LMKDB1108Z85RKPT

Overview

The LMKDB1108Z85RKPT is an ultra-low jitter LP-HCSL clock buffer from the Texas Instruments LMKDB11xx family, designed for PCIe Gen 1 through Gen 7 applications. It features one differential input and eight differential outputs with a fixed 85Ω output impedance. The device supports both Common Clock (CC) and Independent Reference (IR) architectures, handling input clocks with or without Spread Spectrum Clocking (SSC). Key electrical specifications include extremely low additive jitter performance: maximum 3fs RMS for PCIe Gen 6 and 2.1fs RMS for PCIe Gen 7. It operates on dual power supplies of 1.8V and 3.3V ±10% 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
• PCIe Gen 1 to Gen 7 support with 85Ω fixed output impedance
• Fail-safe inputs and flexible power-up sequence with automatic output disable
• SMBus control interface and Side-Band Interface (SBI) for high-speed output enable/disable

Applications

• High Performance Computing systems
• Server Motherboards
• NIC/SmartNIC designs
• Hardware Accelerator boards

Procurement Notes

Verify the complete ordering suffix RKPT against the manufacturer's official documentation to confirm tape-and-reel packaging quantities and specific environmental compliance ratings. Ensure that the Z85 designation matches the required 85Ω output impedance for the target PCB design. Cross-reference the package code RKP with the mechanical drawings to validate footprint compatibility during procurement.

Selection Notes

Select the LMKDB1108Z85RKPT when eight LVCMOS-compatible LP-HCSL outputs are required for PCIe reference clock distribution. Choose this variant over the FS version if fail-safe outputs are not needed but standard fail-safe inputs are sufficient. Confirm that the system requires a fixed 85Ω termination rather than the selectable 85Ω/100Ω options found in other family members like the LMKDB1102.

Part Context

This component belongs to the LMKDB11xx family of PCIe clock buffers, which are compliant with Intel DB2000QL specifications. While the LMKDB1120 is pin-compatible with the legacy DB2000QL, the LMKDB1108 provides a reduced channel count suitable for smaller form-factor server or accelerator designs requiring fewer clock domains.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided source material. Designers should consult the manufacturer's product selection guide for direct replacements or updated revisions within the LMKDB11xx series.