251MI-35LF

Overview

The Renesas Electronics Corporation 251MI-35LF is a discontinued field-programmable clock synthesizer belonging to the VersaClock family. It operates as a single-output device with a 1:1 input-to-output ratio, generating frequencies up to 200 MHz using Phase-Locked Loop (PLL) techniques. The component supports spread spectrum modulation to reduce electromagnetic interference and accepts crystal or clock inputs ranging from 3 MHz to 150 MHz. Designed for industrial environments, it functions within a temperature range of -40°C to 85°C and utilizes an 8-pin SOIC package. The device requires a 3.3V supply voltage and includes a power-down feature for energy management.

Feature Summary

• Field-programmable architecture with One-Time Programmable (OTP) ROM and four selectable configuration registers
• Configurable spread spectrum modulation for EMI reduction
• Single CMOS output with controllable drive levels
• Power-down mode that tri-states outputs and disables PLLs

Applications

• Replacing multiple discrete crystals and oscillators in embedded systems
• Generating precise clock signals for digital logic circuits
• EMI-sensitive applications requiring spread spectrum clock generation

Procurement Notes

The 251MI-35LF is officially listed as obsolete by Renesas Electronics Corporation. Verification of availability should focus on surplus distributors or secondary market sources, as standard manufacturing channels no longer support this part number. Confirm the specific suffix 'MI' indicates the extended industrial temperature range (-40°C to 85°C) and 'LF' denotes lead-free compliance when sourcing replacements.

Selection Notes

Select this component only if legacy compatibility with IDT/Renesas VersaClock II programming tools is required. Ensure the design accommodates the 8-SOIC package dimensions and 3.3V operating voltage. For new designs, consider modern equivalents such as the 5P35021, which offers similar programmability within the VersaClock portfolio but may require schematic and firmware adjustments.

Part Context

This part is part of the VersaClock II series, originally developed by Integrated Device Technology (IDT) before its acquisition by Renesas. The 251 model line was designed to consolidate clock distribution functions, reducing board space and cost compared to traditional oscillator-based solutions. The 'MI' variant specifically targets industrial applications requiring wider thermal tolerance than commercial grades.

Replacement Considerations

Publicly confirmed substitute part numbers include the 5P35021 (VersaClock 3S). Verify pinout compatibility and register programming differences between the VersaClock II and newer generations before implementation.