Increasing the Number of Outputs from a Clock Source Using Low Jitter LVPECL Fanout Buffers (CN0294)
Many systems require low jitter multiple system clocks for mixed signal processing and timing. The circuit shown in Figure 1 interfaces the ADF4351 integrated phase-locked loop (PLL) and voltage-controlled oscillator (VCO) to the ADCLK948, which provides up to eight differential, low voltage, positive emitter coupled logic (LVPECL) outputs from one differential output of the ADF4351.
Figure 1. ADF4351 PLL Connected to ADCLK948 Fanout Buffer (Simplified Schematic: All Connections and Decoupling Not Shown)
Modern digital systems often require many high quality clocks at logic levels that are different from the logic level of the clock source. Extra buffering may be required to guarantee accurate distribution to other circuit components without loss of integrity. The interface between the ADF4351 clock source ADCLK948 clock fanout buffer is described, and measurements show that the additive jitter associated with the clock fanout buffer is 75 fs rms.
Схемы и диаграммы
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