Phase Locked Loop

The 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