Renesas 844201BKI-45LF

Overview

844201BKI-45LF from Integrated Device Technology is a PCI Express-compliant crystal-to-LVDS clock generator that synthesizes 100 MHz or 125 MHz reference clocks from a 25 MHz crystal, features a 490–680 MHz VCO range, delivers 0.773 ps RMS phase jitter at 125 MHz (12 kHz–20 MHz), and operates across –40°C to +85°C in PCIe Gen 1/Gen 2 systems.

For engineers reviewing the 844201BKI-45LF datasheet, 844201BKI-45LF pinout, 844201BKI-45LF application, or 844201BKI-45LF equivalent, this page provides verified pin functions, PCIe jitter compliance details, LVDS output design values, crystal interface requirements, and validated alternative clock generators for reference clock subsystems.

Technical Context

The 844201BKI-45LF implements a PLL-based architecture with fixed M = ÷20 and programmable N = ÷4 (default) or ÷5 via FSEL pin, enabling dual-output-frequency selection. Its phase detector drives a wide-range VCO (490–680 MHz), followed by LVDS output drivers compliant with PCI Express Gen 1 peak-to-peak jitter limits (≤13.48 ps) and Gen 2 RMS limits (≤1.25 ps high-band, ≤0.33 ps low-band).

It integrates an internal crystal oscillator interface optimized for 18 pF, 25 MHz parallel-resonant crystals, with on-chip pullup resistors (51 kΩ) on FSEL and crystal pins, and supports overdrive input modes using LVCMOS or LVPECL sources - all while maintaining full 3.3 V supply operation and RoHS-compliant VFQFN packaging.

Key Specifications

Pinout & Package

844201BKI-45LF is housed in a lead-free 16-pin VFQFN package (3 mm × 3 mm × 0.925 mm body, K suffix), with exposed thermal pad and JEDEC MO-220-compliant outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar crystal-to-LVDS clock generator applications.

Compared with Si5338A-B-GM and ICS844202BKI-45LF, the 844201BKI-45LF delivers the lowest measured RMS phase jitter (0.773 ps) and simplest implementation (no programming, no spread-spectrum overhead), making it optimal for fixed-frequency PCIe Gen 1/Gen 2 reference clocking where jitter margin and design simplicity are critical.

Availability

844201BKI-45LF is available at Aetrix Electronics and suitable for PCIe server motherboards, enterprise SSDs, network switches, and FPGA accelerator cards requiring stable component supply, consistent lead times, and long-term lifecycle support.

Supply support for 844201BKI-45LF 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 sensor signal conditioning ICs for communications, computing, and industrial markets.

The 844201BKI-45LF belongs to IDT's FemtoClock® family of ultra-low-jitter clock generators, designed specifically for PCI Express reference clocking in high-speed serial interconnect applications where phase noise and jitter directly impact link reliability.

FAQ

What is the primary function of the 844201BKI-45LF in a PCIe system?

The 844201BKI-45LF serves as a crystal-to-LVDS clock generator that produces a low-jitter 100 MHz or 125 MHz reference clock for PCIe Gen 1/Gen 2 physical layers. It accepts a 25 MHz crystal input and uses an internal PLL with fixed M/N dividers to synthesize the output, ensuring compliance with PCIe jitter specifications. The 844201BKI-45LF is not a buffer or fanout device - its core role is precise frequency synthesis from a fundamental crystal source.

Does the 844201BKI-45LF require external configuration or programming?

No, the 844201BKI-45LF is a fixed-function device with no serial interface or non-volatile memory. Frequency selection (100 MHz vs. 125 MHz) is controlled solely by the logic level on the FSEL pin (Pin 4), and all PLL parameters - including M = ÷20 and N = ÷4 or ÷5 - are hardwired. No firmware, EEPROM, or I²C setup is needed, simplifying integration and reducing qualification effort for the 844201BKI-45LF.

What crystal specifications are required for reliable operation of the 844201BKI-45LF?

The 844201BKI-45LF is characterized and guaranteed for use with 25 MHz, 18 pF parallel-resonant crystals having ESR ≤50 Ω and shunt capacitance ≤7 pF. External load capacitors C1 and C2 (27 pF each) are recommended for optimal frequency accuracy. Using crystals outside this specification - such as series-resonant types or those with different load capacitance - may cause start-up failure or frequency drift in the 844201BKI-45LF.

How does the 844201BKI-45LF meet PCIe Gen 2 jitter requirements?

The 844201BKI-45LF meets PCIe Gen 2 jitter requirements by delivering 1.13 ps tREFCLK_HF_RMS (1.5 MHz–Nyquist) and 0.32 ps tREFCLK_LF_RMS (10 kHz–1.5 MHz) at 125 MHz - both well below the 3.1 ps and 3.0 ps limits respectively. These values are measured using the official PCIe Common Clock Architecture transfer functions and validated with a 25 MHz crystal input, confirming full compliance for the 844201BKI-45LF in Gen 2 systems.

Can the 844201BKI-45LF drive multiple LVDS receivers simultaneously?

The 844201BKI-45LF's LVDS outputs (Q/nQ) are designed for point-to-point connections with 100 Ω differential termination. Driving multiple receivers directly is not supported - doing so increases capacitive loading, degrades edge rate (tR/tF = 250–450 ps), and raises jitter. For fanout, a dedicated LVDS buffer (e.g., IDT 8T49N241) must be used downstream of the 844201BKI-45LF to maintain signal integrity and PCIe compliance.