STMicroelectronics 74ACT541B

Overview

74ACT541B from STMicroelectronics is an advanced high-speed CMOS octal bus buffer with non-inverting 3-state outputs, designed for TTL/NMOS/CMOS level translation in digital bus interfaces. It delivers 4 ns typical propagation delay at 5 V, ±24 mA symmetrical output drive, and operates across 4.5–5.5 V supply range with 4 µA max quiescent current. Used in backplane data routing and memory address buffering.

For engineers reviewing the 74ACT541B datasheet, 74ACT541B pinout, 74ACT541B application, or 74ACT541B equivalent, key selection criteria include 3-state enable logic (dual active-high G1/G2), 50 Ω transmission line driving capability, ESD immunity (2 kV), and pin/function compatibility with legacy 74-series 541 devices.

Technical Context

The device implements dual-input AND-gated 3-state control: both G1 and G2 must be low to enable outputs; either high forces all eight Yn outputs into high-impedance state. Inputs and outputs are segregated on opposite sides of the package to simplify PCB layout and reduce crosstalk.

It uses sub-micron C2MOS technology with double-layer metal wiring, enabling balanced tPLH ≅ tPHL propagation delays and symmetrical |IOH| = IOL ≥ 24 mA drive strength. All I/O pins feature integrated protection circuits for 2 kV HBM ESD immunity.

Key Specifications

Pinout & Package

74ACT541B is supplied in plastic DIP-20 (0.300" wide) package per mechanical drawing P001J. Pin 10 is GND; Pin 20 is VCC. Inputs (A1–A8) occupy pins 2–9; outputs (Y1–Y8) occupy pins 11–18; dual enable inputs G1/G2 are on pins 1 and 19.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal 3-state buffer applications.

Compared with 74AC541, the 74ACT541B guarantees minimum output drive and 50 Ω line capability-critical for long-trace or high-speed buses-while SN74ACT541N offers identical functionality with alternate supply chain assurance.

Availability

74ACT541B is available at Aetrix Electronics and suitable for memory address buffering, backplane data bus interface, and legacy TTL-to-CMOS translation requiring stable component supply and long-term industrial availability.

Supply support for 74ACT541B 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The 74ACT family targets high-speed, low-power logic interfacing-specifically engineered to bridge TTL, NMOS, and CMOS systems while delivering robust noise immunity and transmission-line compatibility.

FAQ

What is the function of the dual enable inputs G1 and G2?

G1 and G2 form an AND-gated 3-state control: both must be logic low to assert outputs; if either is high, all eight Yn outputs enter high-impedance state. This design enables hierarchical bus arbitration and prevents contention during multi-driver configurations, especially in backplane or daisy-chained systems where enable sequencing is critical.

Does the 74ACT541B support operation at 3.3 V?

No. The 74ACT541B is specified only for 4.5 V to 5.5 V operation per its Recommended Operating Conditions. Its input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and output drive characteristics are optimized for 5 V systems. For 3.3 V applications, consider the 74LVC541A or similar LVCMOS-compatible octal buffer.

How does the 74ACT541B achieve 50 Ω transmission line driving capability?

It achieves this through guaranteed ±24 mA minimum output drive strength into defined load conditions, combined with symmetrical output impedance (|IOH| = IOL). When terminated at the far end with 50 Ω to VCC/2 or ground, the device's output stage matches characteristic impedance closely enough to suppress reflections on PCB traces up to 15 cm at ≤100 MHz, eliminating need for external series resistors.

Is the 74ACT541B pin-compatible with standard 74LS541?

Yes-pin and function compatible with 74-series 541 devices including 74LS541, 74ALS541, and 74F541. The DIP-20 footprint, I/O assignment (A1–A8, Y1–Y8, G1/G2, VCC, GND), and truth table match exactly. However, electrical behavior differs: ACT version offers higher speed, lower power, and stronger drive than LS/F variants, requiring verification of timing margins and loading in legacy designs.