What is the relationship between HCMOS and LVCMOS?

From the perspectives of integrated circuit technology evolution and taxonomy, CMOS, HCMOS, and LVCMOS are not simply parallel or replacement relationships. Instead, they form a hierarchical system based on different classification dimensions, with significant intersections.

Their core relationship can be defined as follows: LVCMOS is not the next generation of HCMOS, but rather a vast branch classified based on the "voltage domain." Modern LVCMOS devices, in terms of performance, have comprehensively surpassed early HCMOS. They are concepts from different dimensions and have become highly integrated in contemporary technology.

1.  The Fundamental Base: CMOS Technology

CMOS technology is the foundation for all subsequent variants. Its defining characteristic is the use of complementary P-MOS and N-MOSFETs to form inverters or other logic gates, thereby achieving theoretically zero static power consumption. All discussed HCMOS and LVCMOS share this fundamental feature.

2.  Technology Evolution Based on Performance Generations (Primary Dimension)

This dimension is categorized by time and performance, reflecting advancements in manufacturing processes.

·Standard CMOS (e.g., 4000 series):

·Characteristics: Early processes with larger feature sizes and high parasitic capacitance. Their advantage was a wide operating voltage range (3-15V), but main disadvantages included long propagation delays (~100ns scale), low speed, and weak output drive capability.

·HCMOS (High-Speed CMOS):

·Characteristics: By proportionally scaling down transistor dimensions, the parasitic capacitance and gate capacitance of the devices were significantly reduced. This improvement drastically shortened propagation delays (~10ns scale) while maintaining low static power consumption. Their output drive capability was also notably enhanced.

·Academic Positioning: HCMOS represents a historic technology node, marking the point where CMOS technology matched and surpassed the speed of the then-mainstream TTL logic, establishing CMOS's comprehensive advantage in performance and power consumption. A typical representative is the 5V-operating 74HC series. Note here: HCMOS stands for High-Speed CMOS, not High-Voltage CMOS. The term "High-Voltage CMOS" is extremely rare in practical application; even if it exists, it should be abbreviated as HVCMOS.

3.  Architecture Division Based on Supply Voltage (Another Intersecting Dimension)

This dimension is categorized by standardized supply voltages and intersects with the performance dimension.

·5V CMOS:

·Includes early standard CMOS and most HCMOS (e.g., 74HC series). This was the first widely standardized voltage domain.

·Low-Voltage CMOS (LVCMOS):

· Definition: Broadly refers to all CMOS logic families operating at voltages significantly lower than the 5V standard. The core driver for its development is the optimization of dynamic power consumption, as a circuit's dynamic power consumption is proportional to the square of the supply voltage.

·Subcategories: LVCMOS itself is further subdivided by voltage, forming a series of standards:

·3.3V (LVCMOS): e.g., 74LVC series

·2.5V, 1.8V, 1.5V, 1.2V...: Voltages continue to decrease with advancing process nodes.

Subordination and Contemporary Integration

1.  Historical Subordination: In the history of technological development, HCMOS (e.g., 74HC) is a performance subclass under CMOS technology.

2.  Dimensional Intersection: HCMOS (emphasizing speed) and LVCMOS (emphasizing voltage) are concepts based on different classification criteria. A single chip can belong to both categories.

·For example, the 74HC series is 5V HCMOS.

·The 74LVC series is 3.3V LVCMOS, but its speed performance typically surpasses that of the 74HC series. Therefore, 74LVC is both LVCMOS and fully qualifies as "high-speed."

3.  Contemporary Integration and Terminology Evolution:

·In today's submicron and deep-submicron CMOS processes, low voltage has become a prerequisite for achieving high speed and low power consumption. Consequently, all newly designed CMOS integrated circuits are inherently "low-voltage."

·"High-speed" is no longer a label for a specific series but a universal characteristic of modern CMOS technology. In academic and engineering practice, the term "HCMOS" is often used broadly to refer to all CMOS circuits based on modern processes that exhibit high-speed performance, and the vast majority of these circuits fall under the LVCMOS category.

In the contemporary context:

·CMOS is the general technological term; in the context of oscillator output signals, it specifically refers to single-ended square-wave signal output.

·Broadly, the term HCMOS describes the high-performance attributes of modern CMOS circuits.

·LVCMOS explicitly describes the electrical standard of low operating voltage.

Therefore, when describing a "3.3V, high-speed CMOS signal," a more precise academic expression is: this signal adheres to the LVCMOS (e.g., LVC) electrical standard and embodies the high-speed characteristics of modern CMOS processes. HCMOS, as a milestone technology, has its core legacy—performance enhancement through process scaling—inherited and surpassed by all modern LVCMOS technologies. While conceptually belonging to different dimensions, they have merged in practice.