03328RHST uniquely combines dual-PLL independence, on-chip EEPROM with 71 presets, and ±50 ppm fine crystal margining - making it optimal for high-reliability telecom and test equipment where reference redundancy and in-system timing validation are mandatory.

Availability

LMK03328RHST is available at Aetrix Electronics and suitable for switches and routers, network and telecom line cards, and servers and storage systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing for industrial and infrastructure deployments.

Supply support for LMK03328RHST 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 clock solutions, with decades of expertise in high-performance timing devices for communications and computing.

The LMK03328RHST belongs to TI's LMK ultra-low-jitter clock generator family, designed specifically for multi-gigabit serial interface timing in networking, data center, and wireless infrastructure where phase noise, jitter, and configurability directly determine system throughput and reliability.

FAQ

What is the maximum output frequency supported by LMK03328RHST in AC-LVPECL mode?

The LMK03328RHST supports up to 1000 MHz output frequency in AC-LVPECL mode when AC-coupled to a 100-Ω differential load. At frequencies above the specified maximum, output swing may fall below the 500 mV minimum VOD, but functional operation remains possible depending on receiver sensitivity and layout integrity. This capability enables direct generation of PCIe Gen6 REFCLK harmonics and high-speed SerDes sampling clocks without external frequency multiplication.

Does LMK03328RHST require external loop filters for its PLLs?

Yes, the LMK03328RHST requires external passive loop filters connected to LF1 (PLL1) and LF2 (PLL2) pins. These filters determine loop bandwidth, stability, and phase margin - critical for optimizing jitter transfer and suppression. TI provides recommended RC component values in the datasheet for standard configurations (e.g., 400 kHz bandwidth with 6.4 mA charge pump current), and the device supports active filters for advanced noise shaping.

How does the EEPROM functionality work on LMK03328RHST?

The LMK03328RHST contains on-chip EEPROM storing up to 71 pre-programmed configuration states, including PLL settings, output formats, and power-up defaults. Configuration is selected at startup via HW_SW_CTRL and GPIO pins, enabling ROM-mode operation without I²C communication. The EEPROM can be updated in-system via I²C (SDA/SCL), allowing field firmware updates and platform-specific calibration storage - a key advantage over mask-ROM alternatives.

Can LMK03328RHST generate both LVCMOS and differential outputs simultaneously?

Yes, the LMK03328RHST can generate LVCMOS and differential outputs (AC-LVPECL, AC-LVDS, etc.) simultaneously. Each of the eight output pairs (OUT0–OUT7) is independently configurable as either differential or two single-ended LVCMOS signals, with dedicated VDDO supplies (1.8/2.5/3.3 V) per channel group. This allows concurrent driving of 1.8-V FPGA I/O banks and 3.3-V legacy ASICs from a single device, reducing board layer count and timing skew.

What is the purpose of the STATUS0 and STATUS1 pins on LMK03328RHST?

STATUS0 and STATUS1 on the LMK03328RHST are multifunction pins configurable as open-drain or push-pull LVCMOS outputs. They report real-time device status including PLL1/PLL2 lock, loss-of-input-clock, or custom events defined in registers. These signals simplify system diagnostics during bring-up and enable autonomous fault recovery in telecom and storage applications - for example, triggering a reference switchover when STATUS0 indicates primary PLL unlock.