74HCXX

The "74HCxx series" refers to a popular family of digital logic integrated circuits using High-speed CMOS (Complementary Metal-Oxide-Semiconductor) technology. They belong to the larger 7400 series of logic ICs, which includes various logic technologies (TTL, LS, HCT, etc.). The "xx" designation represents a specific number identifying the IC's particular logic function (e.g., 74HC00 is a quad 2-input NAND gate, 74HC04 is a hex inverter, 74HC32 is a quad 2-input OR gate, etc.).

Common 74HCxx ICs

IC Number	Function
74HC00	Quad 2-input NAND gate
74HC02	Quad 2-input NOR gate
74HC04	Hex inverter (NOT gate)
74HC08	Quad 2-input AND gate
74HC32	Quad 2-input OR gate
74HC74	Dual D-type flip-flop with preset and clear
74HC138	3-to-8 line decoder/demultiplexer
74HC139	Dual 2-to-4 line decoder/demultiplexer
74HC151	8-to-1 multiplexer
74HC153	Dual 4-to-1 multiplexer
74HC164	8-bit serial-in/parallel-out shift register
74HC165	8-bit parallel-in/serial-out shift register
74HC573	Octal D-type transparent latch (3-state)
74HC574	Octal D-type flip-flop (3-state)
74HC595	8-bit shift register with output storage register (3-state)

This table shows some of the most frequently encountered ICs in the 74HCxx series. Many other ICs exist in this family, offering a wide variety of logic functions for different digital electronics needs.

Detailed Characteristics of 74HCxx Series

1. High-Speed CMOS (HCMOS) Technology

Characteristic	Description
Low power consumption	Very low static current consumption (when inputs aren't changing state) makes them ideal for battery-powered applications
High switching speed	"HC" stands for High-speed CMOS, offering speeds comparable to 74LS TTL while maintaining CMOS power advantages
Wide supply voltage range	Typically 2V to 6V, offering more design flexibility than TTL
High noise immunity	Better noise immunity than TTL due to input thresholds being proportional to supply voltage
High input impedance	Very high input impedance allows connecting more outputs to a single input (high fan-out)
ESD sensitivity	More sensitive to electrostatic discharge than TTL - requires proper handling precautions

2. Compatibility and Logic Functions

Feature	Description
Standard logic functions	Includes basic gates (AND, NAND, OR, NOR, XOR, NOT), flip-flops, counters, shift registers, multiplexers, decoders, buffers, and bus transceivers
Pin compatibility	Designed to be pin-compatible with many 74LS TTL series ICs (though voltage level differences must be considered)
HCT variants	74HCTxx series has TTL-compatible input thresholds while maintaining CMOS output levels

3. Typical Electrical Characteristics

Parameter	Value
Supply voltage (VCC)	2V to 6V (with specified performance at 2V, 4.5V and 6V)
Static supply current (ICC)	Very low, typically a few microamps (µA)
Input voltage levels (VIL max)	Typically 0.8V to 1.5V (varies with VCC)
Input voltage levels (VIH min)	Typically 2.0V to 3.5V (varies with VCC)
Output voltage levels (VOL max)	Very close to 0V with low output current
Output voltage levels (VOH min)	Very close to VCC with low output current
Output current (IOH/IOL)	Moderate current sourcing/sinking capability (a few mA)
Propagation delay (tpd)	Typically a few nanoseconds (ns)

4. Common Applications

74HCxx ICs are used in a wide range of digital electronics applications including:

Control and interface logic
Microcontroller-based digital systems
Automation and robotics
Electronic instrumentation
Embedded systems
Hobbyist and educational electronics projects
"Glue logic" for connecting digital system components

Summary

The 74HCxx series is a family of high-speed CMOS logic ICs offering low power consumption, good switching speed, wide operating voltage range, and compatibility with many TTL logic functions. They provide a versatile solution for various digital applications.