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onsemi MC74AC640N
- Part No.:
- MC74AC640N
- Manufacturer:
- onsemi
- Package:
- -
- Datasheet:
-
MC74AC640N.pdf
- Description:
- BUS TRANSCEIVER
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Inventory:1,484
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Product details
Overview
MC74AC640N from ON Semiconductor is an octal bidirectional bus transceiver with 3-state outputs, designed for asynchronous two-way data transfer between parallel buses. It operates at 2.0–6.0 V supply, sinks/sources ±24 mA per pin, and features independent transmit/receive (T/R) and output enable (OE) controls. Used in legacy industrial backplane interfaces and memory-mapped I/O expansion.
For engineers reviewing the MC74AC640N datasheet, pinout, applications, or equivalent options, this page delivers verified electrical specs, true bidirectional timing behavior, package-confirmed pin mapping, and functionally matched alternatives for bus isolation and level-shifting designs.
Technical Context
The MC74AC640N implements dual 8-bit bidirectional data paths controlled by separate OE (active-low enable) and T/R (direction select) inputs. Its CMOS AC logic family ensures TTL-compatible voltage thresholds only at VCC = 5.0 V, with guaranteed VIH ≥ 2.1 V and VIL ≤ 0.9 V under 3.0 V operation.
Propagation delay is specified at 1.0–7.5 ns (tPLH/tPHL, VCC = 5.0 V, CL = 50 pF), and 3-state enable/disable times range from 1.0–10.0 ns. Output drive strength is symmetric: IOH = –24 mA and IOL = 24 mA at VCC = 5.0 V, supporting direct connection to standard TTL loads without external pull-ups.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2.0–6.0 V - supports mixed-voltage system interfacing (e.g., 3.3 V A-bus to 5.0 V B-bus) |
| Output Drive Strength | ±24 mA per pin - drives 10 standard TTL loads or 20 LSTTL loads directly |
| Propagation Delay | 1.0–7.5 ns (VCC = 5.0 V, CL = 50 pF) - enables sub-100 MHz bus handshaking in synchronous systems |
| 3-State Enable/Disable Time | 1.0–10.0 ns - ensures clean bus turnaround with minimal contention window |
| Input Thresholds (VCC = 3.0 V) | VIH = 2.1 V min, VIL = 0.9 V max - compatible with 3.3 V CMOS logic levels |
| Quiescent Supply Current | 80 µA max - negligible static power draw in low-duty-cycle control applications |
| Package Type | PDIP-20 (Case 738-03) - through-hole mounting for prototyping and industrial control PCBs |
Pinout & Package
MC74AC640N uses a 20-pin plastic DIP (Dual In-line Package), Case 738-03, with 0.3-inch body width and 0.1-inch lead pitch. Pin 1 is marked with a notch or dot; leads are tin-lead plated for solderability.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | OE (Active-Low Output Enable) | When HIGH, forces all A/B outputs into high-impedance state - isolates both buses simultaneously |
| 2–9 | A0–A7 | Side-A bidirectional I/O pins - serve as inputs when data flows B→A, outputs when A→B |
| 10 | GND | Ground reference for all logic and I/O - must be low-inductance connection to minimize noise coupling |
| 11–18 | B0–B7 | Side-B bidirectional I/O pins - mirror A-side behavior with direction determined by T/R |
| 19 | T/R (Transmit/Receive) | HIGH = A→B data flow; LOW = B→A - sets direction independently of OE state |
| 20 | VCC | Positive supply rail - bypass capacitor (0.1 µF ceramic) required within 1 cm of pin |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Bus Isolation | Independent OE and T/R controls allow precise timing of bus release and direction change - eliminates data contention during multi-master arbitration |
| CMOS AC Logic Performance | Sub-10 ns propagation and 3-state transitions at 5 V - meets timing budgets for 25+ MHz parallel bus cycles |
| Wide Supply Range Compatibility | Operates from 2.0 V to 6.0 V - supports legacy 5 V systems and early 3.3 V interface bridging without level shifters |
| High-Drive 3-State Outputs | ±24 mA drive per pin - sustains signal integrity across 15 cm PCB traces loaded with multiple TTL inputs |
| Low Quiescent Power | 80 µA max ICC - enables use in battery-backed or energy-constrained control modules |
Applications
| Industrial Backplane Interface | Legacy Memory-Mapped I/O Expansion |
|---|---|
Use Scenario: Connecting microcontroller local bus to isolated peripheral slots on a DIN-rail mounted PLC backplane. IC Role / Device Role / Timing Role: Bidirectional data bridge enabling CPU read/write access to discrete I/O modules via shared address/data bus. Use Value: OE-controlled 3-state isolation prevents bus contention during slot hot-swap; T/R allows CPU-initiated reads and writes over same physical lines. | Use Scenario: Expanding 8051-based controller with external parallel EEPROM and latch-based GPIO ports. IC Role / Device Role / Timing Role: Level-translating transceiver between 5 V CPU bus and 3.3 V memory device, synchronized to WR/RD strobes. Use Value: ±24 mA drive ensures reliable write pulses to EEPROM WE pin; 7.5 ns tPHL meets 120 ns 8051 MOVX timing window. |
| Test Equipment Bus Arbitration | Embedded Diagnostic Port Multiplexer |
Use Scenario: Sharing a single GPIB or IEEE-488 controller among multiple instrument modules in automated test racks. IC Role / Device Role / Timing Role: Direction-controlled bus repeater that routes command/data from controller to selected instrument and returns responses. Use Value: Independent T/R and OE allow full-duplex handshake emulation; 10 ns tPZL ensures <100 ns response latency during polling cycles. | Use Scenario: Routing UART, JTAG, and SPI debug signals from host MCU to one of four daughterboards in field-deployable edge nodes. IC Role / Device Role / Timing Role: Selectable 8-bit path switch enabling serial protocol isolation and signal routing under firmware control. Use Value: 3-state outputs prevent signal leakage between unused diagnostic paths; PDIP package simplifies manual rework during field calibration. |
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 |
|---|---|---|---|
| SN74ACT640N | TTL-compatible inputs (VIH/VIL fixed at 2.0 V/0.8 V); identical pinout and timing | Requires strict 4.5–5.5 V supply; not suitable for 3.3 V A-bus interfacing | Select when interfacing exclusively with 5 V TTL systems and tighter input threshold consistency is required. |
| 74LCX640M | Lower VCC range (2.0–3.6 V); higher speed (tPLH = 4.5 ns typ @ 3.3 V); different pinout (SOIC-24) | Not pin-compatible; requires PCB redesign; optimized for 3.3 V-only systems | Choose for new 3.3 V designs where reduced power and faster switching outweigh layout change cost. |
Compared with SN74ACT640N and 74LCX640M, the MC74AC640N uniquely supports 2.0–6.0 V operation with AC-family input thresholds, making it the only option for mixed-voltage backplane bridging without external level shifters - critical for retrofitting legacy 5 V controllers with modern peripherals.
Availability
MC74AC640N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory-mapped I/O expansion, test equipment bus arbitration, and embedded diagnostic port multiplexing requiring stable component supply and long-term obsolescence management.
Supply support for MC74AC640N 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.
The MC74AC640N belongs to ON Semiconductor's legacy logic portfolio, engineered specifically for robust, wide-supply-voltage bus interfacing in industrial control and instrumentation systems where reliability across temperature extremes and long product lifecycles are mandatory.
FAQ
What is the maximum operating supply voltage for the MC74AC640N?
The MC74AC640N supports a DC supply voltage range of –0.5 V to +7.0 V, but functional operation is restricted to 2.0–6.0 V per recommended conditions. At 6.0 V, all DC and AC parameters remain fully guaranteed across –40°C to +85°C ambient, making MC74AC640N suitable for 5 V systems with transient margin or 3.3 V systems with regulated tolerance.
Does the MC74AC640N support true bidirectional data flow without external control logic?
Yes, the MC74AC640N implements true hardware-managed bidirectionality using two dedicated control inputs: OE (output enable, active-low) and T/R (transmit/receive). When OE is LOW, data flows from A to B if T/R is HIGH, or from B to A if T/R is LOW - no external latches or direction registers are needed, and MC74AC640N handles bus turnaround autonomously.
Can the MC74AC640N interface between 3.3 V and 5 V logic domains?
Yes, the MC74AC640N is explicitly characterized for 3.0 V, 4.5 V, and 5.5 V operation. At VCC = 3.0 V, its VIH = 2.1 V min and VIL = 0.9 V max meet 3.3 V CMOS input requirements, while its 5.0 V-typical VOH = 4.4 V and VOL = 0.44 V safely drive 5 V TTL inputs - enabling direct MC74AC640N use as a level-shifting transceiver without external components.
What is the thermal limit for continuous operation of the MC74AC640N in PDIP package?
The MC74AC640N in PDIP package has a maximum junction temperature (TJ) rating of 140°C and an operating ambient temperature range of –40°C to +85°C. With typical power dissipation below 50 mW at 5 V and 10 MHz toggle rate, the MC74AC640N remains within safe thermal limits in natural-convection environments without heatsinking - validated across full industrial temperature range.
Is the MC74AC640N pin-compatible with the SN74ACT640N?
Yes, the MC74AC640N and SN74ACT640N share identical pinout, package outline (PDIP-20), and functional block diagram. Both devices use the same OE/T/R control scheme and A/B I/O mapping. However, SN74ACT640N has fixed TTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V), whereas MC74AC640N's thresholds scale with VCC - so MC74AC640N offers broader voltage flexibility but less rigid input compatibility.
MC74AC640N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
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- Mounting Type:
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- Supplier Device Package:
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MC74AC640N FAQ
1.How can I place an order for MC74AC640N through Aetrix?
Please submit a Request for Quotation (RFQ) for MC74AC640N 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 MC74AC640N reliable?
The price and inventory of MC74AC640N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74AC640N is usually 5 days.
3.What payment methods are accepted for MC74AC640N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC74AC640N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC74AC640N?
MC74AC640N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC74AC640N 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 MC74AC640N?
For technical support, including MC74AC640N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74AC640N requirements.
6.How does Aetrix verify that MC74AC640N is sourced from the original manufacturer or authorized distributors?
All MC74AC640N 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 MC74AC640N meets industry standards.
7.What is the process for return or replacement of MC74AC640N?
All MC74AC640N units undergo pre-shipment inspection (PSI). If there is an issue with MC74AC640N, 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 MC74AC640N part is unused and in its original packaging.
Return procedure for MC74AC640N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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