
Renesas FemtoClock™, FemtoClock Next Generation (NG), and FemtoClock 2 devices are advanced, high-performance clock-frequency synthesizers. Employing a simple, low-cost, fundamental-mode quartz crystal as the low-frequency reference these devices synthesize high-quality, low-jitter clock signals with less than 0.5 ps of RMS phase noise, up to 1.3GHz. The RC3 series also offers a jitter attenuation mode where it can take a noisy reference in and still provide 100fs jitter on its outputs.
FemtoClock devices are fully customizable, stand-alone solutions that generate reference frequencies allowing them to replace crystal and SAW oscillators in high-performance applications. This family of devices is often used to replace third overtone and high-frequency fundamental (HFF, inverted mesa) crystal oscillators or expensive surface acoustic wave (SAW) oscillators. They are more reliable, cost less, and are more readily available with shorter lead times.
Unlike fixed frequency oscillators, FemtoClocks are a frequency-synthesis technology (clock synthesizer) capable of multiple clock frequencies and more flexibility in any application. Because FemtoClocks are silicon IC-based clock devices, additional clock tree functions unavailable in a single function fixed-frequency oscillator can be integrated into a single device. The Renesas FemtoClock family delivers a wide range of device packages and capabilities, starting with small 8-pin TSSOP devices that provide one clean, low jitter clock signal, and 4mm x 4mm QFNs which provide 4 outputs. Also available are devices with more integrated functions, multiple outputs, multiple frequencies, and other more complex programmable synthesis functions.
PAM4 technology is enabling a major leap in data transmission rates in both communications and data center segments. This impacts the performance requirements of the timing source in such systems. The Renesas high-performance family of FemtoClock 2 delivers superior jitter performance with low power in a very small form factor, enabling placement of the clock anywhere on the board at the point of use. This greatly simplifies the design by eliminating the additive jitter associated with the extensive clock routing on the board.
Beyond PAM4, Renesas FemtoClock timing solutions are ideal reference clocks for almost any jitter-sensitive application. They are designed to provide a reference clock to PHYs, switches, ASICs, and network processors. The result is a simplified board design and layout, as well as improved time-to-market. Moreover, the FemtoClock family meets the low-jitter clock specification requirements of many interface standards, such as 10 Gigabit Ethernet, PCI Express®, Fibre Channel, and SONET. While generally optimized for synthesizing reference clock frequencies commonly used in communication applications, there are also a variety of FemtoClock devices with frequencies useful for CPU, memory, logic, and other general-purpose clocking applications, including ASICs, DSPs, CPUs, and memory; communication (including SONET/SDH and SPI4.2); HDTV video; networking (including 1Gb, 10 Gb, XAUI and 12Gb Ethernet); PCI Express; SERDES and PHY reference clocks; serial storage (SAS, SATA, fiber channel 4, 8 and 10Gb); and wireless infrastructure (including CPRI, RP3).
Jitter can be defined as the undesired deviation from an ideal periodic timing signal. Jitter may be observed in characteristics such as the frequency, phase, or amplitude of successive pulses. High levels of jitter can result in significant undesired system behavior in high-performance applications. Renesas offers the industry's leading portfolio of low-jitter clock synthesizers and phase-locked oscillators (PLL oscillators) to meet the needs of virtually any application.
Part Number | Description | Datasheet | Order |
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RC32504A | FemtoClock™ 2 Jitter Attenuator or Clock Generator | ![]() |
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RC22504A | FemtoClock™ 2 Clock Generator | ![]() |
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Outputs (#) |
Output Type |
Output Freq Range (MHz) |
Inputs (#) |
Input Type |
Phase Jitter Max RMS (ps) |
Input Freq (MHz) |
Output Banks (#) |
Core Voltage (V) |
Output Voltage (V) |
Output Skew (ps) |
Phase Jitter Typ RMS (ps) |
C-C Jitter Typ P-P (ps) |
C-C Jitter Max P-P (ps) |
Period Jitter Typ P-P (ps) |
Period Jitter Max P-P (ps) |
App Jitter Compliance |
Prog. Clock |
Prog. Interface |
Reference Output |
Spread Spectrum |
Feedback Input |
Chipset Manufacturer |
Chipset Name |
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Part Number | ||||||||||||||||||||||||
FemtoClock™ 2 Clock Generator | 4 | HCSL, LVCMOS, LVDS | 10 - 1000 | 2 | Crystal, HCSL, LVCMOS, LVDS | 0.1 | 25 - 312.5 | 4 | 1.8, 3.3 | 1.8 | 50 | 0.079 | Yes | I2C, SPI | No | No | No | |||||||
FemtoClock™ 2 Clock Generator | 4 | HCSL, LVCMOS, LVDS | 10 - 1000 | 0 | 0.1 | 4 | 1.8, 3.3 | 1.8 | 50 | 0.079 | Yes | I2C, SPI | No | No | No | |||||||||
FemtoClock™ 2 Jitter Attenuator or Clock Generator | 4 | HCSL, LVCMOS, LVDS | 10 - 1000 | 3 | Crystal, HCSL, LVCMOS, LVDS | 0.1 | 5 - 1000 | 4 | 1.8, 3.3 | 1.8 | 50 | 0.079 | Yes | I2C, SPI | No | No | No | |||||||
FemtoClock™ 2 Jitter Attenuator or Clock Generator | 4 | HCSL, LVCMOS, LVDS | 10 - 1000 | 3 | Crystal, HCSL, LVCMOS, LVDS | 0.1 | 1 - 800 | 4 | 1.8, 3.3 | 1.8 | 50 | 0.079 | Yes | I2C, SPI | No | No | No | |||||||
FemtoClock™ NG Crystal-To-HCSL Frequency Synthesizer | 6 | HCSL, LVCMOS, LVPECL | 25 - 100 | 2 | Crystal, HCSL, LVDS, LVPECL | 0.34 | 25 | 4 | 3.3 | 3.3 | 50 | PCIe Gen1, PCIe Gen2, PCIe Gen3 | No | Yes | No | No | ||||||||
FemtoClock NG™ Clock Synthesizer | 10 | LVCMOS, LVPECL | 25, 33.33, 100, 125, 156.25 | 2 | Crystal, LVCMOS | 25 | 5 | 3.3 | 3.3 | 40 | 0.212 | No | Yes | No | No | |||||||||
Programmable FemtoClock™ NG LVPECL/LVDS Clock Generator with 4-Outputs | 4 | LVDS, LVPECL | 15.16 - 1250 | 2 | Crystal, HCSL, LVDS, LVPECL | 0.292 | 10 - 312.5 | 1 | 2.5, 3.3 | 2.5, 3.3 | 50 | 0.212 | 0.78 | 13.2 | Yes | I2C | No, Yes | No | No | |||||
Programmable FemtoClock™ NG LVPECL/LVDS Clock Generator with 6-Outputs | 6 | LVDS, LVPECL | 15.16 - 1250 | 2 | Crystal, HCSL, LVDS, LVPECL | 0.292 | 10 - 312.5 | 1 | 2.5, 3.3 | 2.5, 3.3 | 50 | 0.212 | Yes | I2C | No | No | No | |||||||
Programmable FemtoClock™ NG LVPECL/LVDS Clock Generator with 8-Outputs | 8 | LVDS, LVPECL | 15.16 - 1250 | 2 | Crystal, HCSL, LVDS, LVPECL | 0.292 | 10 - 312.5 | 1 | 2.5, 3.3 | 2.5, 3.3 | 50 | 0.212 | 0.78 | 8.3 | Yes | I2C | No | No | No | |||||
FemtoClock™ NG Crystal-to-3.3V, 2.5V LVPECL/LVCMOS Clock Generator with Fanout Buffer | 12 | CMOS, LVPECL | 15.16 - 1250 | 2 | Crystal, HCSL, LVDS, LVPECL | 0.26 | 10 - 312.5 | 3 | 2.5, 3.3 | 2.5, 3.3 | 50 | 0.19 | Yes | No | No | No | ||||||||
Crystal-to-3.3V, 2.5V Multiple Frequency Clock Generator with Fanout Buffer | 8 | LVDS, LVPECL | 15.16 - 1250 | 2 | Crystal, HCSL, LVDS, LVPECL | 0.292 | 10 - 312.5 | 4 | 2.5, 3.3 | 2.5, 3.3 | 50 | 0.212 | 0.78 | 8.3 | Yes | I2C | Yes | No | No | |||||
FemtoClock NG Triple Universal Frequency Translator | 6 | LVDS, LVPECL | 0.98 - 1300 | 7 | HCSL, LVCMOS, LVDS, LVHSTL, LVPECL, LVTTL | 0.465 | 0.008 - 710 | 3 | 2.5 | 2.5 | 0.333 | 40 | Yes | I2C | No | Yes | Yes | |||||||
FemtoClock™ NG 12-Output Clock Generator | 12 | HCSL | 10.91 - 2500 | 2 | Crystal, HCSL, HSTL, LVCMOS, LVDS, LVHSTL, LVPECL | 5 - 1000 | 4 | 3.3 | 3.3 | 50 | 0.095 | 40 | Yes | I2C | No | No | No | |||||||
FemtoClock™ NG LVDS Clock Synthesizer | 2 | LVDS | 50 - 1200 | 1 | HCSL, LVCMOS, LVDS, LVPECL, Sine Wave | 0.45 | 20 - 500 | 1 | 3.3 | 3.3 | 0.3 | Yes | I2C | Yes | No | No | ||||||||
FemtoClock™ NG 12-Output Clock Generator | 12 | LVDS, LVPECL | 10.91 - 2500 | 2 | Crystal, HCSL, HSTL, LVCMOS, LVDS, LVHSTL, LVPECL | 5 - 1000 | 4 | 3.3 | 3.3 | 30 | 0.089 | 40 | Yes | I2C | No | No | No | |||||||
FemtoClock™ NG 12-Output Clock Generator | 12 | LVDS, LVPECL | 10.91 - 2500 | 2 | Crystal, HCSL, HSTL, LVCMOS, LVDS, LVHSTL, LVPECL | 5 - 1000 | 4 | 3.3 | 3.3 | 50 | 0.08 | 40 | Yes | I2C | No | No | No | |||||||
FemtoClock Clock Generator | ||||||||||||||||||||||||
FemtoClock 2 Jitter Attenuator or Clock Generator | 8 | HCSL, LVCMOS, LVDS | 10 - 1000 | 3 | Crystal, HCSL, LVCMOS, LVDS | -2, 0.1 | 1 - 800 | 8 | 1.8, 3.3 | 1.8 | 0.067 | I2C, SPI |
Demonstration of Renesas’ Lab on the Cloud virtual environment for FemtoClock®2 ultra-low phase noise synthesizer and jitter attenuator.
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Benefits of a Point-of-Use Clock for Jitter Optimization | Blog Post | Apr 27, 2021 |
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Renesas Expands FemtoClock Timing Portfolio for High-Performance Communications and Data Center Applications | News | Apr 26, 2021 |