Texas Instruments SN74HC251DE4

Overview

SN74HC251DE4 from Texas Instruments is an 8-to-1 data selector/multiplexer with complementary 3-state outputs, full binary decoding, and strobe-controlled enable logic. It operates from 2 V to 6 V, delivers ±6 mA output drive at 5 V, and achieves typical propagation delay of 9 ns - enabling reliable parallel-to-serial conversion in bus-interfaced digital systems.

For engineers reviewing the SN74HC251DE4 datasheet, SN74HC251DE4 pinout, SN74HC251DE4 application, or SN74HC251DE4 equivalent, this device serves as a drop-in functional replacement for 'HC151-based designs requiring true/inverted outputs, high-current 3-state bus driving, and low-power CMOS logic-level selection across industrial control, test equipment, and data routing subsystems.

Technical Context

The SN74HC251DE4 implements full 3-bit binary decoding (A/B/C inputs) to select one of eight data inputs (D0–D7), routing it to complementary outputs Y (true) and W (inverted). Its 3-state outputs are jointly controlled by the active-low Output Enable (OE) input, allowing direct connection to shared data buses without contention.

It features CMOS-compatible input thresholds (VIH = 3.15 V, VIL = 1.35 V at VCC = 4.5 V), low input current (≤1 μA), and robust switching performance: tpd = 41 ns (typical, CL = 50 pF, VCC = 4.5 V), with guaranteed operation across −40°C to +85°C.

Key Specifications

Pinout & Package

SN74HC251DE4 is packaged in a 16-pin SOIC (D package) with nominal body size 9.90 mm × 3.90 mm and standard 1.27 mm pitch. Pin numbering follows JEDEC MS-012, with Pin 1 located at the index corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-to-1 multiplexer applications.

Compared with SN74HC151N and CD74HC251E, the SN74HC251DE4 uniquely delivers true/inverted outputs in a single package while maintaining industry-standard SOIC-16 footprint and 5 V bus compatibility - simplifying designs requiring dual-polarity routing without added components or layout changes.

Availability

SN74HC251DE4 is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, digital test equipment signal routing, legacy bus interface logic, and microcontroller peripheral multiplexing requiring stable component supply and long-term production continuity.

Supply support for SN74HC251DE4 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and consumer applications.

The SN74HC251DE4 belongs to TI's 74HC logic family, designed for high-speed, low-power CMOS data routing in bus-oriented systems where 3-state control, complementary outputs, and wide voltage operation are critical.

FAQ

What is the operating voltage range for SN74HC251DE4?

The SN74HC251DE4 operates over a supply voltage range of 2 V to 6 V. This allows direct interface with both 3.3 V and 5 V logic families without level shifters. At VCC = 4.5 V, input thresholds are VIH = 3.15 V and VIL = 1.35 V, ensuring robust noise margins in mixed-voltage systems. The SN74HC251DE4 maintains specified timing and drive performance across this full range.

Does SN74HC251DE4 provide both true and inverted outputs?

Yes, the SN74HC251DE4 provides complementary outputs: Y (true) and W (inverted), both controlled by the same active-low Output Enable (OE) input. When OE is low, Y reflects the selected Dn input and W presents its logical inverse. This eliminates the need for external inverters in applications requiring dual-polarity signals, such as differential bus drivers or latch control circuits using SN74HC251DE4.

What is the maximum output drive capability of SN74HC251DE4?

The SN74HC251DE4 delivers ±6 mA output current at VCC = 5 V, sufficient to drive up to 15 LSTTL loads directly. This high-current 3-state output design enables direct connection to shared data buses without intermediate buffers. The SN74HC251DE4 maintains this drive strength across its full operating temperature range (−40°C to +85°C), supporting reliable bus arbitration in industrial environments.

How does the Output Enable (OE) pin function on SN74HC251DE4?

The OE pin on SN74HC251DE4 is an active-low strobe that simultaneously places both Y and W outputs into high-impedance (3-state) mode when asserted high. When OE is low, outputs are enabled and reflect the selected data input. This shared control simplifies bus arbitration logic and ensures glitch-free transitions - critical when multiple SN74HC251DE4 devices share a common data line in modular systems.

Is SN74HC251DE4 pin-compatible with other 74HC-series multiplexers?

SN74HC251DE4 is pin-compatible with SN74HC151 in the same SOIC-16 package, sharing identical pin assignments for address inputs (A/B/C), data inputs (D0–D7), OE, GND, VCC, Y, and NC. However, SN74HC251DE4 adds the W (inverted) output on Pin 14, whereas SN74HC151 leaves that pin unconnected. This makes SN74HC251DE4 a functional superset - usable as a drop-in replacement when W is unused, or as an upgrade when complementary outputs are needed.