STMicroelectronics 74ACT1284TTR

Overview

74ACT1284TTR from STMicroelectronics is a high-speed IEEE 1284-compliant bidirectional parallel transceiver IC with four non-inverting bidirectional buffers and three open-drain/non-inverting buffers, operating at 4.5–5.5 V, delivering 6.5 ns max propagation delay (85°C), 14 mA B-port drive capability, and TTL-compatible inputs-used in ECP-mode printer interface circuits between PCs and peripherals.

For engineers reviewing the 74ACT1284TTR datasheet, 74ACT1284TTR pinout, 74ACT1284TTR application, or 74ACT1284TTR equivalent, key selection factors include direction control (DIR), high-drive enable (HD), B-port output configuration (open-drain vs. totem-pole), IEEE 1284-I/II compliance, and TSSOP-20 thermal and layout constraints.

Technical Context

The device implements dual-mode B-port output switching: HD = LOW enables open-drain operation (suitable for wired-OR bus sharing), while HD = HIGH activates 14 mA totem-pole sourcing/sinking. DIR controls data flow direction-high enables A→B, low enables B→A-supporting full-duplex parallel handshaking per IEEE 1284 Level 1 and Level 2.

It uses silicon gate C2MOS technology for low ICC (80 µA max at 5.5 V/85°C) and integrates hysteresis (0.35 V typ) on control inputs for noise immunity. ESD protection exceeds 2000 V (MIL-STD-883B Method 3015.7), and all I/Os tolerate −2 V to +7 V on B-side pins under recommended conditions.

Key Specifications

Pinout & Package

TSSOP-20 package: 6.5 mm × 4.4 mm body, 0.65 mm pitch, 1.05 mm max height, lead-free, RoHS-compliant, optimized for automated SMT assembly and thermal dissipation in dense PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar IEEE 1284 transceiver applications.

Compared with 74LVX1284MTR and SN74ACT1284NE4, the 74ACT1284TTR uniquely combines 5 V operation, 6.5 ns speed, 14 mA drive, and TSSOP-20 manufacturability-making it optimal for cost-sensitive, high-reliability ECP interface modules requiring RoHS compliance and automated assembly.

Availability

74ACT1284TTR is available at Aetrix Electronics and suitable for printer interface adapters, industrial parallel controllers, POS terminal hubs, and test equipment bus extenders requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for 74ACT1284TTR 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 applications.

The 74ACT1284 belongs to ST's high-speed ACT logic family, engineered specifically for robust, low-skew parallel interface solutions in PC peripheral and industrial control systems requiring IEEE 1284 compliance and 5 V interoperability.

FAQ

What is the maximum operating temperature for the 74ACT1284TTR?

The 74ACT1284TTR is rated for operation from −40°C to +85°C, with all AC/DC specifications guaranteed across this full commercial temperature range. Propagation delay (6.5 ns max) and supply current (80 µA max) are specified at 85°C, confirming thermal stability in enclosed printer enclosures or industrial control cabinets.

Can the B-port outputs be used simultaneously in open-drain and totem-pole modes?

No. The HD input globally configures all seven B-port outputs (B1–B7) into the same mode: HD = LOW enables open-drain for all, HD = HIGH enables totem-pole for all. There is no per-pin mode control-this uniformity ensures consistent bus behavior during IEEE 1284 handshaking sequences.

Does the 74ACT1284TTR support hot insertion or live bus connection?

While not officially rated for hot-swap, the device features ±2 V absolute minimum/maximum ratings on B-side pins and 40 µA max IOFF leakage at 0 V, enabling limited tolerance during controlled live connections. However, external series resistors and TVS protection are recommended for sustained hot-plug operation in field-deployed systems.

How does the DIR pin interact with the HD pin during direction transitions?

DIR and HD operate independently: DIR sets data flow direction (A↔B), while HD sets B-port output type (open-drain/totem-pole). During direction changes, outputs enter high-impedance state only if both DIR and HD are inactive per truth table-no internal arbitration or metastability risk exists, as all control inputs are CMOS-buffered with hysteresis.