U74HC4046A Datasheet PDF | Unisonic Technologies

Unisonic Technologies U74HC4046A

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 SOP-16 comparator input. The signal can be directly coupled to large voltage signals or with a series capacitor coupled to small voltage signals. The U74HC4046A and a passive low-pass filter form a second-order loop PLL.

Part No.	U74HC4046A
Datasheet	U74HC4046A Download
Manufacturer	Unisonic Technologies
Description	PHASE LOCKED LOOP
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DESCRIPTION

Small voltage signals can be kept within the linear region of the input amplifiers with a self-bias input circuit. With a linear op-amp, the VCO achieves excellent linearity. The VCO requires an external capacitor and resistor. R1 (between R1 TSSOP-16 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.