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

Part Number 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 language 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-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
AN-803 Crystal Timing Budget and Accuracy for Renesas Timing Clock Products Application Note PDF 108 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
ICS843N571 IBIS Model Model - IBIS IBS 549 KB
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB