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I2C Programmable Ethernet Clock Generator

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 Specification

Outputs (#)Output TypeOutput Freq Range (MHz)Input Freq (MHz)Inputs (#)Input TypeOutput Banks (#)Core Voltage (V)Output Voltage (V)
13LVDS, LVCMOS, LVPECL8.330000 - 125.00000010.000000 - 120.0000002Differential, Crystal52.5, 3.32.5, 3.3

Product Options

Orderable Part IDPart StatusPkg. CodePkg. TypeLead Count (#)Temp. GradePb (Lead) FreeCarrier TypeSample & Buy
8T49N4811NLGIActiveNLG56VFQFPN56IYesTrayCheck Availability
8T49N4811NLGI8ActiveNLG56VFQFPN56IYesReelCheck Availability


Technical Documentation

Title Other Languages Type Format File Size Datesort icon
Datasheets & Errata
8T49N4811 Final Data Sheet Datasheet PDF 545 KB Nov 20, 2015
Apps Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 229 KB Jul 5, 2016
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 82 KB May 13, 2014
AN-845 Termination - LVCMOS Application Note PDF 62 KB May 13, 2014
show all (11)
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-835 Differential Input with VCMR being VIH Referenced Application Note PDF 77 KB May 6, 2014
AN-834 Hot-Swap Recommendations Application Note PDF 67 KB May 6, 2014
AN-836 Differential Input to Accept Single-ended Levels Application Note PDF 37 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
IDT Clock Distribution Overview 日本語 Overview PDF 3.79 MB Apr 25, 2016