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87951I - Block Diagram
87951I - Pinout


Low Skew, 1-to-9 Differential-to-LVCMOS/LVTTL Zero Delay Buffer

Alternative Products
NOTICE - The following device(s) are recommended alternatives:
Functional replacement

The 87951I is a low voltage, low skew 1-to-9 Differential-to-LVCMOS/LVTTL Cock Generator. The CS87951I has two selectable clock inputs. The single ended clock input accepts LVCMOS or LVTTL input levels. The CLK1, nCLK1 pair can accept most standard differential input levels. With output frequencies up to 180MHz, the 87951I is targeted for high performance clock applications. Along with a fully integrated PLL, the 87951I contains frequency configurable outputs and an external feedback input for regenerating clocks with "zero delay".


  • Fully integrated PLL
  • Nine single ended 3.3V LVCMOS/LVTTL outputs
  • Selectable single ended CLK0 or differential CLK1, nCLK1 inputs
  • The single ended CLK0 input can accept the following input levels: LVCMOS or LVTTL input levels
  • CLK1, nCLK1 supports the following input types: LVDS, LVPECL, LVHSTL, SSTLHCSL
  • Output frequency range: 25MHz to 180MHz
  • VCO range: 200MHz to 480MHz
  • External feedback for “zero delay” clock regeneration
  • Cycle-to-cycle jitter: ±100ps (typical)
  • Output skew: 375ps (maximum)
  • PLL reference zero delay: 350ps window (maximum)
  • 3.3V operating supply
  • -40°C to 85°C ambient operating temperature
  • Available in lead-free RoHS-compliant package

Product Specification

Outputs (#)Output TypeOutput Freq Range (MHz)Input Freq (MHz)Inputs (#)Input TypeOutput Banks (#)Core Voltage (V)Output Voltage (V)
9LVCMOS25.000000 - 180.0000000.000000 - 100.0000002LVCMOS, HSTL, LVDS, LVPECL, SSTL, HCSL43.33.3

Product Options

Orderable Part IDPart StatusPkg. CodePkg. TypeLead Count (#)Temp. GradePb (Lead) FreeCarrier TypeSample & Buy
87951AYILFObsoletePRG32TQFP32IYesTrayCheck Availability
87951AYILFTObsoletePRG32TQFP32IYesReelCheck Availability


Technical Documentation

Title Other Languages Type Format File Size Datesort icon
Apps Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 229 KB Jul 5, 2016
AN-845 Termination - LVCMOS Application Note PDF 62 KB May 13, 2014
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 82 KB May 13, 2014
show all (12)
AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 403 KB May 12, 2014
AN-840 Jitter Specifications for Timing Signals Application Note PDF 349 KB May 8, 2014
AN-836 Differential Input to Accept Single-ended Levels Application Note PDF 37 KB May 6, 2014
AN-835 Differential Input with VCMR being VIH Referenced Application Note PDF 77 KB May 6, 2014
AN-833 Differential Input Self Oscillation Prevention Application Note PDF 94 KB May 6, 2014
AN-834 Hot-Swap Recommendations Application Note PDF 67 KB May 6, 2014
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.06 MB Apr 24, 2014
AN-815 Understanding Jitter Units Application Note PDF 476 KB Apr 24, 2014
AN-805 Recommended Ferrite Beads Application Note PDF 38 KB Jan 15, 2014
PDN# : CQ-15-01 (R1) Quarter PDN for Declined Market Product Discontinuation Notice PDF 550 KB Mar 11, 2015
PDN# : CQ-15-01 Quarter PDN for Declined Market Product Discontinuation Notice PDF 547 KB Jan 23, 2015
PCN# : A1401-02 Alternate Copper Wire Assembly Site Product Change Notice PDF 36 KB Feb 16, 2014
show all (4)
PCN# : TB1303-01 Change of Carrier Tape for TQFP-32, TQFP-48 Product Change Notice PDF 472 KB Mar 31, 2013
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 25, 2016

Software & Tools

Title Type Format File Size Datesort icon
87951I IBIS Model Model - IBIS ZIP 20 KB Jun 22, 2009