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Texas Instruments SN74AS245DW
- Part No.:
- SN74AS245DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74AS245DW.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,556
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Product details
Overview
SN74AS245DW from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in 5-V TTL systems. It operates from 4.5 V to 5.5 V, delivers max propagation delay of 7.5 ns at 5 V, supports ±64 mA low-level output drive, and features direction (DIR) and output-enable (OE) control for isolated bus communication in industrial backplanes and legacy computing interfaces.
For engineers reviewing the SN74AS245DW datasheet, SN74AS245DW pinout, SN74AS245DW application, or SN74AS245DW equivalent, this page provides verified electrical specs, SOIC-20 package details, real-world use cases in bus isolation and level translation, and two validated alternative parts with documented functional and parametric differences.
Technical Context
The SN74AS245DW implements TTL-compatible bipolar Schottky logic with pnp input stages that reduce DC loading on driving sources. Its dual 8-bit bidirectional path is controlled by a single DIR pin to select A→B or B→A data flow, while OE independently places all outputs in high-impedance state to isolate buses.
Switching performance is characterized under CL = 50 pF with R1/R2 = 500 Ω, delivering tPHL/tPLH ≤ 7 ns and enable/disable times (tPZH/tPLZ) ≤ 9.5 ns - optimized for high-speed 5-V bus arbitration without external timing components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - compatible with standard 5-V TTL power rails and tolerant of supply ripple. |
| Max Propagation Delay | 7.5 ns at VCC = 5 V, CL = 50 pF - enables reliable operation in sub-100-MHz synchronous bus environments. |
| IOL (Low-Level Output) | 64 mA - drives heavy capacitive loads or multiple TTL inputs without external buffers. |
| IOH (High-Level Output) | –15 mA - sustains valid VOH ≥ 2.0 V when sourcing current to TTL-compatible inputs. |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - matches standard TTL logic levels for seamless interface with 74LS/74AS families. |
| Thermal Resistance | θJA = 58°C/W (SOIC-DW) - supports continuous operation up to 70°C ambient with minimal heatsinking. |
Pinout & Package
SN74AS245DW is housed in a 20-pin SOIC (DW) package measuring 7.5 mm × 12.8 mm × 2.65 mm, with 1.27 mm lead pitch and gull-wing terminations suitable for surface-mount reflow assembly.
| 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 direction synchronously. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to one bus segment; internally buffered with TTL-compatible drivers. |
| 10 (GND) | Ground Reference | Primary signal return path; must be low-impedance to maintain noise margin and switching integrity. |
| 11 (VCC) | Power Supply | +5 V supply input; requires local 0.1 µF ceramic decoupling adjacent to pin for transient current delivery. |
| 12 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter high-impedance state - enables bus sharing and hot-swap isolation. |
| 13–20 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to second bus segment; electrically identical to A-side terminals. |
Key Features
| Feature | Design Value |
|---|---|
| 3-State Outputs | Full bus isolation via OE control eliminates contention during multi-master arbitration or power sequencing. |
| pnp Input Structure | Reduces input DC loading to ≤0.5 mA per control pin - preserves fanout capability in large bus trees. |
| High Sink Current | 64 mA IOL supports direct drive of up to 16 standard TTL loads without external drivers. |
| Fast Enable/Disable | tPHZ/tPLZ ≤ 5.5 ns ensures rapid bus release for time-critical DMA or interrupt-driven transfers. |
Applications
| Industrial Backplane Interface | Legacy Computing Data Bus |
|---|---|
Use Scenario: Isolating CPU and peripheral modules on a 20-slot VMEbus chassis where multiple controllers access shared memory space. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between processor and I/O cards, with DIR set per transaction and OE asserted during arbitration. Use Value: 7.5 ns propagation delay and 64 mA sink capability ensure deterministic timing and robust signal integrity across 30 cm backplane traces. | Use Scenario: Interfacing Z80 CPU address/data bus to ISA-compatible expansion slots in retro-computing hardware replicas. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled data coupling between 8-bit CPU bus and peripheral card bus, synchronized to /IOR and /IOW strobes. Use Value: TTL-compatible VIH/VIL thresholds and pnp inputs prevent loading-induced timing skew in multi-drop bus configurations. |
| Test Equipment Bus Arbitration | Programmable Logic Controller I/O Expansion |
Use Scenario: Enabling shared GPIB or IEEE-488 bus access among multiple instruments in automated test racks. IC Role / Device Role / Timing Role: Bus isolator activated only during active talker/listener sessions, with OE tied to controller handshake signals. Use Value: Sub-10 ns enable/disable latency allows dynamic bus reconfiguration within tight measurement cycle windows. | Use Scenario: Extending discrete I/O capacity of Allen-Bradley SLC-500 PLCs using custom carrier boards with opto-isolated inputs. IC Role / Device Role / Timing Role: Data bridge between PLC's internal 5-V data bus and external 24-V I/O module backplane, translating logic levels and buffering current. Use Value: 64 mA sink rating directly drives LED status indicators and solid-state relay drivers without added transistors. |
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 | ALS family: lower IOL (24 mA), slower tPHL/tPLH (10 ns), reduced ICC (≤55 mA). | Suitable for low-power, lower-speed bus extensions where fanout < 10 and timing budget > 15 ns. | Select when power efficiency and cost outweigh speed requirements; not drop-in due to timing and drive mismatch. |
| SN74LVC245APWR | CMOS-based: 3.3-V operation, 32 mA IOL, 5.4 ns tPD, 3.6-V tolerant inputs. | Required for mixed-voltage systems interfacing 3.3-V FPGAs or microcontrollers to legacy 5-V peripherals. | Choose for modern low-voltage designs; requires level-shifting or voltage translation if interfacing pure 5-V buses. |
Compared with SN74ALS245ADWR and SN74LVC245APWR, the SN74AS245DW delivers superior speed and drive strength in native 5-V environments but consumes more quiescent current; it remains optimal for legacy industrial and test equipment where timing determinism and TTL compatibility are mandatory.
Availability
SN74AS245DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy computing bus extensions, test equipment arbitration, and programmable logic controller I/O expansion requiring stable component supply across long production lifecycles.
Supply support for SN74AS245DW 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 founded in 1930, specializing in analog, embedded processing, and logic ICs for industrial, automotive, and communications markets.
The SN74AS245DW belongs to TI's 74AS logic family, engineered for high-speed, high-drive 5-V TTL systems where propagation delay, output current, and noise immunity are critical in mission-critical infrastructure.
FAQ
What is the maximum operating temperature range for the SN74AS245DW?
The SN74AS245DW is rated for commercial operation from 0°C to +70°C. This range is specified in TI's official datasheet and confirmed in the ordering information table, where SN74AS245DW is listed under TA = 0°C to 70°C. It does not support extended or military temperature grades - those require SN54AS245 variants in J or FK packages.
Can the SN74AS245DW be used with 3.3-V logic inputs?
No, the SN74AS245DW is not 3.3-V input-tolerant. Its VIH minimum is 2.0 V and VIL maximum is 0.8 V - designed specifically for 5-V TTL signaling. Applying 3.3-V logic levels risks marginal or non-functional operation, especially under voltage or temperature variation. For mixed-voltage systems, use SN74LVC245APWR instead.
What is the recommended decoupling for the SN74AS245DW?
Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 11) and GND (pin 10) pins of the SN74AS245DW. This minimizes high-frequency supply noise and stabilizes switching transients, particularly critical given its 64 mA output drive and sub-10 ns edge rates. A bulk 4.7 µF electrolytic may be added nearby for low-frequency regulation.
Is the SN74AS245DW pin-compatible with the SN74ALS245A series?
Yes, the SN74AS245DW shares identical pinout, package footprint (SOIC-20 DW), and terminal functions with SN74ALS245A variants. However, it is not functionally interchangeable: SN74AS245DW offers higher speed (7.5 ns vs. 10 ns) and stronger drive (64 mA vs. 24 mA), but draws more supply current. PCB layout reuse is possible, but timing and power design must be revalidated.
Does the SN74AS245DW support hot-swap insertion into a live bus?
The SN74AS245DW supports controlled hot-swap via its 3-state outputs: asserting OE high before insertion places all A/B pins in high-impedance, preventing bus contention. However, the device itself lacks built-in hot-swap protection circuitry (e.g., slew-rate limiting or current limiting), so external series resistors or dedicated hot-swap controllers are recommended for robust field deployment.
SN74AS245DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74AS245DW FAQ
1.How can I place an order for SN74AS245DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS245DW 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 SN74AS245DW reliable?
The price and inventory of SN74AS245DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS245DW is usually 5 days.
3.What payment methods are accepted for SN74AS245DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS245DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS245DW?
SN74AS245DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS245DW 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 SN74AS245DW?
For technical support, including SN74AS245DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS245DW requirements.
6.How does Aetrix verify that SN74AS245DW is sourced from the original manufacturer or authorized distributors?
All SN74AS245DW 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 SN74AS245DW meets industry standards.
7.What is the process for return or replacement of SN74AS245DW?
All SN74AS245DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS245DW, 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 SN74AS245DW part is unused and in its original packaging.
Return procedure for SN74AS245DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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