MM74HC4046MX

Overview

The MM74HC4046MX is a low-power CMOS Phase-Locked Loop (PLL) utilizing advanced silicon-gate technology. It integrates a linear Voltage Controlled Oscillator (VCO), a source follower, and three distinct phase comparators: an Exclusive OR gate (Comparator I), an edge-sensitive digital sequential network (Comparator II), and an SR flip-flop (Comparator III). The device operates on a supply voltage of 2 V to 6 V with a maximum VCO frequency of 12 MHz at 4.5 V. It features fast comparator response times ranging from 25 ns to 30 ns and includes an inhibit pin for power management. The component is housed in a 16-lead Small Outline Integrated Circuit (SOIC) package.

Feature Summary

• Integrates a low-power linear VCO with high linearity and temperature stability.
• Includes three phase comparators: XOR (I), Edge-Sensitive Sequential (II), and SR Flip-Flop (III).
• Maximum VCO operating frequency reaches 12 MHz at VCC = 4.5 V.
• Features a self-biasing amplifier allowing AC or direct coupling of input signals.

Applications

• Frequency synthesis circuits requiring stable clock generation.
• Demodulation systems utilizing the integrated source follower output.
• Clock recovery applications leveraging the zero-phase-shift capability of Comparator II.

Procurement Notes

Verify the ordering suffix 'X' confirms the tape and reel packaging format as specified in the datasheet. Confirm that the manufacturer designation aligns with the original Fairchild Semiconductor specifications now managed by onsemi. Ensure the SOIC-16 package dimensions match the M16A JEDEC standard for PCB footprint compatibility.

Selection Notes

Select this component when a single-chip PLL solution with multiple detector options is required. Comparator II is suitable for applications demanding zero phase shift and equal lock/capture ranges. Comparator I is preferred for better noise rejection despite harmonic susceptibility. Ensure external components R1, R2, and C1 are selected to define the desired center frequency and lock range within the 2 V to 6 V supply window.

Part Context

The MM74HC4046MX belongs to the 74HC4046 family of high-speed CMOS logic devices. It serves as a low-power alternative to older metal-gate CD4046B devices, replacing the internal Zener diode with a third phase comparator. The 'MX' suffix specifically denotes the SOIC-16 package variant supplied in tape and reel configuration for automated assembly processes.

Replacement Considerations

Public confirmed substitute part numbers include MM74HC4046M (tube packaging) and MM74HC4046N (PDIP packaging). Cross-vendor equivalents such as CD74HC4046APWR (Texas Instruments) offer similar functionality but may differ in package type and specific electrical limits.

FAQ

How does the signal input handle different signal types?

The signal input features a self-biasing amplifier that allows signals to be capacitively coupled for small signals or directly coupled with standard logic levels.

What is the function of the source follower output?

The source follower provides access to the VCO input voltage without loading the loop filter, typically achieved by connecting a resistor from the demodulator output pin to ground.

Which phase comparator ensures zero phase shift between input and VCO?

Phase Comparator II is an edge-sensitive digital sequential network that locks the VCO output to the input signal with 0 phase shift between their positive waveform edges.