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

Texas Instruments CD74HCT243E

Name: CD74HCT243E
Brand: Texas Instruments
SKU: CD74HCT243E
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: CD74HCT243E

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

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

Datasheet:: CD74HCT243E.pdf

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

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Product details

Overview

CD74HCT243E 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, CL = 15 pF, and supports industrial temperature range (–55°C to +125°C). It is used in microcontroller peripheral expansion, memory-mapped I/O interfacing, and legacy TTL-to-CMOS bus bridging.

For engineers reviewing the CD74HCT243E datasheet, CD74HCT243E pinout, CD74HCT243E application, or CD74HCT243E equivalent, key selection criteria include LSTTL-compatible input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), three-state control via dual enable inputs (OEA/OEB), bidirectional channel directionality, and PDIP-14 package compatibility with through-hole prototyping and industrial control PCBs.

Technical Context

The CD74HCT243E implements four independent noninverting bidirectional buffer channels, each controlled by shared OEA and OEB inputs that jointly determine both data flow direction (A→B or B→A) and high-impedance output state. Its HCT logic family ensures direct interface with standard LSTTL outputs without level-shifting.

It features buffered inputs with CMOS input leakage ≤1 µA, fanout of 15 LSTTL loads per bus driver output, and balanced propagation delays (t_PLH/t_PHL matched within specification). The device uses silicon-gate CMOS technology and meets MIL-STD-883 Class B screening requirements for high-reliability applications.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.5 V to 5.5 V - Ensures stable operation across standard 5 V supply rails with ±5% tolerance.
Propagation Delay (t_pd)	9 ns typical at 5 V, CL = 15 pF - Enables reliable timing in 33 MHz synchronous bus systems.
V_IL/V_IH	≤0.8 V / ≥2.0 V - Guarantees direct compatibility with LSTTL logic outputs without external level translation.
Output Drive	±25 mA per pin - Sufficient to drive 15 LSTTL loads or moderate-capacitance backplanes (≤50 pF).
Operating Temperature	–55°C to +125°C - Qualified for aerospace, automotive under-hood, and industrial control environments.
Three-State Leakage (I_OZ)	±10 µA max at –55°C to +125°C - Minimizes bus contention current when outputs are disabled.
Input Capacitance (C_i)	10 pF - Low loading on upstream drivers preserves signal integrity in high-speed parallel interfaces.

Pinout & Package

CD74HCT243E is housed in a 14-pin plastic dual in-line package (PDIP-N), body size 19.31 mm × 6.35 mm, with 2.54 mm lead pitch and through-hole mounting. Pin 1 is marked by a notch or dot at the top-left corner.

Pin/Terminal	Circuit Role	Design Meaning
1 (A1)	Data input/output A-side channel 1	Bidirectional I/O terminal; driven by B1 when OEA=LOW/OEB=LOW; high-Z when enables inactive.
2 (A2)	Data input/output A-side channel 2	Same functional role as A1; electrically isolated but shares OEA/OEB control logic.
3 (A3)	Data input/output A-side channel 3	Supports full 4-bit parallel transfer; no internal bus contention due to three-state isolation.
4 (A4)	Data input/output A-side channel 4	Enables byte-wide data exchange between separate address/data buses or processor/peripheral domains.
5 (GND)	Ground reference	Common return path for all signals; must be low-inductance connection to minimize ground bounce.
6 (OEB)	Output enable B	Active-low control: LOW enables B-side outputs; HIGH forces B1–B4 into high-impedance state.
7 (B4)	Data input/output B-side channel 4	Bidirectional terminal mirroring A4; direction determined jointly by OEA and OEB states.
8 (B3)	Data input/output B-side channel 3	Paired with A3; simultaneous A↔B transfer possible only when OEA=OEB=LOW.
9 (B2)	Data input/output B-side channel 2	Used in multiplexed bus architectures where B-side connects to memory or peripheral data lines.
10 (B1)	Data input/output B-side channel 1	Primary interface point for downstream devices; requires termination if driving long traces.
11 (V_CC)	Positive supply	Must be bypassed with 0.1 µF ceramic capacitor placed ≤5 mm from pin to suppress switching noise.
12 (OEA)	Output enable A	Active-low control: LOW enables A-side outputs; HIGH disables A1–A4 regardless of OEB state.
13 (Y1)	Unused (NC)	No internal connection; must remain unconnected or tied to GND/V_CC per layout guidelines.
14 (Y2)	Unused (NC)	No internal connection; floating NC pins may cause EMI; tie to GND if unused in design.

Key Features

Feature	Design Value
True bidirectional bus interface	Single device replaces two unidirectional transceivers; reduces component count and board area in 8-bit data paths.
LSTTL-compatible input thresholds	V_IL ≤ 0.8 V and V_IH ≥ 2.0 V at V_CC = 4.5–5.5 V - eliminates need for external pull-ups or level shifters when interfacing with 74LS/ALS families.
Dual independent enable control (OEA/OEB)	Four distinct operational modes (A→B, B→A, both disabled, both enabled) - enables flexible bus arbitration and hot-swap capability.
High noise immunity	NIL/NIL = 30% of V_CC - maintains logic integrity in electrically noisy industrial environments with >1.5 V noise margin at 5 V.
Low static power consumption	I_CC ≤ 160 µA over full temperature range - suitable for battery-backed or low-power standby modes in embedded controllers.

Applications

Microcontroller Peripheral Expansion	Legacy System Bus Bridging
Use Scenario: Expanding GPIO count of an 8-bit MCU (e.g., PIC16F877A) to drive external 8-bit peripherals like LCD modules or ADCs. IC Role / Device Role / Timing Role: Bidirectional data shuttle between MCU port and peripheral data bus; direction controlled by software-configured OEA/OEB lines. Use Value: Eliminates need for discrete direction-control logic and reduces firmware complexity by enabling single-cycle read/write handshaking.	Use Scenario: Interfacing a modern 5 V CMOS microprocessor with legacy TTL-based memory subsystems (e.g., 27C256 EPROM). IC Role / Device Role / Timing Role: Level- and drive-compatible bus translator ensuring setup/hold timing compliance across mixed-logic families. Use Value: Maintains 7 ns propagation delay margin for 33 MHz bus clocks while providing 15-LSTTL load drive capability.
Industrial PLC I/O Module	Test Equipment Data Acquisition
Use Scenario: Isolating and conditioning digital I/O signals in programmable logic controller backplane modules operating from –40°C to +85°C ambient. IC Role / Device Role / Timing Role: Robust bidirectional interface between field-side optocouplers and controller-side data bus with ESD-tolerant inputs. Use Value: Extended –55°C to +125°C rating ensures reliability in uncontrolled cabinet environments; three-state outputs prevent bus contention during fault conditions.	Use Scenario: High-fidelity digital sampling in automated test equipment requiring synchronized capture of 8-bit sensor data streams. IC Role / Device Role / Timing Role: Low-skew, low-capacitance bus transceiver minimizing jitter on parallel data lines feeding FPGA acquisition logic. Use Value: 10 pF input capacitance and matched t_PLH/t_PHL preserve signal edge fidelity for sub-30 ns sampling windows.

Microcontroller Peripheral Expansion

Legacy System Bus Bridging

Use Scenario: Expanding GPIO count of an 8-bit MCU (e.g., PIC16F877A) to drive external 8-bit peripherals like LCD modules or ADCs.

IC Role / Device Role / Timing Role: Bidirectional data shuttle between MCU port and peripheral data bus; direction controlled by software-configured OEA/OEB lines.

Use Value: Eliminates need for discrete direction-control logic and reduces firmware complexity by enabling single-cycle read/write handshaking.

Use Scenario: Interfacing a modern 5 V CMOS microprocessor with legacy TTL-based memory subsystems (e.g., 27C256 EPROM).

IC Role / Device Role / Timing Role: Level- and drive-compatible bus translator ensuring setup/hold timing compliance across mixed-logic families.

Use Value: Maintains 7 ns propagation delay margin for 33 MHz bus clocks while providing 15-LSTTL load drive capability.

Industrial PLC I/O Module

Test Equipment Data Acquisition

Use Scenario: Isolating and conditioning digital I/O signals in programmable logic controller backplane modules operating from –40°C to +85°C ambient.

IC Role / Device Role / Timing Role: Robust bidirectional interface between field-side optocouplers and controller-side data bus with ESD-tolerant inputs.

Use Value: Extended –55°C to +125°C rating ensures reliability in uncontrolled cabinet environments; three-state outputs prevent bus contention during fault conditions.

Use Scenario: High-fidelity digital sampling in automated test equipment requiring synchronized capture of 8-bit sensor data streams.

IC Role / Device Role / Timing Role: Low-skew, low-capacitance bus transceiver minimizing jitter on parallel data lines feeding FPGA acquisition logic.

Use Value: 10 pF input capacitance and matched t_PLH/t_PHL preserve signal edge fidelity for sub-30 ns sampling windows.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74HCT243N	Identical logic function, pinout, and DC specs; TI second-source part with same PDIP-14 package and –55°C to +125°C rating.	No functional difference; validated drop-in replacement with identical timing and drive strength.	Select SN74HCT243N when sourcing from alternate TI distribution channels or requiring dual-lot traceability.
74ACT243PC	Higher speed (t_pd = 5.5 ns typ), wider V_CC range (4.5–5.5 V), but higher ICC (2 mA max) and reduced noise margin (NIL = 20% of V_CC).	Better suited for high-frequency bus applications (>40 MHz), but less tolerant of supply ripple or EMI in industrial settings.	Choose 74ACT243PC only when propagation delay is critical and system-level noise immunity has been independently verified.

Compared with SN74HCT243N and 74ACT243PC, CD74HCT243E offers optimal balance of LSTTL compatibility, industrial temperature resilience, and low static power-making it preferred for cost-sensitive, reliability-critical embedded control designs where timing margins exceed 7 ns.

Availability

CD74HCT243E is available at Aetrix Electronics and suitable for microcontroller peripheral expansion, legacy system bus bridging, and industrial PLC I/O modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT243E 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 industrial, automotive, and communications markets.

CD74HCT243E belongs to TI's industry-standard HCT logic family, engineered for seamless interoperability between TTL and CMOS systems in harsh-environment control applications.

FAQ

What is the maximum clock frequency supported by CD74HCT243E in a synchronous bus application?

The CD74HCT243E is not a clocked device-it operates asynchronously. Its 9 ns typical propagation delay supports reliable data transfer in systems with bus cycle times ≥30 ns, corresponding to effective throughput up to ~33 MHz in tightly timed parallel interfaces. Actual maximum frequency depends on trace length, load capacitance, and system-level timing margins-not an internal clock.

Can CD74HCT243E be used to interface 3.3 V logic with 5 V logic buses?

No. CD74HCT243E requires V_CC = 4.5–5.5 V and has LSTTL-compatible inputs (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), making it unsuitable for direct 3.3 V signal reception. For 3.3 V ↔ 5 V translation, use dedicated level-shifters such as TXB0104 or SN74AVCH series instead of CD74HCT243E.

How do the OEA and OEB pins control data direction in CD74HCT243E?

In CD74HCT243E, OEA and OEB are active-low enables: when OEA=LOW and OEB=HIGH, A-side outputs are enabled (A→B); when OEA=HIGH and OEB=LOW, B-side outputs are enabled (B→A); when both are LOW, both sides drive simultaneously (bidirectional mode); when both are HIGH, all outputs enter high-impedance state.

Is CD74HCT243E RoHS compliant and lead-free?

Yes. Per TI's packaging addendum, CD74HCT243E carries NIPDAU (nickel-palladium-gold) lead finish and is RoHS-compliant (Pb-free), with full documentation available in the official TI product folder and orderable part number listing.

What is the recommended bypass capacitor value for CD74HCT243E?

Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible (≤5 mm) to the V_CC pin of CD74HCT243E to suppress high-frequency switching noise. For enhanced stability, this can be paralleled with a 1 µF tantalum or ceramic capacitor on the same power rail.

CD74HCT243E Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74HCT

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

Packaging:: Tube

Product Status:: Active

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

CD74HCT243E FAQ

1.How can I place an order for CD74HCT243E through Aetrix?

Please submit a Request for Quotation (RFQ) for CD74HCT243E 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 CD74HCT243E reliable?

The price and inventory of CD74HCT243E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT243E is usually 5 days.

3.What payment methods are accepted for CD74HCT243E?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT243E transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for CD74HCT243E?

CD74HCT243E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your CD74HCT243E 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 CD74HCT243E?

For technical support, including CD74HCT243E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT243E requirements.

6.How does Aetrix verify that CD74HCT243E is sourced from the original manufacturer or authorized distributors?

All CD74HCT243E 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 CD74HCT243E meets industry standards.

7.What is the process for return or replacement of CD74HCT243E?

All CD74HCT243E units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT243E, 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 CD74HCT243E part is unused and in its original packaging.

Return procedure for CD74HCT243E:

1.Submit a request within 90 days.

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

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