The CD4046BC micropower phase-locked loop (PLL) consists
of a low power, linear, voltage-controlled oscillator
(VCO), a source follower, a zener diode, and two phase
comparators. The two phase comparators have a common
signal input and a common comparator input. The signal
input can be directly coupled for a large voltage signal, or
capacitively coupled to the self-biasing amplifier at the signal
input for a small voltage signal.
Phase comparator I, an exclusive OR gate, provides a digital
error signal (phase comp. I Out) and maintains 90°
phase shifts at the VCO center frequency. Between signal
input and comparator input (both at 50% duty cycle), it may
lock onto the signal input frequencies that are close to harmonics
of the VCO center frequency.
Phase comparator II is an edge-controlled digital memory
network. It provides a digital error signal (phase comp. II
Out) and lock-in signal (phase pulses) to indicate a locked
condition and maintains a 0° phase shift between signal
input and comparator input.

The linear voltage-controlled oscillator (VCO) produces an
output signal (VCO Out) whose frequency is determined by
the voltage at the VCOIN input, and the capacitor and resistors
connected to pin C1A, C1B, R1 and R2.
The source follower output of the VCOIN (demodulator Out)
is used with an external resistor of 10 kW or more.
The INHIBIT input, when high, disables the VCO and
source follower to minimize standby power consumption.
The zener diode is provided for power supply regulation, if
necessary.