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Home > Products > Integrated Circuits (ICs) > Logic > Buffers, Drivers, Receivers, Transceivers

Texas Instruments CD74HCT243EG4

Name: CD74HCT243EG4
Brand: Texas Instruments
SKU: CD74HCT243EG4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: CD74HCT243EG4

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 14-DIP (0.300", 7.62mm)

Datasheet:: CD74HCT243EG4.pdf

Description:: IC TXRX NON-INVERT 5.5V 14DIP

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Product details

Overview

CD74HCT243EG4 from Texas Instruments is a quad-bus transceiver with three-state outputs, designed for bidirectional asynchronous data bus communication between two 4-bit buses. It operates at 4.5 V to 5.5 V, delivers 7 ns typical propagation delay (A↔B) at V_CC = 5 V and C_L = 15 pF, supports -55°C to +125°C operation, and drives up to 15 LSTTL loads - used in industrial backplane interfaces and legacy system bus expansion.

For engineers reviewing the CD74HCT243EG4 datasheet, CD74HCT243EG4 pinout, CD74HCT243EG4 application, or CD74HCT243EG4 equivalent, key selection criteria include its LSTTL-compatible input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), three-state control via OEA/OEB, balanced A↔B propagation symmetry, and PDIP-14 packaging for through-hole prototyping and ruggedized embedded systems.

Technical Context

The CD74HCT243EG4 implements four independent noninverting bidirectional channels, each controlled by shared OEA and OEB enable inputs that jointly determine direction (A→B or B→A) and high-impedance state. Its CMOS silicon-gate process ensures low static current (I_CC ≤ 160 µA over temperature) while maintaining TTL-level input compatibility and rail-to-rail output swing.

Propagation delay is symmetric across both directions (t_pd = 9 ns typ @ 5 V, 15 pF), and transition times are tightly matched (t_t = 12 ns typ), enabling reliable timing in synchronous bus arbitration. Three-state leakage (I_OZ ≤ ±10 µA) and input leakage (I_I ≤ ±1 µA) remain stable across the full -55°C to +125°C range, supporting mission-critical industrial control applications.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.5 V to 5.5 V - Ensures direct drop-in replacement for 5 V LSTTL systems without level-shifting.
Propagation Delay (t_pd)	9 ns typical (A↔B) at 5 V, 15 pF - Enables >50 MHz bus toggle rates in point-to-point configurations.
Input Thresholds	V_IL ≤ 0.8 V, V_IH ≥ 2.0 V - Guarantees robust noise margin and seamless interfacing with standard TTL logic families.
Output Drive	±25 mA per output - Sustains signal integrity driving 15 LSTTL loads or 50 pF bus capacitance.
Operating Temperature	-55°C to +125°C - Qualified for extended-range industrial, aerospace, and under-hood automotive subsystems.
Three-State Leakage (I_OZ)	±10 µA max at -55°C to +125°C - Minimizes bus contention current during high-Z states in multi-master environments.
Supply Current (I_CC)	160 µA max over full temperature range - Supports low-power standby modes in battery-backed or energy-constrained systems.

Pinout & Package

CD74HCT243EG4 is supplied in a 14-pin plastic dual in-line package (PDIP-N), with 19.31 mm × 6.35 mm body size and 2.54 mm lead pitch. The package features through-hole mounting, industry-standard pin 1 notch marking, and RoHS-compliant NiPdAu lead finish.

Pin/Terminal	Circuit Role	Design Meaning
1 (OEB)	Output Enable B	Active-low control for B-side drivers; when low, enables B→A data flow and disables A→B.
2–5 (A1–A4)	Bus A Inputs/Outputs	Bidirectional I/O ports connected to Bus A; direction determined by OEA/OEB logic state.
6 (GND)	Ground Reference	Primary return path for all internal logic and output currents; requires local 0.1 µF bypass capacitor.
7–10 (B1–B4)	Bus B Inputs/Outputs	Bidirectional I/O ports connected to Bus B; functionally mirrored to A-side with independent enable control.
11 (V_CC)	Positive Supply	5 V nominal power rail; must be decoupled within 10 mm of pin using 0.1 µF ceramic capacitor.
12 (OEA)	Output Enable A	Active-low control for A-side drivers; when low, enables A→B data flow and disables B→A.
13, 14	No Connect	Internally unused; must remain unconnected per TI design guidance to avoid parasitic coupling.

Key Features

Feature	Design Value
Three-state bidirectional control	OEA and OEB inputs jointly define direction and high-Z state - eliminates need for external direction logic or bus buffers.
LSTTL-compatible inputs	V_IL ≤ 0.8 V / V_IH ≥ 2.0 V at 5 V - allows direct connection to legacy TTL peripherals without interface resistors or translators.
Low dynamic power dissipation	C_pd = 91 pF - reduces switching current and heat generation in high-frequency bus applications versus LS-TTL equivalents.
Wide temperature operation	-55°C to +125°C - supports deployment in uncontrolled environments such as factory automation controllers and avionics subsystems.
Buffered inputs	Input hysteresis and drive strength prevent false triggering from slow-rising signals or noisy bus lines.

Applications

Industrial Backplane Interface	Legacy System Bus Expansion
Use Scenario: Interfacing a microcontroller-based master module to multiple peripheral cards on a 4-bit parallel backplane with shared address/data lines. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between master and slave cards under software-controlled OEA/OEB gating. Use Value: Eliminates discrete direction-control logic and reduces PCB footprint while maintaining deterministic 9 ns A↔B latency for real-time response.	Use Scenario: Upgrading an aging 80C51-based test instrument with additional I/O modules while retaining existing 5 V TTL bus architecture. IC Role / Device Role / Timing Role: Level-translating and bus-isolating transceiver enabling new modules to coexist with legacy peripherals on the same data bus. Use Value: Direct LSTTL compatibility avoids redesign of timing budgets or addition of voltage translators, preserving system timing margins.
Military Data Acquisition Subsystem	Automotive Engine Control Diagnostics Port
Use Scenario: Isolating sensor acquisition logic from command-and-control logic in a ruggedized field-deployable DAQ unit operating across extreme ambient temperatures. IC Role / Device Role / Timing Role: High-reliability bus buffer providing galvanic separation between analog front-end and digital processing domains. Use Value: -55°C to +125°C qualification and <10 µA three-state leakage ensure stable bus isolation under thermal cycling and EMI stress.	Use Scenario: Implementing a diagnostic access port on an engine control unit (ECU) that connects proprietary debug tools to internal 4-bit status registers. IC Role / Device Role / Timing Role: Controlled-direction transceiver enabling tool-initiated read/write cycles without interfering with normal ECU bus operations. Use Value: Symmetric 9 ns propagation ensures precise timing alignment between tool commands and register responses, critical for JTAG-over-parallel protocols.

Industrial Backplane Interface

Legacy System Bus Expansion

Use Scenario: Interfacing a microcontroller-based master module to multiple peripheral cards on a 4-bit parallel backplane with shared address/data lines.

IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between master and slave cards under software-controlled OEA/OEB gating.

Use Value: Eliminates discrete direction-control logic and reduces PCB footprint while maintaining deterministic 9 ns A↔B latency for real-time response.

Use Scenario: Upgrading an aging 80C51-based test instrument with additional I/O modules while retaining existing 5 V TTL bus architecture.

IC Role / Device Role / Timing Role: Level-translating and bus-isolating transceiver enabling new modules to coexist with legacy peripherals on the same data bus.

Use Value: Direct LSTTL compatibility avoids redesign of timing budgets or addition of voltage translators, preserving system timing margins.

Military Data Acquisition Subsystem

Automotive Engine Control Diagnostics Port

Use Scenario: Isolating sensor acquisition logic from command-and-control logic in a ruggedized field-deployable DAQ unit operating across extreme ambient temperatures.

IC Role / Device Role / Timing Role: High-reliability bus buffer providing galvanic separation between analog front-end and digital processing domains.

Use Value: -55°C to +125°C qualification and <10 µA three-state leakage ensure stable bus isolation under thermal cycling and EMI stress.

Use Scenario: Implementing a diagnostic access port on an engine control unit (ECU) that connects proprietary debug tools to internal 4-bit status registers.

IC Role / Device Role / Timing Role: Controlled-direction transceiver enabling tool-initiated read/write cycles without interfering with normal ECU bus operations.

Use Value: Symmetric 9 ns propagation ensures precise timing alignment between tool commands and register responses, critical for JTAG-over-parallel protocols.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74HCT243N	Same pinout, identical electrical specs, but TI's newer production variant with enhanced ESD protection (4 kV HBM) and tighter I_OZ control (±5 µA max).	Preferred for new designs requiring higher reliability in electrostatic-prone manufacturing or field service environments.	Select SN74HCT243N when long-term supply continuity and improved robustness are prioritized over legacy part pedigree.
74ACT243PC	Higher drive (±24 mA), faster t_pd (6.5 ns typ), but requires 4.5–5.5 V and exhibits higher I_CC (250 µA max) and C_pd (110 pF).	Suitable for speed-critical applications where power budget allows; not drop-in due to increased supply current and thermal load.	Choose 74ACT243PC only if measured bus timing demands sub-7 ns latency and thermal management is confirmed.

Compared with CD74HCT243EG4, SN74HCT243N offers superior ESD immunity and tighter leakage control for field-deployed systems, while 74ACT243PC trades higher power for measurable speed gain - making CD74HCT243EG4 the optimal balance of legacy compatibility, thermal efficiency, and industrial temperature resilience.

Availability

CD74HCT243EG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus expansion, military data acquisition subsystems, and automotive engine control diagnostics ports requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT243EG4 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 innovation in high-reliability logic ICs.

The CD74HCT243EG4 belongs to TI's HCT logic family, engineered specifically for seamless integration into 5 V TTL-based systems requiring industrial-grade temperature performance and low-power CMOS efficiency.

FAQ

What is the maximum clock frequency supported by CD74HCT243EG4 in a bidirectional bus configuration?

The CD74HCT243EG4 does not operate on a clock signal - it is a combinatorial transceiver. Its usable data rate depends on propagation delay and bus loading: with 9 ns typical t_pd and 50 pF load, it reliably supports bus toggle rates up to 50 MHz in point-to-point configurations. For multi-drop buses, timing must be verified against actual trace capacitance and termination.

Can CD74HCT243EG4 be used with 3.3 V logic systems?

No - CD74HCT243EG4 is specified only for 4.5 V to 5.5 V operation and requires TTL-compatible input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V). Direct connection to 3.3 V systems violates V_IH minimum and risks unreliable logic detection; a level-shifter such as TXB0104 is required for interoperability.

How do OEA and OEB control signal direction in CD74HCT243EG4?

In CD74HCT243EG4, direction is determined by the logic combination of OEA and OEB: when OEA = L and OEB = H, data flows A→B; when OEA = H and OEB = L, data flows B→A; when both are H, all outputs enter high-Z; when both are L, the device enters undefined state and must be avoided per datasheet truth table.

Is CD74HCT243EG4 RoHS compliant?

Yes - CD74HCT243EG4 carries RoHS-compliant NiPdAu lead finish and is marked "Yes" in TI's official packaging addendum. It meets EU Directive 2011/65/EU requirements with lead content below 0.1 wt% and full exemption reporting per Annex II.

What is the recommended bypass capacitor for CD74HCT243EG4?

Texas Instruments specifies a 0.1 µF ceramic capacitor placed as close as possible to the V_CC (pin 11) and GND (pin 6) pins of CD74HCT243EG4. For systems with high-frequency noise, paralleling with a 1 µF tantalum or ceramic capacitor further improves suppression across broader frequency bands.

CD74HCT243EG4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74HCT

Package/Case:: 14-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Discontinued at Digi-Key

Logic Type:: Transceiver, Non-Inverting

Number of Elements:: 1

Number of Bits per Element:: 4

Input Type:: -

Output Type:: 3-State

Current - Output High, Low:: 6mA, 6mA

Voltage - Supply:: 4.5V ~ 5.5V

Operating Temperature:: -55°C ~ 125°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 14-PDIP

CD74HCT243EG4 FAQ

1.How can I place an order for CD74HCT243EG4 through Aetrix?

Please submit a Request for Quotation (RFQ) for CD74HCT243EG4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for CD74HCT243EG4 reliable?

The price and inventory of CD74HCT243EG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT243EG4 is usually 5 days.

3.What payment methods are accepted for CD74HCT243EG4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT243EG4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for CD74HCT243EG4?

CD74HCT243EG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your CD74HCT243EG4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for CD74HCT243EG4?

For technical support, including CD74HCT243EG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT243EG4 requirements.

6.How does Aetrix verify that CD74HCT243EG4 is sourced from the original manufacturer or authorized distributors?

All CD74HCT243EG4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that CD74HCT243EG4 meets industry standards.

7.What is the process for return or replacement of CD74HCT243EG4?

All CD74HCT243EG4 units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT243EG4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The CD74HCT243EG4 part is unused and in its original packaging.

Return procedure for CD74HCT243EG4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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