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onsemi MC74ACT640MELG
- Part No.:
- MC74ACT640MELG
- Manufacturer:
- onsemi
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
MC74ACT640MELG.pdf
- Description:
- IC TXRX INVERT 5.5V SOEIAJ-20
- Quantity:
- Payment:
- Shipping:
Inventory:4,510
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Product details
Overview
MC74ACT640MELG from onsemi is an octal 3-state inverting bus transceiver enabling asynchronous bidirectional data transfer between two 8-bit buses. It operates at 4.5–5.5 V, supports ±24 mA output drive, features TTL-compatible inputs, and uses a single T/R control line to select A→B or B→A direction. It is used in industrial backplane interfaces requiring isolated bus communication.
For engineers reviewing the MC74ACT640MELG datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional 3-state control timing (tPLH/tPHL ≤ 8.5 ns), output enable/disable latency (tPZH/tPZL ≤ 11.0 ns), and SOIC-20W package compatibility with legacy 5 V logic systems.
Technical Context
The MC74ACT640MELG implements dual 8-bit bidirectional I/O paths controlled by independent OE (output enable) and T/R (transmit/receive) inputs. Its logic architecture ensures that only one bus side drives at a time, with high-impedance isolation when OE is high.
All inputs are TTL-compatible (VIH = 2.0 V min, VIL = 0.8 V max), and outputs deliver guaranteed VOH ≥ 4.4 V and VOL ≤ 0.1 V under −24 mA/24 mA loads at VCC = 4.5 V. Propagation delays are characterized across −40°C to +85°C with CL = 50 pF.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures interoperability with standard 5 V TTL and CMOS systems. |
| Output Drive | ±24 mA - Sustains robust signal integrity across loaded backplane traces without external buffers. |
| Propagation Delay | tPLH/tPHL ≤ 8.5 ns - Enables reliable operation in high-speed 8-bit parallel interfaces up to ~100 MHz effective throughput. |
| Enable/Disable Time | tPZH/tPZL ≤ 11.0 ns - Supports rapid bus arbitration and dynamic direction switching in multiplexed architectures. |
| Input Compatibility | TTL-level VIH/VIL - Directly interfaces with legacy 74LS, 74ALS, and microcontroller GPIO without level-shifting. |
| 3-State Leakage | IOZ ≤ ±5.0 μA - Maintains bus integrity during disable mode with negligible DC loading on adjacent lines. |
| Operating Temp | −40°C to +85°C - Qualified for industrial temperature environments including factory automation and instrumentation. |
Pinout & Package
MC74ACT640MELG is housed in a Pb-free SOIC-20WB (Case 751D) package, 12.8 mm × 7.5 mm × 2.5 mm body, with 1.27 mm pitch gull-wing leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A7 | Side A bidirectional I/O | Configurable as input or 3-state output depending on T/R and OE state; connects to Bus A. |
| B0–B7 | Side B bidirectional I/O | Configurable as input or 3-state output depending on T/R and OE state; connects to Bus B. |
| OE | Active-low output enable | When high, forces all A/B pins into high-impedance; enables bus isolation. |
| T/R | Direction control | High = A→B data flow; Low = B→A data flow; synchronous with OE for glitch-free switching. |
| VCC | Positive supply | 5 V nominal power rail; decoupling required within 10 mm of pin 20 per layout guidelines. |
| GND | Ground reference | Common return for all I/O and supply currents; must be low-inductance connection to system ground plane. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 3-state control | Independent OE and T/R inputs allow precise timing of bus enable and direction change without contention. |
| ±24 mA output drive | Supports direct driving of multiple TTL loads or long PCB traces without fanout buffers. |
| TTL-compatible inputs | Eliminates need for external level shifters when interfacing with legacy 74-series logic or microcontrollers. |
| Pb-free SOIC-20WB | RoHS-compliant package with moisture sensitivity level 1 - no bake required before reflow assembly. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Connecting a modern microcontroller-based module to an older 8-bit ISA-style backplane with separate address/data buses. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between CPU-side and peripheral-side buses under software-controlled T/R and OE signals. Use Value: Enables drop-in replacement of obsolete 74ACT245 while maintaining identical timing, drive strength, and pinout compatibility. | Use Scenario: Extending a PLC's internal I/O expansion bus across a multi-board chassis using daisy-chained daughterboards. IC Role / Device Role / Timing Role: Isolating and routing 8-bit parallel I/O between boards via shared backplane, with OE used for slot-select arbitration. Use Value: Prevents bus contention during hot-swap events and supports deterministic read/write cycles with sub-10 ns propagation delay. |
| Test Equipment Data Capture | Digital Logic Analyzer Front-End |
Use Scenario: Capturing parallel digital signals from DUTs running at 5 V logic levels into a 3.3 V FPGA acquisition system. IC Role / Device Role / Timing Role: Level-translating and buffering 8-bit wide data streams with configurable direction for trigger-gated capture windows. Use Value: Provides clean, slew-controlled transitions and 3-state isolation during idle periods to prevent signal reflection on unterminated traces. | Use Scenario: Interfacing a logic analyzer's probe bank to a target board's 5 V parallel bus while preserving signal fidelity. IC Role / Device Role / Timing Role: Acting as a high-fidelity, low-skew buffer between passive probes and acquisition ASIC, with OE used for channel gating. Use Value: Delivers <10 ns propagation skew across all 8 bits and supports hot-plug-safe high-impedance disconnect during probe reconfiguration. |
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 |
|---|---|---|---|
| SN74ACT245N | Same 5 V operation, ±24 mA drive, but non-inverting logic; SOIC-20 package; slightly higher tPLH/tPHL (9 ns max). | Requires inverted control logic for direction mapping; not functionally identical due to non-inverting data path. | Select when system design assumes non-inverting transceivers and can accommodate minor timing increase. |
| MC74ACT245MELG | Identical package, pinout, and AC/DC specs, but non-inverting; same manufacturer, same Pb-free SOIC-20WB construction. | No logic inversion - eliminates need for external inverters on T/R or data lines in new designs. | Preferred for new designs where data polarity preservation simplifies firmware and reduces component count. |
Compared with SN74ACT245N and MC74ACT245MELG, the MC74ACT640MELG provides inverting data transfer essential for certain legacy bus protocols (e.g., IEEE 1149.1 boundary-scan test access port), while maintaining identical timing, drive, and packaging - making it the sole choice where signal inversion is architecturally required.
Availability
MC74ACT640MELG is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, test equipment data capture, and digital logic analyzer front-ends requiring stable component supply and long-term manufacturability.
Supply support for MC74ACT640MELG 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
onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.
The MC74ACT640MELG belongs to the 74ACT advanced CMOS logic family, designed specifically for high-speed, low-power 5 V digital interface applications demanding TTL compatibility, robust noise immunity, and industrial temperature reliability.
FAQ
What is the logic function of the MC74ACT640MELG?
The MC74ACT640MELG is an octal 3-state inverting bus transceiver. It transfers data between two 8-bit buses (A and B) with polarity inversion: each bit output is the logical complement of its corresponding input. Direction is controlled by the T/R pin, and output enable is managed by the active-low OE pin. This inversion behavior is intrinsic to the MC74ACT640MELG and differs from non-inverting equivalents like the MC74ACT245MELG.
Does the MC74ACT640MELG support 3.3 V operation?
No, the MC74ACT640MELG is specified only for 4.5 V to 5.5 V operation per its Recommended Operating Conditions. It does not guarantee functionality or DC/AC performance below 4.5 V. For 3.3 V systems, designers should consider level translators or 3.3 V–compatible transceivers such as the SN74LVC245A. The MC74ACT640MELG requires a stable 5 V supply to meet its ±24 mA drive and timing specifications.
What is the maximum capacitive load the MC74ACT640MELG can drive reliably?
The MC74ACT640MELG AC characteristics (propagation delay, enable/disable times) are characterized with CL = 50 pF. While the device can physically drive higher capacitance, timing margins degrade beyond this value. For loads exceeding 50 pF, designers must verify setup/hold timing in their specific application. The MC74ACT640MELG's typical CI/O capacitance is 15 pF, minimizing added loading on driven nodes.
Is the MC74ACT640MELG pin-compatible with the 74ACT245?
No, the MC74ACT640MELG is not pin-compatible with the 74ACT245. Although both are octal transceivers in SOIC-20 packages, the MC74ACT640MELG has an inverting data path and different pin assignments: its T/R pin is on pin 11, whereas the 74ACT245 uses pin 1 for DIR. The MC74ACT640MELG pinout matches the industry-standard 74ACT640 layout, not the 74ACT245. Always verify against the MC74ACT640MELG datasheet Figure 1.
What does the "MELG" suffix indicate in MC74ACT640MELG?
The "MELG" suffix in MC74ACT640MELG denotes a Pb-free SOIC-20WB (wide-body) package per onsemi's standardized marking convention: "ME" = SOIC-20WB, "L" = tape-and-reel packaging, and "G" = lead-free (RoHS-compliant). This matches the ordering information on page 5 of the datasheet, confirming the MC74ACT640MELG is identical in form, fit, and function to the MC74ACT640DWR2G variant, differing only in reel quantity and date coding.
MC74ACT640MELG Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74ACT
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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:
- SOEIAJ-20
MC74ACT640MELG FAQ
1.How can I place an order for MC74ACT640MELG through Aetrix?
Please submit a Request for Quotation (RFQ) for MC74ACT640MELG 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 MC74ACT640MELG reliable?
The price and inventory of MC74ACT640MELG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74ACT640MELG is usually 5 days.
3.What payment methods are accepted for MC74ACT640MELG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC74ACT640MELG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC74ACT640MELG?
MC74ACT640MELG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC74ACT640MELG 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 MC74ACT640MELG?
For technical support, including MC74ACT640MELG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74ACT640MELG requirements.
6.How does Aetrix verify that MC74ACT640MELG is sourced from the original manufacturer or authorized distributors?
All MC74ACT640MELG 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 MC74ACT640MELG meets industry standards.
7.What is the process for return or replacement of MC74ACT640MELG?
All MC74ACT640MELG units undergo pre-shipment inspection (PSI). If there is an issue with MC74ACT640MELG, 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 MC74ACT640MELG part is unused and in its original packaging.
Return procedure for MC74ACT640MELG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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