Texas Instruments CD74AC138EG4

Overview

CD74AC138EG4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in PDIP-16 package, operating from 1.5 V to 5.5 V with ±24 mA output drive, balanced propagation delays, and SCR-latchup-resistant CMOS process. It supports high-speed memory decoding and data routing in industrial control and instrumentation systems.

For engineers reviewing the CD74AC138EG4 datasheet, CD74AC138EG4 pinout, CD74AC138EG4 application, or CD74AC138EG4 equivalent, key selection criteria include supply voltage range (1.5–5.5 V), output drive capability (±24 mA), propagation delay at 5 V (2.8–11 ns), enable-input logic configuration (G1 active-high, G2A/G2B active-low), and thermal performance in PDIP package (R_θJA = 67 °C/W).

Technical Context

The CD74AC138EG4 implements positive-logic 3-to-8 decoding with three independent enable inputs (G1, G2A, G2B) that must satisfy G1 = HIGH and G2A = G2B = LOW for output activation. Its Schmitt-trigger inputs provide noise immunity at 30% of V_CC, and outputs are actively driven (not open-drain) with 3-state capability only via enable control-not individual output gating.

Propagation delays are balanced across all eight Y₀–Y₇ outputs and vary with supply voltage: t_PLH/t_PHL = 2.8–10 ns at V_CC = 5 V, 3.9–14 ns at 3.3 V, and 125–138 ns at 1.5 V (all measured at C_L = 50 pF). The device meets MIL-STD-883 ESD rating of ±2000 V (HBM).

Key Specifications

Pinout & Package

CD74AC138EG4 uses a 16-pin plastic dual in-line package (PDIP-N) with body size 19.3 mm × 6.35 mm and overall footprint 19.3 mm × 9.4 mm. Thermal performance is characterized by R_θJA = 67 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74AC138EG4, SN74AC138N offers identical functionality at lower cost but sacrifices extended temperature capability, while 74LV138N trades speed and drive strength for lower quiescent current-making CD74AC138EG4 optimal for high-reliability, wide-temp, high-drive applications.

Availability

CD74AC138EG4 is available at Aetrix Electronics and suitable for industrial control systems, test equipment design, and high-reliability embedded memory subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74AC138EG4 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 over 90 years of innovation in high-reliability components.

The CD74AC138EG4 belongs to TI's Advanced CMOS (AC) logic family, engineered for high-speed memory decoding and data-routing applications demanding short propagation delays and robust noise immunity in harsh environments.

FAQ

What is the maximum operating supply voltage for CD74AC138EG4?

The CD74AC138EG4 supports a maximum supply voltage of 5.5 V, with absolute maximum rating at 6 V. Operation beyond 5.5 V violates recommended conditions and risks parametric degradation or reliability failure. All electrical characteristics-including propagation delay, output drive, and noise immunity-are specified up to 5.5 V.

Does CD74AC138EG4 support 3.3 V logic systems?

Yes, CD74AC138EG4 operates fully within 3.3 V ±0.3 V recommended conditions. At 3.3 V, it delivers t_PLH/t_PHL of 3.9–14 ns and maintains ±24 mA output drive, making it compatible with standard 3.3 V LVTTL and LVCMOS interfaces without level translation.

How many enable inputs does CD74AC138EG4 have, and what are their logic polarities?

CD74AC138EG4 has three enable inputs: G1 (active-high), G2A (active-low), and G2B (active-low). All three must satisfy G1 = HIGH and G2A = G2B = LOW for any Y₀–Y₇ output to activate. This configuration enables flexible hierarchical decoding and cascading with minimal external logic.

What is the thermal resistance (R_θJA) of CD74AC138EG4 in its PDIP package?

The CD74AC138EG4 in PDIP-N package has a junction-to-ambient thermal resistance (R_θJA) of 67 °C/W, as specified in the Thermal Information table. This value assumes standard JEDEC test board conditions and informs heatsinking requirements for continuous operation at maximum ambient temperature.

Is CD74AC138EG4 pin-compatible with other 74AC138 variants like CD74AC138M96?

Yes, CD74AC138EG4 (PDIP-16) shares identical pinout and function mapping with CD74AC138M96 (SOIC-16) and CD74AC138PWR (TSSOP-16). All variants use the same 16-pin layout per Figure 3-1, enabling direct PCB footprint substitution when mechanical constraints permit.