Analog Devices Inc. ADCLK944BCPZ-R7

Product Summary

The Analog Devices ADCLK944 is a high-speed clock fanout buffer tailored to demanding timing distribution applications. Designed around Analog Devices’ proprietary XFCB3 silicon germanium (SiGe) bipolar technology, the ADCLK944 delivers outstanding speed, low jitter, and broad signal compatibility, making it a choice component for engineers dealing with high-speed data acquisition, clock signal restoration, and advanced test equipment. Housed in a 16-lead space-saving LFCSP package with an exposed pad, it ensures robust performance under industrial temperature ranges while facilitating integration in dense PCB layouts.

Primary Attributes and Performance Details of ADCLK944

The ADCLK944 stands out due to its combination of speed, precision, and output versatility:

Supports clock frequencies up to 7 GHz, providing headroom for next-generation high-speed designs.

Features four full-swing differential LVPECL outputs capable of directly driving 800 mV (1.6 V differential swing) into 50 Ω terminations.

Broadband root-mean-square (rms) random jitter is as low as 50 fs, meeting stringent low-jitter clock requirements for advanced communications, instrumentation, and imaging applications.

Operates across a 2.375 V to 3.63 V supply range, providing flexibility for systems requiring either standard 2.5 V or 3.3 V rails.

Inputs accept LVPECL, CML, LVDS, as well as both dcand ac-coupled CMOS signaling, enhancing interoperability in mixed-environment systems.

Integrated input termination resistors (100 Ω differential) and accessible voltage reference (VREF) pin streamline interface design with various signaling standards and facilitate AC-coupled connections.

The device is fully RoHS 3 compliant and unaffected by REACH regulations, supporting environmentally conscious design and global deployment.

Functional Architecture and Pin Configuration of ADCLK944

At its core, the ADCLK944 supports a 1:4 differential clock distribution topology. Incoming clock signals are received via the CLK and CLK differential input pins, with the addition of a VREF pin to ease biasing for AC-coupled signals. On-chip 100 Ω center-tapped differential termination ensures clean signal reception and minimizes external BOM. The clock input stage fans out to four pairs of LVPECL drivers (Q0/Q0, Q1/Q1, Q2/Q2, Q3/Q3).

The compact 16-lead LFCSP package arranges outputs and supply rails for straightforward PCB routing. The exposed thermal pad must be connected to VEE for optimal thermal dissipation. Key pin assignments include:

Inputs: CLK (1, 4), VR (2), VREF (3)

Outputs: Four differential pairs on adjacent pins, simplifying termination and routing

Power: Vcc (8,13), VEE (5,16)

The careful layout supports minimized skew and enhanced signal fidelity.

Electrical Parameters and Timing Capabilities of ADCLK944

Precision and timing fidelity are core strengths of the ADCLK944:

Maximum output frequency ranges from 6.2 GHz (guaranteed) to 7.0 GHz (typical), with output swing maintained above 0.8 V differential.

Output rise and fall times are exceptionally sharp, specified at 35 ps (typical) differential (20%-80%), supporting low additive jitter and minimal data eye closure.

Propagation delay, from input to output, stands at 70-130 ps, with output-to-output skew as low as 15 ps (typical), critical for synchronous system performance.

Additive time jitter is specified at 26 fs rms (12 kHz to 20 MHz), and broadband random jitter at 50 fs rms, making the ADCLK944 ideal for jitter-sensitive DAC/ADC clocking, high-resolution imaging, and precise test systems.

Power supply current is 139 mA (typical at 2.5 V) or 138-165 mA (at 3.3 V), allowing careful power budgeting in multi-rail designs.

Input/Output Functionality and Signal Support of ADCLK944

The ADCLK944’s input flexibility addresses challenges in heterogeneous systems:

The differential input supports DC-coupled standards (LVPECL, CML, 3.3 V CMOS (single-ended)) and AC-coupled LVDS/LVPECL/CMOS.

Input common-mode range spans VEE + 1.35 V to Vcc – 0.1 V, and differential input swing from 0.4 to 3.4 Vp-p.

For AC-coupled inputs, the VREF pin provides (Vcc + 1)/2 reference for biasing, simplifying coupling network design.

Output format is native LVPECL, but can be interfaced with ECL and, through level translation, to other logic standards. Outputs provide a robust 1.6 V differential swing into 50 Ω.

The ADCLK944 can be configured for LVPECL (positive supply referenced) or ECL (negative supply referenced) operation, offering system-level flexibility.

Thermal Characteristics and PCB Design Considerations for ADCLK944

Thermal management is supported via an exposed pad LFCSP:

Junction-to-ambient thermal resistance is 78°C/W in still air, improving to 68°C/W with 1 m/s airflow and further with higher airflow.

The junction-to-case and junction-to-board characteristics facilitate accurate PCB thermal modeling, essential for high-output-frequency operation where power dissipation may be significant.

For accurate junction temperature prediction, the equation TJ = TA + (θJA × PD) guides layout strategy, with recommendations to tie the exposed pad to the board ground for maximum heat sinking.

Wide operating temperature support (-40°C to +85°C) makes the ADCLK944 suitable for industrial and communications infrastructure environments.

Reliability, Environmental Conditions, and Maximum Ratings for ADCLK944

For robust implementation, the ADCLK944’s key reliability and environmental factors include:

Absolute maximum supply voltage is 6.0 V, and the device tolerates transient input voltages from VEE 0.5 V to Vcc + 0.5 V.

Output pins withstand up to Vcc + 0.5 V and 35 mA source/sink currents.

The device offers full RoHS 3 compliance, with unaffected REACH status, and supports a Moisture Sensitivity Level (MSL) of 3 (168 hours).

ESD precautions are necessary during handling and assembly, following best practices for SiGe and high-speed ECL components.

Possible Alternatives or Substitute Models for ADCLK944

In projects considering alternatives or second sourcing, engineers may evaluate:

Analog Devices’ own ADCLK series (e.g., ADCLK946) for similar 1:4 LVPECL fanout buffers with varied maximum frequency and jitter profiles.

Texas Instruments LMK1Dxx family, offering high-frequency, low-jitter LVPECL fanout options.

ON Semiconductor NB6L14 series as alternative ECL/LVPECL buffers for slightly lower frequency regimes.

Selection should consider specific parameters such as maximum frequency, additive jitter, input compatibility, and supply voltage range, ensuring alignment with application priorities.

Conclusion

The ADCLK944 from Analog Devices is a benchmark device for ultrafast, multi-output clock distribution in data converters, high-speed communications, instrumentation, and medical imaging front-ends. Delivering up to 7 GHz bandwidth and femtosecond-level jitter, it addresses the growing need for precision and flexibility in timing-critical architectures. Its robust interface options, careful thermal design, and proven reliability make it a compelling choice for selection and procurement specialists seeking to future-proof performance-driven hardware platforms.