The 843N252-45 is a 1 LVPECL and 1 LVCMOS output Synthesizer optimized to generate Ethernet reference clock frequencies. The device uses IDT's fourth generation FemtoClock ® NG technology for an optimum of high clock frequency and low phase noise performance, combined with a low power consumption and high power supply noise rejection. Using a 25MHz parallel resonant crystal, the following frequencies can be generated: 156.25MHz and 125MHz. With a very low phase noise VCO it is targeted to achieve 0.4ps or lower typical rms phase jitter, easily meeting Ethernet jitter requirements. The 843N252-45 is packaged in a small 16-pin TSSOP package.


  • Fourth generation FemtoClock® Next Generation (NG) technology
  • One differential 3.3V LVPECL output and one LVCMOS/LVTTL output
  • Crystal oscillator interface designed for a 25MHz parallel resonant crystal
  • A 25MHz crystal generates output frequencies of: 156.25MHz and 125MHz
  • VCO frequency: 625MHz
  • RMS Phase Jitter @ 156.25MHz, (12kHz – 20MHz) using a 25MHz crystal: 0.33ps (typical)
  • RMS Phase Jitter @ 125MHz, (12kHz – 20MHz) using a 25MHz crystal: 0.39ps (typical)
  • Power supply noise rejection PSNR: -60dB (typical)
  • Full 3.3V supply mode
  • 0°C to 70°C ambient operating temperature
  • Available in lead-free (RoHS 6) package

Product Options

Orderable Part ID Part Status Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
Not Recommended for New Designs 16 C Yes Tube
Not Recommended for New Designs 16 C Yes Reel

Documentation & Downloads

Title Other Languages Type Format File Size Date
Datasheets & Errata
843N252-45 Datasheet Datasheet PDF 381 KB
Errata# NEN-11-03 Errata PDF 62 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-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-832 Timing Budget and Accuracy Application Note PDF 131 KB
AN-834 Hot-Swap Recommendations Application Note PDF 153 KB
AN-837 Overdriving the Crystal Interface Application Note PDF 133 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# : A1602-01(R1) Add Greatek Taiwan as Alternate Assembly Product Change Notice PDF 611 KB
PCN# : A1602-01 Add Greatek Taiwan as Alternate Assembly Product Change Notice PDF 611 KB
PCN# : A1511-01(R1) Add SPEL India as Alternate Assembly Location Product Change Notice PDF 596 KB
PCN# : A1511-01 Add SPEL India as Alternate Assembly Location Product Change Notice PDF 544 KB
PCN# : TB1403-01 Changed in Carrier Tape, Plastic Reel and Quantity per Reel on TSSOP-14, TSSOP-16 Product Change Notice PDF 663 KB
PCN# : W1308-01 Change of Passivation Thickness Product Change Notice PDF 941 KB
PCN# : TB1303-02 Change of Tape & Reel Packing Method for Selective Products Product Change Notice PDF 361 KB
Clock Distribution Overview 日本語 Overview PDF 217 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