Texas Instruments CD74AC251M96

Overview

CD74AC251M96 from Texas Instruments is an 8-input, three-state CMOS multiplexer with true (Y) and complement (Y̅) outputs, 16-pin SOIC package, ±24mA output drive, 3.5ns typical propagation delay at 5V/25°C, and 1.5V–5.5V supply operation - used in digital signal routing for test equipment and industrial control logic.

For engineers reviewing the CD74AC251M96 datasheet, CD74AC251M96 pinout, CD74AC251M96 application, or CD74AC251M96 equivalent, this page delivers verified functional modes, switching characteristics across -55°C to +125°C, ESD immunity (2kV), and precise truth-table behavior for deterministic select-to-output timing in high-reliability systems.

Technical Context

The CD74AC251M96 implements a single 8:1 data selector using Harris Advanced CMOS logic, where address inputs S2–S0 determine which of eight data inputs (I0–I7) routes to both Y and Y̅ outputs when OE is low; all outputs enter high-impedance state when OE is high. It supports dual-rail logic-level compatibility across its full 1.5V–5.5V VCC range.

Propagation delays are balanced between true and complement paths, with worst-case tPLH/tPHL of 13.5ns (5V, -55°C to +125°C) for data-to-Y and 18.2ns for select-to-Y. Output enable/disable transitions exhibit 12.3ns typical delay, enabling synchronized bus isolation in multi-device systems.

Key Specifications

Pinout & Package

CD74AC251M96 is housed in a 16-pin SOIC (D) package measuring 9.9mm × 6mm (including pins), with body size 9.9mm × 3.9mm. Pin 1 orientation follows Q1 quadrant per tape-and-reel specification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AC251N and CD74HC251M96, CD74AC251M96 uniquely balances high-speed routing (3.5ns), robust drive capability (±24mA), and industrial temperature support (-55°C to +125°C) in a surface-mount SOIC package optimized for automated assembly and thermal performance.

Availability

CD74AC251M96 is available at Aetrix Electronics and suitable for automated test equipment, industrial PLC I/O modules, and legacy system interface adapters requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for CD74AC251M96 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 specializing in analog, embedded processing, and logic solutions, with decades of expertise in high-reliability CMOS design and industrial-grade qualification.

The CD74AC251M96 belongs to TI's Advanced CMOS (AC) logic family, engineered for high-speed, low-power digital signal routing in demanding industrial, test, and control applications where timing precision and voltage flexibility are critical.

FAQ

What is the maximum operating frequency supported by CD74AC251M96?

The CD74AC251M96 does not specify a maximum clock or data rate in its datasheet. Its usable frequency depends on propagation delay and system setup/hold timing. With a worst-case tPLH/tPHL of 13.5ns (5V, -55°C to +125°C), it supports reliable operation up to approximately 37MHz in simple combinational routing paths - assuming adequate board layout and load capacitance ≤50pF. For synchronous applications, full timing analysis including select-input stability must be performed using TI's published switching characteristics tables.

Does CD74AC251M96 support 1.8V logic levels?

Yes, CD74AC251M96 supports 1.8V operation within its specified 1.5V–5.5V VCC range. At VCC = 1.8V, VIH is guaranteed ≥1.2V and VIL ≤0.3V per electrical characteristics, delivering ~0.6V noise margin. Input thresholds scale with supply voltage, and output VOH/VOL remain compatible with standard 1.8V CMOS receivers. Propagation delay increases to 153ns (typical) at 1.5V, so timing margins must be verified for 1.8V designs.

Can CD74AC251M96 replace the older CD74ACT251?

No, CD74AC251M96 is not a direct replacement for CD74ACT251. The ACT version uses different input threshold specifications (TTL-compatible VIH/VIL), has faster propagation delays (~3ns typical at 5V), and operates only from 4.5V to 5.5V. CD74AC251M96 uses CMOS-compatible thresholds, supports 1.5V–5.5V, and trades some speed for broader voltage flexibility and lower power. Functional substitution requires redesigning input drive levels and verifying timing closure across the new VCC range.

What is the purpose of the Y̅ (complement) output on CD74AC251M96?

The Y̅ output on CD74AC251M96 provides the logical inverse of the selected input signal with matched propagation delay and drive strength to the Y output. This eliminates the need for external inverters in applications requiring both polarities - such as differential line drivers, XOR-based parity generation, or zero-crossing detectors. Both outputs transition simultaneously and enter high-impedance together when OE is HIGH, preserving signal integrity during bus sharing.

Is CD74AC251M96 pin-compatible with the 74LS251?

No, CD74AC251M96 is not pin-compatible with the 74LS251. While both are 16-pin 8:1 multiplexers with true/complement outputs and OE control, their pin assignments differ: 74LS251 places Y on pin 5 and Y̅ on pin 6 (same as CD74AC251M96), but assigns S0/S1/S2 to pins 3/2/1 - whereas CD74AC251M96 places S0/S1/S2 on pins 11/10/9. Direct replacement would require PCB layout revision. Functional equivalence exists, but mechanical compatibility does not.