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onsemi MC74ACT245MELG
- Part No.:
- MC74ACT245MELG
- Manufacturer:
- onsemi
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
MC74ACT245MELG.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOEIAJ
- Quantity:
- Payment:
- Shipping:
Inventory:3,500
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Product details
Overview
MC74ACT245MELG from onsemi is an octal bidirectional transceiver IC with 3-state inputs/outputs, designed for bus-oriented data transfer between two 8-bit ports (A and B). It supports TTL-compatible inputs, delivers ±24 mA output drive at both ports, operates at 4.5–5.5 V supply, and features independent Transmit/Receive (T/R) and Output Enable (OE) controls. It is used in microprocessor bus interface, memory expansion, and peripheral data routing applications.
For engineers reviewing the MC74ACT245MELG datasheet, pinout, applications, or equivalent options, key selection considerations include its 5 V operation, bidirectional flow control logic (T/R active-HIGH for A→B, active-LOW for B→A), 3-state output disable behavior, and SOIC-20W package compatibility with industrial temperature range (−40°C to +85°C).
Technical Context
The MC74ACT245MELG implements eight non-inverting bidirectional buffers with dual 3-state control: OE disables both A and B ports simultaneously into high-impedance, while T/R determines directionality-HIGH enables A→B, LOW enables B→A. Its TTL-compatible inputs accept standard 5 V logic thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V at VCC = 5.5 V), ensuring interoperability with legacy 5 V systems.
Propagation delay is specified at 1.5–8.0 ns (tPLH/tPHL, CL = 50 pF, VCC = 5.0 V), output enable/disable times range from 1.0–11.0 ns, and it maintains rail-to-rail output voltage swing (VOH ≥ 4.4 V, VOL ≤ 0.44 V at IOL = 24 mA), supporting robust noise margins in noisy bus environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5–5.5 V - Ensures stable operation in standard 5 V digital systems with ±10% tolerance. |
| Output Drive | ±24 mA per port - Supports direct connection to multiple TTL loads without external buffering. |
| Propagation Delay | 1.5–8.0 ns - Enables high-speed bus arbitration in microcontroller and FPGA peripheral interfaces. |
| Input Compatibility | TTL-compatible - Accepts standard 5 V logic levels, eliminating level-shifting requirements in mixed-logic designs. |
| Operating Temperature | −40°C to +85°C - Qualified for industrial-grade embedded and automotive body-control applications. |
| 3-State Leakage | ±6.0 µA max - Minimizes bus contention current when outputs are disabled, critical for hot-swap and multi-master buses. |
| Input Capacitance | 4.5 pF - Low capacitive loading preserves signal integrity and timing margins on high-frequency data lines. |
Pinout & Package
MC74ACT245MELG is housed in a Pb-free SOIC-20 wide-body (Case 751D) package, 12.95 mm × 7.60 mm × 2.65 mm, with 1.27 mm pitch, suitable for automated SMT assembly and industrial thermal cycling.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OE (Pin 1) | Global 3-State Enable | Active-HIGH signal that places both A and B ports in high-Z state - essential for bus arbitration and multi-device sharing. |
| T/R (Pin 2) | Data Direction Control | Active-HIGH enables A→B transfer; active-LOW enables B→A - provides deterministic, single-wire directional control. |
| A0–A7 (Pins 3–10) | Port A I/O Terminals | Bidirectional 3-state pins - serve as inputs or outputs depending on T/R state; sink/source 24 mA. |
| VCC (Pin 20) | Positive Supply | 5 V power rail - must be decoupled locally to suppress switching noise affecting propagation delay and output stability. |
| GND (Pin 11) | Ground Reference | Common return path for all I/O and supply currents - requires low-inductance layout to maintain noise immunity. |
| B0–B7 (Pins 12–19) | Port B I/O Terminals | Complementary bidirectional 3-state pins - mirror A-port functionality and share same drive strength and timing specs. |
Key Features
| Feature | Design Value |
|---|---|
| Octal bidirectional data path | Enables full-duplex 8-bit bus bridging between two independent subsystems using only one control line (T/R). |
| TTL-compatible input thresholds | VIH ≥ 2.0 V and VIL ≤ 0.8 V at 5.5 V allow seamless integration with legacy 5 V microcontrollers and peripherals. |
| Matched propagation delays (A↔B) | tPLH/tPHL symmetry (1.5–8.0 ns) ensures consistent timing regardless of data direction - simplifies timing closure in bidirectional protocols. |
| Low 3-state leakage current | IOZT ≤ ±6.0 µA prevents unintended current paths during bus contention or power-down states. |
| Pb-free SOIC-20W packaging | RoHS-compliant, industry-standard footprint compatible with existing reflow profiles and test fixtures. |
Applications
| Microprocessor Bus Interface | Memory Expansion Module |
|---|---|
Use Scenario: Interfacing an 8-bit microcontroller data bus to external peripherals such as UARTs, ADCs, or GPIO expanders. IC Role / Device Role / Timing Role: Bidirectional data buffer that isolates the MCU bus during idle cycles and enables controlled read/write bursts via OE and T/R. Use Value: Eliminates need for separate transmit/receive transceivers - reduces component count and PCB area while maintaining timing predictability (tPLH ≤ 8.0 ns). | Use Scenario: Adding parallel SRAM or EPROM to an embedded system with limited address/data bus drive capability. IC Role / Device Role / Timing Role: Data bus transceiver that buffers and directionally routes 8-bit data between CPU and memory during read/write cycles. Use Value: ±24 mA drive supports fan-out to multiple memory devices; 3-state control prevents bus conflicts during memory refresh or wait-state insertion. |
| Industrial I/O Expansion | Legacy System Bus Bridge |
Use Scenario: Connecting programmable logic controllers (PLCs) to distributed I/O modules over extended backplane traces. IC Role / Device Role / Timing Role: Robust bus repeater that restores signal integrity and enforces direction control across noisy industrial environments. Use Value: −40°C to +85°C rating and low VOL (≤0.44 V at 24 mA) ensure reliable operation under voltage droop and EMI stress. | Use Scenario: Migrating legacy ISA or PC/104 bus designs to modern controllers while retaining original peripheral cards. IC Role / Device Role / Timing Role: Protocol-transparent bridge that mirrors data flow direction based on host-side control signals (T/R, OE). Use Value: TTL-compatible inputs accept legacy bus signaling without level shifters; SOIC-20W footprint matches common board layouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT245N | Same logic function, identical AC/DC specs, but offered in PDIP-20 package - no surface-mount option. | Not suitable for automated SMT production; higher thermal resistance (JA = 70°C/W vs. 96°C/W for SOIC). | Select when through-hole prototyping or legacy socket-based systems require pin-compatible replacement. |
| 74LCX245MTCX | Lower VCC range (2.0–3.6 V), CMOS input thresholds, 24 mA drive - not TTL-compatible; different VIH/VIL. | Designed for 3.3 V systems only; incompatible with 5 V logic families without level translation. | Choose only for new 3.3 V designs where power efficiency and lower voltage operation outweigh compatibility needs. |
Compared with SN74ACT245N and 74LCX245MTCX, the MC74ACT245MELG uniquely combines 5 V TTL compatibility, SOIC-20W surface-mount packaging, and industrial temperature support - making it the optimal choice for upgrading legacy 5 V bus architectures with automated manufacturing requirements.
Availability
MC74ACT245MELG is available at Aetrix Electronics and suitable for microprocessor bus interface, memory expansion, industrial I/O expansion, and legacy system bus bridge applications requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.
Supply support for MC74ACT245MELG 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 specializing in energy-efficient silicon solutions for automotive, industrial, cloud, and IoT applications.
The MC74ACT245MELG belongs to onsemi's legacy logic family, engineered specifically for robust 5 V bus interfacing in industrial and embedded systems where reliability, noise immunity, and backward compatibility are critical.
FAQ
What is the recommended operating voltage range for MC74ACT245MELG?
The MC74ACT245MELG is rated for 4.5 V to 5.5 V supply operation. Operation outside this range may cause functional failure or reduced noise margin. The device is not specified for 3.3 V use, and applying voltages below 4.5 V risks violating input threshold guarantees (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and output drive specifications. Always verify VCC stability within this window during system power-up and brownout conditions for reliable MC74ACT245MELG performance.
How does the T/R pin control data direction in MC74ACT245MELG?
In the MC74ACT245MELG, the T/R (Transmit/Receive) pin is an active-HIGH control: when T/R = HIGH, data flows from Port A to Port B; when T/R = LOW, data flows from Port B to Port A. This unidirectional control is independent of OE - if OE is HIGH, both ports enter high-Z regardless of T/R state. The MC74ACT245MELG truth table confirms this behavior, enabling deterministic bus arbitration in systems like microcontroller peripheral interfaces.
Is MC74ACT245MELG pin-compatible with MC74AC245 variants?
Yes, MC74ACT245MELG shares identical pinout, package (SOIC-20W), and terminal functions with MC74AC245 variants such as MC74AC245DWG. However, MC74ACT245MELG features TTL-compatible inputs (VIH/VIL optimized for 5 V), whereas MC74AC245 uses CMOS thresholds - making them electrically interchangeable only when driving sources meet both input standards. The MC74ACT245MELG marking "ACT245" distinguishes it on-package for quick identification.
What is the maximum capacitive load the MC74ACT245MELG can drive reliably?
The MC74ACT245MELG AC characteristics are characterized at CL = 50 pF, with propagation delays up to 8.0 ns and output enable/disable times up to 12.0 ns under those conditions. Driving loads significantly above 50 pF increases delay and may degrade edge rates; for >100 pF, series termination or buffer staging is recommended. The MC74ACT245MELG's CI/O = 15 pF minimizes added load, but total net capacitance (trace + stub + receiver inputs) must remain within design margins to preserve timing integrity in high-speed bus implementations.
Does MC74ACT245MELG support hot-swap or live-insertion scenarios?
The MC74ACT245MELG is not explicitly qualified for hot-swap operation. While its absolute maximum ratings include ±20 mA input diode current and ±50 mA output current, and it features 3-state outputs controllable by OE, there is no built-in bus-hold, power-up/down sequencing protection, or I²C-style slew-rate control. For hot-swap applications, external current-limiting resistors, TVS diodes, and controlled OE assertion timing are required. The MC74ACT245MELG should be powered and stabilized before enabling OE or T/R to avoid undefined states or latch-up risk.
MC74ACT245MELG 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, Non-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
MC74ACT245MELG FAQ
1.How can I place an order for MC74ACT245MELG through Aetrix?
Please submit a Request for Quotation (RFQ) for MC74ACT245MELG 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 MC74ACT245MELG reliable?
The price and inventory of MC74ACT245MELG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74ACT245MELG is usually 5 days.
3.What payment methods are accepted for MC74ACT245MELG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC74ACT245MELG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC74ACT245MELG?
MC74ACT245MELG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC74ACT245MELG 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 MC74ACT245MELG?
For technical support, including MC74ACT245MELG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74ACT245MELG requirements.
6.How does Aetrix verify that MC74ACT245MELG is sourced from the original manufacturer or authorized distributors?
All MC74ACT245MELG 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 MC74ACT245MELG meets industry standards.
7.What is the process for return or replacement of MC74ACT245MELG?
All MC74ACT245MELG units undergo pre-shipment inspection (PSI). If there is an issue with MC74ACT245MELG, 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 MC74ACT245MELG part is unused and in its original packaging.
Return procedure for MC74ACT245MELG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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