Octal Buffers/Line Drivers/Line Receivers (with inverted 3-state outputs) # Technical Documentation: HD74HCT241P Octal Bus Buffer/Line Driver with 3-State Outputs
Manufacturer : HIT (Hitachi, now part of Renesas Electronics)
Component Type : Integrated Circuit (IC) - Logic Device
Family : 74HCT Series (High-Speed CMOS with TTL Compatibility)
Package : DIP-20 (HD74HCT241P), where "P" denotes Plastic DIP
---
## 1. Application Scenarios
### Typical Use Cases
The HD74HCT241P is an octal bus buffer and line driver designed primarily for bus-oriented applications where multiple devices share a common data path. Its fundamental use case is to isolate, amplify, and control the direction of data flow on bidirectional or unidirectional buses. Each of its eight channels features non-inverting buffers with independent output enable controls, organized into two groups of four (1G and 2G). This allows flexible control—enabling one group while placing the other in a high-impedance (Hi-Z) state—which is critical for preventing bus contention (multiple devices driving the same line simultaneously).
A classic use is in microprocessor or microcontroller systems interfacing with multiple memory chips (RAM, ROM) or peripheral devices (ADCs, DACs, other ICs). It acts as an interface between the CPU's address/data bus and the peripheral buses, ensuring the CPU can read from or write to the correct device without electrical interference. Another common scenario is signal buffering in long PCB traces or backplanes , where the IC regenerates digital signals weakened by capacitance and resistance, preserving signal integrity over distance.
### Industry Applications
* Industrial Control Systems: Used in PLCs (Programmable Logic Controllers) and industrial automation boards to drive signals to sensors, actuators, and display modules across noisy factory environments. Its CMOS technology offers good noise immunity.
* Telecommunications Equipment: Employed in routers, switches, and communication interfaces for buffering data and control lines between processing units, memory, and network PHY chips.
* Automotive Electronics: Found in non-critical control modules (e.g., infotainment, body control modules) for signal isolation and level shifting, though careful environmental qualification is needed for extended temperature ranges.
* Consumer Electronics: Used in set-top boxes, printers, and older computer motherboards for bus management and I/O port expansion.
* Test and Measurement Equipment: Serves as a programmable driver for signal generation or as a buffer in digital logic probe circuits.
### Practical Advantages and Limitations
Advantages:
* Bus Isolation: Prevents back-feeding of signals, protecting sensitive circuits like microprocessors.
* High Drive Capability: Can sink/sink up to 6mA (typical), sufficient to drive multiple TTL inputs or moderate capacitive loads.
* 3-State Outputs: Essential for shared bus architectures; Hi-Z state allows other devices to use the bus.
* Wide Operating Voltage: 4.5V to 5.5V (standard 5V logic), with HCT inputs compatible with both TTL (0.8V/2.0V thresholds) and CMOS voltage levels.
* Low Power Consumption: Inherits the low static power dissipation of CMOS technology, though dynamic power increases with frequency.
Limitations:
* Propagation Delay: Introduces a finite signal delay (typically 10-20ns). This can be a critical timing factor in high-speed synchronous systems (>25-30 MHz).
* Limited Current Drive: Not suitable for directly driving high-current loads like LEDs, relays, or long cables without additional driver stages.
* No Internal Pull-Ups/Downs: Inputs float if left unconnected, potentially causing erratic behavior and increased power consumption. External
