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Fanout Buffers, Clock Dividers, and Multiplexers (MUX)

Fanout Buffers

Fanout buffers are a useful building block of many clock trees, providing signal buffering and multiple low-skew copies of the input signal. The clock fanout from a single input reduces loading on the preceding driver and provides an efficient clock distribution network. Single output buffers are useful for translating a clock from one signaling standard to another (e.g. LVCMOS-in to LVPECL-out). Some devices have an integrated crystal oscillator, requiring only a low cost external fundamental-mode quartz crystal. The integrated oscillator provides an extremely low phase noise reference clock to drive jitter-sensitive devices such as the clock inputs of PHYs. If the exact buffer configuration is not found in the extensive IDT fanout buffer offerings, please also consider devices in the IDT clock divider portfolio that, when used in divide-by-1 mode, can also function as a fanout buffer. 

► Download the High-performance, Low-phase Noise Clocks Buffers Product Brief

Clock Dividers

Clock dividers provide an output clock signal that is a divided frequency of the input. They can also be used to provide signal buffering and make multiple copies of the output frequency. Clock divider devices, when used in divide-by-1 mode, can also function as a fanout buffer. 

IDT’s “8” series of fanout buffers and clock dividers feature fully differential internal architecture, even devices with single-ended I/Os. This improves jitter due to inherent common-mode noise rejection and improves output skew. The differential circuitry is constant-current and therefore injects less noise into system power supplies than single-ended solutions, reducing EMI compliance concerns. 

The IDT fanout buffer and clock divider portfolio includes devices with up to 27 outputs. Differential outputs such as LVPECL, LVDS, HCSL, CML, HSTL, as well as selectable outputs, are supported for output frequencies up to 3.2 GHz and single-ended LVCMOS outputs for frequencies up to 350 MHz. Some buffers are available with mixed output signaling. IDT’s buffer portfolio has devices supporting supply voltages from 1.2 V up to 5 V and that are available in the commercial and industrial temperature ranges. Fanout buffers and clock dividers are general-purpose clock building block devices that can be used in any number of applications. They are ideal for clock and signal distribution in a large variety of systems, from personal computers to consumer electronics or industrial systems, as well as high-performance networking and communications systems.

Clock Dividers and Fanout Buffers

High-performance 1.8V Fanout Buffers Video

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