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Texas Instruments SN74ALS245A-1DWG4
- Part No.:
- SN74ALS245A-1DWG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS245A-1DWG4.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,706
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Product details
Overview
SN74ALS245A-1DWG4 from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-compatible systems. It operates from 4.5 V to 5.5 V, delivers a maximum propagation delay of 5.5 ns at 5 V, supports ±48 mA low-level output drive (–1 version), and features pnp input structure to reduce DC loading. It is used in industrial backplane interfaces requiring robust bus isolation and direction control.
For engineers reviewing the SN74ALS245A-1DWG4 datasheet, SN74ALS245A-1DWG4 pinout, SN74ALS245A-1DWG4 application, or SN74ALS245A-1DWG4 equivalent, this page provides verified functional specifications, SOIC-20 package layout, directional bus control logic, 3-state enable timing, and validated alternatives for legacy TTL system upgrades.
Technical Context
This device implements dual 8-bit bidirectional data paths controlled by DIR (direction) and OE (output enable) inputs. The DIR signal determines data flow direction-low enables B→A transmission, high enables A→B transmission-while OE independently disables all outputs into high-impedance state. Its ALS logic family ensures compatibility with standard TTL voltage thresholds and fan-out requirements.
It uses pnp input circuitry to minimize input current draw, reducing bus loading in multi-drop configurations. The –1 suffix denotes enhanced IOL capability (48 mA vs. 24 mA standard), validated only under 4.75–5.25 V VCC conditions, making it suitable for driving heavier capacitive loads or longer trace lengths without signal degradation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across industrial-grade 5 V supply tolerances. |
| Max Propagation Delay | 5.5 ns at 5 V - Enables high-speed bus handshaking in real-time control subsystems. |
| IOL (–1 version) | 48 mA - Supports direct drive of multiple TTL inputs or moderate PCB trace capacitance without buffers. |
| VIH / VIL | 2.0 V / 0.8 V - Matches standard TTL input thresholds for seamless integration into legacy logic systems. |
| 3-State Enable Time (tPZL) | 20 ns max - Guarantees fast bus release during arbitration or multiplexer switching. |
| Package | SOIC-20 (DW) - Surface-mount footprint compatible with automated assembly and IPC-7351 land patterns. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial and industrial ambient environments. |
Pinout & Package
SN74ALS245A-1DWG4 is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body size, 1.27 mm lead pitch, 2.65 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: Low = B→A data flow; High = A→B data flow. |
| 2–9 | A1–A8 | Input/output port A - Bidirectional data lines connected to local bus or microcontroller side. |
| 10 | GND | Ground reference for all logic and power domains. |
| 11 | VCC | Positive supply (4.5–5.5 V) powering internal logic and output drivers. |
| 12 | OE | Output enable active-low: Low = outputs enabled; High = all outputs in high-Z state. |
| 13–20 | B1–B8 | Input/output port B - Bidirectional data lines connected to peripheral or expansion bus side. |
Key Features
| Feature | Design Value |
|---|---|
| Octal bidirectional data path | Enables full-duplex communication between two 8-bit buses using single control signals (DIR/OE). |
| Enhanced sink current (–1 version) | 48 mA IOL allows direct interface with up to 12 standard TTL loads per line without external buffering. |
| pnp input structure | Reduces input current to ≤0.1 mA, minimizing DC loading on upstream drivers and improving noise margin. |
| 3-state output isolation | OE-controlled high-impedance state prevents bus contention during multi-master arbitration or hot-swap events. |
| TTL-compatible voltage thresholds | VIH = 2.0 V and VIL = 0.8 V ensure reliable interfacing with legacy 74LS/74F and microcontroller GPIOs. |
Applications
| Industrial Backplane Interface | Legacy System Bus Expansion |
|---|---|
Use Scenario: Connecting a microcontroller-based control module to a distributed I/O rack via parallel backplane wiring. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between CPU address/data bus and remote I/O register space. Use Value: DIR-controlled directionality eliminates need for separate transmit/receive buffers; 48 mA IOL drives long traces with up to 100 pF load per line. |
Use Scenario: Adding memory-mapped peripherals (e.g., ADCs, DACs) to an aging 8086/8088-based embedded controller. IC Role / Device Role / Timing Role: Isolating and translating between processor bus and peripheral bus while maintaining TTL timing integrity. Use Value: 5.5 ns tpd meets 8 MHz bus cycle timing budgets; OE-controlled tri-state enables shared bus arbitration with other peripherals. |
| Test Equipment Data Capture | Programmable Logic Interfacing |
Use Scenario: Capturing parallel digital waveform data from DUTs in automated test fixtures with limited board space. IC Role / Device Role / Timing Role: Transferring captured 8-bit samples from FPGA acquisition logic to host microcontroller over short-run ribbon cable. Use Value: SOIC-20 footprint fits dense test head layouts; pnp inputs reduce FPGA I/O loading during high-frequency sampling. |
Use Scenario: Interfacing CPLD-based glue logic to microprocessor data bus in custom instrumentation designs. IC Role / Device Role / Timing Role: Level-shifting and bus buffering between 3.3 V CPLD I/O and 5 V CPU bus, with direction managed by CPLD control signals. Use Value: VIH/VIL compatibility avoids level translators; DIR/OE pins directly driven by CPLD outputs for deterministic bus control. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245ADWR | Standard version (non–1); rated IOL = 24 mA instead of 48 mA. | Suitable where bus loading is light (<6 TTL loads) and lower drive strength suffices. | Select when cost sensitivity outweighs need for enhanced drive; identical pinout and timing. |
| SN74AS245DWR | Faster propagation delay (7.5 ns max vs. 5.5 ns), higher ICC (97 mA vs. 55 mA), AS-family logic thresholds (VIL = 0.8 V same, but VIH = 2.0 V unchanged). | Better suited for high-speed synchronous bus systems where timing margin is critical and power budget permits. | Choose for speed-critical upgrades where existing layout supports higher supply current and thermal dissipation. |
Compared with SN74ALS245ADWR, SN74ALS245A-1DWG4 offers double the sink current for heavy bus loading; compared with SN74AS245DWR, it trades 2 ns of speed for significantly lower power consumption and better noise immunity in electrically noisy industrial settings.
Availability
SN74ALS245A-1DWG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus expansion, test equipment data capture, and programmable logic interfacing requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS245A-1DWG4 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 specializing in analog, embedded processing, and logic solutions, with decades of heritage in TTL and advanced logic families.
SN74ALS245A-1DWG4 belongs to TI's legacy ALS (Advanced Low-Power Schottky) logic product line, engineered for high-speed, low-power bidirectional bus interfacing in industrial and computing systems requiring TTL compatibility and reliability.
FAQ
What is the key functional difference between SN74ALS245A-1DWG4 and the standard SN74ALS245ADWR?
The SN74ALS245A-1DWG4 is the –1 version, specifying a guaranteed low-level output current (IOL) of 48 mA under 4.75–5.25 V VCC, whereas SN74ALS245ADWR is rated for 24 mA. This doubled sink capability allows SN74ALS245A-1DWG4 to drive heavier capacitive loads or more TTL inputs directly, reducing need for external buffers in demanding bus environments.
Does SN74ALS245A-1DWG4 support 3.3 V logic levels?
No. SN74ALS245A-1DWG4 is a 5 V-only TTL-compatible device with VIH = 2.0 V and VIL = 0.8 V. It requires a 4.5–5.5 V VCC supply and is not 3.3 V tolerant. Direct connection to 3.3 V logic without level translation risks damage or unreliable operation due to input overvoltage and incompatible threshold margins.
What is the thermal performance of SN74ALS245A-1DWG4 in SOIC-20 package?
SN74ALS245A-1DWG4 in SOIC-20 (DW) package has a specified thermal impedance θJA of 58°C/W. Under worst-case conditions (VCC = 5.5 V, all outputs sinking 48 mA), total power dissipation reaches ~55 mA × 5.5 V ≈ 300 mW, resulting in ~17.4°C junction-to-ambient rise above ambient-well within safe operating limits for commercial temperature range.
Can SN74ALS245A-1DWG4 be used in place of SN74LS245?
Yes, SN74ALS245A-1DWG4 is a drop-in functional replacement for SN74LS245 in SOIC-20 footprint, offering identical pinout, logic function, and voltage thresholds. It improves upon LS with faster propagation delay (5.5 ns vs. 10–15 ns), lower power consumption, and enhanced output drive (48 mA vs. 24 mA), making it a recommended upgrade path.
How does the DIR and OE control logic interact in SN74ALS245A-1DWG4?
In SN74ALS245A-1DWG4, DIR controls data direction (Low = B→A, High = A→B), while OE independently enables/disables all outputs (Low = active, High = high-Z). When OE is high, both A and B ports enter high-impedance regardless of DIR state-enabling complete bus isolation. This decoupled control allows flexible arbitration schemes in multi-master systems.
SN74ALS245A-1DWG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- 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:
- 15mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74ALS245A-1DWG4 FAQ
1.How can I place an order for SN74ALS245A-1DWG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS245A-1DWG4 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 SN74ALS245A-1DWG4 reliable?
The price and inventory of SN74ALS245A-1DWG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS245A-1DWG4 is usually 5 days.
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SN74ALS245A-1DWG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS245A-1DWG4 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 SN74ALS245A-1DWG4?
For technical support, including SN74ALS245A-1DWG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS245A-1DWG4 requirements.
6.How does Aetrix verify that SN74ALS245A-1DWG4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS245A-1DWG4 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 SN74ALS245A-1DWG4 meets industry standards.
7.What is the process for return or replacement of SN74ALS245A-1DWG4?
All SN74ALS245A-1DWG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS245A-1DWG4, 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 SN74ALS245A-1DWG4 part is unused and in its original packaging.
Return procedure for SN74ALS245A-1DWG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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