Texas Instruments SN74F243D

Overview

SN74F243D from Texas Instruments is a quadruple bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between two 4-bit buses (A↔B). It supports true logic operation, local bus-latch capability via dual-enable control (OEAB/OEBA), and operates at 4.5 V to 5.5 V supply over 0°C to 70°C. Used in legacy TTL-based system interconnects requiring bus isolation and direction control.

For engineers reviewing the SN74F243D datasheet, SN74F243D pinout, SN74F243D application, or SN74F243D equivalent, key selection factors include its 3-state output drive strength (IOL = 64 mA), propagation delay (tPLH/tPHL ≤ 6.2 ns), latch mode behavior (A = B when both enables active), and D-package SOIC-16 footprint compatibility.

Technical Context

The SN74F243D implements dual independent 4-bit bidirectional data paths controlled by separate OEAB (A→B enable) and OEBA (B→A enable) inputs. Its logic allows four distinct functional states: A-to-B transmission, B-to-A transmission, high-impedance isolation, and simultaneous latch mode where both buses retain their last valid states.

It uses standard F-series TTL circuitry with guaranteed VIH ≥ 2 V, VIL ≤ 0.8 V, VOH ≥ 2.4 V (at I_OH = –15 mA), and VOL ≤ 0.55 V (at I_OL = 64 mA). Switching performance is specified under CL = 50 pF, RL = 500 Ω, and operates across full recommended VCC (4.5–5.5 V) and temperature (0°C to 70°C) ranges.

Key Specifications

Pinout & Package

SN74F243D is supplied in a 16-pin plastic small-outline integrated circuit (SOIC) package (D package), 300-mil width, with standard pin spacing and gull-wing leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS243N and SN74F244N, the SN74F243D provides higher drive strength and faster switching for bidirectional bus arbitration, while retaining full pin compatibility with other '243 variants - making it optimal for upgrading existing designs requiring improved timing or load capacity.

Availability

SN74F243D is available at Aetrix Electronics and suitable for industrial control backplanes, legacy microprocessor bus expansion, and automated test fixture interfaces requiring stable component supply and long-term obsolescence management.

Supply support for SN74F243D 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial and automotive portfolio coverage.

The SN74F243D belongs to the 74F (Fast TTL) logic family, engineered for high-speed digital system interconnects where propagation delay and drive strength outweigh power efficiency concerns.

FAQ

What is the maximum output sink current specification for SN74F243D?

The SN74F243D guarantees a minimum low-level output current (IOL) of 64 mA per output pin under recommended operating conditions (VCC = 4.5 V, TA = 0°C to 70°C). This rating ensures reliable driving of multiple TTL inputs or moderate capacitive loads without external buffering. Exceeding this current may cause VOL to exceed 0.55 V or induce thermal stress. The SN74F243D datasheet specifies this value in the "Recommended Operating Conditions" table.

Does SN74F243D support true bidirectional data flow without external control logic?

Yes, the SN74F243D supports true bidirectional data flow using only its two dedicated control inputs: OEAB (A→B enable) and OEBA (B→A enable). When OEAB is low and OEBA is high, data flows from A to B; when OEBA is low and OEAB is high, data flows from B to A. Both can be asserted low simultaneously to enter latch mode (A = B), eliminating need for external direction registers or multiplexers in many legacy bus designs.

What is the function of the NC pins on SN74F243D?

SN74F243D has two NC (No Connection) pins: Pin 2 and Pin 10. These pins have no internal bond wires or circuit connections and serve only mechanical or package alignment purposes. They must remain unconnected in PCB layout - neither tied to VCC nor GND - to prevent unintended coupling or ESD pathways. Their presence maintains pin compatibility with other 16-pin D-package logic devices in the 74F family.

Can SN74F243D operate reliably at 4.5 V supply voltage?

Yes, SN74F243D is fully characterized for operation at VCC = 4.5 V, the minimum recommended supply voltage. At this level, it meets all AC and DC specifications including VOH ≥ 2.4 V (at I_OH = –15 mA), VOL ≤ 0.55 V (at I_OL = 64 mA), and tPLH/tPHL ≤ 6.2 ns. This makes the SN74F243D suitable for systems with marginal 5 V rails or brown-out conditions where stable 4.5 V operation is required.

Is SN74F243D pin-compatible with SN74F243N?

Yes, SN74F243D and SN74F243N share identical pin functions and numbering for all 16 terminals, including OEAB, OEBA, A1–A4, B1–B4, VCC, GND, and NC pins. The only difference is package type: D denotes SOIC-16, N denotes PDIP-16. PCB footprints differ, but logic design, schematic symbol, and netlist connectivity are fully interchangeable - enabling direct substitution in new layouts or rework of through-hole boards with adapter carriers.