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Texas Instruments SN74AS245DWR
- Part No.:
- SN74AS245DWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74AS245DWR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,205
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Product details
Overview
SN74AS245DWR 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 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 control backplanes.
For engineers reviewing the SN74AS245DWR datasheet, SN74AS245DWR pinout, SN74AS245DWR application, or SN74AS245DWR equivalent, key selection criteria include its 20-pin SOIC-DW package, 3-state bus isolation capability, 7.5 ns tPHL/tPLH timing, high-current drive (64 mA IOL), and compatibility with legacy TTL and AS logic families in embedded data-path designs.
Technical Context
The SN74AS245DWR implements dual 8-bit bidirectional data paths controlled by a single DIR input to select A→B or B→A flow, and an active-low OE input to place all outputs in high-impedance state. Its AS-family silicon ensures faster switching than ALS variants while maintaining TTL voltage thresholds.
It uses bipolar Schottky-clamped transistor architecture for reduced propagation delay and improved noise immunity. The pnp input stage minimizes DC loading on driving sources, and the 3-state outputs directly drive terminated or unterminated bus lines without external pull-ups.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures robust operation across standard TTL supply tolerances and brown-out conditions. |
| Max Propagation Delay | 7.5 ns (tPHL/tPLH @ VCC = 5 V, CL = 50 pF) - Enables reliable 133+ MHz bus clocking in synchronous systems. |
| IOL (Low-Level Output) | 64 mA - Drives heavy capacitive loads or multiple TTL inputs without external buffers. |
| IOH (High-Level Output) | –15 mA - Sinks sufficient current to maintain valid VOH ≥ 2.4 V under load. |
| Input Thresholds | VIH = 2 V, VIL = 0.8 V - Fully compatible with standard TTL logic levels and noise margins. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade industrial and computing applications. |
| Package | SOIC-DW (20-pin, 0.300" wide) - Surface-mount footprint with 1.27 mm pitch, JEDEC MS-013 compliant. |
Pinout & Package
SN74AS245DWR is housed in a 20-pin SOIC-DW package (7.5 mm × 12.8 mm, 2.65 mm max height), RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A1–A8 Inputs/Outputs | Bidirectional data terminals for A-side bus; high-impedance when OE = H or device disabled. |
| 11, 12, 13, 14, 15, 16, 17, 18 | B1–B8 Inputs/Outputs | Bidirectional data terminals for B-side bus; direction determined by DIR state. |
| 9 | GND | Ground reference for all internal circuitry and I/O structures. |
| 10 | VCC | Positive supply rail (4.5–5.5 V); decoupling capacitor required near pin. |
| 19 | DIR | Direction control: L = B→A transfer, H = A→B transfer; TTL-compatible input. |
| 20 | OE | Output enable (active low): L = enabled, H = all outputs high-Z; enables bus isolation. |
Key Features
| Feature | Design Value |
|---|---|
| Octal bidirectional data path | Single DIR pin controls full 8-bit flow direction-reduces PCB routing complexity vs. discrete unidirectional buffers. |
| 3-State bus isolation | Active-low OE disables all outputs simultaneously, enabling multi-master arbitration and hot-swap-safe bus sharing. |
| High-current drive capability | 64 mA IOL supports direct connection to unterminated 50 Ω transmission lines or fan-out to >20 TTL loads. |
| AS-family speed grade | 7.5 ns max propagation delay exceeds ALS performance by >30%, critical for high-throughput data acquisition interfaces. |
| pnp input structure | Reduces input DC loading to ≤0.5 mA per control pin-minimizes power draw and driver stress in large bus systems. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Isolating CPU address/data bus from peripheral expansion slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional transceiver managing A→B (CPU→peripheral) and B→A (peripheral→CPU) transfers under DIR control, with OE synchronized to bus grant signals. Use Value: Eliminates need for separate transmit/receive buffers; 64 mA drive sustains signal integrity over 15 cm backplane traces. | Use Scenario: Extending ISA or VMEbus segments between chassis in test equipment racks. IC Role / Device Role / Timing Role: Level-shifting and isolating legacy TTL buses across modular sub-systems using OE for slot arbitration. Use Value: 7.5 ns timing allows cycle rates up to 100 MHz; SOIC-DW package fits dense Eurocard layouts. |
| Microcontroller Peripheral Bridge | Test Equipment Data Path Switching |
Use Scenario: Connecting an ARM microcontroller's GPIO port to an external 8-bit ADC/DAC in mixed-voltage test instrumentation. IC Role / Device Role / Timing Role: Voltage-level translator and bus driver, with DIR set statically and OE toggled during conversion windows. Use Value: TTL-compatible thresholds ensure clean interfacing with 3.3 V MCU I/O via series resistors; 0.8 V VIL prevents false triggering. | Use Scenario: Routing sensor data streams between FPGA-based acquisition modules and display processors in automated test systems. IC Role / Device Role / Timing Role: Reconfigurable data path switch enabling dynamic channel mapping via DIR/OE software control. Use Value: 3-state isolation prevents bus contention during reconfiguration; 20-pin SOIC simplifies rework and replacement. |
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: slower (10 ns max tPHL), lower IOL (24 mA), higher VIH (2.0 V), same pinout/package. | Lower-speed, lower-power legacy systems where 64 mA drive is unnecessary. | Select SN74ALS245ADWR only if timing budget allows ≥10 ns delay and drive requirements are ≤24 mA. |
| SN74LVC245APWR | CMOS-based: 3.3 V only (1.65–3.6 V), 3.5 ns max tPD, 24 mA IOL, different voltage thresholds and pinout. | Modern low-voltage digital systems requiring level translation between 3.3 V and 5 V domains. | Choose SN74LVC245APWR for 3.3 V core logic; not a drop-in replacement due to voltage and timing incompatibility. |
Compared with SN74ALS245ADWR, SN74AS245DWR provides 2.5× faster propagation and 2.7× higher sink current; versus SN74LVC245APWR, it offers 5 V tolerance and direct TTL compatibility but lacks 3.3 V operation and consumes more quiescent current.
Availability
SN74AS245DWR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, and microcontroller peripheral bridges requiring stable component supply, long-term lifecycle support, and RoHS-compliant surface-mount packaging.
Supply support for SN74AS245DWR 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 for industrial, automotive, and communications markets.
The SN74AS245DWR belongs to TI's 74AS logic family, engineered for high-speed, high-drive TTL-compatible data-path applications where propagation delay and output current are critical design constraints.
FAQ
What is the maximum operating frequency supported by the SN74AS245DWR?
The SN74AS245DWR does not specify a maximum clock frequency in its datasheet, as it is an asynchronous transceiver. However, its 7.5 ns maximum propagation delay (tPHL/tPLH) enables reliable operation in bus systems with cycle times ≥15 ns-equivalent to a theoretical upper limit of ~67 MHz for single-data-rate transfers under typical 50 pF loading conditions. Actual usable frequency depends on board layout, termination, and driver strength.
Can the SN74AS245DWR be used with 3.3 V logic systems?
No, the SN74AS245DWR is not rated for 3.3 V operation. Its absolute minimum VCC is 4.5 V, and input thresholds (VIH = 2.0 V, VIL = 0.8 V) are optimized for 5 V TTL signaling. Driving its inputs from 3.3 V logic may result in marginal or non-functional high-level recognition. For 3.3 V systems, TI recommends the SN74LVC245A or similar CMOS transceivers.
What is the thermal resistance (θJA) of the SN74AS245DWR in its SOIC-DW package?
The SN74AS245DWR in the SOIC-DW package has a specified junction-to-ambient thermal resistance (θJA) of 58°C/W, measured per JESD 51-7. This value assumes standard JEDEC high-K test board conditions. Actual thermal performance in end equipment will vary based on PCB copper area, airflow, and nearby heat sources-designers should verify junction temperature under worst-case ICC conditions (97 mA max).
How does the DIR pin function in the SN74AS245DWR?
The DIR pin on the SN74AS245DWR is a TTL-compatible control input that determines data flow direction: when DIR = LOW, data passes from the B bus (pins 11–18) to the A bus (pins 1–8); when DIR = HIGH, data flows from A to B. DIR has no effect when OE = HIGH (outputs disabled). Its logic threshold is VIL ≤ 0.8 V and VIH ≥ 2.0 V, matching standard TTL levels.
Is the SN74AS245DWR pin-compatible with the SN74ALS245A series?
Yes, the SN74AS245DWR is pin-compatible with SN74ALS245A variants (e.g., SN74ALS245ADWR, SN74ALS245AN) in the same package type (SOIC-DW, PDIP-N, SOP-NS). All share identical 20-pin assignments, electrical pin functions, and mechanical footprints. However, differences in propagation delay, output drive, and input current require verification in timing-critical or high-fanout designs.
SN74AS245DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm 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:
- 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
SN74AS245DWR FAQ
1.How can I place an order for SN74AS245DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS245DWR 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 SN74AS245DWR reliable?
The price and inventory of SN74AS245DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS245DWR is usually 5 days.
3.What payment methods are accepted for SN74AS245DWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS245DWR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS245DWR?
SN74AS245DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS245DWR 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 SN74AS245DWR?
For technical support, including SN74AS245DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS245DWR requirements.
6.How does Aetrix verify that SN74AS245DWR is sourced from the original manufacturer or authorized distributors?
All SN74AS245DWR 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 SN74AS245DWR meets industry standards.
7.What is the process for return or replacement of SN74AS245DWR?
All SN74AS245DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS245DWR, 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 SN74AS245DWR part is unused and in its original packaging.
Return procedure for SN74AS245DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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