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发表于 2011-10-16 17:06:26
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Crystal Oscillator
This application note addresses issues commonly raised during the selection of the reference crystal, typically
14.318 MHz, for Chrontel's product line.
Pierce Oscillator
A simplified schematic of the oscillator circuit used in Chrontel products is shown in Figure 1. Note that the
typical 2-pin crystal has been replaced by its equivalent circuit model.
• Co is the pin-to-pin capacitance. Its value is associated with the crystal electrode design and the crystal holder.
• Rs is the motion resistance. Its value is specified by the crystal manufacturer.
• Cs is the motion capacitance and Ls is the motion inductance, which are not specified, and are functions of the
crystal frequency.
• Rbias is a feedback resistor, implemented on-chip in Chrontel products, which provides DC bias to the inverting
amplifier.
• C1 and C2 are total capacitance-to-ground at the input and output nodes of the amplifier, respectively. If
external capacitance is not added, the values of the internal......... |
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