ICS841N254AKILFT

Clock Generators, PLLs, Frequency Synthesizers Overview

The ICS841N254AKILFT 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 selectable 25MHz fundamental mode crystal or REF_CLK input. The device synthesizes output 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 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 component status as the base model ICS841N254I is listed as obsolete by the manufacturer. Confirm availability of the specific 'K' package variant and ensure compliance with current RoHS standards before procurement planning.

Clock Generators, PLLs, Frequency Synthesizers Selection Notes

Select this component when driving IDT S-RIO switches requiring 156.25MHz reference clocks. Ensure the design accommodates the 32-VFQFN exposed pad package for thermal management and utilizes appropriate termination resistors for LVDS and HCSL loads.

Clock Generators, PLLs, Frequency Synthesizers Part Context

This part belongs to the FemtoClock NG series, originally manufactured by Integrated Device Technology (IDT), which was subsequently acquired by Renesas Electronics Corporation. The 'AKILFT' suffix denotes the lead-free, RoHS-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. Verify compatibility with direct pin-compatible alternatives if the original part is discontinued.

Clock Generators, PLLs, Frequency Synthesizers FAQ

How is the output frequency selected?

The output frequency is determined by the logic levels on the F_SEL0 and F_SEL1 asynchronous control pins, selecting between 250MHz, 156.25MHz, 125MHz, or 100MHz based on a 25MHz reference.

What is the recommended termination for HCSL outputs?

For point-to-point connections, use a series resistor (0Ω to 33Ω) at the driver and a matched termination (e.g., 49.9Ω) at the receiver. 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, provided the amplitude is between 500mV and 1.8V.