STMicroelectronics 74ACT273B

Overview

74ACT273B from STMicroelectronics is an octal D-type flip-flop with asynchronous clear, designed for high-speed synchronous data latching in TTL- and CMOS-compatible digital systems. It operates at 4.5–5.5 V, delivers 190 MHz max clock frequency (typ.), supports 24 mA symmetrical output drive, and features balanced propagation delays (tPLH ≅ tPHL) with 1.5 ns typical delay. Used in address/data register stages of industrial controllers and communication interface logic.

For engineers reviewing the 74ACT273B datasheet, 74ACT273B pinout, 74ACT273B application, or 74ACT273B equivalent, key selection criteria include its 50 Ω transmission line driving capability, ±2 kV ESD immunity, latch-up robustness, and strict 1.0 ns setup / –0.5 ns hold timing margins at 5 V.

Technical Context

The 74ACT273B implements eight edge-triggered D flip-flops sharing a common clock and asynchronous active-low clear. Its sub-micron C2MOS process enables fast switching while maintaining low ICC (4 µA max at 25°C) and high noise immunity.

All inputs tolerate TTL voltage levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V), and outputs drive 50 Ω transmission lines directly with matched |IOH| = |IOL| = 24 mA (min), ensuring clean signal integrity in backplane and bus-interface applications.

Key Specifications

Pinout & Package

74ACT273B is supplied in a plastic dual-in-line package (DIP-20) with 2.54 mm lead pitch, 25.4 mm body width, and through-hole mounting compatibility.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal D-type flip-flop applications.

Compared with 74ACT273B, the SOP and TSSOP variants offer identical logic behavior and timing but differ in mechanical fit, thermal characteristics, and assembly method-making them drop-in replacements only in footprint-aware layouts.

Availability

74ACT273B is available at Aetrix Electronics and suitable for industrial PLC I/O registers, legacy bus interface buffers, and video timing controllers requiring stable component supply across extended temperature ranges (–55°C to +125°C).

Supply support for 74ACT273B 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, Switzerland, specializing in automotive, industrial, and power management solutions.

The 74ACT family targets high-speed, low-power 5 V logic interfacing-designed specifically to bridge TTL, NMOS, and CMOS systems with robust noise immunity and transmission-line drive capability.

FAQ

Is 74ACT273B compatible with 3.3 V logic systems?

No. The 74ACT273B is specified only for 4.5–5.5 V operation and lacks 3.3 V input thresholds or output voltage compliance. Its VIH minimum is 2.0 V at 5 V supply, but it cannot be reliably driven by 3.3 V CMOS outputs without level translation due to insufficient noise margin and undefined behavior below 4.5 V VCC.

What is the minimum pulse width required on the CLEAR input?

The minimum CLEAR pulse width is 2.3 ns (typ.) at VCC = 5 V and TA = 25°C, with a maximum of 4.0 ns across full temperature and voltage range. This ensures reliable asynchronous reset even in high-frequency clock domains where narrow glitches may occur.

Does 74ACT273B require external pull-up or pull-down resistors on unused inputs?

No. All inputs feature internal protection diodes and defined DC thresholds; however, floating D or CLOCK inputs risk metastability or unintended toggling. Unused D inputs should be tied to VCC or GND, and CLOCK must remain inactive (held LOW or HIGH) when not in use to prevent spurious triggering.

Can 74ACT273B drive multiple loads on a single output?

Yes, but total capacitive load per output must stay ≤ 50 pF for guaranteed AC performance (e.g., tPLH ≤ 9.0 ns). Driving multiple CMOS inputs is feasible if their combined input capacitance plus trace capacitance remains within this limit; exceeding it increases propagation delay and may cause signal integrity issues.