Texas Instruments SN74ALS253D

Overview

SN74ALS253D from Texas Instruments is a dual 4-line to 1-line data selector/multiplexer with independent 3-state outputs, designed for bus-organized digital systems. It features two independent 4-input sections (1C0–1C3 and 2C0–2C3), separate output-enable (1OE/2OE) controls per section, and operates over 0°C to 70°C at VCC = 4.5 V to 5.5 V. It enables parallel-to-serial conversion and multiplexing in TTL-compatible logic designs.

For engineers reviewing the SN74ALS253D datasheet, SN74ALS253D pinout, SN74ALS253D application, or SN74ALS253D equivalent, this device is selected for high-drive bus interfacing, discrete logic routing, and legacy system upgrades requiring ALS-family speed-power tradeoffs and true 3-state isolation.

Technical Context

The SN74ALS253D implements two independent 4:1 multiplexer sections sharing common select inputs A and B, each with dedicated output-enable (1OE, 2OE) and 3-state output (1Y, 2Y). Its internal architecture uses binary-decoded AND-OR logic with inverters and drivers to route one of four data inputs per section to the respective output.

Each section supports full TTL-level compatibility: VIH = 2 V min, VIL = 0.8 V max, VOH = 2.4 V min at IOL = 12 mA, VOL = 0.4 V max, and provides 24 mA low-level drive capability. Propagation delays are as low as 2 ns (data-to-Y) and 5 ns (select-to-Y), with enable/disable times down to 2 ns (tPHZ/tPLZ).

Key Specifications

Pinout & Package

SN74ALS253D is housed in a 16-pin plastic small-outline integrated circuit (SOIC) package (D), measuring 9.9 mm × 3.91 mm × 1.75 mm, with 1.27 mm pitch and RoHS-compliant NiPdAu lead finish (Level-1 moisture sensitivity).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual 4:1 multiplexer applications.

Compared with SN74ALS253D, SN74AS253AD trades power efficiency for speed and drive strength, while SN74LS253N sacrifices performance for broader voltage tolerance and legacy footprint compatibility-neither is pin-compatible without layout revision due to differing thermal and electrical characteristics.

Availability

SN74ALS253D is available at Aetrix Electronics and suitable for industrial PLC expansion, legacy microprocessor bus demultiplexing, and automotive diagnostic interface design requiring stable component supply and long-term obsolescence management.

Supply support for SN74ALS253D includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74ALS253D belongs to TI's Advanced Low-Power Schottky (ALS) logic family, engineered for optimal balance of speed (vs. LS) and power (vs. AS) in commercial-grade digital systems.

FAQ

What is the maximum clock frequency supported by SN74ALS253D in a multiplexed data path?

The SN74ALS253D does not operate on a clock signal-it is a combinational logic device. Its usable data rate is determined by propagation delay and system timing margins. With tPLH/tPHL ≤ 3 ns (data-to-Y) and tPZH/tPHZ ≤ 3 ns (enable-to-output), it supports reliable operation in synchronous systems up to ~100 MHz when used with appropriate setup/hold timing. The SN74ALS253D must be evaluated in context of the full signal path, including driver strength and load capacitance.

Can SN74ALS253D drive a 50-pF bus load while maintaining TTL logic levels?

Yes. Per the datasheet, SN74ALS253D guarantees VOL ≤ 0.4 V at IOL = 12 mA and CL = 50 pF, and VOH ≥ 2.4 V at IOH = −2.6 mA under the same conditions. These parameters were measured with exactly 50 pF load capacitance and 500 Ω source impedance, confirming direct compatibility with standard TTL bus loading requirements. The SN74ALS253D meets specification across its full operating temperature range (0°C to 70°C).

Is SN74ALS253D pin-compatible with SN74LS253 or SN74AS253A?

No. While all three devices share the same 16-pin SOIC (D) package outline and identical pin numbering (per TI logic symbol and top-view diagrams), their electrical behaviors differ significantly: SN74LS253 has slower timing and lower drive, SN74AS253A draws more current and has tighter VIH/VIL thresholds. Substitution requires verification of timing closure, noise margin, and power delivery-none are drop-in replacements. The SN74ALS253D must be validated independently in the target design.

Does SN74ALS253D support hot-swap or live-insertion into a powered bus?

No. The SN74ALS253D is not designed for hot-swap operation. Its absolute maximum ratings specify VI ≤ 7 V and disabled output voltage ≤ 5.5 V, but it lacks bus-fault protection, current-limiting circuitry, or controlled slew-rate outputs. Applying signal or supply voltage before VCC stabilization may cause latch-up or parametric shift. Always power-cycle the SN74ALS253D with system rails-never insert it into an active bus.

What is the function of the NC pins on SN74ALS253D?

The SN74ALS253D has no NC (no-connect) pins in the SOIC-16 (D) package. All 16 pins are assigned functional roles as defined in the datasheet: pins 1–16 correspond to 1OE, 1C0–1C3, 1Y, GND, 2C0–2C3, 2Y, 2OE, A, B, and VCC. Any reference to NC pins applies only to ceramic packages (e.g., FK, J) and does not apply to the SN74ALS253D variant. Every pin on the SN74ALS253D serves a defined logic or power function.