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Texas Instruments SN54AS645J
- Part No.:
- SN54AS645J
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN54AS645J.pdf
- Description:
- 54AS645 OCTAL BUS TRANSCEIVERS W
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Inventory:309
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Product details
Overview
SN54AS645J from Texas Instruments is a military-grade octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in high-reliability systems. It operates across –55°C to 125°C, supports 5 V supply (4.5–5.5 V), delivers 64 mA low-level output current, and features direction-control (DIR) and output-enable (OE) logic for bus isolation - used in avionics backplane interfaces and ruggedized test equipment.
For engineers reviewing the SN54AS645J datasheet, SN54AS645J pinout, SN54AS645J application, or SN54AS645J equivalent, key selection criteria include its CDIP-J package compatibility, military temperature range, 3-state drive strength (IOL = 64 mA), propagation delay (tPLH/tPHL ≤ 11 ns), and DIR/OE control architecture for deterministic bus arbitration.
Technical Context
The SN54AS645J implements TTL-compatible bipolar Schottky (AS) logic with true dual-rail bidirectional data flow: DIR selects A→B or B→A path while OE independently enables/disables all outputs into high-impedance state. Its internal circuitry ensures simultaneous 8-bit transfer with matched propagation delays and no bus contention during direction switching.
It uses open-collector–compatible output stages with guaranteed VOL ≤ 0.55 V at IOL = 64 mA and VOH ≥ 2.4 V at IOH = –15 mA under VCC = 4.5 V, meeting MIL-STD-883 Class B requirements for radiation-hardened environments and legacy 5 V digital systems requiring robust noise margins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation in noisy military power rails with ±10% tolerance. |
| Operating Temperature | –55°C to 125°C - Qualified per MIL-PRF-38535 for deployment in extreme-environment platforms. |
| IOL (Low-Level Output) | 64 mA - Drives heavy capacitive loads (e.g., long backplane traces) without signal degradation. |
| tPLH / tPHL | ≤11 ns - Enables high-speed synchronous bus handshaking up to ~90 MHz effective throughput. |
| VOH / VOL | ≥2.4 V / ≤0.55 V at full load - Maintains >0.4 V noise margin against TTL/LS logic thresholds. |
| ICC (Active) | 95–149 mA - Predictable power budgeting for thermal design in sealed chassis applications. |
| 3-State Enable Time | tPZH ≤12 ns - Rapid bus release prevents metastability during dynamic reconfiguration. |
Pinout & Package
SN54AS645J is housed in a 20-pin Ceramic Dual-In-Line Package (CDIP-J), 300-mil width, hermetically sealed for moisture resistance and thermal stability in aerospace deployments.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: Low = B→A transfer; High = A→B transfer. |
| 2–9 | A1–A8 | Input/output port A - Bidirectional data lines tied to local subsystem bus. |
| 10 | GND | Ground reference - Dedicated pin for low-noise return path in mixed-signal enclosures. |
| 11–18 | B1–B8 | Input/output port B - Bidirectional data lines connected to remote or expansion bus. |
| 19 | OE | Output enable: Low = active transceiver; High = all outputs high-Z for bus isolation. |
| 20 | VCC | Positive supply - Requires local 5 V decoupling (0.1 µF ceramic + 10 µF tantalum) per MIL-HDBK-454. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 8-bit data path | Eliminates need for separate transmitter/receiver pairs - reduces PCB area and interconnect count in space-constrained modules. |
| 64 mA sink capability | Drives terminated 50 Ω transmission lines directly - avoids external buffer stages in instrumentation front-ends. |
| MIL-STD-883 qualified | Meets screening requirements for burn-in, temperature cycling, and mechanical shock - suitable for flight-critical subsystems. |
| Independent DIR and OE controls | Enables atomic bus arbitration: direction change occurs only when OE is asserted, preventing transient bus conflicts. |
| True TTL-compatible voltage thresholds | VIH = 2 V, VIL = 0.8 V - Interoperates seamlessly with legacy 74LS/74ALS logic without level-shifting. |
Applications
| Avionics Data Bus Interface | Secure Test Equipment Backplane |
|---|---|
Use Scenario: Interfacing mission computer ARINC 429 interface cards with sensor acquisition modules via shared 8-bit parallel bus. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing time-critical telemetry packet routing under DIR-controlled flow direction. Use Value: 11 ns max propagation delay ensures sub-microsecond latency for real-time health monitoring updates. | Use Scenario: Isolating DUT (device under test) signals from automated test system controller during calibration sequences. IC Role / Device Role / Timing Role: 3-state bus isolator activated by OE to prevent back-driving during hot-swap of test fixtures. Use Value: 64 mA drive strength maintains signal integrity across 30 cm ribbon cable runs at 10 MHz clock rates. |
| Ruggedized Industrial PLC I/O Module | Military Communications Chassis |
Use Scenario: Buffering fieldbus data between CPU board and isolated I/O expansion slots in explosion-proof enclosures. IC Role / Device Role / Timing Role: Temperature-hardened transceiver enabling deterministic data exchange across –55°C to 125°C ambient range. Use Value: Hermetic CDIP-J package prevents moisture ingress and solder joint fatigue in high-vibration environments. | Use Scenario: Synchronizing encrypted payload data streams between crypto module and RF modem in tactical radios. IC Role / Device Role / Timing Role: Direction-controlled bus bridge ensuring secure unidirectional data flow during key exchange handshake. Use Value: Independent DIR/OE logic allows cryptographic state machine to gate bus access without timing jitter. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN54ALS645AJ | ALS family: lower power (ICC ≈ 60 mA), reduced IOL (24 mA), slower speed (tPLH ≤ 19 ns). | Suitable for low-power, non-real-time subsystems where thermal dissipation is constrained. | Select when power budget is tighter than speed requirement and bus loading is light. |
| SN74AS645N | Commercial grade: same AS logic but rated 0°C to 70°C; PDIP-N package (plastic, non-hermetic). | Applicable in ground-based lab equipment or non-mission-critical industrial controllers. | Choose for cost-sensitive designs where extended temperature and hermeticity are unnecessary. |
Compared with SN54ALS645AJ and SN74AS645N, the SN54AS645J uniquely combines military temperature range, hermetic CDIP packaging, and highest drive strength (64 mA), making it irreplaceable in airborne or deployed systems demanding both speed and environmental resilience.
Availability
SN54AS645J is available at Aetrix Electronics and suitable for avionics data bus interfaces, secure test equipment backplanes, and ruggedized industrial PLC I/O modules requiring stable component supply across extended lifecycle programs.
Supply support for SN54AS645J 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 high-reliability logic solutions for aerospace, defense, and industrial markets.
The SN54AS645J belongs to TI's military logic family, engineered specifically for deterministic, high-drive bidirectional bus interfacing in safety-critical systems operating under extreme thermal and mechanical stress.
FAQ
What is the maximum operating temperature range for the SN54AS645J?
The SN54AS645J is characterized for operation from –55°C to 125°C, fully compliant with MIL-PRF-38535 Class B screening requirements. This range enables use in jet engine-mounted controllers, satellite power distribution units, and other environments where ambient temperatures exceed commercial-grade limits. The SN54AS645J maintains specified VOH/VOL and timing performance across this full span without derating.
Does the SN54AS645J support true bidirectional data flow without external logic?
Yes, the SN54AS645J implements native bidirectional data transfer using its dedicated DIR pin: when DIR = Low, data flows from B bus to A bus; when DIR = High, data flows from A bus to B bus. No external multiplexers or control glue logic are required. This architecture simplifies PCB layout and eliminates timing skew between forward/reverse paths - a key advantage over discrete unidirectional driver pairs.
What is the recommended decoupling strategy for SN54AS645J in high-reliability designs?
TI recommends placing a 0.1 µF ceramic capacitor and a 10 µF tantalum capacitor in parallel between VCC (pin 20) and GND (pin 10), located within 5 mm of the SN54AS645J package. This dual-capacitor approach suppresses both high-frequency switching noise (ceramic) and low-frequency rail droop (tantalum), critical for maintaining signal integrity in MIL-STD-461E-compliant avionics enclosures.
Can SN54AS645J be used as a direct replacement for SN74AS645N in existing designs?
No - while functionally identical, the SN54AS645J uses a ceramic DIP (J) package versus the plastic DIP (N) of SN74AS645N, and is screened for –55°C to 125°C operation. Substituting SN54AS645J requires validation of board-level thermal expansion matching and hermetic seal integration. It is not a drop-in replacement unless the design already specifies CDIP mounting and military temperature compliance.
What is the minimum pulse width required on the OE pin to ensure reliable 3-state activation for SN54AS645J?
The SN54AS645J requires a minimum OE pulse width of 13 ns (tPLZ max) to guarantee full transition into high-impedance state. For robust operation in systems with fast control clocks, maintain OE assertion for ≥20 ns. This timing ensures complete output disable before bus masters initiate new transactions - preventing glitches during hot-plug events in modular test systems.
SN54AS645J Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN54AS645J FAQ
1.How can I place an order for SN54AS645J through Aetrix?
Please submit a Request for Quotation (RFQ) for SN54AS645J 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 SN54AS645J reliable?
The price and inventory of SN54AS645J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN54AS645J is usually 5 days.
3.What payment methods are accepted for SN54AS645J?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN54AS645J transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN54AS645J?
SN54AS645J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN54AS645J 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 SN54AS645J?
For technical support, including SN54AS645J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN54AS645J requirements.
6.How does Aetrix verify that SN54AS645J is sourced from the original manufacturer or authorized distributors?
All SN54AS645J 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 SN54AS645J meets industry standards.
7.What is the process for return or replacement of SN54AS645J?
All SN54AS645J units undergo pre-shipment inspection (PSI). If there is an issue with SN54AS645J, 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 SN54AS645J part is unused and in its original packaging.
Return procedure for SN54AS645J:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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