Texas Instruments CY54FCT138TLMB

Overview

CY54FCT138TLMB from Texas Instruments is a military-grade 1-of-8 active-low decoder IC with three binary address inputs (A0–A2), three enable inputs (E1, E2 low-active; E3 high-active), and eight mutually exclusive outputs (O0–O7). It delivers 32-mA sink / 12-mA source drive, operates from –55°C to +125°C, and supports partial-power-down via Ioff. It is used in aerospace data routing, avionics bus decoding, and high-reliability control logic expansion.

For engineers reviewing the CY54FCT138TLMB datasheet, CY54FCT138TLMB pinout, CY54FCT138TLMB application, or CY54FCT138TLMB equivalent, key selection factors include its LCCC-20 package, MIL-PRF-38535 compliance, 12 ns max propagation delay, Ioff-enabled power-down isolation, and compatibility with TTL-level inputs/outputs in harsh-environment systems.

Technical Context

The CY54FCT138TLMB implements combinational logic decoding with dual low-enable (E1, E2) and single high-enable (E3) control, enabling cascaded 1-of-32 expansion using four devices and one inverter. Its output structure is totem-pole with active-low assertion and no internal pull-ups.

It features edge-rate control circuitry for reduced switching noise, matched rise/fall times, and JESD22-certified ESD protection (2000-V HBM, 200-V MM, 1000-V CDM). The Ioff specification ensures outputs are high-impedance when VCC = 0 V, preventing backflow during partial power-down.

Key Specifications

Pinout & Package

LCCC-20 (FK) ceramic leadless chip carrier package with 20 terminals, hermetically sealed, suitable for high-reliability and high-temperature environments. Pin 1 orientation marked by corner notch per MIL-STD-883.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-of-8 decoder applications.

Compared with CY74FCT138TDMB and SN74F138N, the CY54FCT138TLMB uniquely combines military temperature range, MIL-PRF-38535 qualification, Ioff, and edge-rate control - making it the sole choice for new aerospace and defense designs requiring guaranteed reliability under thermal stress and partial power-down.

Availability

CY54FCT138TLMB is available at Aetrix Electronics and suitable for aerospace data routing, avionics bus decoding, and high-reliability control logic expansion requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CY54FCT138TLMB 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 industrial, automotive, and defense markets.

The CY54FCT series is designed for military and aerospace applications demanding extended temperature operation, radiation tolerance, and MIL-PRF-38535 qualification - delivering robust 5-V logic performance in mission-critical systems.

FAQ

What is the maximum propagation delay of the CY54FCT138TLMB?

The CY54FCT138TLMB has a maximum propagation delay of 12 ns for any input-to-output path (A→O or E→O) over its full operating temperature range of –55°C to +125°C. This value is specified under worst-case conditions (VCC = 4.5 V, TA = 125°C) and ensures timing predictability in high-speed control logic applications where deterministic decode latency is essential.

Does the CY54FCT138TLMB support partial-power-down operation?

Yes, the CY54FCT138TLMB supports partial-power-down operation via its Ioff feature. When VCC = 0 V, the outputs are disabled with leakage current limited to ±1 µA, preventing damaging current backflow into powered sections of the system. This capability is explicitly verified per MIL-PRF-38535 and is critical for hot-swap architectures and fault-isolated subsystems in aerospace platforms.

What package type is used for the CY54FCT138TLMB?

The CY54FCT138TLMB uses a 20-terminal LCCC (Leadless Chip Carrier) package designated FK, with hermetic ceramic construction. It is supplied in tubes of 55 units and is compliant with MIL-STD-883 for mechanical and environmental robustness - making it suitable for high-vibration, high-temperature, and vacuum environments typical in space and defense systems.

Is the CY54FCT138TLMB compatible with standard TTL logic levels?

Yes, the CY54FCT138TLMB is fully compatible with standard TTL input and output logic levels. Its VIH threshold is 2 V minimum and VIL is 0.8 V maximum, matching legacy TTL families. Output VOH is ≥2.4 V at –12 mA and VOL is ≤0.55 V at 32 mA, ensuring reliable interfacing with 5-V TTL, LS-TTL, and other FCT-series devices without level translation.

How many enable inputs does the CY54FCT138TLMB have, and what are their polarities?

The CY54FCT138TLMB has three enable inputs: E1 and E2 are active-low, and E3 is active-high. All three must be satisfied (E1 = L, E2 = L, E3 = H) for decoding to occur. This triple-enable architecture enables flexible hierarchical expansion - for example, cascading four CY54FCT138TLMB units with one inverter achieves 1-of-32 decoding with no additional logic gates.