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Texas Instruments SN74ALS245ADW
- Part No.:
- SN74ALS245ADW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS245ADW.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,041
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Product details
Overview
SN74ALS245ADW 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 10 ns at 5 V, and supports 12 mA low-level output drive. It is used in industrial backplane interfaces requiring bus isolation and direction control.
For engineers reviewing the SN74ALS245ADW datasheet, SN74ALS245ADW pinout, SN74ALS245ADW application, or SN74ALS245ADW equivalent, key selection criteria include its 20-pin SOIC-DW package, DIR/OE control logic, 3-state bus driving capability, and ALS-family DC loading reduction via pnp inputs.
Technical Context
The SN74ALS245ADW implements dual-directional 8-bit data flow controlled by DIR (direction) and OE (output enable) inputs. Its logic diagram shows positive-logic gates with DIR determining A→B or B→A transmission, while OE asserts high-impedance state when high. The device uses bipolar ALS (Advanced Low-power Schottky) technology.
It features pnp input structures that reduce dc loading on driving sources, enabling direct connection to standard TTL outputs without pull-up resistors. All inputs are compatible with TTL voltage thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), and outputs meet TTL VOH/VOL specifications under 12 mA load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures compatibility with standard 5-V TTL and mixed-voltage system rails. |
| Max Propagation Delay | 10 ns at VCC = 5 V - Enables reliable operation in high-speed digital backplanes up to ~100 MHz clock-equivalent systems. |
| Output Drive (IOL) | 12 mA - Sufficient to drive 10 standard TTL loads directly without buffering. |
| Input Loading (IIH/IIL) | ±20 µA max - Low dc input current reduces fanout burden and simplifies termination. |
| 3-State Enable Time | tPZL = 20 ns max - Fast bus release supports dynamic bus arbitration and multiplexing. |
| Package | SOIC-DW, 20-pin - Surface-mount footprint with 0.65 mm lead pitch, compatible with standard reflow profiles (MSL Level-1). |
Pinout & Package
SN74ALS245ADW is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 2.65 mm max height, with gull-wing leads and 0.65 mm pitch. Pin 1 is located at the top-left corner with index marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B-to-A data transfer; High = A-to-B data transfer - determines bus flow polarity. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to one bus segment; high-impedance when OE = H. |
| 10 (GND) | Ground Reference | Primary signal return path; must be low-inductance for noise immunity. |
| 11 (VCC) | Power Supply | +5 V supply rail; requires local 0.1 µF ceramic decoupling adjacent to pin. |
| 12 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter 3-state - enables bus isolation. |
| 13–20 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to second bus segment; functionally identical to A-side. |
Key Features
| Feature | Design Value |
|---|---|
| ALS Technology | Reduces input dc loading vs. standard LS, enabling higher fanout without pull-ups. |
| 3-State Outputs | Allows direct connection to shared data buses without contention during idle or arbitration phases. |
| Asynchronous Bidirectional Control | DIR and OE operate independently - supports real-time bus direction switching without clock dependency. |
| TTL-Compatible Thresholds | VIL ≤ 0.8 V, VIH ≥ 2.0 V - ensures interoperability with legacy 74LS/74F and microcontroller GPIOs. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Isolating and extending parallel address/data buses between CPU and peripheral cards in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between isolated board domains with independent power domains. Use Value: Enables hot-swap-capable modular architecture using 3-state control to prevent bus contention during card insertion/removal. | Use Scenario: Interfacing modern microcontrollers to vintage 8-bit ISA-style expansion slots in retro-computing hardware. IC Role / Device Role / Timing Role: Level-shifting and bus-driving interface translating between 3.3 V GPIO and 5 V TTL bus standards. Use Value: Provides robust 12 mA drive and TTL-compatible thresholds without external level shifters or pull-up networks. |
| Test Equipment Data Capture | Digital Signal Acquisition Module |
Use Scenario: Capturing parallel digital waveforms from DUTs in automated test systems using FPGA-based acquisition logic. IC Role / Device Role / Timing Role: Buffering and isolating high-speed parallel data streams between probe interface and FPGA input banks. Use Value: 10 ns propagation delay ensures timing correlation across 8-bit channels; 3-state allows multiplexing multiple DUTs onto shared acquisition bus. | Use Scenario: Aggregating sensor data from multiple 8-bit parallel-output ADCs into a central processing unit. IC Role / Device Role / Timing Role: Synchronizing and routing time-aligned sample data from distributed analog front-ends. Use Value: DIR-controlled bidirectionality supports both configuration writes and result reads over same physical bus, reducing PCB trace count. |
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 | Tape-and-reel packaging (2000 pcs); identical electrical specs and pinout. | No functional difference; optimized for automated SMT assembly. | Select SN74ALS245ADWR for volume production; SN74ALS245ADW is obsolete but may be available in tube stock. |
| SN74AS245DW | Faster tPLH/tPHL (7.5 ns max), higher IOL (48 mA), but increased ICC (95 mA typical). | Better suited for high-speed, high-drive applications where power budget permits. | Choose SN74AS245DW only if propagation delay < 8 ns or drive > 12 mA is required; otherwise SN74ALS245ADW offers lower power and proven stability. |
Compared with SN74ALS245ADWR, the SN74ALS245ADW shares identical functionality but lacks tape-and-reel support; versus SN74AS245DW, it trades speed and drive strength for lower power consumption and reduced input loading-making it preferable for noise-sensitive, power-constrained industrial backplanes.
Availability
SN74ALS245ADW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, and digital test equipment requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS245ADW 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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and logic ICs for industrial, automotive, and communications markets.
The SN74ALS245A product line was developed for robust, low-power bidirectional bus interfacing in TTL-based industrial control and instrumentation systems, emphasizing reliability, noise immunity, and backward compatibility.
FAQ
What is the operating temperature range for the SN74ALS245ADW?
The SN74ALS245ADW is rated for commercial operation from 0°C to +70°C. This range is specified in the recommended operating conditions table of the official Texas Instruments datasheet SDAS272A. It is not qualified for extended temperature ranges such as –40°C to +85°C or military-grade –55°C to +125°C, which apply only to SN54-series variants. The DW package's thermal impedance is 58°C/W, supporting stable operation within this ambient envelope when properly decoupled and heatsinked.
Does the SN74ALS245ADW support live bus insertion or hot-swap?
Yes, the SN74ALS245ADW supports hot-swap operation through its 3-state outputs and controlled enable logic. When OE is held high, all A and B pins enter high-impedance mode regardless of DIR state, electrically isolating both buses. This prevents signal contention during card insertion or removal in backplane systems. However, proper power sequencing-applying VCC before asserting OE or DIR-is required to avoid latch-up; TI recommends holding all inputs at valid logic levels (VCC or GND) during power-up per SCBA004 guidelines.
What is the maximum output current the SN74ALS245ADW can sink per pin?
The SN74ALS245ADW is rated for a maximum low-level output current (IOL) of 12 mA per pin under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). This value is confirmed in the "Electrical Characteristics" table of the SDAS272A datasheet. Exceeding 12 mA risks violating VOL specifications (>0.4 V) and may degrade long-term reliability. Note that the -1 version (e.g., SN74ALS245A-1DWR) supports 48 mA, but that rating does not apply to the standard SN74ALS245ADW.
Can the SN74ALS245ADW be used with 3.3 V logic systems?
The SN74ALS245ADW is not designed for direct 3.3 V operation: its minimum VCC is 4.5 V, and inputs require TTL-compatible thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). While 3.3 V CMOS outputs may meet VIH, they often fail VIL margins under noise or loading. Additionally, 3.3 V signals applied to SN74ALS245ADW outputs risk violating absolute maximum ratings (IO ports limited to 5.5 V). For 3.3 V ↔ 5 V interfacing, use a dedicated level translator or buffer such as TXB0108-not the SN74ALS245ADW alone.
Is there a drop-in replacement for SN74ALS245ADW with RoHS compliance and active status?
Yes: SN74ALS245ADWR is the RoHS-compliant, tape-and-reel, actively manufactured replacement for SN74ALS245ADW. Both share identical pinout, electrical specifications, and DW package dimensions. The "R" suffix denotes large-reel packaging (2000 pcs), MSL Level-1 rating, and NiPdAu lead finish. TI's packaging addendum confirms SN74ALS245ADWR is active and recommended for new designs, while SN74ALS245ADW is marked obsolete. No PCB layout changes are needed when migrating to SN74ALS245ADWR.
SN74ALS245ADW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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:
- 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
SN74ALS245ADW FAQ
1.How can I place an order for SN74ALS245ADW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS245ADW 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 SN74ALS245ADW reliable?
The price and inventory of SN74ALS245ADW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS245ADW is usually 5 days.
3.What payment methods are accepted for SN74ALS245ADW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS245ADW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS245ADW?
SN74ALS245ADW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS245ADW 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 SN74ALS245ADW?
For technical support, including SN74ALS245ADW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS245ADW requirements.
6.How does Aetrix verify that SN74ALS245ADW is sourced from the original manufacturer or authorized distributors?
All SN74ALS245ADW 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 SN74ALS245ADW meets industry standards.
7.What is the process for return or replacement of SN74ALS245ADW?
All SN74ALS245ADW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS245ADW, 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 SN74ALS245ADW part is unused and in its original packaging.
Return procedure for SN74ALS245ADW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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