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Texas Instruments SNJ54HC645FK
- Part No.:
- SNJ54HC645FK
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SNJ54HC645FK.pdf
- Description:
- 54HC645 OCTAL BUS TRANSCEIVERS W
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Product details
Overview
SNJ54HC645FK from Texas Instruments is a military-grade octal bus transceiver in LCCC-20 package, enabling bidirectional asynchronous data transfer between A and B buses via DIR control and 3-state isolation via OE. It operates from –55°C to 125°C, supports 2 V–6 V supply, delivers ±6-mA drive at 5 V, and achieves typical propagation delay of 12 ns at 6 V - used in avionics backplane interface and radiation-tolerant telemetry systems.
For engineers reviewing the SNJ54HC645FK datasheet, SNJ54HC645FK pinout, SNJ54HC645FK application, or SNJ54HC645FK equivalent, this page provides verified functional specifications, military-qualified thermal and timing behavior, LCCC package layout guidance, and direct alternatives for high-reliability bus bridging designs.
Technical Context
This device implements dual 8-bit non-inverting transceivers with independent direction (DIR) and output-enable (OE) controls. Each channel supports true CMOS logic levels, rail-to-rail input voltage range (0–VCC), and high-current 3-state outputs capable of driving up to 15 LSTTL loads.
It features low static current (≤80 µA ICC max), input leakage ≤1 µA, and guaranteed switching performance across full military temperature range (–55°C to 125°C). Propagation delay (tpd) is specified at 12 ns (typ) / 27 ns (max) at VCC = 6 V and CL = 50 pF.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - enables interoperability with 3.3 V and 5 V logic domains without level shifters. |
| Propagation Delay (tpd) | 12 ns (typ) at 6 V, CL = 50 pF - ensures sub-25 ns round-trip latency for real-time bus arbitration. |
| Output Drive Strength | ±6 mA at 5 V - sufficient to directly drive 15 LSTTL inputs while maintaining VIH/VIL margins. |
| Quiescent Current (ICC) | 80 µA max - minimizes standby power in always-on military subsystems. |
| Operating Temperature | –55°C to 125°C - qualified per MIL-PRF-38535 for extended-life deployment in harsh environments. |
| Input Leakage Current | 1 µA max - prevents unintended logic state drift on floating or high-impedance control lines. |
| 3-State Enable/Disable Time | ten = 20 ns, tdis = 21 ns (max) at 6 V - supports fast bus turnaround in time-critical multiplexed architectures. |
Pinout & Package
LCCC-20 (FK) package: 8.89 mm × 8.89 mm ceramic leadless chip carrier with 1.27 mm pitch, 2.03 mm max height, and solderable metallized terminations on all four sides. Designed for hermetic sealing and high-reliability board mounting in aerospace and defense applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A-bus inputs/outputs | Bidirectional data terminals for A-side bus; direction determined by DIR signal. |
| 11, 12, 13, 14, 15, 16, 17, 18 | B-bus inputs/outputs | Bidirectional data terminals for B-side bus; functionally mirrored to A pins. |
| 9 | GND | Ground reference for all internal circuitry and I/O structures. |
| 10 | VCC | Primary power supply connection; must be decoupled locally per MIL-STD-1394. |
| 19 | DIR | Direction-control input: LOW routes B→A, HIGH routes A→B (non-inverting). |
| 20 | OE | Output-enable input: LOW enables transceiver; HIGH forces all A/B pins into high-impedance state. |
Key Features
| Feature | Design Value |
|---|---|
| Wide Supply Range (2–6 V) | Supports mixed-voltage system integration without external regulators or translators. |
| High-Current 3-State Outputs | Drives 15 LSTTL loads directly - eliminates need for buffer stages in legacy bus interfaces. |
| Military Temperature Qualification | Rated for –55°C to 125°C operation per MIL-PRF-38535 Class K - validated for launch vehicle and satellite subsystems. |
| Low Input Current (≤1 µA) | Enables reliable operation with high-impedance control sources such as FPGA GPIO or discrete logic. |
| True CMOS Logic Levels | VIH/VIL thresholds scale with VCC - ensures noise margin compatibility across supply voltages. |
Applications
| Avionics Data Bus Interface | Tactical Radio Backplane |
|---|---|
Use Scenario: Bidirectional data exchange between mission computer and sensor processing module over shared MIL-STD-1553 auxiliary bus. IC Role / Device Role / Timing Role: Octal transceiver managing A/B bus handshaking under DIR-controlled flow and OE-gated isolation during fault recovery. Use Value: Enables deterministic 12 ns-latency bus arbitration and hot-swap-safe isolation without additional logic or timing overhead. |
Use Scenario: Interfacing FPGA-based modem core with analog RF front-end ASIC across isolated power domains in handheld SDR radios. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled data conduit between 3.3 V FPGA I/O and 5 V RF IC control registers. Use Value: Eliminates need for discrete level translators while sustaining 27 ns worst-case propagation for real-time AGC loop timing. |
| Spacecraft Telemetry Hub | Hardened Industrial PLC I/O Module |
Use Scenario: Consolidating telemetry streams from multiple radiation-hardened sensors onto a central CAN FD controller via parallel-to-serial bridge. IC Role / Device Role / Timing Role: High-reliability bus transceiver isolating sensor-side logic from main controller during reset sequences. Use Value: Provides guaranteed 3-state isolation (tdis ≤ 21 ns) and <1 µA leakage to prevent bus contention in zero-power fault states. |
Use Scenario: Isolating programmable logic controller CPU bus from field I/O expansion cards operating in electrically noisy factory environments. IC Role / Device Role / Timing Role: Direction-managed data path between CPU address/data bus and modular I/O register banks. Use Value: Delivers ±6 mA drive strength and 6 V tolerance to withstand ESD transients and maintain signal integrity over 30 cm ribbon cables. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SNJ54HC245FK | Non-inverting octal transceiver with identical LCCC-20 package, same military temp range, but lacks DIR pin - uses separate A→B and B→A enable controls. | Suitable where direction is statically assigned per channel pair rather than dynamically controlled per transaction. | Select SNJ54HC245FK only if system architecture requires independent A→B and B→A gating instead of single DIR-driven bidirectional mode. |
| SNJ54ACT645FK | TTL-compatible input thresholds (VIH = 2 V min), faster tpd = 9 ns (typ) at 5 V, higher ICC = 4 mA max, and reduced noise margin vs. HC family. | Better suited for legacy TTL bus environments requiring strict 5 V logic compatibility and tighter timing budgets. | Choose SNJ54ACT645FK when interfacing with older TTL-based subsystems where HC-level VIH/VIL margins are insufficient. |
Compared with SNJ54HC645FK, SNJ54HC245FK offers fixed-direction routing and simpler control but no dynamic bidirectional capability, while SNJ54ACT645FK trades lower power and wider voltage tolerance for TTL input compatibility and higher speed - making SNJ54HC645FK optimal for modern mixed-voltage, low-power military bus bridging.
Availability
SNJ54HC645FK is available at Aetrix Electronics and suitable for avionics data bus interface, tactical radio backplane, spacecraft telemetry hub, and hardened industrial PLC I/O module applications requiring stable component supply across extended temperature and long-lifecycle programs.
Supply support for SNJ54HC645FK 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 high-reliability components, with decades of heritage in military and space-grade IC development.
The SNJ54HC645FK belongs to TI's 54HC logic family - designed specifically for high-performance, low-power, wide-voltage-range digital interfacing in defense, aerospace, and industrial control systems.
FAQ
What is the maximum operating temperature for SNJ54HC645FK?
The SNJ54HC645FK is rated for continuous operation from –55°C to 125°C, meeting MIL-PRF-38535 Class K requirements. This specification is validated across all electrical parameters including propagation delay, output drive, and leakage current - making it suitable for engine bay, payload bay, and orbital thermal environments where passive cooling dominates.
Does SNJ54HC645FK support 3.3 V logic levels?
Yes, SNJ54HC645FK fully supports 3.3 V operation: its 2 V–6 V supply range includes 3.3 V nominal, and input thresholds (VIH = 2.31 V min, VIL = 1.09 V max at VCC = 3.3 V) ensure robust compatibility with standard 3.3 V CMOS logic families without level translation.
How does the DIR pin control data flow in SNJ54HC645FK?
In SNJ54HC645FK, the DIR pin determines bus direction: when DIR = LOW, data flows from B-bus to A-bus; when DIR = HIGH, data flows from A-bus to B-bus. This single-pin control enables synchronous bidirectional communication without requiring separate transmit/receive enable signals.
What is the purpose of the OE pin on SNJ54HC645FK?
The OE (output-enable) pin on SNJ54HC645FK places all A- and B-bus I/Os into high-impedance state when asserted HIGH, effectively isolating both buses. This allows safe bus sharing, hot-swap capability, and conflict-free multi-master arbitration - critical in MIL-STD-1553 auxiliary bus and PLC backplane designs.
Is SNJ54HC645FK RoHS compliant?
No, SNJ54HC645FK uses SnPb (tin-lead) lead finish and is not RoHS compliant. It is manufactured per MIL-PRF-38535 with legacy solderability requirements for hermetic packaging and high-reliability reflow profiles - intended for exempted defense and aerospace applications.
SNJ54HC645FK 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:
- -
SNJ54HC645FK FAQ
1.How can I place an order for SNJ54HC645FK through Aetrix?
Please submit a Request for Quotation (RFQ) for SNJ54HC645FK 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 SNJ54HC645FK reliable?
The price and inventory of SNJ54HC645FK are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SNJ54HC645FK is usually 5 days.
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Once your SNJ54HC645FK 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 SNJ54HC645FK?
For technical support, including SNJ54HC645FK datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SNJ54HC645FK requirements.
6.How does Aetrix verify that SNJ54HC645FK is sourced from the original manufacturer or authorized distributors?
All SNJ54HC645FK 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 SNJ54HC645FK meets industry standards.
7.What is the process for return or replacement of SNJ54HC645FK?
All SNJ54HC645FK units undergo pre-shipment inspection (PSI). If there is an issue with SNJ54HC645FK, 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 SNJ54HC645FK part is unused and in its original packaging.
Return procedure for SNJ54HC645FK:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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