Texas Instruments LMK05318BRGZT

Overview

LMK05318BRGZT from Texas Instruments is a high-performance network synchronizer and jitter cleaner integrating one digital phase-locked loop (DPLL) and two analog PLLs (APLLs), featuring a Bulk Acoustic Wave (BAW) VCO for ultra-low-jitter Ethernet clock generation. It delivers 50fs typical RMS jitter at 312.5MHz, supports eight programmable differential outputs (AC-LVPECL/AC-CML/AC-LVDS/HSCL/1.8V LVCMOS), and operates across –40°C to +85°C for SyncE, IEEE 1588, and 400G/800G data center switch timing.

For engineers reviewing the LMK05318BRGZT datasheet, LMK05318BRGZT pinout, LMK05318BRGZT application, or LMK05318BRGZT equivalent, key selection criteria include DPLL loop bandwidth programmability (1mHz–4kHz), BAW-based jitter performance, dual-reference hitless switching, PCIe Gen 1–6 compliance, and support for 1.8V/2.5V/3.3V output supplies in a 48-pin VQFN package.

Technical Context

The LMK05318BRGZT implements a hierarchical timing architecture: its DPLL accepts two differential or single-ended reference inputs (1Hz–800MHz) with digital holdover and hitless switching, while APLL1 uses TI's proprietary BAW VCO to generate ultra-low-jitter 312.5MHz clocks independent of input jitter. APLL2 employs a conventional LC VCO for secondary frequency domains or synchronization isolation.

Internal LDO regulators provide PSNR >60dB, enabling clean power delivery without external low-noise LDOs; integrated EEPROM stores custom startup configurations, and I²C/3-wire/4-wire SPI interfaces allow flexible register control. The device supports IEEE 1588 PTP clock steering with <1ppt per step DCO adjustment and meets G.8262 (SyncE), Stratum 3E, and OTN G.709 timing standards.

Key Specifications

Pinout & Package

The LMK05318BRGZT is housed in a 7mm × 7mm, 48-pin VQFN (RGZ) package with exposed thermal pad. Pin assignment follows TI's standard RGZ top-view layout, supporting high-density PCB routing and thermal dissipation via 5×5 thermal vias to ground plane.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar network synchronizer applications.

Compared with LMK05318B-Q1 and LMK5B12204, the LMK05318BRGZT uniquely combines 8 BAW-enabled outputs, full PCIe Gen 6 compliance, and 1.8V LVCMOS support-making it the only option for high-channel-count, ultra-low-jitter data center timing cards operating at +85°C.

Availability

LMK05318BRGZT is available at Aetrix Electronics and suitable for 400G/800G data center switches, telecom timing cards, and industrial test equipment requiring stable component supply, long-lifecycle assurance, and traceable sourcing.

Supply support for LMK05318BRGZT 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 timing solutions for industrial, communications, and enterprise markets.

The LMK05318BRGZT belongs to TI's high-precision network synchronizer product line, engineered specifically for Ethernet-based infrastructure demanding sub-100fs jitter, multi-domain synchronization, and carrier-grade reliability.

FAQ

What is the primary timing function of the LMK05318BRGZT in Ethernet networking systems?

The LMK05318BRGZT serves as a network synchronizer and jitter cleaner, implementing a DPLL with two APLLs to recover, clean, and distribute ultra-low-jitter clocks for SyncE, IEEE 1588, and 400G/800G SerDes. Its BAW VCO delivers 50fs typical RMS jitter at 312.5MHz-enabling compliance with ITU-T G.8262 and IEEE 802.3bs specifications. The LMK05318BRGZT is explicitly designed for this role in line cards, timing cards, and optical modules.

Does the LMK05318BRGZT support PCIe Gen 6 clocking requirements?

Yes, the LMK05318BRGZT supports PCIe Gen 1 through Gen 6 compliant clock outputs. Its AC-LVPECL, AC-CML, and AC-LVDS drivers meet Gen 6 jitter and slew rate specifications, and its 50fs typical RMS jitter at 312.5MHz satisfies the stringent phase noise floor requirement (<−110 dBc/Hz @ 100kHz offset) for Gen 6 reference clocks. This capability is documented in TI's SNAS801D datasheet Section 1 and Table 6-6.

Can the LMK05318BRGZT generate both 156.25MHz and 312.5MHz simultaneously from independent sources?

Yes, the LMK05318BRGZT can generate 156.25MHz and 312.5MHz simultaneously using its dual-APLL architecture: APLL1 (BAW VCO) generates 312.5MHz with ultra-low jitter, while APLL2 (LC VCO) independently synthesizes 156.25MHz. Each APLL accepts separate reference inputs (XO_P/N and DPLL outputs), enabling true multi-domain timing-e.g., SyncE distribution and IEEE 1588 PTP steering on the same die. This is confirmed in the "Description" section and Figure 8-1 of the LMK05318BRGZT datasheet.

What output voltage supplies does the LMK05318BRGZT require for AC-LVDS and 1.8V LVCMOS operation?

The LMK05318BRGZT requires separate output supply rails: AC-LVDS outputs need VDDO_x = 1.8V ±5% (1.71–1.89V), while 1.8V LVCMOS outputs also require VDDO_x = 1.8V ±5% to achieve full rail-to-rail swing. These supplies are delivered via dedicated VDDO_01 through VDDO_7 pins, allowing mixed-format operation-for example, OUT0–OUT3 configured as AC-LVDS (1.8V) and OUT4–OUT5 as 1.8V LVCMOS (1.8V). This is specified in Section 6.3 and Table 5-1 of the LMK05318BRGZT datasheet.

How does the LMK05318BRGZT handle reference failure or loss-of-signal conditions?

The LMK05318BRGZT implements digital holdover with automatic hitless switching between PRIREF and SECREF inputs. Upon reference loss, the DPLL enters holdover mode using its internal oscillator and stored frequency/phase history to maintain output stability within ±0.1ppm over 24 hours (per G.8262). The device continues distributing clean clocks without interruption, and resumes lock seamlessly when reference returns-no software intervention required. This behavior is detailed in Sections 3 and 8.4 of the LMK05318BRGZT datasheet.