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Texas Instruments SN74AS245N
- Part No.:
- SN74AS245N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74AS245N.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,898
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Product details
Overview
SN74AS245N 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 pnp input structure to reduce DC loading. It is used in industrial backplane interfaces requiring robust signal integrity and bus isolation.
For engineers reviewing the SN74AS245N datasheet, SN74AS245N pinout, SN74AS245N application, or SN74AS245N equivalent, key selection criteria include its 20-pin PDIP package, 3-state control via DIR/OE inputs, guaranteed 7.5 ns tPHL/tPLH at 5 V, -55°C to 125°C military-grade thermal rating (per SN54AS245 spec), and compatibility with legacy AS-family logic systems.
Technical Context
The SN74AS245N implements dual-directional 8-bit data routing controlled by a single DIR input: low enables B→A transmission, high enables A→B. Its OE input independently disables all outputs into high-impedance state, enabling bus sharing without contention. The device uses bipolar Schottky (AS) technology, delivering faster switching than ALS variants while maintaining TTL voltage thresholds.
Input structure includes pnp-based inputs that minimize DC current draw on driving sources, reducing loading on upstream logic. Output stages are designed for direct bus-line driving with 64 mA sink capability at VCC = 4.5 V, supporting stub-loaded or lightly terminated parallel buses typical in industrial control and instrumentation subsystems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across standard TTL supply tolerances and noisy industrial rails. |
| Max Propagation Delay | 7.5 ns at 5 V - Enables reliable 133 MHz bus clocking in synchronous designs with margin. |
| IOL (Low-Level Output) | 64 mA - Drives heavy capacitive loads or multiple TTL inputs directly without external buffers. |
| tPZH / tPZL | 9 ns max - Guarantees fast bus release during output disable, minimizing bus turnaround latency. |
| VIH / VIL | 2.0 V / 0.8 V - Matches standard TTL input thresholds for seamless integration with 74LS/74F/74AS families. |
| Operating Temperature | 0°C to 70°C (commercial) - Validated for use in non-extended-temperature embedded control environments. |
| Package | 20-pin PDIP (N) - Through-hole mounting compatible with legacy prototyping, repair, and industrial PCB assembly. |
Pinout & Package
SN74AS245N is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300-inch body width, with 0.100-inch lead pitch. Pin 1 is located at the top-left corner with notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control: LOW = B→A data flow; HIGH = A→B data flow. |
| 2–9 | A1–A8 | Input/output port A - Bidirectional I/O pins connected to first data bus. |
| 10 | GND | Ground reference for all internal circuitry and I/O. |
| 11 | VCC | Positive supply (4.5–5.5 V) powering internal logic and output drivers. |
| 12 | OE | Output enable: LOW = outputs active; HIGH = all outputs in high-Z state. |
| 13–20 | B1–B8 | Input/output port B - Bidirectional I/O pins connected to second data bus. |
Key Features
| Feature | Design Value |
|---|---|
| 3-State Outputs with Independent Control | OE pin disables all A/B outputs simultaneously into high-impedance, enabling multi-master bus arbitration. |
| pnp Input Structure | Reduces input DC loading to ≤0.5 mA per control input, preserving fanout of upstream TTL drivers. |
| AS-Series Speed Performance | 7.5 ns max tPHL/tPLH at 5 V - 30% faster than comparable 74ALS245A, improving system throughput. |
| Robust Output Drive | 64 mA sink capability supports driving 20+ TTL loads or long trace runs without signal degradation. |
| TTL-Compatible Voltage Thresholds | VIH = 2.0 V, VIL = 0.8 V - Interoperates directly with 74LS, 74F, and other TTL logic families without level shifting. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Connecting microcontroller local bus to a modular I/O backplane with multiple slot-mounted peripherals. IC Role / Device Role / Timing Role: Bidirectional data bridge isolating CPU address/data bus from peripheral slots; DIR set by address decoder, OE synchronized to bus grant. Use Value: Eliminates need for separate transceivers per direction; 7.5 ns delay ensures timing closure in 8-MHz Z80 or 68K-based systems. | Use Scenario: Extending a vintage 16-bit ISA-style bus across two PCBs in a test equipment rack. IC Role / Device Role / Timing Role: Level-shifting and bus buffering between main controller board and expansion module; DIR fixed for unidirectional extension, OE used for hot-swap isolation. Use Value: 64 mA drive sustains signal integrity over 15 cm ribbon cable; PDIP package allows hand-soldered field repair. |
| Programmable Logic Interfacing | Test Equipment Data Acquisition |
Use Scenario: Interfacing FPGA I/O banks to external TTL-level memory or peripheral chips with mismatched voltage domains. IC Role / Device Role / Timing Role: Voltage-domain translator and bus driver; DIR controlled by FPGA state machine, OE tied to reset or configuration mode. Use Value: TTL-compatible thresholds eliminate external bias networks; pnp inputs prevent FPGA I/O leakage from affecting timing margins. | Use Scenario: Multiplexing analog-to-digital converter outputs onto a shared digital bus in automated test equipment. IC Role / Device Role / Timing Role: Isolating ADC data lines during conversion; OE asserted during sampling, released only after conversion complete. Use Value: Fast 9 ns tPZL ensures minimal bus occupation time; 3-state isolation prevents digital noise coupling into sensitive analog sections. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245AN | Slower max tPHL/tPLH (10 ns), lower IOL (24 mA), same pinout and voltage specs. | Suitable for lower-speed legacy systems where power consumption is prioritized over speed. | Select SN74ALS245AN only if design budget or thermal constraints require reduced ICC (max 55 mA vs. 143 mA). |
| SN74AS245NSR | Identical electrical specs, but in 20-pin SOP-NS package (surface-mount, 0.65 mm pitch). | Required for space-constrained or automated SMT production; not suitable for through-hole prototyping. | Choose SN74AS245NSR when board area or assembly process mandates surface-mount packaging. |
Compared with SN74ALS245AN, SN74AS245N provides 25% faster propagation and 2.7× higher sink drive, making it preferable for timing-critical industrial buses; versus SN74AS245NSR, it offers identical performance in a serviceable through-hole form factor ideal for lab validation and field-replaceable modules.
Availability
SN74AS245N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, programmable logic interfacing, and test equipment data acquisition requiring stable component supply and long-term obsolescence management.
Supply support for SN74AS245N 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 ICs, with decades of heritage in TTL and advanced logic families.
The SN74AS245N belongs to TI's 74AS logic family, engineered for high-speed, low-noise digital interfacing in industrial, military, and instrumentation applications where reliability and deterministic timing are critical.
FAQ
What is the maximum operating temperature range for the SN74AS245N?
The SN74AS245N is rated for commercial operation from 0°C to 70°C. While the related SN54AS245 variant supports –55°C to 125°C, the SN74AS245N specifically conforms to the 0°C to 70°C range per its datasheet specifications and ordering information. This makes SN74AS245N appropriate for indoor industrial control cabinets and laboratory equipment where ambient temperatures remain within this envelope.
Does the SN74AS245N support true bidirectional data flow on each pin?
Yes, the SN74AS245N supports true bidirectional data flow per channel: each A1–A8 and B1–B8 pin functions as both input and output depending on the logic level applied to the DIR pin. When DIR = LOW, data flows from B-side to A-side; when DIR = HIGH, data flows from A-side to B-side. This eliminates the need for separate transmitter/receiver pairs in point-to-point bus architectures.
Can the SN74AS245N be used with 3.3 V logic systems?
No, the SN74AS245N is not compatible with 3.3 V logic systems. It requires a 4.5 V to 5.5 V supply and has TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max). Driving its inputs from 3.3 V CMOS outputs may result in marginal or unreliable logic recognition. For 3.3 V systems, consider level translators or 3.3 V–compatible transceivers such as the SN74LVC245A.
What is the purpose of the pnp input structure in the SN74AS245N?
The pnp input structure in the SN74AS245N reduces DC input current to ≤0.5 mA per control input (DIR, OE), significantly lowering loading on upstream drivers compared to standard TTL inputs. This preserves fanout capability-enabling one 74AS gate to drive up to 20 SN74AS245N inputs-while improving noise immunity and reducing power dissipation in large bus systems.
Is the SN74AS245N pin-compatible with the SN74ALS245A series?
Yes, the SN74AS245N is pin-compatible and functionally compatible with the SN74ALS245A series, including identical 20-pin PDIP layout, DIR/OE control scheme, and A/B port mapping. However, SN74AS245N delivers faster propagation (7.5 ns vs. 10 ns), higher output drive (64 mA vs. 24 mA), and greater ICC (143 mA vs. 55 mA), requiring verification of power delivery and thermal design in drop-in replacements.
SN74AS245N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- 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:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74AS245N FAQ
1.How can I place an order for SN74AS245N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS245N 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 SN74AS245N reliable?
The price and inventory of SN74AS245N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS245N is usually 5 days.
3.What payment methods are accepted for SN74AS245N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS245N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS245N?
SN74AS245N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS245N 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 SN74AS245N?
For technical support, including SN74AS245N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS245N requirements.
6.How does Aetrix verify that SN74AS245N is sourced from the original manufacturer or authorized distributors?
All SN74AS245N 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 SN74AS245N meets industry standards.
7.What is the process for return or replacement of SN74AS245N?
All SN74AS245N units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS245N, 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 SN74AS245N part is unused and in its original packaging.
Return procedure for SN74AS245N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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