The 8T49N281i has one fractional-feedback PLL that can be used as a jitter attenuator or frequency translator. It is equipped with six integer and two fractional output dividers, allowing the generation of up to eight different output frequencies, ranging from 8kHz to 1GHz. Three of these frequencies are completely independent of each other and the inputs. The other five are related frequencies. The eight outputs may select among LVPECL, LVDS or LVCMOS output levels.

IDT's 3rd generation Universal Frequency Translator family also includes the 8T49N282i (4-in / 2-PLL / 8-out) and the 8T49N283i (2-in / 2-PLL / 8-out).

To see other devices in this product family, visit the Universal Frequency Translators page.


  • Two differential outputs meet jitter limits for 100G Ethernet and STM-256/OC-768
    • <0.3ps RMS (including spurs): 12kHz to 20MHz
  • Accepts up to two LVPECL, LVDS, LVHSTL, HCSL or LVCMOS input clocks ranging from 8kHz up to 875MHz
    • Auto and manual input clock selection with hitless switching
    • Clock input monitoring, including support for gapped clocks
  • Phase-Slope Limiting and Fully Hitless Switching options to control output phase transients
  • Operates from a 10MHz to 40MHz fundamental-mode crystal
  • Generates eight LVPECL / LVDS or 16 LVCMOS output clocks ranging from 8kHz up to 1.0GHz (diff),8kHz to 250MHz (LVCMOS)
  • Register programmable through I2C / SPI or via external I2C EEPROM
  • Supported by IDT Timing Commander Software

Product Options

Orderable Part ID Part Status Pkg. Code Pkg. Type Lead Count (#) Carrier Type Advanced Features Buy Sample
8T49N281C-998NLGI Active NLG56P2 VFQFPN 56 Tray Programmable Clock
8T49N281C-998NLGI8 Active NLG56P2 VFQFPN 56 Reel Programmable Clock
8T49N281C-999NLGI Active NLG56P2 VFQFPN 56 Tray External Feedback, Fractional-N PLL, Programmable Hitless Reference Switching
8T49N281C-999NLGI8 Active NLG56P2 VFQFPN 56 Reel External Feedback, Fractional-N PLL, Programmable Hitless Reference Switching
8T49N281C-003NLGI Active NLG56P2 VFQFPN 56 Tray External Feedback, Fractional-N PLL, Hitless Reference Switching, Tilera Reference Design
8T49N281C-003NLGI8 Active NLG56P2 VFQFPN 56 Reel External Feedback, Fractional-N PLL, Hitless Reference Switching, Tilera Reference Design

Technical Documentation

Title Other Languages Type Format File Size Date
Datasheets & Errata
8T49N281 Datasheet Datasheet PDF 1.35 MB
8T49N281-003 Datasheet Tilera Reference Design Datasheet PDF 1.38 MB
User Guides & Manuals
FemtoNG Universal Frequency Translator Ordering Product Information Guide Manual - User Reference PDF 447 KB
Timing Commander Installation Guide Guide PDF 497 KB
Application Notes & White Papers
App Note 932 - Description for Startup and Calibration for UFT3G Family Application Note PDF 490 KB
AN-949 UFT3G Register Write Sequences Application Note PDF 57 KB
AN-807 Recommended Crystal Oscillators for NetSynchro WAN PLL Application Note PDF 77 KB
AN-828 Termination - LVPECL Application Note PDF 229 KB
AN-872 How to Setup UFT3G Devices as a Zero Delay Buffer (ZDB) Application Note PDF 442 KB
AN-831 The Crystal Load curve Application Note PDF 308 KB
AN-860 8T49N28X Frequency Programming Guide Application Note PDF 214 KB
AN-846 Termination - LVDS Application Note PDF 50 KB
AN-845 Termination - LVCMOS Application Note PDF 62 KB
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 82 KB
AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 403 KB
AN-835 Differential Input with VCMR being VIH Referenced Application Note PDF 77 KB
AN-803 Crystal Timing Budget and Accuracy for IDT Timing Clock Products Application Note PDF 44 KB
AN-840 Jitter Specifications for Timing Signals Application Note PDF 349 KB
AN-839 RMS Phase Jitter Application Note PDF 149 KB
AN-838 Peak-to-Peak Jitter Calculations Application Note PDF 32 KB
AN-834 Hot-Swap Recommendations Application Note PDF 67 KB
AN-833 Differential Input Self Oscillation Prevention Application Note PDF 94 KB
AN-836 Differential Input to Accept Single-ended Levels Application Note PDF 37 KB
AN-832 Timing Budget and Accuracy Application Note PDF 48 KB
AN-830 Quartz Crystal Drive Level Application Note PDF 59 KB
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.06 MB
AN-815 Understanding Jitter Units Application Note PDF 476 KB
AN-802 Crystal-Measuring Oscillator Negative Resistance Application Note PDF 52 KB
AN-805 Recommended Ferrite Beads Application Note PDF 38 KB
AN-801 Crystal-High Drive Level Application Note PDF 109 KB
AN-806 Power Supply Noise Rejection Application Note PDF 353 KB
PCN# : A1904-01 Add Greatek, Taiwan as an Alternate Assembly Facility Product Change Notice PDF 983 KB
PCN#: TP1901-01 Datasheet Correction for I2C Read Sequence Diagrams for the UFT Product Family Product Change Notice PDF 454 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
PCN# : N1609-01 Minor Design Change on Select Devices Product Change Notice PDF 227 KB
PCN# : W1512-01 Wafer Size change from 200mm to 300mm at Global Foundries Product Change Notice PDF 188 KB
Timing Solutions Products Overview Overview PDF 4.11 MB
IDT Products for Wired Broadband Applications Application Briefs PDF 686 KB
IDT Clock Generation Overview 日本語 Overview PDF 1.83 MB
IDT Clock Distribution Overview 日本語 Overview PDF 3.79 MB
IDT Jitter Attenuator Product Overview 简体中文 Overview PDF 1.95 MB
Universal Frequency Translator Third Generation Product Brief PDF 565 KB
8T49N281I IBIS Model Engineering IBS 972 KB

Software & Tools

Title Other Languages Type Format File Size Date
Timing Commander Installer (v1.15.0.27471) Software ZIP 19.57 MB
8T49N28x (UFT) Timing Commander Personality Software TCP 4.81 MB

Evaluation Boards

Part Number Title Sort ascending
EVK-UFT281-2-3 UFT 3G Evaluation Kit For 8T49N281I, 8T49N282I and 8T49N283I