Texas Instruments CD74HC243EG4

Overview

CD74HC243EG4 from Texas Instruments is a high-speed CMOS quad-bus transceiver with three-state outputs, designed for bidirectional asynchronous data bus communication between two 4-bit buses. It features 7ns typical propagation delay at 5V/15pF, operates across -55°C to 125°C, and supports 2V–6V supply voltage. Used in industrial control backplanes and legacy system bus interfacing where level translation and bus isolation are required.

For engineers reviewing the CD74HC243EG4 datasheet, CD74HC243EG4 pinout, CD74HC243EG4 application, or CD74HC243EG4 equivalent, this page delivers verified functional modes, truth table behavior, thermal metrics, switching characteristics under temperature extremes, and precise package mechanical data - all confirmed for the PDIP-14 (N) variant with NIPDAU lead finish and RoHS compliance.

Technical Context

The CD74HC243EG4 implements four independent noninverting bidirectional channels, each controlled by dual active-low output-enable inputs (OEA, OEB) that jointly determine both direction (A→B or B→A) and three-state output mode. Its silicon-gate CMOS architecture enables high-drive-current outputs capable of driving 15 LSTTL loads while maintaining low ICC (≤160 µA at 6V over full temperature range).

Propagation delay is balanced across A→B and B→A paths, with tpd = 7ns (typ) at VCC = 4.5V, CL = 15pF, TA = 25°C; transition times (tt) are tightly controlled at 12ns (typ), and three-state enable/disable delays (tPZL/tPHZ) are matched within 1ns across channels. Input hysteresis and noise immunity (NIL/NIH = 30% of VCC at 5V) ensure robust operation in electrically noisy environments.

Key Specifications

Pinout & Package

CD74HC243EG4 is housed in a 14-pin plastic dual in-line package (PDIP-N), with nominal body dimensions of 19.31 mm × 6.35 mm and maximum height of 5.08 mm. The package uses NIPDAU lead finish, is RoHS-compliant, and rated for moisture sensitivity level N/A (tube packaging).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC243EG4, SN74HC243N offers marginal thermal improvement but identical electrical behavior, while CD74HCT243E trades supply flexibility for guaranteed TTL input compatibility - neither is pin-compatible with HC-series devices in mixed-voltage systems requiring 3.3 V logic thresholds.

Availability

CD74HC243EG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus isolation, military data link buffering, and automotive ECU diagnostic port designs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC243EG4 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 50 years of high-reliability logic IC development.

The CD74HC243EG4 belongs to TI's legacy HC logic family, engineered for robust, low-power bidirectional bus interfacing in harsh-environment systems where wide supply range, noise immunity, and extended temperature operation are mandatory.

FAQ

What is the maximum clock frequency supported by CD74HC243EG4 in a bus-switching application?

The CD74HC243EG4 does not operate on a clock; it is a combinatorial transceiver. Its usable data rate depends on propagation delay and load. With 7 ns tpd and 15 pF load, it reliably supports bus toggle rates up to 30 MHz in point-to-point configurations. For 50 pF loads, maximum usable frequency drops to ~15 MHz based on measured tpd = 18 ns (max) at -40°C to 85°C.

Does CD74HC243EG4 support mixed-voltage operation between 3.3 V and 5 V buses?

Yes - CD74HC243EG4 operates from 2 V to 6 V and has CMOS-compatible inputs. When powered at 3.3 V, it accepts 5 V-tolerant inputs only if external clamping is provided; the device itself is not 5 V tolerant. For safe 3.3 V ↔ 5 V translation, use series resistors and ensure VOH/VOL specs meet receiver thresholds at both voltage levels.

How do OEA and OEB pins control direction and three-state behavior in CD74HC243EG4?

In CD74HC243EG4, OEA and OEB are active-low controls: both low enables A→B data flow; both high enables B→A flow; any mismatch (one high, one low) forces all eight I/Os into high-impedance state. This dual-control scheme prevents bus contention during direction changes and allows independent gating of each bus segment.

Is CD74HC243EG4 suitable for automotive under-hood applications?

Yes - CD74HC243EG4 is qualified for -55°C to +125°C operation and meets TI's extended-temperature logic standards. Its RθJA = 80 °C/W and low ICC (<160 µA at 6 V) support placement near ECUs in engine compartments, provided board-level thermal design maintains case temperature ≤110°C at peak ambient.

What is the recommended bypass capacitor for CD74HC243EG4?

Texas Instruments specifies a 0.1 µF ceramic capacitor placed as close as possible to the VCC (Pin 14) and GND (Pin 7) pins of CD74HC243EG4. For systems with high-frequency noise, paralleling with a 1 µF capacitor improves broadband suppression. Avoid electrolytic or tantalum types due to ESL limitations above 10 MHz.