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. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
Active VFQFPN 40 I Yes Tray
Active VFQFPN 40 I Yes Reel

Documentation & Downloads

Title Other Languages Type Format File Size Date
Datasheets & Errata
ICS843N571I Datasheet Datasheet PDF 548 KB
Application Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 322 KB
AN-831 The Crystal Load curve Application Note PDF 395 KB
AN-845 Termination - LVCMOS Application Note PDF 146 KB
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 170 KB
AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 495 KB
AN-803 Crystal Timing Budget and Accuracy for IDT Timing Clock Products Application Note PDF 128 KB
AN-840 Jitter Specifications for Timing Signals Application Note PDF 442 KB
AN-838 Peak-to-Peak Jitter Calculations Application Note PDF 115 KB
AN-839 RMS Phase Jitter Application Note PDF 233 KB
AN-834 Hot-Swap Recommendations Application Note PDF 153 KB
AN-837 Overdriving the Crystal Interface Application Note PDF 133 KB
AN-832 Timing Budget and Accuracy Application Note PDF 131 KB
AN-836 Differential Input to Accept Single-ended Levels Application Note PDF 120 KB
AN-835 Differential Input with VCMR being VIH Referenced Application Note PDF 160 KB
AN-830 Quartz Crystal Drive Level Application Note PDF 143 KB
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.15 MB
AN-815 Understanding Jitter Units Application Note PDF 565 KB
AN-802 Crystal-Measuring Oscillator Negative Resistance Application Note PDF 136 KB
AN-801 Crystal-High Drive Level Application Note PDF 202 KB
AN-806 Power Supply Noise Rejection Application Note PDF 438 KB
AN-805 Recommended Ferrite Beads Application Note PDF 121 KB
PCN# : A1904-01 Add Greatek, Taiwan as an Alternate Assembly Facility Product Change Notice PDF 983 KB
PCN# : A1611-02 Add JCET China as Alternate Assembly and Change of Material Set at Alternate Assembly Location Product Change Notice PDF 583 KB
PCN# : TB1504-01R1 Qty per Reel Standardization for Selective Packages Product Change Notice PDF 95 KB
PCN# : TB1504-01 Qty per Reel Standardization for Selective Packages Product Change Notice PDF 50 KB
PCN# : TB1311-01 New Carrier Tape on VFQFPN-28, VFQFPN-40, VFQFPN-48 Product Change Notice PDF 790 KB
PCN# : W1308-01 Change of Passivation Thickness Product Change Notice PDF 941 KB
PCN# : N1302-03 Product Change Notice PDF 55 KB
PCN# : TB1110-05 NEW SHIPPING TRAY Product Change Notice PDF 653 KB
ICS843N571 IBIS Model Model - IBIS IBS 549 KB
Timing Solutions Products Overview Overview PDF 4.11 MB
IDT Products for Radio Applications 日本語 Product Brief PDF 2.34 MB
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB