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onsemi MC74AC640DT
- Part No.:
- MC74AC640DT
- Manufacturer:
- onsemi
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
MC74AC640DT.pdf
- Description:
- IC TXRX INVERT 5.5V 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,527
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Product details
Overview
MC74AC640DT from ON Semiconductor is an octal 3-state inverting bus transceiver designed for asynchronous bidirectional data transfer between two 8-bit buses. It features TTL-compatible inputs, ±24 mA output drive capability, 5 V supply operation, and TSSOP-20 packaging. It enables A→B or B→A data flow controlled by the T/R input, with independent 3-state control via OE - used in legacy industrial backplane interfaces and memory-mapped I/O expansion.
For engineers reviewing the MC74AC640DT datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, validated pin functions, real-world use cases in bus isolation and level translation, and confirmed alternative parts with documented functional and timing differences.
Technical Context
The MC74AC640DT implements dual-directional 8-bit data routing using a single active-low Output Enable (OE) and a Transmit/Receive (T/R) control signal that determines data direction without requiring external logic inversion. Its CMOS AC-series architecture ensures compatibility with TTL input thresholds while delivering rail-to-rail output swing under load.
All 16 I/O pins (A0–A7, B0–B7) operate as bidirectional 3-state buffers with defined high-impedance behavior when OE is HIGH; propagation delays are symmetric (tPLH/tPHL ≤ 8.5 ns at VCC = 5.0 V, CL = 50 pF), and output disable times (tPLZ/tPHZ ≤ 11.0 ns) support fast bus arbitration in shared-memory systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Supply | 4.5 V to 5.5 V - operates reliably across standard 5 V ±10% industrial rails |
| IOH/IOL Drive | −24 mA / +24 mA - drives standard TTL loads without external pull-ups or buffers |
| tPLH/tPHL | ≤ 8.5 ns - supports >100 MHz bus toggle rates in point-to-point configurations |
| VIH/VIL Thresholds | 2.0 V / 0.8 V - fully compatible with 5 V TTL logic families without level shifters |
| IOZ Leakage | ±5.0 μA max - ensures stable high-impedance state during bus contention or power sequencing |
| Power Dissipation | 450 mW max (TSSOP-20) - enables use in thermally constrained PCB layouts without forced air |
| ESD Rating | HBM > 2000 V - meets industrial handling requirements per JESD22-A114-A |
Pinout & Package
TSSOP-20 package (Case 948E), 0.65 mm pitch, 6.6 mm × 4.4 mm footprint, 1.2 mm max height - optimized for high-density PCB layouts with automated assembly compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A0–A7 | Side A bidirectional I/O: inputs when driving A→B, outputs when driving B→A (3-state) |
| 9 | OE | Active-low output enable: HIGH disables all A/B outputs into high-impedance state |
| 10 | T/R | Transmit/Receive control: HIGH enables A→B, LOW enables B→A data flow |
| 11, 12, 13, 14, 15, 16, 17, 18 | B0–B7 | Side B bidirectional I/O: inputs when driving B→A, outputs when driving A→B (3-state) |
| 19 | VCC | Positive supply pin - must be decoupled locally with 0.1 μF ceramic capacitor |
| 20 | GND | Ground reference - low-inductance connection required for noise immunity |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 8-bit data path | Single device replaces two unidirectional octal buffers, reducing component count and layout area |
| 3-state outputs with independent OE | Enables multiple devices on shared bus without external arbitration logic or bus keepers |
| TTL-compatible input thresholds | Accepts standard 5 V TTL logic levels directly - eliminates need for input voltage translators |
| Matched propagation delays | tPLH ≈ tPHL ensures symmetrical setup/hold timing margins in synchronous bus protocols |
| Low quiescent ICC | 80 μA max - minimizes standby current in power-sensitive embedded control modules |
Applications
| Industrial Backplane Interface | Legacy Memory-Mapped I/O Expansion |
|---|---|
|
Use Scenario: Isolating CPU local bus from peripheral expansion slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional data bridge between microcontroller address/data bus and add-on I/O cards. Use Value: Enables hot-swap-capable slot design via OE-controlled bus isolation and T/R-driven direction switching without glue logic. |
Use Scenario: Connecting 8-bit microcontrollers to parallel EEPROM or SRAM in cost-sensitive instrumentation. IC Role / Device Role / Timing Role: Level-translating and bus-driving interface between MCU data bus and external memory chips. Use Value: Delivers ±24 mA drive to meet memory chip input current requirements while maintaining TTL-compatible voltage thresholds. |
| Microcontroller Peripheral Multiplexing | Test Equipment Signal Routing |
|
Use Scenario: Sharing a single 8-bit data port among multiple peripherals (ADC, DAC, display driver) in embedded test fixtures. IC Role / Device Role / Timing Role: Direction-controlled data switch enabling time-multiplexed access to shared bus resources. Use Value: Reduces MCU GPIO usage by 16 pins and eliminates software-controlled tristate management overhead. |
Use Scenario: Reconfigurable signal path selection in automated test equipment for DUT interface adaptation. IC Role / Device Role / Timing Role: Low-latency bidirectional signal router between test controller and device-under-test interface banks. Use Value: Sub-9 ns propagation delay ensures deterministic timing alignment across multiple test channels. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT640DBR | SOIC-20 package; identical AC-series specs but 96 °C/W θJA vs. 128 °C/W for MC74AC640DT | Higher thermal margin in convection-cooled environments; same pinout and logic behavior | Select when board-level airflow is limited and junction temperature rise must be minimized |
| 74LCX640MTCX | Lower VCC range (2.0–3.6 V); 24 mA drive only at 3.3 V; not TTL-input compatible | Requires level-shifting for 5 V systems; suited for mixed-voltage 3.3 V/5 V interface designs | Choose only if migrating to 3.3 V core logic and redesigning input conditioning circuitry |
Compared with SN74ACT640DBR and 74LCX640MTCX, the MC74AC640DT offers optimal thermal performance in space-constrained TSSOP layouts while retaining full 5 V TTL interoperability - making it the preferred choice for retrofitting legacy 5 V industrial controllers without board revision.
Availability
MC74AC640DT is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory-mapped I/O expansion, microcontroller peripheral multiplexing, and test equipment signal routing requiring stable component supply and long-term obsolescence mitigation.
Supply support for MC74AC640DT 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
ON Semiconductor is a global semiconductor supplier focused on energy-efficient electronics, delivering power management, analog, sensor, and logic solutions for automotive, industrial, and cloud infrastructure markets.
The MC74AC640DT belongs to the AC-series logic family, engineered for high-speed 5 V TTL-compatible operation in industrial control and legacy system upgrades where reliability and pin-for-pin compatibility with older 74-series devices are critical.
FAQ
What is the maximum operating temperature range for the MC74AC640DT?
The MC74AC640DT is rated for operation from −40 °C to +85 °C across all package types, including the TSSOP-20 variant. This range is validated per the Recommended Operating Conditions table in the official ON Semiconductor datasheet (Rev. 2, March 2006), and applies to both commercial and industrial ambient conditions without derating.
Does the MC74AC640DT support live insertion or hot-swap operation?
The MC74AC640DT supports controlled hot-swap operation when OE is held HIGH during insertion, placing all A/B pins in high-impedance state. Its ±5.0 μA IOZ leakage and 2000 V HBM ESD rating reduce risk of bus disturbance, but external current-limiting resistors and staggered VCC/GND pin entry are still recommended per system-level hot-swap design practices.
Can the MC74AC640DT be used with 3.3 V logic systems?
The MC74AC640DT is specified only for 4.5 V to 5.5 V VCC operation and requires TTL-compatible input voltages (VIH ≥ 2.0 V). It is not guaranteed to function correctly with 3.3 V-only logic families. For 3.3 V systems, ON Semiconductor's 74LCX640 or 74VCX640 series are appropriate alternatives - the MC74AC640DT must be used in 5 V domains.
What is the purpose of the T/R pin on the MC74AC640DT?
The T/R (Transmit/Receive) pin on the MC74AC640DT controls data direction: when T/R = HIGH, data flows from A-side inputs to B-side outputs; when T/R = LOW, data flows from B-side inputs to A-side outputs. This single-pin control eliminates the need for external inverters or dual-control signals in bidirectional bus architectures.
How does the MC74AC640DT differ from the MC74ACT640DT?
The MC74AC640DT uses AC-series logic (CMOS with TTL-compatible inputs), while MC74ACT640DT uses ACT-series logic (advanced CMOS with tighter AC specs and lower ICC). Key differences include propagation delay (AC: ≤8.5 ns vs. ACT: ≤7.5 ns), quiescent current (AC: 80 μA vs. ACT: 4.0 μA), and output drive symmetry - the MC74AC640DT is optimized for cost-sensitive 5 V industrial applications where marginal speed gain is unnecessary.
MC74AC640DT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 24mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP
MC74AC640DT FAQ
1.How can I place an order for MC74AC640DT through Aetrix?
Please submit a Request for Quotation (RFQ) for MC74AC640DT 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 MC74AC640DT reliable?
The price and inventory of MC74AC640DT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74AC640DT is usually 5 days.
3.What payment methods are accepted for MC74AC640DT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC74AC640DT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC74AC640DT?
MC74AC640DT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC74AC640DT 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 MC74AC640DT?
For technical support, including MC74AC640DT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74AC640DT requirements.
6.How does Aetrix verify that MC74AC640DT is sourced from the original manufacturer or authorized distributors?
All MC74AC640DT 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 MC74AC640DT meets industry standards.
7.What is the process for return or replacement of MC74AC640DT?
All MC74AC640DT units undergo pre-shipment inspection (PSI). If there is an issue with MC74AC640DT, 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 MC74AC640DT part is unused and in its original packaging.
Return procedure for MC74AC640DT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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