The MC14046B phase locked loop contains two phase comparators, a voltage-controlled oscillator (VCO), source follower, and zener diode. The comparators have two common signal inputs, PCA
and PCB
. Input PCA
can be used directly coupled to large voltage signals, or indirectly coupled (with a series capacitor) to small voltage signals. The self-bias circuit adjusts small voltage signals in the linear region of the amplifier. Phase comparator 1 (an exclusive OR gate) provides a digital error signal PC1
, and maintains 90phase shift at the center frequency between PCA
and PCB
signals (both at 50% duty cycle). Phase comparator 2 (with leading edge sensing logic) provides digital error signals, PC2
and LD, and maintains a 0phase shift between PCA
and PCB
signals (duty cycle is immaterial). The linear VCO produces an output signal VCO
whose frequency is determined by the voltage of input VCO
and the capacitor and resistors connected to pins C1
, C1
, R1, and R2. The source-follower output SF
with an external resistor is used where the VCO
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.
Applications include FM and FSK modulation and demodulation, frequency synthesis and multiplication, frequency discrimination, tone decoding, data synchronization and conditioning, voltage-to-frequency conversion and motor speed control.

• Buffered Outputs Compatible with HTL and Low-Power TTL
• Diode Protection on All Inputs
• Supply Voltage Range = 3.0 to 18 V
• Pin-for-Pin Replacement for CD4046B
• Phase Comparator 1 is an Exclusive Or Gate and is Duty Cycle Limited
• Phase Comparator 2 switches on Rising Edges and is not Duty Cycle
• Pb-Free Packages are Available*