Renesas 251PMLF

Overview

251PMLF from Integrated Device Technology (IDT) is a field-programmable, single-output spread-spectrum clock synthesizer based on PLL architecture. It generates output frequencies from 314 kHz to 200 MHz using a 5–27 MHz crystal or 3–150 MHz clock input, operates at 3.3 V, and supports configurable center/down spread spectrum modulation for EMI reduction in embedded timing applications.

For engineers reviewing the 251PMLF datasheet, 251PMLF pinout, 251PMLF application, or 251PMLF equivalent, key selection considerations include its OTP-based field programmability via VersaClock software, 8-pin SOIC package with S0/S1 frequency select pins, power-down control via PDTS, and drive-level configuration for outputs up to 200 MHz.

Technical Context

The 251PMLF implements a single PLL with M/N dividers (M = 1–2048, N = 1–1024) and independent output divide values (2–20), enabling precise frequency synthesis from a single reference. Its architecture supports both crystal (fundamental mode) and external clock inputs, with internal pull-up resistors on S0/S1 and no internal pull-up on PDTS.

It features two output drive modes-low drive for ≤100 MHz and high drive for >100 MHz-with nominal 20 Ω output impedance and guaranteed rise/fall times ≤1 ns under 15 pF load. Spread spectrum modulation operates at either 30–33 kHz (PCI/zero-delay buffer compatible) or 120 kHz, with center-spread (±0.125% to ±2.0%) or down-spread (−0.25% to −4.0%) options.

Key Specifications

Pinout & Package

251PMLF is housed in an 8-pin SOIC (150 mil body, DCG8 package) with exposed pad not present and RoHS-compliant lead-free finish (LF suffix). Pin assignments are validated per IDT's official datasheet revision October 10, 2017.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock synthesizer applications.

Compared with Si5351A-B-GM and ICS8430M-01LFT, the 251PMLF uniquely balances field programmability, hardware-selectable frequency presets, integrated spread spectrum, and minimal external component count-all in a low-cost 8-pin SOIC package optimized for volume production and EMI-sensitive designs.

Availability

251PMLF is available at Aetrix Electronics and suitable for consumer audio systems, industrial PLC controllers, and medical imaging interfaces requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for 251PMLF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Integrated Device Technology (IDT), now part of Renesas Electronics, is a fabless semiconductor company specializing in timing, memory interface, RF, and power management ICs for communications, computing, and industrial markets.

The ICS251 product line was designed as a low-cost, field-programmable clock synthesizer family targeting cost-sensitive, EMI-constrained embedded systems needing flexible yet simple clock generation without MCU involvement.

FAQ

What is the operating temperature range for the 251PMLF?

The 251PMLF is rated for commercial temperature operation from 0 °C to +70 °C, as confirmed in the IDT ordering information table and recommended operating conditions section of the October 2017 datasheet. This distinguishes it from the industrial-grade 251PMILF variant, which supports −40 °C to +85 °C. The 251PMLF's thermal resistance (θJA) is 150 °C/W in still air, consistent with its SOIC-8 package construction.

Does the 251PMLF require external programming hardware to configure its output frequency?

No, the 251PMLF does not require external programming hardware after initial configuration. Its One-Time Programmable (OTP) ROM is programmed in-system using IDT's VersaClock software and a standard USB-to-I²C adapter or compatible programmer. Once programmed, the 251PMLF retains settings and uses S0/S1 pins for hardware-selectable frequency recall-no ongoing MCU interaction or reprogramming is needed during normal operation.

Can the 251PMLF generate a 100 MHz output clock with low jitter for FPGA applications?

Yes, the 251PMLF supports 100 MHz output with verified jitter performance: one-sigma period jitter ≤50 ps and maximum absolute jitter ≤200 ps under typical conditions. Its high-drive mode is recommended for ≥100 MHz outputs, and the device's 20 Ω nominal output impedance enables clean signal integrity when paired with proper PCB layout and optional 33 Ω series termination-making it suitable for FPGA clocking in non-ultra-low-jitter applications.

How does spread spectrum modulation work on the 251PMLF, and can it be disabled?

The 251PMLF implements frequency modulation (FM) spread spectrum in either center-spread (±0.125% to ±2.0%) or down-spread (−0.25% to −4.0%) modes, with modulation rates selectable at 30–33 kHz or 120 kHz. Spread spectrum is configured during OTP programming and cannot be dynamically enabled/disabled in-circuit; however, unmodulated operation is achieved by setting spread percentage to 0% during VersaClock configuration prior to programming the 251PMLF.

What external components are mandatory for reliable operation of the 251PMLF?

Three external components are mandatory: (1) a 0.01 µF ceramic decoupling capacitor between VDD and GND, placed adjacent to the VDD pin with no vias; (2) two crystal load capacitors (value = (CL − 6 pF) × 2) from X1 and X2 to GND when using a crystal; and (3) a pull-up or pull-down resistor (<15 kΩ) on PDTS to define power-down state. Series termination (e.g., 33 Ω) is recommended-but not mandatory-for CLK traces longer than 1 inch.