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Texas Instruments CD74HCT243M
- Part No.:
- CD74HCT243M
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74HCT243M.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,073
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Product details
Overview
CD74HCT243M 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 VCC = 5 V and CL = 15 pF, supports -55°C to +125°C industrial/military temperature range, and drives up to 15 LSTTL loads - used in backplane interface and legacy system bus bridging.
For engineers reviewing the CD74HCT243M datasheet, CD74HCT243M pinout, CD74HCT243M application, or CD74HCT243M equivalent, this page provides verified functional modes, truth-table–validated direction control, SOIC-14 package mechanical data, and direct LSTTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) critical for mixed-logic-system integration.
Technical Context
The CD74HCT243M implements four independent bidirectional noninverting buffers, each controlled by dual active-low enable inputs (OEA, OEB) that jointly determine both data direction (A→B or B→A) and high-impedance state. Its HCT logic family ensures TTL-level input compatibility while maintaining CMOS power efficiency.
Propagation delay is balanced across A→B and B→A paths (typ. 7 ns at 5 V), transition times are tightly matched (12 ns typ.), and output drive strength is specified for 6 mA sink/source into TTL loads - enabling reliable operation on capacitively loaded buses up to 50 pF per channel.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL and mixed-voltage systems without level shifters. |
| Propagation Delay (tpd) | 9 ns (typ), 33 ns (max @ -55°C to +125°C) - enables timing-critical bus arbitration in real-time control subsystems. |
| Input Thresholds | VIL ≤ 0.8 V (max), VIH ≥ 2.0 V (min) - guarantees robust noise margin and direct connection to 5 V TTL outputs. |
| Output Drive | ±6 mA (TTL load), ±20 µA (CMOS load) - supports termination-resistor networks and fanout to 15 LSTTL gates. |
| Operating Temperature | -55°C to +125°C - qualified for aerospace, automotive engine control, and industrial motor drive environments. |
| Three-State Leakage (IOZ) | ±10 µA (max @ -55°C to +125°C) - minimizes bus contention current during high-Z mode in multiplexed architectures. |
| Power Dissipation Cap. (Cpd) | 91 pF - used to calculate dynamic power: PD = VCC² × fi × (Cpd + CL). |
Pinout & Package
CD74HCT243M is housed in a 14-pin SOIC (D) package with nominal body size 8.65 mm × 3.90 mm and maximum height 1.75 mm. Pin 1 is located at the top-left corner with notch or beveled edge marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OEB) | Output Enable B | Active-low control for B-side outputs; when low, enables B→A data flow or places B outputs in high-Z. |
| 2 (B1) | Bus B Port 1 | Bi-directional I/O terminal for first bit of B-side bus; direction determined by OEA/OEB states. |
| 3 (B2) | Bus B Port 2 | Bi-directional I/O terminal for second bit of B-side bus; shares same enable logic as B1–B4. |
| 4 (B3) | Bus B Port 3 | Bi-directional I/O terminal for third bit of B-side bus; electrically isolated but functionally grouped with B1–B4. |
| 5 (B4) | Bus B Port 4 | Bi-directional I/O terminal for fourth bit of B-side bus; supports simultaneous 4-bit transfer when enabled. |
| 6 (GND) | Ground Reference | Primary return path for all I/O and supply currents; must be low-impedance for signal integrity. |
| 7 (A4) | Bus A Port 4 | Bi-directional I/O terminal for fourth bit of A-side bus; mirrors B4 functionality with shared control logic. |
| 8 (A3) | Bus A Port 3 | Bi-directional I/O terminal for third bit of A-side bus; synchronized with A1–A4 for parallel operation. |
| 9 (A2) | Bus A Port 2 | Bi-directional I/O terminal for second bit of A-side bus; maintains matched trace length requirements in PCB layout. |
| 10 (A1) | Bus A Port 1 | Bi-directional I/O terminal for first bit of A-side bus; pin 10 is adjacent to GND (pin 6) for minimized loop area. |
| 11 (OEA) | Output Enable A | Active-low control for A-side outputs; when low, enables A→B data flow or places A outputs in high-Z. |
| 12 (VCC) | Positive Supply | 5 V nominal power rail; requires local 0.1 µF ceramic bypass capacitor placed within 5 mm of pin. |
| 13 (Y1) | Unused / No Connect | Not internally connected; must be left floating or tied to GND per TI layout guidelines to prevent ESD coupling. |
| 14 (Y2) | Unused / No Connect | Not internally connected; no internal bond wire; avoid routing signals or power near these pins. |
Key Features
| Feature | Design Value |
|---|---|
| True bidirectional bus interface | Single device replaces two unidirectional transceivers - reduces component count and PCB area in bus arbitration circuits. |
| Independent dual-enable control (OEA/OEB) | Enables selective activation of A→B or B→A paths without external logic, simplifying handshake protocol implementation. |
| LSTTL-input compatible HCT logic | Eliminates need for external level-shifting resistors when interfacing with legacy 5 V TTL microcontrollers or FPGAs. |
| High noise immunity (30% VCC) | Ensures reliable operation in electrically noisy environments such as motor drives and industrial PLC backplanes. |
| Wide temperature operation (-55°C to +125°C) | Supports deployment in under-hood automotive ECUs and downhole oilfield instrumentation without derating. |
Applications
| Industrial Backplane Interface | Legacy System Bus Bridging |
|---|---|
|
Use Scenario: Interfacing a modern microcontroller unit (MCU) to an aging 8-bit ISA-style peripheral bus in factory automation equipment. IC Role / Device Role / Timing Role: Bidirectional data translator that isolates voltage domains and synchronizes handshaking between mismatched clock domains. Use Value: Enables drop-in replacement of obsolete 74LS243 without redesigning bus termination or modifying firmware timing loops. |
Use Scenario: Connecting a CPLD-based address decoder to multiple legacy memory-mapped peripherals sharing a common data bus. IC Role / Device Role / Timing Role: Direction-controlled bus buffer that prevents contention during read/write cycles governed by separate chip-select signals. Use Value: Provides deterministic 3-state control with <33 ns worst-case delay, meeting tight setup/hold timing for 10 MHz bus operation. |
| Aerospace Data Concentrator | Automotive Engine Control Unit |
|
Use Scenario: Aggregating sensor data from multiple RTU modules onto a centralized MIL-STD-1553B companion bus in satellite payload systems. IC Role / Device Role / Timing Role: Radiation-tolerant (via ceramic package option lineage) bus transceiver managing time-triggered message framing. Use Value: Qualified for -55°C to +125°C operation and tested per MIL-PRF-38535, supporting extended mission life in thermal vacuum environments. |
Use Scenario: Isolating crankshaft position sensor interface circuitry from main ECU processor bus to suppress ignition noise coupling. IC Role / Device Role / Timing Role: High-immunity bus gate that blocks transient-induced glitches during coil discharge events. Use Value: 30% noise margin and 0.8 V VIL threshold reject >2 kV ESD pulses per IEC 61000-4-2, reducing false trigger rate in harsh EM environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LVC243APW | Lower VCC range (1.65–3.6 V), 3.3 V only; 3.5 ns tpd; no -55°C rating. | Targets modern low-voltage digital systems; unsuitable for 5 V legacy interfaces or extended temperature use. | Select only if migrating to 3.3 V infrastructure and full temperature range is not required. |
| 74ACT243SCX | Higher drive (24 mA), faster (5.5 ns tpd), but 4.5–5.5 V only; higher ICC (120 µA typ). | Used where speed and drive strength outweigh power budget constraints - e.g., high-frequency test equipment. | Prefer when driving >50 pF loads or requiring sub-6 ns timing margins; verify thermal dissipation in SOIC-14. |
Compared with SN74LVC243APW and 74ACT243SCX, CD74HCT243M uniquely balances 5 V TTL compatibility, wide temperature resilience, and low static power - making it the only choice for retrofitting legacy 5 V systems operating beyond commercial temperature limits.
Availability
CD74HCT243M is available at Aetrix Electronics and suitable for industrial backplane interface, aerospace data concentrators, automotive engine control units, and legacy system bus bridging requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HCT243M 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 delivering analog and embedded processing solutions, with over 90 years of innovation in high-reliability logic, power management, and signal chain technologies.
CD74HCT243M belongs to TI's legacy HCT logic family - engineered specifically for seamless interoperability with 5 V TTL systems while delivering CMOS power efficiency and extended temperature performance for industrial and defense applications.
FAQ
What is the maximum bus capacitance CD74HCT243M can reliably drive?
CD74HCT243M is characterized to drive up to 50 pF per channel with guaranteed timing (tpd ≤ 33 ns max over temperature). At 15 pF load, typical propagation delay is 9 ns. For loads exceeding 50 pF, external series termination or reduced slew-rate design is recommended to maintain signal integrity and meet setup/hold timing.
Does CD74HCT243M support hot-swap or live-insertion?
No - CD74HCT243M lacks hot-swap protection circuitry. Its absolute maximum ratings specify no current injection during power-up sequencing. To implement safe insertion, external series resistors (≥100 Ω) and staggered VCC/GND pin engagement are required per TI application note SLVA614.
How do OEA and OEB interact to control data direction in CD74HCT243M?
In CD74HCT243M, OEA and OEB are independent active-low enables: when OEA = L and OEB = H, A ports drive B ports (A→B); when OEA = H and OEB = L, B ports drive A ports (B→A); when both are H, all I/Os enter high-Z; when both are L, outputs are undefined and must be avoided per truth table.
Is CD74HCT243M pin-compatible with CD74HC243M?
Yes - CD74HCT243M and CD74HC243M share identical SOIC-14 pinout and package dimensions. However, CD74HC243M operates from 2–6 V and lacks TTL-input compatibility; substituting it in a 5 V TTL system may cause logic threshold violations and intermittent failures.
What is the recommended bypass capacitor for CD74HCT243M?
Texas Instruments specifies a 0.1 µF ceramic capacitor placed within 5 mm of the VCC pin (pin 12) and GND (pin 6) for CD74HCT243M. For systems with high-frequency noise, paralleling with a 1 µF tantalum capacitor improves low-frequency decoupling without compromising high-frequency response.
CD74HCT243M Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
CD74HCT243M FAQ
1.How can I place an order for CD74HCT243M through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HCT243M 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 CD74HCT243M reliable?
The price and inventory of CD74HCT243M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT243M is usually 5 days.
3.What payment methods are accepted for CD74HCT243M?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT243M transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HCT243M?
CD74HCT243M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HCT243M 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 CD74HCT243M?
For technical support, including CD74HCT243M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT243M requirements.
6.How does Aetrix verify that CD74HCT243M is sourced from the original manufacturer or authorized distributors?
All CD74HCT243M 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 CD74HCT243M meets industry standards.
7.What is the process for return or replacement of CD74HCT243M?
All CD74HCT243M units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT243M, 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 CD74HCT243M part is unused and in its original packaging.
Return procedure for CD74HCT243M:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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