U74HC4046A

DESCRIPTION 

The U74HC4046A is a phase-locked-loop circuit including a linear 

voltage-controlled oscillator (VCO), three different phase comparators 

(PC1, PC2 and PC3), a common signal input amplifier and a common 

comparator input. 

The signal can be directly coupled to large voltage signals or with a 

series capacitor coupled to small voltage signals. Small voltage signals 

can be kept within the linear region of the input amplifiers with a self-bias 

input circuit. The U74HC4046A and a passive low-pass filter form a 

second-order loop PLL. With a linear op-amp, the VCO achieves excellent 

linearity. 

The VCO requires an external capacitor and resistor. R1 (between R1 

and GND) and capacitor C1 (between C1A and C1B) determine the 

frequency range of the VCO. R2 (between R2 and GND) enables the 

VCO to have a frequency offset if required. 

For the high input impedance of the VCO, the design of low-pass filters is 

simplified, and the designer has a wide choice of resistor/capacitor ranges. 

At pin 10 (DEMOUT), a demodulator output of the VCO input voltage is 

provided in order not to load the low-pass filter. In conventional 

techniques, the DEMOUT voltage is one threshold voltage lower than the 

VCO input voltage, but the DEMOUT voltage of U74HC4046 equals the 

VCO input voltage. When DEMOUT is used, a load resistor (RS) should 

be connected from DEMOUT to GND; but if unused, DEMOUT should 

be left open. The VCO output (VCOOUT) can be connected directly or 

via a frequency-divider to the comparator input (COMPIN). If the VCO 

input is held at a constant DC level, the VCO output signal has a duty 

factor of 50% (maximum expected deviation 1%). A LOW level at the 

inhibit input (INH) enables the VCO and demodulator, while a HIGH 

level turns both off to minimize standby power consumption. 

FEATURES 

* Low Power Consumption 

* Operating Power Supply Voltage Range:   Digital Section 2.0 to 6.0 V 

                                                                       VCO Section 3.0 to 6.0 V 

* Up to 17 MHz (typ.) Centre Frequency at VCC = 4.5 V 

* Excellent VCO Frequency Linearity 

* VCO-Inhibit Control For ON/OFF Keying and for Low Standby Power Consumption 

* Minimal Frequency Drift 

* Three Phase Comparators:     EXCLUSIVE-OR; 

                                                  Edge-Triggered JK Flip-Flop; 

                                                  Edge-Triggered RS Flip-Flop 

* Zero Voltage Offset due to OP-Amp Buffering 

* Standard Output Capability 

* MSI ICC Category

规格书U74HC4046A