LVPECL FemtoClock Dynamic Clock Switch/Generator

NOTICE - The following device(s) are recommended alternatives:

The 873995 is a Zero Delay/Multiplier/Divider with hitless input clock switching capability. The 873995 is ideal for use in redundant, fault tolerant clock trees where low phase noise and low jitter are critical. The device receives two differential LVPECL clock signals from which it generates 6 LVPECL clock outputs with "zero" delay. The output divider and feedback divider selections also allow for frequency multiplication or division. The 873995 Dynamic Clock Switch (DCS) circuit continuously monitors both input clock signals. Upon detection of a failure (input clock stuck LOW or HIGH for at least 1 period), INP_BAD for that clock will be set HIGH. If that clock is the primary clock, the DCS will switch to the good secondary clock and phase/frequency alignment will occur with minimal output phase disturbance. The low jitter characteristics combined with input clock monitoring and automatic switching from bad to good input clocks make the 873995 an ideal choice for mission critical applications that utilize 1G or 10G Ethernet or 1G/4G/10G Fibre Channel.


  • Six differential 3.3V LVPECL outputs
  • Selectable differential clock inputs
  • CLKx, nCLKx pair can accept the following differential input levels: LVPECL, LVDS, LVHSTL, HCSL, SSTL
  • Input clock frequency range: 49MHz to 213.33MHz
  • Output clock frequency range: 49MHz to 640MHz
  • VCO range: 490MHz to 640MHz
  • External feedback for "zero delay" clock regeneration with configurable frequencies
  • Output skew: 100ps (maximum)
  • RMS phase jitter (1.875MHz - 20MHz): 0.77ps (typical) assuming a low phase noise reference clock input
  • 3.3V supply voltage
  • 0°C to 70°C ambient operating temperature
  • Available in lead-free (RoHS 6) package

Product Options

Orderable Part ID Part Status Pkg. Code Pkg. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
873995AYLF Obsolete DXG48 PTQFP 48 C Yes Tray Availability
873995AYLFT Obsolete DXG48 PTQFP 48 C Yes Reel Availability

Technical Documentation

Title Other Languages Type Format File Size Date
Datasheets & Errata
873995 Datasheet Datasheet PDF 307 KB Jan 24, 2017
Application Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 229 KB Jul 5, 2016
AN-831 The Crystal Load curve Application Note PDF 308 KB Sep 22, 2014
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 82 KB May 12, 2014
AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 403 KB May 11, 2014
AN-835 Differential Input with VCMR being VIH Referenced Application Note PDF 77 KB May 10, 2014
AN-803 Crystal Timing Budget and Accuracy for IDT Timing Clock Products Application Note PDF 44 KB May 7, 2014
AN-840 Jitter Specifications for Timing Signals Application Note PDF 349 KB May 7, 2014
AN-839 RMS Phase Jitter Application Note PDF 149 KB May 6, 2014
AN-838 Peak-to-Peak Jitter Calculations Application Note PDF 32 KB May 6, 2014
AN-834 Hot-Swap Recommendations Application Note PDF 67 KB May 5, 2014
AN-833 Differential Input Self Oscillation Prevention Application Note PDF 94 KB May 5, 2014
AN-836 Differential Input to Accept Single-ended Levels Application Note PDF 37 KB May 5, 2014
AN-832 Timing Budget and Accuracy Application Note PDF 48 KB May 5, 2014
AN-830 Quartz Crystal Drive Level Application Note PDF 59 KB May 4, 2014
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.06 MB Apr 23, 2014
AN-815 Understanding Jitter Units Application Note PDF 476 KB Apr 23, 2014
AN-802 Crystal-Measuring Oscillator Negative Resistance Application Note PDF 52 KB Mar 11, 2014
AN-805 Recommended Ferrite Beads Application Note PDF 38 KB Jan 14, 2014
AN-801 Crystal-High Drive Level Application Note PDF 109 KB Jan 14, 2014
AN-806 Power Supply Noise Rejection Application Note PDF 353 KB Jan 14, 2014
PDN# : CQ-15-04 Quarterly Market Declined PDN Product Discontinuation Notice PDF 545 KB Aug 12, 2015
Timing Solutions Products Overview Overview PDF 964 KB Sep 19, 2018
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB Apr 28, 2016
IDT Clock Distribution Overview 日本語 Overview PDF 3.79 MB Apr 24, 2016

Software & Tools

Title Other Languages Type Format File Size Date
873995 IBIS Model Model - IBIS ZIP 58 KB Jan 12, 2009