Texas Instruments CD74HC243MT

Overview

CD74HC243MT 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 supports 2 V to 6 V operation, delivers 7 ns typical propagation delay (A↔B) at 5 V/15 pF/25°C, and operates across -55°C to 125°C. It is used in industrial control backplanes requiring level-shifted, direction-controlled bus interfacing.

For engineers reviewing the CD74HC243MT datasheet, CD74HC243MT pinout, CD74HC243MT application, or CD74HC243MT equivalent, this page provides verified functional modes, real-world timing behavior under load, thermal derating guidance, and validated alternatives for bus isolation and direction control in harsh-temperature embedded systems.

Technical Context

The CD74HC243MT implements four independent noninverting bidirectional buffers, each controlled by dual active-low enable inputs (OEA, OEB) that jointly determine both data direction (A→B or B→A) and three-state output mode. Its silicon-gate CMOS architecture enables LSTTL-compatible drive strength (15 loads) while maintaining low ICC (≤160 µA over full temperature range).

Propagation delay is balanced across A→B and B→A paths, and transition times remain tightly matched (e.g., 10–15 ns typ at 4.5 V), ensuring deterministic timing in synchronous and asynchronous bus handshaking. Input hysteresis and noise immunity (NIL/NIH = 30% of VCC at 5 V) support reliable operation in electrically noisy environments.

Key Specifications

Pinout & Package

CD74HC243MT is supplied in a 14-pin SOIC package (body size 8.65 mm × 3.90 mm, height ≤1.75 mm), RoHS-compliant with NiPdAu lead finish and moisture sensitivity level 1 (unlimited floor life at ≤30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC243MT, SN74LVC243APWR offers faster switching at lower voltage but sacrifices temperature resilience, while CD74HCT243M retains full pin-and-function compatibility for strict 5 V/TTL environments - making CD74HC243MT the optimal choice for wide-supply, extended-temperature, mixed-voltage bus bridging.

Availability

CD74HC243MT is available at Aetrix Electronics and suitable for industrial automation backplanes, avionics data concentrators, and automotive diagnostic interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC243MT 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 decades of heritage in high-reliability logic families for industrial and aerospace applications.

CD74HC243MT belongs to TI's CDx4HC logic series, engineered for robust bidirectional bus interfacing in harsh environments - emphasizing wide VCC range, extended temperature operation, and precise timing control without external direction logic.

FAQ

What is the maximum clock/data toggle rate supported by CD74HC243MT?

The CD74HC243MT is not a clocked device but a combinational transceiver; its usable data rate depends on propagation delay and load. With 7 ns typical tpd and 15 pF load, it reliably supports bus toggle frequencies up to ~10 MHz in point-to-point configurations. For 50 pF loads, tpd increases to 23 ns (max), limiting practical rates to ~5 MHz - always validate with actual board trace capacitance and termination.

Can CD74HC243MT interface directly between 3.3 V and 5 V buses?

Yes - CD74HC243MT operates from 2 V to 6 V and has CMOS-compatible inputs. When powered at 5 V, it accepts 3.3 V logic-high inputs (VIH min = 3.15 V at VCC = 5 V), making it suitable for 3.3 V → 5 V level shifting. For 5 V → 3.3 V translation, ensure downstream receivers tolerate 5 V inputs or add series resistors to limit current.

How do OEA and OEB interact to control direction and three-state behavior in CD74HC243MT?

In CD74HC243MT, OEA and OEB are active-low enables: (1) OEA low + OEB high → A→B direction, A outputs active; (2) OEA high + OEB low → B→A direction, B outputs active; (3) both high → all outputs high-Z; (4) both low → undefined (avoid per datasheet). This dual-control scheme prevents bus contention during state transitions.

Is CD74HC243MT pin-compatible with CD74HCT243M?

Yes - CD74HC243MT (SOIC-14) and CD74HCT243M (SOIC-14) share identical pinout, package dimensions, and functional block diagram. The only differences are supply voltage range (HC: 2–6 V; HCT: 4.5–5.5 V) and input threshold compatibility (HCT accepts TTL levels). No PCB redesign is required for substitution.

What thermal derating applies to CD74HC243MT at 125°C ambient?

At TA = 125°C, CD74HC243MT's RθJA = 86°C/W (SOIC) limits allowable power dissipation to ~280 mW before exceeding TJ(max) = 150°C. With typical ICC = 160 µA at 6 V, static power is ~1 mW - derating primarily affects dynamic power. At 10 MHz and CL = 50 pF, PD ≈ 15 mW, well within safe margin even at max temperature.