Texas Instruments CD54HC138F

Overview

CD54HC138F from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with active-low outputs, designed for memory address decoding and I/O port selection in military-grade embedded systems. It operates across -55°C to +125°C, supports 2 V to 6 V supply, features three enable inputs (E1, E2, E3), and delivers 13 ns typical propagation delay at 5 V with 15 pF load.

For engineers reviewing the CD54HC138F datasheet, CD54HC138F pinout, CD54HC138F application, or CD54HC138F equivalent, this page provides verified functional specifications, CERDIP package details, truth table behavior, thermal derating guidance, and validated drop-in alternatives for high-reliability aerospace and defense designs.

Technical Context

The CD54HC138F implements a fully decoded 3-bit binary input (A0–A2) to eight independent active-low output lines (Y0–Y7), with three enable terminals (E1, E2 active-low; E3 active-high) enabling hierarchical cascading without external logic. Its silicon-gate CMOS architecture ensures rail-to-rail output swing and low static current.

It uses standard HC logic thresholds (VIH = 3.15 V min, VIL = 1.35 V max at VCC = 4.5 V), exhibits balanced tPLH/tPHL propagation delays, and maintains fanout of 10 LSTTL loads over full temperature range - critical for deterministic timing in avionics bus arbitration and sensor multiplexing.

Key Specifications

Pinout & Package

CD54HC138F is supplied in a 16-lead Ceramic Dual In-line Package (CERDIP), hermetically sealed for moisture resistance and long-term reliability in harsh environments. Package drawing J per JEDEC MS-012, 0.300-inch wide body, 0.100-inch lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC138M, CD54HC138F offers guaranteed operation at -55°C and hermetic sealing for mission-critical deployments; compared with CD54HCT138F, it provides superior noise immunity and wider VCC tolerance but requires CMOS-compatible input drivers.

Availability

CD54HC138F is available at Aetrix Electronics and suitable for avionics data bus arbitration, secure bootloader memory mapping, and tactical radio frequency channel switching requiring stable component supply across extended temperature extremes and long production lifecycles.

Supply support for CD54HC138F 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 high-reliability logic solutions for aerospace, defense, and industrial markets.

CD54HC138F belongs to TI's military-grade HC logic family, engineered for deterministic timing, radiation-tolerant operation, and long-term stability in mission-critical systems where failure is not an option.

FAQ

What is the maximum clock frequency supported by CD54HC138F for reliable address decoding?

The CD54HC138F does not operate on a clock signal - it is a combinational logic device. Its usable frequency limit is determined by propagation delay: with 13 ns typical tPD at 5 V, it supports address transitions up to approximately 38 MHz for clean setup/hold timing. For CD54HC138F deployed in synchronous systems, ensure address valid time exceeds tPD + board trace delay + receiver setup time.

Can CD54HC138F drive standard TTL loads directly without buffer stages?

Yes, CD54HC138F can drive up to 10 LSTTL loads per output across its full -55°C to +125°C range, as confirmed in the datasheet's fanout specification. This capability eliminates need for 74LS244 buffers in most military I/O expansion designs, reducing component count and board area while maintaining signal integrity.

Is CD54HC138F pin-compatible with CD54HCT138F?

Yes, CD54HC138F and CD54HCT138F share identical pinout, package (16-lead CERDIP), and functional behavior. The only difference is input threshold compatibility: CD54HC138F requires CMOS-level inputs (VIH ≥ 3.15 V at 4.5 V), while CD54HCT138F accepts TTL-level inputs (VIH ≥ 2 V). Both drive identical active-low outputs.

What is the recommended decoupling strategy for CD54HC138F in high-reliability PCB layouts?

Place a 0.1 µF X7R ceramic capacitor between pins 7 (GND) and 16 (VCC), with pad-to-pad distance ≤5 mm and vias placed within 2 mm of each pin. Add a second 4.7 µF tantalum capacitor per power domain for bulk filtering. Avoid shared return paths with switching regulators to prevent ground bounce-induced false decoding.

Does CD54HC138F support hot-swap or live-insertion in backplane applications?

No, CD54HC138F is not hot-swap rated. Its absolute maximum ratings specify no intentional biasing of inputs or outputs before VCC reaches stable regulation. For backplane applications, implement power-sequencing controllers or use TI's SN65LVDS31-based hot-swap interface ICs upstream of CD54HC138F to prevent latch-up or EOS damage during insertion.