The 851S201I is a high performance 2:2 Differential-to-HCSL Multiplexer with a 2 output fanout buffer. The 851S201I operates up to 250MHz and accepts HCSL and other low level differential inputs levels. Input level detection circuitry is available to flag input levels that drops below a specified value and on the selected input. This signal is latched until the status is reset via the alarm reset input. The 851S201I is packaged in a small 3 x 3 mm 16 lead VFQFN package, making it ideal for use on space constrained boards.


  • Two differential HCSL output pairs
  • Two selectable differential clock input pairs
  • CLKx, nCLKx pairs can accept HCSL level inputs
  • Low level input detection on selected input (latched)
  • Maximum Input frequency : 250MHz
  • Output skew: 5ps (typical)
  • Propagation delay: 1.4ns (typical)
  • Additive RMS phase jitter at 133.33MHz (12kHz - 20MHz): 0.151ps (typical)
  • Full 3.3V operating supply
  • -40°C to 85°C 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 Package Buy Sample
851S201CKILF Active VFQFPN 16 I 1 Cut Tape Package Info
851S201CKILFT Active VFQFPN 16 I 1 Reel Package Info

Documentation & Downloads

Title Other Languages Type Format File Size Date
Datasheets & Errata
851S201 Datasheet Datasheet PDF 550 KB
Application Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 322 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-834 Hot-Swap Recommendations Application Note PDF 153 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-827 Application Relevance of Clock Jitter Application Note PDF 1.15 MB
AN-815 Understanding Jitter Units Application Note PDF 565 KB
AN-805 Recommended Ferrite Beads Application Note PDF 121 KB
PCN# : TB1912-02 Convert Shipping Media
from Tube or Tray to Cut Reel
Product Change Notice PDF 5.61 MB
PCN# : A1904-01 Add Greatek, Taiwan as an Alternate Assembly Facility Product Change Notice PDF 983 KB
PCN# : A1807-01 Gold wire to Copper Wire Product Change Notice PDF 32 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
Timing Solutions Products Overview Overview PDF 4.11 MB
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB
IDT Clock Distribution Overview 日本語 Overview PDF 3.79 MB