Texas Instruments 74AC11138N

Overview

74AC11138N from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in a 16-pin PDIP package, designed for high-speed memory decoding and data routing. It features three enable inputs (G1 active-high, G2A/G2B active-low), propagation delays as low as 5.1 ns at 5 V, and operates across –40°C to 85°C. It is used in memory address decoding subsystems where minimal signal delay and cascading flexibility are critical.

For engineers reviewing the 74AC11138N datasheet, 74AC11138N pinout, 74AC11138N application, or 74AC11138N equivalent, this page delivers verified functional modes, switching characteristics at 3.3 V and 5 V, thermal metrics, and real-world implementation guidance for memory systems and demultiplexing circuits.

Technical Context

The 74AC11138N implements positive-logic decoding with binary-select inputs A, B, C and three independent enables (G1, G2A, G2B) enabling flexible cascading without external inverters. Its EPIC™ 1-µm CMOS process ensures latch-up immunity of 500 mA at 125 °C and supports both memory-decoding and demultiplexing roles via enable-as-data-input capability.

It delivers sub-8 ns propagation delays (tPLH/tPHL) across all input-to-output paths at 5 V, with output drive strength of ±24 mA at VCC = 4.5–5.5 V and input transition rate tolerance up to 10 ns/V - confirming suitability for high-speed synchronous bus interfaces and address expansion in embedded controllers.

Key Specifications

Pinout & Package

74AC11138N uses a standard 16-pin plastic dual in-line package (PDIP, N), 19.3 mm × 9.4 mm body size, with center-pin VCC (pin 12) and GND (pin 4) configuration to minimize high-speed switching noise.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar decoder/demultiplexer applications.

Compared with 74ACT138N and SN74LS138N, the 74AC11138N provides optimal balance of speed (5.1 ns), low static current (4 µA), and 3–5.5 V supply flexibility - making it the preferred choice for new industrial and embedded designs requiring both performance and power efficiency.

Availability

74AC11138N is available at Aetrix Electronics and suitable for memory address decoding, bus demultiplexing, industrial I/O expansion, and FPGA configuration support requiring stable component supply and long-term industrial temperature qualification.

Supply support for 74AC11138N 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 experience in high-reliability industrial and automotive IC design.

The 74AC11138N belongs to TI's advanced CMOS logic family, engineered specifically for high-speed memory decoding and data-routing applications demanding minimal propagation delay and robust noise immunity.

FAQ

What is the maximum operating frequency supported by the 74AC11138N?

The 74AC11138N does not specify a maximum clock frequency because it is a combinational logic device without an internal clock. Its usable switching rate is determined by propagation delay (as low as 5.1 ns at 5 V) and input transition rate (up to 10 ns/V). In practice, it reliably supports address strobe rates exceeding 100 MHz in memory subsystems when paired with compatible drivers and loads.

Can the 74AC11138N operate at 3.3 V supply voltage?

Yes, the 74AC11138N is fully specified for operation at 3.3 V (±0.3 V), with guaranteed switching characteristics including tPLH/tPHL down to 8.3 ns and output drive of ±12 mA. Its VIH/VIL thresholds scale with VCC, ensuring reliable interfacing with 3.3 V microcontrollers and FPGAs without level-shifting circuitry.

How does the enable-input architecture of the 74AC11138N simplify cascading?

The 74AC11138N uses two active-low enables (G2A, G2B) and one active-high enable (G1), allowing direct connection of Y outputs from a master decoder to G2A/G2B inputs of slave devices. This eliminates external inverters for 24-line decoding and requires only one inverter for 32-line expansion - reducing component count and propagation delay in multi-stage decode trees.

Is the 74AC11138N pin-compatible with the standard 74LS138?

Yes, the 74AC11138N shares identical pinout, terminal numbering, and functional truth table with the 74LS138 and 74HC138. However, differences in electrical characteristics - such as input thresholds, output drive, and propagation delay - require validation of timing margins and voltage compatibility in the target system before substitution.

What thermal considerations apply to the 74AC11138N in continuous operation?

The 74AC11138N in PDIP package has a junction-to-ambient thermal resistance (RθJA) of 110 °C/W. At maximum recommended ambient temperature (85 °C) and worst-case ICC (40 µA) plus dynamic power, junction temperature remains well within safe limits. No heatsink is required, but proper PCB copper pour on VCC/GND pads improves thermal dissipation in high-density layouts.