The 843N571I is a PLL based clock synthesizer for use in Ethernet applications. The device uses IDT's fourth generation FemtoCLock® NG technology for optimal high clock frequency and low phase noise performance, combined with a low power consumption and high power supply noise rejection. Using IDT's latest FemtoClock NG PLL technology, the 843N571I achieves <0.3ps RMS phase jitter performance. 843N571I can synthesize 100MHz, 125MHz, 156.25MHz and a low frequency 33.33MHz CPU clock from a single device. Six LVCMOS outputs also serve as additional buffering of the 25MHz crystal reference.


  • Fourth generation FemtoClock® Next Generation (NG) technology
  • Seven single-ended LVCMOS outputs, 30? output impedance
  • Three LVPECL output pairs One differential LVPECL (QA, nQA) output pair: 156.25MHz Two selectable differential LVPECL output pairs (QB, nQB and QC, nQC): 100MHz and 125MHz
  • One single-ended LVCMOS (QD0) 33.33MHz CPU clock
  • Selectable external crystal or single-ended input source
  • Crystal oscillator interface designed for 25MHz, parallel resonant crystal
  • FemtoClock NG frequency multiplier provides low jitter, high frequency output
  • FemtoClock NG VCO frequency: 2.5GHz
  • RMS phase jitter @ 125MHz, using a 25MHz crystal (12kHz – 20MHz): 0.283ps (typical)
  • Power supply noise rejection PSNR: -80dB
  • 3.3V supply voltage
  • -40C to 85C ambient operating temperature
  • Available in lead-free (RoHS 6) packages

Product Options

Orderable Part ID Part Status Pkg. Code Pkg. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
843N571BKILF Active NLG40P1 VFQFPN 40 I Yes Tray
843N571BKILFT Active NLG40P1 VFQFPN 40 I Yes Reel

Technical Documentation

Title Other Languages Type Format File Size Date
Datasheets & Errata
ICS843N571I Datasheet Datasheet PDF 452 KB Nov 29, 2018
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-845 Termination - LVCMOS Application Note PDF 62 KB May 12, 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-837 Overdriving the Crystal Interface Application Note PDF 50 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
PCN# : A1611-02 Add JCET China as Alternate Assembly and Change of Material Set at Alternate Assembly Location Product Change Notice PDF 583 KB Dec 19, 2016
PCN# : TB1504-01R1 Qty per Reel Standardization for Selective Packages Product Change Notice PDF 95 KB Oct 21, 2015
PCN# : TB1504-01 Qty per Reel Standardization for Selective Packages Product Change Notice PDF 50 KB Jul 20, 2015
PCN# : TB1311-01 New Carrier Tape on VFQFPN-28, VFQFPN-40, VFQFPN-48 Product Change Notice PDF 790 KB Apr 7, 2014
PCN# : W1308-01 Change of Passivation Thickness Product Change Notice PDF 941 KB Sep 10, 2013
PCN# : N1302-03 Product Change Notice PDF 55 KB Feb 26, 2013
PCN# : TB1110-05 NEW SHIPPING TRAY Product Change Notice PDF 653 KB Dec 5, 2011
Timing Solutions Products Overview Overview PDF 4.11 MB Oct 31, 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
ICS843N571 IBIS Model Model - IBIS IBS 549 KB Oct 8, 2012