Texas Instruments CD54HCT157F3A

Overview

CD54HCT157F3A from Texas Instruments is a military-grade quad 2-input non-inverting multiplexer in 16-lead CERDIP package, operating from 4.5 V to 5.5 V, with -55°C to +125°C temperature range, active-low enable (E), common select (S), and guaranteed LSTTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2.0 V). It is used in radiation-tolerant avionics data routing where dual-register selection onto shared buses is required.

For engineers reviewing the CD54HCT157F3A datasheet, CD54HCT157F3A pinout, CD54HCT157F3A application, or CD54HCT157F3A equivalent, key selection criteria include its HCT logic family compatibility with legacy TTL systems, CERDIP hermetic packaging for high-reliability environments, propagation delay of 27 ns (max) at 4.5 V/50 pF, and guaranteed operation across full military temperature range without derating.

Technical Context

The CD54HCT157F3A implements four independent 2:1 multiplexers sharing one common select line (S) and one active-low enable input (E). When E is high, all outputs (1Y–4Y) are forced low regardless of S or data inputs - a hard reset behavior critical for deterministic bus initialization in safety-critical control systems.

Each multiplexer channel routes either I0 or I1 to Y based on S state, with no inversion (157 type), unlike the inverting 158 variant. Input loading is specified as 0.95 unit loads per data input and 3 unit loads on S, enabling predictable fanout planning in mixed-logic backplanes.

Key Specifications

Pinout & Package

CD54HCT157F3A uses a 16-lead Ceramic Dual In-line Package (CERDIP, package code J), hermetically sealed for moisture resistance and long-term reliability in harsh environments. Pin 1 is located at top-left corner when notch faces up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2-input multiplexer applications.

Compared with CD74HCT157E, CD54HCT157F3A provides hermetic reliability and identical logic behavior but trades RoHS compliance for MIL-STD-883 qualification; compared with CD54HC157F3A, it sacrifices supply voltage flexibility to guarantee seamless TTL interoperability in legacy avionics upgrades.

Availability

CD54HCT157F3A is available at Aetrix Electronics and suitable for avionics data routing, spacecraft telemetry consolidation, rad-hard microcontroller peripheral switching, and military radio baseband control requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for CD54HCT157F3A 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 and embedded processing technologies, with leadership in high-reliability logic, precision analog, and aerospace-grade components.

The CD54HCT157F3A belongs to TI's military-grade HCT logic family, designed specifically for demanding defense, aerospace, and industrial applications where extended temperature operation, hermetic packaging, and proven reliability are mandatory.

FAQ

What is the maximum propagation delay of CD54HCT157F3A at 4.5 V?

The maximum propagation delay (tPLH/tPHL) for CD54HCT157F3A is 27 ns under conditions of VCC = 4.5 V, CL = 50 pF, and TA = -55°C to +125°C. This value is measured from input transition (S or E or data) to valid output transition and is guaranteed across the full military temperature range - critical for timing closure in synchronous avionics buses.

Is CD54HCT157F3A pin-compatible with CD74HCT157E?

Yes, CD54HCT157F3A and CD74HCT157E share identical pinout, function, and logic behavior. Both are quad 2-input non-inverting multiplexers with common S and active-low E. However, CD54HCT157F3A uses CERDIP packaging for hermetic reliability, while CD74HCT157E uses plastic DIP - making them mechanically interchangeable only if socket or footprint supports both packages.

Does CD54HCT157F3A support 3.3 V operation?

No, CD54HCT157F3A is specified only for 4.5 V to 5.5 V operation. Its HCT input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and internal design require minimum 4.5 V for guaranteed TTL compatibility and correct internal node biasing. Operating below 4.5 V may result in undefined logic states or increased propagation delay beyond specification.

What is the meaning of "F3A" in CD54HCT157F3A?

The "F3A" suffix in CD54HCT157F3A denotes Texas Instruments' military-grade CERDIP package variant with 16 leads, tube packaging (25 units per tube), and qualification per MIL-PRF-38535 Class B. It indicates full QML certification, hermetic sealing, and screening for extended temperature and reliability - distinguishing it from commercial "E" (PDIP) or "M" (SOIC) variants.

Can CD54HCT157F3A be used as a function generator?

Yes, CD54HCT157F3A can implement basic combinational logic functions such as AND, OR, XOR, and inverters by fixing certain inputs (I0/I1) to VCC or GND and using S and E as function-select controls. Its truth table and non-inverting architecture allow direct mapping of 2-input Boolean operations - a documented use case in TI's application guidance for logic-based control circuits.