The 8T49N4811 is a highly flexible FemtoClock® NG pin-programmable clock generator suitable for networking and communications applications. It is able to generate five different output frequencies with multiple copies of each. A fundamental mode crystal, single-ended, or differential input reference may be used as the source for the output frequency.
The use of pin-programming to select the input source / frequency, desired output frequencies and output styles allow a single device to be used in a wide variety of applications without the need for register programming.
Selection pins use 3-level options to maximize flexibility while minimizing package size. Selection is performed by tying a selection pin high or low or by leaving it floating, eliminating the need for passive components to drive a desired logic level.


  • Fourth generation FemtoClock® NG technology
  • Generates multiple copies of 25MHz, 50MHz, 100MHz, 125MHz, 156.25MHz or 312.5MHz
  • Typical input frequency is 25MHz, with optional 125MHz and 156.25MHz input support
  • Differential outputs are pin programmable for LVDS or LVPECL
  • RMS phase jitter at 156.25MHz: <300fs typical
  • Power Supply Rejection Ratio better than -50dBc from 10k-1.5MHz at 3.3V power supply
  • Full 3.3V and 2.5V Supply Voltages
  • -40°C to +85°C ambient operating temperature
  • 56-pin VFQFPN, lead-free (RoHS 6) packaging

Product Options

Part Number Part Status Pkg. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
Active VFQFPN 56 I Yes Tray
Active VFQFPN 56 I Yes Reel


Title language Type Format File Size Date
Datasheets & Errata
8T49N4811 Final Data Sheet Datasheet PDF 648 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-845 Termination - LVCMOS Application Note PDF 146 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-835 Differential Input with VCMR being VIH Referenced Application Note PDF 160 KB
AN-836 Differential Input to Accept Single-ended Levels Application Note PDF 120 KB
AN-815 Understanding Jitter Units Application Note PDF 565 KB
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.15 MB
AN-805 Recommended Ferrite Beads Application Note PDF 121 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
Clock Distribution Overview 日本語 Overview PDF 217 KB
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB