Texas Instruments CD74HCT154E

Overview

CD74HCT154E from Texas Instruments is a 4-to-16-line decoder/demultiplexer with dual enable inputs (E1, E2), operating at 4.5V–5.5V, delivering 35ns typical propagation delay (CL = 50pF, TA = 25°C), 15 LSTTL fanout, and -55°C to +125°C operation - used in address decoding for memory expansion and I/O port selection in industrial control systems.

For engineers reviewing the CD74HCT154E datasheet, CD74HCT154E pinout, CD74HCT154E application, or CD74HCT154E equivalent, key selection criteria include LSTTL-compatible input thresholds (VIL ≤ 0.8V, VIH ≥ 2.0V), active-low output logic (Y0–Y15 high-true when enabled), dual-enable cascading capability, and PDIP-24 package compatibility with legacy through-hole PCB layouts.

Technical Context

The CD74HCT154E implements combinational logic decoding using standard CMOS process with TTL-level input stage, enabling direct interface to 5V LSTTL outputs without level shifting. Its two independent enable inputs (E1, E2) support hierarchical demultiplexing: one acts as data input while the other holds low, or both serve as gating controls for 16-output selection.

Propagation delay is tightly balanced across all 16 outputs (tPLH/tPHL ≤ 53ns max over -55°C to +125°C), and output transition times remain under 22ns (CL = 50pF), ensuring deterministic timing in synchronous address decode trees. Input hysteresis is not specified; noise immunity relies on guaranteed VIH/VIL margins (30% of VCC at 5V).

Key Specifications

Pinout & Package

CD74HCT154E is housed in a 24-pin plastic dual in-line package (PDIP) with 0.600-inch body width, compatible with standard through-hole sockets and wave-solder processes. Pin 1 is located at the top-left corner (notch-side left), with GND at pin 12 and VCC at pin 24.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-to-16 decoder/demultiplexer applications.

Compared with SN74HCT154N and 74ACT154PC, the CD74HCT154E offers identical pinout and electrical behavior to legacy 74LS154 systems while maintaining TI's extended temperature qualification - making it optimal for repair, obsolescence replacement, and ruggedized embedded deployments where reliability across extreme thermal cycles is non-negotiable.

Availability

CD74HCT154E is available at Aetrix Electronics and suitable for industrial control systems, aerospace avionics interfaces, and legacy test equipment maintenance requiring stable component supply with long-term lifecycle assurance.

Supply support for CD74HCT154E 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and defense market reach.

The CD74HCT154E belongs to TI's High-Speed CMOS Logic (HCT) family, designed specifically to replace bipolar TTL in 5V systems while delivering CMOS power efficiency, extended temperature operation, and seamless interoperability with legacy LSTTL components.

FAQ

What is the maximum clock frequency supported by CD74HCT154E in address decode applications?

The CD74HCT154E does not operate on a clock; it is a combinational logic device. Its usable switching rate depends on propagation delay: with 53ns maximum tPD over full temperature range, it reliably supports address decode cycles up to approximately 14 MHz in systems where setup/hold timing margins permit. The CD74HCT154E's performance is governed by input transition times and load capacitance, not a clock signal.

Can CD74HCT154E be used with 3.3V microcontrollers?

No - the CD74HCT154E requires 4.5V–5.5V supply and has LSTTL-compatible inputs (VIH ≥ 2.0V min), but its VIL specification (≤ 0.8V) does not guarantee reliable recognition of 3.3V logic LOW levels. Direct interface to 3.3V MCUs risks marginal input interpretation; level translation or use of 74AHCT154 is recommended instead. The CD74HCT154E is strictly a 5V-only device.

How does the dual-enable architecture of CD74HCT154E support cascading?

The CD74HCT154E uses E1 and E2 as OR-gated enables: if either is high, all outputs go high (disabled). For cascading, one CD74HCT154E's Y0–Y15 outputs drive the E1/E2 inputs of downstream units. For example, first-stage outputs Y0–Y3 can each enable a separate second-stage CD74HCT154E, achieving 1-of-64 decoding. This preserves timing coherence because enable-to-output delay matches address-to-output delay (34–53ns).

Is CD74HCT154E pin-compatible with the older 74LS154?

Yes - the CD74HCT154E shares identical pinout, terminal functions, and mechanical dimensions with the 74LS154 in PDIP-24 package. It substitutes directly in legacy designs, offering identical logic behavior, improved noise immunity, lower power consumption, and extended temperature range (-55°C to +125°C vs. 0°C to +70°C for LS), with no PCB changes required.

What is the output drive strength of CD74HCT154E, and how many LSTTL loads can it sink/source?

The CD74HCT154E provides ±25mA output current per pin (IO) and is rated for 15 LSTTL loads - defined as driving 15 standard TTL inputs (each drawing 0.4mA low, 0.04mA high). This allows direct fanout to multiple 74LS-series devices without buffers. Output voltage specifications (VOH ≥ 3.7V, VOL ≤ 0.4V at 4mA) confirm robust LSTTL compatibility across the full operating temperature range.