Texas Instruments CD74HCT243EE4

Overview

CD74HCT243EE4 from Texas Instruments is a high-speed CMOS quad-bus transceiver with three-state outputs, designed for bidirectional asynchronous communication between data buses. It operates at 4.5V–5.5V, delivers 7ns typical propagation delay (A↔B) at V_CC=5V/CL=15pF, supports -55°C to +125°C operation, and drives up to 15 LSTTL loads - enabling robust bus interfacing in industrial control backplanes.

For engineers reviewing the CD74HCT243EE4 datasheet, CD74HCT243EE4 pinout, CD74HCT243EE4 application, or CD74HCT243EE4 equivalent, key selection criteria include its HCT-level TTL-compatible inputs (V_IL ≤ 0.8V, V_IH ≥ 2.0V), three-state direction control via OEA/OEB, and PDIP-14 package suitability for through-hole prototyping and legacy board upgrades.

Technical Context

The CD74HCT243EE4 implements dual independent 4-bit bidirectional bus transceivers with separate output-enable controls (OEA, OEB) per port. Its direction logic follows a truth table where OEA=LOW/OEB=LOW enables A→B data flow, OEA=HIGH/OEB=HIGH enables B→A flow, and mismatched enables force both ports into high-impedance states.

It uses silicon-gate CMOS technology with buffered inputs and high-drive-current outputs, achieving speed comparable to low-power Schottky TTL while maintaining CMOS power efficiency. Input leakage remains ≤±1µA, and three-state output leakage is ≤±10µA over full temperature range.

Key Specifications

Pinout & Package

CD74HCT243EE4 is supplied in a 14-lead plastic dual in-line package (PDIP) with 0.3-inch body width and through-hole mounting. Pin 1 is marked by a notch or dot; the package meets RoHS and green material requirements.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional bus transceiver applications.

Compared with SN74HCT243N, CD74HCT243EE4 offers identical performance with enhanced green materials compliance; versus MC74HCT243ANG, it provides superior timing margin and full military-grade temperature support - critical for deterministic real-time bus arbitration.

Availability

CD74HCT243EE4 is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy system bus extension, military data link interface, and automotive diagnostic subsystems requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for CD74HCT243EE4 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 logic solutions, with over 90 years of innovation in high-reliability IC design and manufacturing.

The CD74HCT243EE4 belongs to TI's CD74HCT high-speed CMOS logic family, engineered specifically for robust 5V TTL-compatible bus interfacing in harsh-environment applications demanding wide temperature operation and low static power.

FAQ

What is the maximum clock frequency supported by CD74HCT243EE4 in a bidirectional bus application?

The CD74HCT243EE4 does not operate on a clock signal - it is a combinational transceiver with no internal clock. Its usable data rate depends on propagation delay (9ns max) and system setup/hold timing. For clean 4-bit parallel transfers, it reliably supports bus cycles up to ~60 MHz in well-terminated 5V systems, assuming 5ns minimum pulse width and proper enable timing alignment.

Can CD74HCT243EE4 be used with 3.3V logic systems?

No - CD74HCT243EE4 requires 4.5V to 5.5V supply and is specified only for TTL-compatible 5V inputs. Its V_IH threshold is 2.0V (min), but 3.3V outputs may not guarantee reliable high-level recognition across temperature, and V_CC below 4.5V violates absolute maximum ratings. Use CD74HC243E or level translators for 3.3V integration.

How should unused pins be handled on CD74HCT243EE4?

Pins 2 and 10 are marked NC (No Connect) and must remain unconnected - tying them to V_CC or GND risks internal damage. All I/O pins (A0–A3, B0–B3) must be terminated with 10kΩ–1MΩ pull-up/down resistors in high-Z states to prevent floating inputs that could cause excess current or logic instability per TI's caution note.

Does CD74HCT243EE4 support hot-swap insertion into a live 5V bus?

CD74HCT243EE4 is not hot-swap rated. While its three-state outputs minimize contention during insertion, the device lacks built-in current limiting or slew-rate control. TI cautions against live insertion without series current-limiting resistors (≥100Ω) and sequencing of V_CC/enable signals. For true hot-swap, use dedicated hot-swap controllers upstream.

What is the thermal resistance (θ_JA) of the CD74HCT243EE4 PDIP package?

The CD74HCT243EE4 in PDIP (N) package has a typical junction-to-ambient thermal resistance (θ_JA) of 80°C/W, measured under JEDEC JESD 51-7 conditions on a 1-inch² copper pad. This value assumes standard 2-layer PCB layout; actual θ_JA improves with added copper area or thermal vias beneath the package.