Texas Instruments 74AC11257N

Overview

74AC11257N from Texas Instruments is a quadruple 2-line-to-1-line data selector/multiplexer with 3-state outputs in a 20-pin PDIP package. It supports bus interface applications with ±24 mA output drive at 5 V, 8.9 ns max propagation delay (VCC = 3.3 V), and operates across −40°C to 85°C. Its flow-through pinout and center-pin VCC/GND reduce switching noise in high-speed digital systems.

For engineers reviewing the 74AC11257N datasheet, 74AC11257N pinout, 74AC11257N application, or 74AC11257N equivalent, key selection criteria include 3-state bus compatibility, AC-series speed-power tradeoff, PDIP through-hole mounting, and logic-level translation capability between 3 V and 5 V domains.

Technical Context

This device implements four independent 2:1 multiplexers sharing a common output-enable (OE) control input. Each channel selects between A or B inputs based on the A/B select line, driving its dedicated Y output with 3-state capability.

It uses advanced CMOS AC technology for improved speed over standard TTL, with 500-mA latch-up immunity at 125°C and absolute maximum ratings up to 7 V supply. The center-aligned VCC and GND pins minimize ground bounce and power-supply noise during simultaneous switching.

Key Specifications

Pinout & Package

74AC11257N is housed in a 20-pin plastic dual in-line package (PDIP-N) with 0.3-inch body width and through-hole mounting. Pin 1 is located at the top-left corner adjacent to the notch, with VCC (pin 10) and GND (pins 5, 6, 7, 8) centrally positioned to suppress simultaneous switching noise.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar data selector/multiplexer applications.

Compared with 74AC11257N, the 74ACT11257N delivers tighter timing margins at identical voltage and drive levels, while SN74LV138APWR serves a fundamentally different logic function and cannot substitute without circuit redesign.

Availability

74AC11257N is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy bus arbitration, and test equipment signal routing requiring stable component supply and long-term obsolescence management.

Supply support for 74AC11257N 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial and automotive qualification.

The 74AC logic family was designed for high-speed, low-power digital systems requiring TTL-compatible interfaces with CMOS efficiency, targeting industrial control, instrumentation, and communications infrastructure.

FAQ

What is the recommended pull-up resistor value for OE on the 74AC11257N?

The OE pin should be tied to VCC through a pull-up resistor to ensure high-impedance state during power-up or power-down. Minimum resistor value depends on the current-sinking capability of the driver; TI recommends ≥10 kΩ for typical 5 V systems, balancing noise immunity and rise time. For 3.3 V operation, 4.7 kΩ is commonly used to maintain adequate noise margin while limiting quiescent current.

Does the 74AC11257N support mixed-voltage operation between 3.3 V and 5 V logic domains?

Yes, the 74AC11257N supports mixed-voltage operation: it accepts 3.3 V or 5 V inputs across its full VIH/VIL range and drives outputs to full rail at either supply voltage. When powered at 5 V, it correctly interprets 3.3 V logic-high inputs (VIH = 3.15 V min), enabling seamless interface between 3.3 V microcontrollers and 5 V peripherals without level shifters.

How does the center-pin VCC/GND configuration in the 74AC11257N improve noise performance?

The center-pin VCC (pin 10) and quad-GND (pins 5–8) placement reduces high-frequency ground loop inductance and equalizes power distribution across all four multiplexer sections. This configuration lowers simultaneous switching output (SSO) noise by up to 30% versus edge-fed DIP packages, improving signal integrity in bus-oriented systems operating above 20 MHz.

Can unused inputs on the 74AC11257N be left floating?

No, all unused inputs must be held at a defined logic level-either VCC or GND-to prevent oscillation, excessive current draw, or unpredictable output states. TI's application report SCBA004 explicitly warns that floating CMOS inputs cause increased power consumption and potential device malfunction; tie-off resistors (e.g., 10 kΩ to VCC or GND) are required for any unconnected A/B, OE, or data inputs.

What is the maximum clock rate supported by the 74AC11257N in a synchronous bus application?

The 74AC11257N supports reliable operation in synchronous bus applications up to approximately 100 MHz, based on its worst-case propagation delay of 7.9 ns (tPHL at VCC = 5 V, TA = 85°C) and 3-state enable/disable times under 8 ns. System-level timing must account for PCB trace delays and setup/hold margins, but the device itself meets timing budgets for 10 ns cycle-time buses in industrial control systems.