ICS841N254AKILF

Clock Generators, PLLs, Frequency Synthesizers Overview

The ICS841N254AKILF is a FemtoClock NG crystal-to-LVDS/HCSL clock synthesizer designed for S-RIO reference clock applications. It generates four differential outputs (two LVDS, two HCSL) from a 25MHz fundamental mode crystal or REF_CLK input. The device synthesizes selectable frequencies of 250MHz, 156.25MHz, 125MHz, or 100MHz using fourth-generation technology. It operates on 3.3V or 2.5V supplies within an ambient temperature range of -40°C to 85°C. Key electrical parameters include a typical RMS phase jitter of 0.27ps at 156.25MHz (1MHz-20MHz) and power supply noise rejection of -50dB.

Clock Generators, PLLs, Frequency Synthesizers Feature Summary

• Fourth generation FemtoClock NG technology for low phase noise and high power supply noise rejection (-50dB typical).
• Four differential outputs organized in two banks: two LVDS and two HCSL interfaces.
• Selectable output frequencies of 250MHz, 156.25MHz, 125MHz, or 100MHz via F_SEL pins.
• Supports both crystal oscillator interface and single-ended LVCMOS/LVTTL REF_CLK input.

Clock Generators, PLLs, Frequency Synthesizers Applications

• S-RIO 1.3 and 2.0 switch reference clock generation.
• Telecommunication infrastructure equipment.
• Networking end equipment requiring low-jitter differential clocks.

Clock Generators, PLLs, Frequency Synthesizers Procurement Notes

Verify the component status as discontinued by checking current manufacturer announcements. Confirm that the 'K' package suffix corresponds to the 32-VFQFN exposed pad form factor. Ensure compatibility with RoHS 6 lead-free standards if required by the design specifications.

Clock Generators, PLLs, Frequency Synthesizers Selection Notes

Select this component when driving IDT S-RIO switches requiring 156.25MHz reference clocks. Choose between LVDS or HCSL outputs based on receiver requirements; note that HCSL requires external source termination resistors while LVDS does not. Ensure the application supports the specific 25MHz parallel resonant crystal interface or LVCMOS reference input constraints.

Clock Generators, PLLs, Frequency Synthesizers Part Context

This part belongs to the FemtoClock NG series, originally manufactured by Integrated Device Technology (IDT), which was acquired by Renesas Electronics Corporation. The datasheet revision A dates to April 18, 2011. The 'AKI' designation indicates the lead-free RoHS 6 compliant version in the K package.

Clock Generators, PLLs, Frequency Synthesizers Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. As the product is listed as discontinued, alternative solutions require manual evaluation of pinout and electrical parameter compatibility.

Clock Generators, PLLs, Frequency Synthesizers FAQ

How is the output frequency selected?

The output frequency is determined by the logic levels on the asynchronous F_SEL0 and F_SEL1 pins. For a 25MHz reference, F_SEL=00 yields 156.25MHz, 01 yields 125MHz, 10 yields 100MHz, and 11 yields 250MHz.

What is the recommended termination for HCSL outputs?

For point-to-point connections on the same PCB, use a matched termination resistor (Rt) at the receiver and an optional series resistor (Rs) at the driver. For separate PCBs, standard PCI Express source termination is recommended.

Can the XTAL_IN pin be driven by an external clock?

Yes, the XTAL_IN pin can be overdriven by an LVCMOS or differential driver through an AC coupling capacitor. The input amplitude should be between 500mV and 1.8V with a slew rate no less than 0.2V/ns.