Phase Locked LoopThe SC14046B Phase locked loop contains two phase Comparators
a voltagecontrolled Oscillator (VCO), source follower, and zener
Diode The Comparators have two common signal inputs, PCAin and
PCBin. Input PCAin CAN be used directly coupled to large voltage
signals, or indirectly coupled (with a series capacitor) to small voltage
signals. The selfbias circuit adjusts small voltage signals in the linear
region of the Amplifier Phase Comparator 1 (an exclusive OR gate)
provides a digital error signal PC1out, and maintains 90 phase shift at
the center frequency between PCAin and PCBin signals (both at 50%
duty cycle). Phase Comparator 2 (with leading edge sensing logic)
provides digital error signals, PC2out and LD, and maintains a 0
phase shift between PCAin and PCBin signals (duty cycle is
immaterial). The linear VCO produces an output signal VCOout
whose frequency is determined by the voltage of input VCOin and the
capacitor and resistors connected to pins C1A, C1B, R1, and R2. The
sourcefollower output SFout with an external resistor is used where
the VCOin signal is needed but no loading CAN be tolerated. The inhibit
input Inh, when high, disables the VCO and source follower to
minimize standby power consumption. The Zener Diode CAN be used to
assist in power supply regulation. By ON Semiconductor
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