Texas Instruments 74AC11138NSR

Overview

74AC11138NSR from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in SOP-16 package, featuring active-high G1 and active-low G2A/G2B enables, propagation delays as low as 5.7 ns at 5 V, and operation across –40°C to 85°C. It serves high-speed memory decoding and data routing in industrial control backplanes and FPGA I/O expansion systems.

For engineers reviewing the 74AC11138NSR datasheet, 74AC11138NSR pinout, 74AC11138NSR application, or 74AC11138NSR equivalent, key selection criteria include enable-input logic configuration (G1 high-active, G2A/G2B low-active), worst-case tPHL/tPLH timing at 3.3 V and 5 V, output drive capability (±24 mA at 5.5 V), latch-up immunity (500 mA at 125 °C), and SOP-16 thermal resistance (RθJA = 50 °C/W).

Technical Context

The 74AC11138NSR implements a positive-logic 3-to-8 decoder with three independent enable inputs-G1 (active-high), G2A and G2B (both active-low)-enabling cascaded decoding without external inverters. Its EPIC™ 1-µm CMOS process ensures stable operation under fast switching transients.

Functional mode selection follows a strict truth table where all three enables must be asserted (G1 = H, G2A = L, G2B = L) for any Y0–Y7 output to activate low; otherwise all outputs remain high. Input transition rate is limited to 10 ns/V to maintain timing integrity.

Key Specifications

Pinout & Package

SOP-16 (NS) package: 10.2 mm × 7.8 mm body size, 2.00 mm max height, 1.27 mm lead pitch, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with SN74HC138DR and 74ACT138SCX, the 74AC11138NSR delivers the fastest propagation, highest output drive, and lowest power-delay product in the SOP-16 form factor-making it optimal for timing-critical industrial and computing infrastructure designs where both speed and robustness are mandatory.

Availability

74AC11138NSR is available at Aetrix Electronics and suitable for industrial control backplanes, FPGA I/O expansion, memory address decoding, and test equipment signal switching requiring stable component supply and long-term lifecycle support.

Supply support for 74AC11138NSR 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 specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The 74AC logic family was engineered for high-speed, low-noise digital signal routing in memory subsystems and programmable logic interfaces-prioritizing propagation delay consistency, enable flexibility, and latch-up resilience.

FAQ

What is the maximum operating frequency supported by the 74AC11138NSR?

The 74AC11138NSR does not specify a maximum clock frequency because it is a combinational logic device-not a clocked sequential circuit. Its usable switching rate is determined by propagation delay and system-level timing margins. With tPLH/tPHL ≤ 5.7 ns at 5 V, the 74AC11138NSR supports effective decode rates exceeding 100 MHz in well-designed PCB layouts with controlled impedance and proper decoupling. Actual system frequency depends on fanout, trace length, and load capacitance.

Can the 74AC11138NSR be used as a demultiplexer?

Yes, the 74AC11138NSR can function as a 1-to-8 demultiplexer. When the three select inputs (A, B, C) are used as address lines and one enable input (e.g., G1) is driven by the data signal, the selected Yx output mirrors the data state while all others remain high. This behavior is explicitly confirmed in the device functional modes section of the TI datasheet, where G1 is described as usable "as a data input for demultiplexing applications." The 74AC11138NSR maintains full timing and drive specifications in this mode.

Does the 74AC11138NSR support mixed-voltage operation (e.g., 3.3 V inputs with 5 V VCC)?

No, the 74AC11138NSR does not support true mixed-voltage operation. Its absolute maximum input voltage is VCC + 0.5 V, and recommended VIH/VIL thresholds scale with VCC. Driving 3.3 V logic inputs into a 5 V-powered 74AC11138NSR violates the VIH specification (requires ≥3.85 V at VCC = 5.5 V) and risks unreliable switching or increased static current. For level translation, use dedicated translators or select a device with TTL-compatible inputs like the 74ACT138SCX.

What is the thermal resistance (RθJA) of the 74AC11138NSR in its SOP-16 (NS) package?

The 74AC11138NSR in SOP-16 (NS) package has a junction-to-ambient thermal resistance (RθJA) of 50 °C/W, as specified in Section 4.3 of the TI datasheet. This value assumes standard JEDEC 2-layer board conditions (1-inch² copper pad, 2 oz Cu). Actual board-level RθJA will vary based on PCB layout, copper area, airflow, and nearby heat sources. For thermal design, use this value with the device's typical power dissipation (ICC × VCC ≈ 22 µA × 5 V = 0.11 mW) to estimate junction temperature rise.

Is the 74AC11138NSR pin-compatible with other 74AC138 variants?

Yes, the 74AC11138NSR is functionally and pinout-compatible with all industry-standard 74AC138-family decoders in SOP-16 (NS), SOIC-16 (D), and TSSOP-16 (PW) packages-including SN74AC138N, 74AC138DR, and 74AC138PWR. Pin numbering, signal names (Y0–Y7, A–C, G1, G2A, G2B, VCC, GND), and electrical behavior match identically. The "11" prefix denotes TI's internal part numbering convention and does not indicate functional deviation from the 74AC138 standard.