LMKDB1108Z85RKPR

Overview

The LMKDB1108Z85RKPR is an ultra-low jitter LP-HCSL clock buffer from Texas Instruments, designed for PCIe Gen 1 through Gen 7 architectures. It features eight differential outputs with a fixed 85Ω impedance and supports both Common Clock (CC) and Independent Reference (IR) topologies. The device accepts a single differential input clock, which may include Spread Spectrum Clocking (SSC). Key electrical specifications include a maximum additive jitter of 31fs RMS (12kHz to 20MHz at 156.25MHz), with performance scaling down to 2.1fs for PCIe Gen 7. It operates on dual power supplies: 1.8V ±10% for analog circuits and 3.3V ±10% for output drivers, within an ambient temperature range of -40°C to +105°C.

Feature Summary

• Ultra-low additive jitter: 31fs max (12kHz-20MHz) at 156.25MHz; 2.1fs max for PCIe Gen 7
• Eight LP-HCSL differential outputs with 85Ω impedance
• Supports PCIe Gen 1 to Gen 7 CC and IR architectures
• Fail-safe input functionality and Loss of Signal (LOS) detection
• SMBus control interface and individual output enable pins

Applications

• High Performance Computing systems
• Server Motherboards
• Network Interface Cards (NIC/SmartNIC)
• Hardware Accelerators

Procurement Notes

Verify the specific ordering suffix 'Z85' confirms the 85Ω output impedance variant. Confirm the 'RKP' package designation corresponds to the VQFN-40 form factor. Ensure compatibility with the required 1.8V and 3.3V supply rails during component sourcing.

Selection Notes

Select this model when eight buffered LP-HCSL outputs are required for high-speed serial links. The Z85 suffix is mandatory for designs requiring 85Ω termination. Consider the LMKDB1108FS variant if fail-safe outputs are necessary in addition to the standard fail-safe inputs provided by the Z85 version.

Part Context

This component belongs to the LMKDB11xx family of PCIe clock buffers. It shares functional similarities with the LMKDB1120 and LMKDB1112 but offers a reduced channel count. Unlike the LMKDB1108FS, it lacks fail-safe outputs. It serves as a direct replacement for legacy Intel DB2000QL compliant devices in multi-channel configurations.

Replacement Considerations

The LMKDB1108FS85 is a compatible alternative that adds fail-safe output capabilities. For pin-compatible replacements in existing designs, verify that the target device supports the same LP-HCSL output swing and impedance requirements.