The ICS650-21 is a low cost, low-jitter, high-performance clock synthesizer for system peripheral applications. Using analog/digital Phase Locked Loop (PLL) techniques, the device accepts a parallel resonant 25 MHz crystal input to produce up to eight output clocks. The device provides clocks for PCI, SCSI, Fast Ethernet, Ethernet, USB, and AC97. The user can select one of three USB frequencies and also one of two AC97 audio frequencies. The OE pin puts all outputs into a high-impedance state for board level
testing. All frequencies are generated with less than one ppm error, meeting the demands of SCSI and Ethernet clocking.


  • Packaged in 20-pin SSOP (QSOP)
  • Pb (lead) free package, RoHS compliant 
  • Lower jitter version of ICS650-01
  • Operating voltage of 3.3 V or 5 V
  • Zero ppm synthesis error in all clocks
  • Inexpensive 25 MHz crystal or clock input
  • Provides Ethernet and Fast Ethernet clocks
  • Provides SCSI clocks
  • Provides PCI clocks
  • Selectable AC97 audio clock
  • Selectable USB clock
  • OE pin tri-states the outputs for testing
  • Selectable frequencies on three clocks
  • Duty cycle of 45/55 for Processor clock and Audio clock
  • Advanced, low-power CMOS process
  • Industrial temperature range available

Product Options

Orderable Part ID Part Status Pkg. Code Pkg. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
650R-21ILF Last Time Buy PCG20 QSOP 20 I Yes Tube
650R-21ILFT Last Time Buy PCG20 QSOP 20 I Yes Reel
650R-21LF Active PCG20 QSOP 20 C Yes Tube
650R-21LFT Active PCG20 QSOP 20 C Yes Reel

Technical Documentation

Title Other Languages Type Format File Size Date
Datasheets & Errata
650-21 Datasheet Datasheet PDF 197 KB May 13, 2010
Application Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 229 KB Jul 5, 2016
AN-831 The Crystal Load curve Application Note PDF 308 KB Sep 22, 2014
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 82 KB May 12, 2014
AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 403 KB May 11, 2014
AN-803 Crystal Timing Budget and Accuracy for IDT Timing Clock Products Application Note PDF 44 KB May 7, 2014
AN-840 Jitter Specifications for Timing Signals Application Note PDF 349 KB May 7, 2014
AN-839 RMS Phase Jitter Application Note PDF 149 KB May 6, 2014
AN-838 Peak-to-Peak Jitter Calculations Application Note PDF 32 KB May 6, 2014
AN-834 Hot-Swap Recommendations Application Note PDF 67 KB May 5, 2014
AN-832 Timing Budget and Accuracy Application Note PDF 48 KB May 5, 2014
AN-830 Quartz Crystal Drive Level Application Note PDF 59 KB May 4, 2014
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.06 MB Apr 23, 2014
AN-815 Understanding Jitter Units Application Note PDF 476 KB Apr 23, 2014
AN-802 Crystal-Measuring Oscillator Negative Resistance Application Note PDF 52 KB Mar 11, 2014
AN-805 Recommended Ferrite Beads Application Note PDF 38 KB Jan 14, 2014
AN-801 Crystal-High Drive Level Application Note PDF 109 KB Jan 14, 2014
AN-806 Power Supply Noise Rejection Application Note PDF 353 KB Jan 14, 2014
PCN# : A1808-01 Transfer Assembly Location from Amkor Philippines for select pacakges Product Change Notice PDF 39 KB Aug 29, 2018
PDN# : CQ-18-03 Product Discontinuance Notice Product Discontinuation Notice PDF 218 KB Apr 26, 2018
PCN# : TB1504-01R1 Qty per Reel Standardization for Selective Packages Product Change Notice PDF 95 KB Oct 21, 2015
PCN# : TB1504-01 Qty per Reel Standardization for Selective Packages Product Change Notice PDF 50 KB Jul 20, 2015
PCN# : TB1303-02 Change of Tape & Reel Packing Method for Selective Products Product Change Notice PDF 361 KB Mar 23, 2013
PCN# : A1208-01R1 Gold to Copper Wire Product Change Notice PDF 254 KB Dec 20, 2012
Timing Solutions Products Overview Overview PDF 4.11 MB Oct 31, 2018
IDT Products for Radio Applications 日本語 Product Brief PDF 2.34 MB Nov 29, 2016
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 24, 2016