Analog Devices Inc. LTC6955IUKG#TRPBF

Overview

LTC6955IUKG#TRPBF from Analog Devices is an ultralow-jitter, 11-output CML clock buffer operating from DC to 7.5GHz with 45fs RMS additive jitter (ADC SNR method), ±25ps max output skew, and –40°C to 125°C junction temperature range. It serves as a high-fidelity fanout stage for data converter clocking in RF sampling systems.

For engineers reviewing the LTC6955IUKG#TRPBF datasheet, LTC6955IUKG#TRPBF pinout, LTC6955IUKG#TRPBF application, or LTC6955IUKG#TRPBF equivalent, key selection criteria include its 7.5GHz bandwidth, CML output compatibility with JESD204B interfaces, programmable output enable/inversion via 4-bit parallel control, and integrated input slew-rate–adaptive filtering.

Technical Context

The LTC6955IUKG#TRPBF implements a fully differential, self-biased input stage with 250Ω internal termination and supports AC- or DC-coupled inputs up to 7.5GHz. Its eleven CML outputs each feature 100Ω differential impedance, 320–550mV_P-P swing, and <50ps rise/fall times.

Output configuration is controlled by four CMOS SEL pins (SEL0–SEL3), enabling any 3–11 outputs active simultaneously with optional polarity inversion on alternating outputs. The FILT pin enables broadband noise filtering for low-slew-rate inputs (<2V/ns), improving phase noise floor to –155.2dBc/Hz at 7.5GHz.

Key Specifications

Pinout & Package

52-lead (7mm × 8mm) plastic QFN package with exposed ground pad (Pin 53). Requires soldering of exposed pad to PCB ground plane with multiple thermal vias for thermal management and low-inductance grounding.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock buffer applications.

Compared with LMK04832RHAT and ADCLK948BCPZ-R7, the LTC6955IUKG#TRPBF delivers the highest output count (11), widest bandwidth (7.5GHz), and most flexible configuration (4-bit parallel control) while maintaining industry-leading 45fs jitter-making it optimal for high-channel-count RF sampling systems where minimal added jitter and maximum routing flexibility are critical.

Availability

LTC6955IUKG#TRPBF is available at Aetrix Electronics and suitable for high-speed data converter clocking, wireless infrastructure timing, and optical transport network synchronization requiring stable component supply across extended temperature ranges.

Supply support for LTC6955IUKG#TRPBF 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, communications, and industrial markets.

The LTC6955IUKG#TRPBF belongs to Analog Devices' ultralow-jitter clock buffer family, engineered specifically for demanding data converter clocking and high-speed serial interface applications where phase noise and timing integrity directly impact system-level SNR and spectral purity.

FAQ

What is the maximum input frequency supported by the LTC6955IUKG#TRPBF?

The LTC6955IUKG#TRPBF supports differential input frequencies from DC to 7.5GHz, as specified in its Electrical Characteristics table. This enables direct buffering of VCO outputs used in RF sampling ADCs and high-speed SerDes applications without intermediate division or level-shifting stages. Operation at 7.5GHz is fully characterized over temperature and supply voltage.

Does the LTC6955IUKG#TRPBF require external termination resistors on its CML outputs?

Yes, the LTC6955IUKG#TRPBF CML outputs require 100Ω differential termination at the far end of the transmission line. Each output pair (e.g., OUT0+, OUT0–) presents ~50Ω impedance per side, forming a nominal 100Ω differential path. Proper termination is essential to maintain signal integrity, minimize reflections, and achieve the specified 45fs RMS jitter performance.

How does the FILT pin affect jitter performance of the LTC6955IUKG#TRPBF?

The FILT pin enables an internal broadband noise filter optimized for low-slew-rate inputs (<2V/ns). When FILT = V+, additive phase noise improves for slow-rising signals, reducing RMS jitter. However, setting FILT = V+ for inputs with slew rate ≥2V/ns degrades phase noise. The datasheet specifies this trade-off explicitly, and optimal configuration depends on measured input slew rate-not frequency alone.

Can the LTC6955IUKG#TRPBF drive both top-layer and bottom-layer components on a PCB simultaneously?

Yes, the LTC6955IUKG#TRPBF supports this via its parallel SEL control: odd-numbered outputs (OUT1, OUT3, etc.) can be configured with inverted polarity relative to even-numbered outputs. This allows matching trace lengths between top- and bottom-layer devices-e.g., non-inverted clocks to top-side ADCs and inverted clocks to bottom-side ADCs-without external inverters or layer-crossing vias.

Is the LTC6955IUKG#TRPBF pin-compatible with the LTC6955-1 variant?

No, the LTC6955IUKG#TRPBF and LTC6955IUKG-1#TRPBF share identical pinout and package (52-lead QFN), but differ functionally: the -1 variant replaces one CML output (OUT10) with a ÷2 divider, introducing a spur on other outputs. While physically interchangeable, functional substitution requires board-level validation of spurious content and SYSREF alignment requirements.