NOTICE - The following device(s) are recommended alternatives:

The 873991 is a low voltage, low skew, 3.3V LVPECL or ECL Clock Generator. The 873991 has two selectable clock inputs. The PCLK, nPCLK pair can accept an LVPECL input and the TEST_CLK pin can accept a LVCMOS or LVTTL input. This device has a fully integrated PLL along with frequency configurable outputs. An external feedback input and output regenerates clocks with "zero delay". The four independent banks of outputs each have their own output dividers, which allow the device to generate a multitude of different bank frequency ratios and output-toinput frequency ratios. The output frequency range is 25MHz to 400MHz and the input frequency range is 6.25MHz to 125MHz. The PLL_SEL input can be used to bypass the PLL for test and system debug purposes. In bypass mode, the input clock is routed around the PLL and into the internal output dividers. The 873991 also has a SYNC output which can be used for system synchronization purposes. It monitors Bank A and Bank C outputs for coincident rising edges and signals a pulse per the timing diagrams in this data sheet. This feature is used primarily in applications where Bank A and Bank C are running at different frequencies, and is particularly useful when they are running at non-integer multiples of each other.


  • 14 differential LVPECL outputs
  • Selectable differential LVPECL or TEST_CLK inputs
  • PCLK, nPCLK can accept the following input levels: LVPECL, CML, SSTL
  • TEST_CLK accepts the following input levels: LVCMOS, LVTTL
  • Input frequency range: 6.25MHz to 125MHz
  • Output frequency: 400MHz (maximum)
  • VCO range: 200MHz to 800MHz
  • Output skew: 250ps (maximum)
  • Cycle-to-cyle jitter: ±50ps (typical)
  • LVPECL mode operating voltage supply range: VCC = 3.135V to 3.465V, VEE = 0V
  • ECL mode operating voltage supply range: VCC = 0V, VEE = -3.465V to -3.135V
  • 0°C to 70°C ambient operating temperature
  • Industrial temperature available upon request
  • Lead-Free package fully RoHS compliant

Product Options

Orderable Part ID Part Status Pkg. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
Obsolete TQFP 52 C Yes Tray
Obsolete TQFP 52 C Yes Reel

Documentation & Downloads

Title Other Languages Type Format File Size Date
Datasheets & Errata
873991 Datasheet Datasheet PDF 424 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-833 Differential Input Self Oscillation Prevention Application Note PDF 180 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
PDN# : CQ-15-04 Quarterly Market Declined PDN Product Discontinuation Notice PDF 545 KB
PCN# : A1401-02 Alternate Copper Wire Assembly Site Product Change Notice PDF 36 KB
PCN#: A1309-03 Additional Assembly Sources Product Change Notice PDF 398 KB
PDN# : N-12-22R2 PRODUCT DISCONTINUANCE NOTICE Product Discontinuation Notice PDF 363 KB
873991 IBIS Model Model - IBIS ZIP 30 KB
Clock Distribution Overview 日本語 Overview PDF 217 KB
Timing Solutions Products Overview Overview PDF 4.11 MB
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB