Overview
The DM74LS253MX is a member of the 74LS series of TTL logic integrated circuits, specifically designed as a dual 4-input multiplexer with 3-state outputs. Manufactured by Fairchild Semiconductor (now ON Semiconductor), this device is widely used in digital systems for data routing applications. Housed in a 16-pin SOIC package, the DM74LS253MX offers two independent 4-channel multiplexers in a single IC. Each multiplexer selects one of four binary data inputs and routes it to the output, controlled by two select lines and an output enable pin.
Structure and Working Principle
The IC contains two identical 4-to-1 multiplexers with separate data inputs (I0-I3) but common select lines (S0, S1). The truth table follows standard multiplexer logic where the binary value on the select lines determines which input is routed to the output. When the output enable (OE) is active low, the selected input appears at the output in non-inverted form. The 3-state outputs allow multiple devices to be connected to a common bus, with only one enabled at a time. Internal circuitry includes input buffering, selection logic, and output drivers.
Key Features
The DM74LS253MX operates with standard TTL voltage levels (4.75V to 5.25V) and offers typical propagation delays of 15-20ns. The 3-state outputs can be put in high-impedance mode, making them ideal for bus-oriented systems. Key specifications include 8mA output drive capability, 400mV maximum low-level output voltage, and 2.7V minimum high-level output voltage. The device has a maximum power dissipation of 75mW per multiplexer and operates over the industrial temperature range (-40°C to +85°C).
Application Areas
This IC finds extensive use in digital systems requiring data routing, including computer memory systems, data acquisition systems, and communication equipment. Typical applications include bus selection, function generation, and parallel-to-serial conversion. In embedded systems, the DM74LS253MX is often used for peripheral selection or input expansion. Its 3-state outputs make it particularly valuable in bus architectures where multiple devices share common data lines under microprocessor control.
Maintenance and Precautions
When working with the DM74LS253MX, observe standard ESD precautions as with all MOS devices. Use proper grounding when handling and avoid exceeding absolute maximum ratings. For reliable operation, ensure clean power supply decoupling with 0.1μF capacitors near the power pins. Thermal considerations are generally minimal due to low power dissipation, but in high-density PCB layouts, ensure adequate airflow. For unused inputs, follow standard TTL practices - tie them high or low rather than leaving them floating to prevent erratic behavior.
B2B Procurement Guide
When sourcing DM74LS253MX chips, verify the manufacturer (original Fairchild/ON Semiconductor or qualified second sources). Check for RoHS compliance if required for your application. Consider purchasing from authorized distributors to ensure authenticity. For volume purchases (100+ units), prices typically range between $0.50-$1.20 per unit. Lead times vary but are commonly 4-8 weeks for large orders. Verify packaging (tape and reel vs. tube) matches your assembly process requirements. Some suppliers offer programming or testing services for additional quality assurance.