8T49N242-998NLGI8

Overview

The Renesas 8T49N242-998NLGI8 is a FemtoClock NG Universal Frequency Translator featuring one fractional-feedback PLL and four integer output dividers. It generates up to four independent output frequencies ranging from 8kHz to 1.0GHz (differential) or 250MHz (LVCMOS). The device accepts two differential/single-ended input clocks (8kHz–875MHz) or a fundamental-mode crystal (10MHz–50MHz). It supports LVPECL, LVDS, HCSL, and LVCMOS outputs with supply voltages of 2.5V or 3.3V. Key specifications include 0.35ps RMS typical jitter (12kHz–20MHz), ±50ppb initial holdover accuracy, and programmable loop bandwidth from 0.2Hz to 6.4kHz.

Feature Summary

• Universal frequency translation supporting SDH/SONET and Synchronous Ethernet FEC rates with 0ppm conversion error for most configurations.
• Hitless reference switching between two input clocks with automatic/manual selection and gapped clock support.
• I2C programmable with external EEPROM boot capability; supports I2C master mode for register configuration reading.
• Four general-purpose I/O pins providing status/control functions including Output Enable, Clock Select, and interrupt generation.

Applications

• OTN or SONET/SDH equipment
• Gigabit and Terabit IP switches/routers including Synchronous Ethernet
• Video broadcast systems

Procurement Notes

Verify the ordering suffix '998' indicates 'Boot from EEPROM' functionality as specified in the datasheet. Confirm package type is 40-VFQFPN (6mm x 6mm) and RoHS compliance. Check current product status as this component family may have discontinuation notices.

Selection Notes

Select this model when four independent output clocks are required with high-frequency jitter attenuation. Ensure input references fall within the 8kHz to 875MHz range. Verify that the required output voltage levels (1.8V, 2.5V, or 3.3V) match the VCCO pin configurations. Consider the 0.35ps RMS jitter specification for high-speed serial applications.

Part Context

The 8T49N242 belongs to the FemtoClock NG series of universal frequency translators. It integrates a fractional-N PLL with integer output dividers to provide flexible clock synthesis. The device is designed for network infrastructure requiring precise timing and low jitter performance across various standard protocols.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided source material. Consult manufacturer documentation for cross-reference information if replacement is necessary.

FAQ

What is the initial holdover accuracy of the 8T49N242?

The device has an initial holdover accuracy of ±50ppb from the point where loss of all applicable input references is detected.

Can the 8T49N242 operate without input clock references?

Yes, it can operate as a frequency synthesizer using only the crystal input by setting the SYN_MODE register bit and STATE field to Freerun.

How does the device handle input clock failures?

It monitors inputs for Loss of Signal (LOS) and supports automatic or manual hitless switching to a backup reference. If no valid references remain, it enters holdover mode.