MM74HC4046MTCX

Overview

The MM74HC4046MTCX is a CMOS Phase Lock Loop (PLL) integrated circuit manufactured by onsemi, formerly Fairchild Semiconductor. It utilizes advanced silicon-gate CMOS technology to provide high-frequency operation within both the phase comparator and Voltage Controlled Oscillator (VCO) sections. The device integrates a low-power linear 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 gate (Comparator III). It operates on a supply voltage ranging from 2 V to 6 V and supports a maximum VCO operating frequency of 12 MHz at 4.5 V. The component is housed in a 16-lead Thin Shrink Small Outline Package (TSSOP).

Feature Summary

• Integrates three phase comparators: XOR (Comparator I), Edge-Sensitive Sequential Network (Comparator II), and SR Flip-Flop (Comparator III).
• Features a low-power linear Voltage Controlled Oscillator (VCO) with high linearity and temperature stability.
• Includes a source follower output for monitoring the VCO input without loading the loop filter.
• Fast comparator response times: Comparator I and III at 25 ns; Comparator II at 30 ns (at VCC = 4.5 V).

Applications

• Frequency synthesis circuits requiring stable clock generation.
• Demodulation systems utilizing the VCO demodulator output.
• Clock recovery applications leveraging the specific phase detection characteristics of Comparator II.

Procurement Notes

Verify that the ordering code includes the 'X' suffix to confirm the Tape and Reel packaging format associated with the MM74HC4046MTCX designation. Confirm the package type corresponds to the 16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153 standard, as specified in the manufacturer's ordering guide.

Selection Notes

Select this component when a low-power CMOS PLL with multiple phase detector options is required. Comparator II is suitable for applications demanding zero phase shift lock and equal capture/lock ranges, while Comparator I offers better noise rejection. Ensure external components R1, R2, and C1 are selected to define the desired VCO center frequency and lock range according to the provided performance curves.

Part Context

The MM74HC4046MTCX belongs to the MM74HC4046 family of CMOS Phase Lock Loops. It is functionally similar to the CD4046 but replaces the metal gate Zener diode with a third phase comparator. The 'MTC' prefix indicates the TSSOP package variant, while the 'X' suffix denotes tape and reel availability. This part is produced by onsemi, which acquired the semiconductor assets of Fairchild Semiconductor.

Replacement Considerations

The datasheet notes functional similarity to the CD4046, though pinouts may differ due to the internal architecture changes. Verify compatibility with existing designs referencing the CD4046 by comparing pin assignments and electrical characteristics carefully.

FAQ

What is the difference between Phase Comparator I and Phase Comparator II?

Phase Comparator I is an XOR gate that provides a 90-degree phase shift at lock and is more susceptible to locking onto harmonics. Phase Comparator II is an edge-sensitive network that forces a 0-degree phase shift and has a lock range equal to its capture range, making it less likely to lock onto harmonics but more susceptible to noise.

How is the VCO frequency determined?

The VCO operating frequency is set by three external components connected to pins C1A, C1B, R1, and R2. Resistor R1 and capacitor C1 determine the center frequency, while R1 also controls the lock range.

What is the purpose of the source follower output?

The source follower allows access to the VCO input signal without loading down or modifying the characteristics of the PLL loop filter. It is typically used by connecting a resistor from the output pin to ground.