Dual 4-Line to 1-Line Data Selectors / Multiplexers # Technical Documentation: HD74LS153P Dual 4-Line to 1-Line Data Selector/Multiplexer
Manufacturer : HITACHI
Component Type : TTL (Transistor-Transistor Logic) IC, 74LS Series
Package : DIP-16 (Plastic Dual In-line Package)
Description : The HD74LS153P is a high-speed dual 4-input multiplexer. Each multiplexer selects one of four data sources based on two select inputs (S0, S1) and provides the selected data to a single output (Y), enabled by an active-low strobe (G).
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## 1. Application Scenarios
### Typical Use Cases
The HD74LS153P is primarily employed in digital systems for data routing, signal selection, and function generation. Key use cases include:
* Data Routing and Selection : Selecting one of multiple data streams (e.g., from different sensors, memory banks, or registers) to be processed by a single input port of a microprocessor or logic unit.
* Function Generator : Implementing combinational logic functions. By tying the four data inputs (I0-I3) to fixed logic levels (VCC or GND) or other signals, the multiplexer can generate any Boolean function of the two select lines (S0, S1), effectively acting as a 2-variable lookup table.
* Parallel-to-Serial Conversion (Partial) : When used in conjunction with a counter driving the select lines, it can sequentially output data from parallel inputs, forming part of a parallel-to-serial converter.
* Signal Gating and Control : The active-low enable/strobe input (`G`) allows for easy gating of the multiplexer's output, enabling system-level control and bus management.
### Industry Applications
* Legacy Computer & Peripheral Systems : Found in data bus control, I/O port selection, and address decoding circuits of older PCs, industrial controllers, and test equipment.
* Telecommunications : Used in switching circuits and data path selection in older digital communication hardware.
* Industrial Automation : Employed in PLCs (Programmable Logic Controllers) and control panels for signal conditioning and routing of digital status signals.
* Automotive Electronics (Classic Systems) : Utilized in dashboard logic and simple control units for function selection.
* Educational & Prototyping : Widely used in academic labs and hobbyist projects to teach digital logic principles due to its simplicity and DIP packaging.
### Practical Advantages and Limitations
Advantages:
* High Speed : Typical propagation delay of 15 ns (max) makes it suitable for moderate-speed logic systems.
* Low Power Consumption : As part of the 74LS (Low-Power Schottky) family, it offers a good balance between speed and power draw compared to standard 74-series TTL.
* Dual Function in One Package : Contains two independent multiplexers, saving board space and cost.
* TTL Compatibility : Directly interfaces with other TTL families (74, 74S, 74ALS) and can drive up to 10 standard TTL loads (fan-out of 10).
* Robust Design : DIP packaging is mechanically robust for through-hole applications.
Limitations:
* Legacy Technology : Being a pure TTL device, it is not optimized for modern low-voltage, high-density, surface-mount designs.
* Limited Voltage Range : Requires a strict 5V ±5% supply (VCC). Not compatible with 3.3V or lower voltage systems without level shifters.
* Higher Power than CMOS : Consumes significantly more static and dynamic power than equivalent HC or HCT CMOS parts.
* Fixed Functionality : Unlike programmable logic (CPLD/FPGA
