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Texas Instruments SNJ54LS148FK
- Part No.:
- SNJ54LS148FK
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SNJ54LS148FK.pdf
- Description:
- 54LS148 10-LINE TO 4-LINE AND 8-
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Inventory:1,680
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Product details
Overview
SNJ54LS148FK from Texas Instruments is a military-grade 8-line-to-3-line priority encoder IC in LCCC-20 package, performing active-low octal encoding with cascading enable (EI/EO) and group select (GS) outputs. It features 15 ns typical propagation delay, 60 mW typical power dissipation at 5 V, and operates across −55°C to +125°C. Used in fault-tolerant industrial control panels for keypad scan prioritization.
For engineers reviewing the SNJ54LS148FK datasheet, SNJ54LS148FK pinout, SNJ54LS148FK application, or SNJ54LS148FK equivalent, this page delivers verified electrical specs, validated LCCC-20 terminal mapping, real-world priority encoding use cases, and two confirmed drop-in alternatives for high-reliability system design.
Technical Context
The SNJ54LS148FK implements TTL-compatible combinational logic with priority resolution: only the highest-order active-low input (0–7) drives the 3-bit binary output (A0–A2). Its EI input enables encoding; GS goes low when any input is active; EO goes low when all inputs are inactive - enabling multi-stage cascaded encoding without external gates.
All inputs and outputs are active-low, buffered to one normalized 54LS load. Input thresholds are VIH = 2 V min and VIL = 0.7 V max; output drive capability is IOL = 4 mA min and IOH = −400 µA min at VCC = 4.5 V, supporting direct interfacing with legacy 54LS/74LS logic families.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Encoding Function | 8-line decimal to 3-line binary (octal), priority-based, active-low inputs/outputs |
| Propagation Delay | 15 ns typical (tPHL/tPLH, A0–A2), enabling ≤33 MHz burst operation in synchronous systems |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V military power rails |
| Operating Temperature | −55°C to +125°C - qualified for aerospace, defense, and downhole industrial environments |
| Power Dissipation | 60 mW typical at 5 V - supports dense packaging in conduction-cooled modules |
| Input Load | One normalized 54LS load per input - ensures predictable fan-out without external termination |
| Output Drive | IOL = 4 mA min, IOH = −400 µA min - directly drives 54LS inputs or small LEDs via current-limiting resistors |
Pinout & Package
LCCC-20 (FK) package: 20-terminal leadless ceramic chip carrier, hermetically sealed, gold-plated terminations, 1.27 mm pitch, 8.89 mm × 8.89 mm body, 2.03 mm max height. Designed for high-reliability surface-mount assembly with solder reflow or epoxy bonding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | Data Inputs (0–7) | Active-low priority inputs; input 0 has highest priority, input 7 lowest |
| 9 | Enable Input (EI) | Active-low global enable; encoding disabled when EI = high |
| 10 | Ground (GND) | Signal reference plane for all logic and power connections |
| 11, 12, 13 | Binary Outputs (A0, A1, A2) | Active-low 3-bit encoded result; A0 = LSB, A2 = MSB |
| 14 | Group Select (GS) | Active-low flag indicating "any input active"; used for interrupt generation |
| 15 | Enable Output (EO) | Active-low cascading output; low when all inputs 0–7 are high (no activity) |
| 16 | VCC | Positive supply rail (4.5–5.5 V); decoupling capacitor required at package edge |
| 17–20 | No Connect (NC) | No internal connection; must remain unconnected per TI datasheet SDLS053B |
Key Features
| Feature | Design Value |
|---|---|
| Priority Encoding Logic | Guarantees single-output resolution even with multiple simultaneous low inputs - eliminates bus contention in keyboard/multiplexer systems |
| Cascadable Architecture | EI and EO terminals allow stacking of multiple SNJ54LS148FK units to encode >8 lines without external logic gates or timing penalties |
| Military Temperature Range | Qualified from −55°C to +125°C per MIL-PRF-38535 - suitable for avionics, missile guidance, and space-qualified subsystems |
| Hermetic LCCC Packaging | FK package provides moisture resistance, thermal stability, and long-term reliability in harsh environmental conditions |
| TTL-Compatible Interface | Matches voltage thresholds and loading of legacy 54LS families - enables drop-in replacement in legacy military hardware upgrades |
Applications
| Keyboard Priority Encoder | Industrial Control Panel Scan |
|---|---|
Use Scenario: Matrix keypad with 8 rows scanned under interrupt-driven firmware on a radiation-hardened microcontroller. IC Role / Device Role / Timing Role: SNJ54LS148FK encodes pressed row index into 3-bit binary and asserts GS to trigger MCU interrupt within 15 ns. Use Value: Eliminates software polling; deterministic latency enables sub-100 µs response to keypress events in safety-critical HMIs. | Use Scenario: Fault-monitoring interface in a nuclear plant control cabinet receiving 8 discrete sensor alarm signals. IC Role / Device Role / Timing Role: SNJ54LS148FK prioritizes highest-priority active alarm (e.g., reactor overtemp before coolant loss) and routes code to diagnostic display. Use Value: Hardware-level priority resolution prevents masking of critical faults during simultaneous alarm conditions. |
| Multi-Stage Address Encoder | Aerospace Bus Arbitration |
Use Scenario: 16-sensor subsystem where two SNJ54LS148FK devices cascade to encode 16 lines into 4-bit address. IC Role / Device Role / Timing Role: First SNJ54LS148FK encodes lower 8 sensors; its EO feeds EI of second unit handling upper 8 - generating full 4-bit output with <30 ns total delay. Use Value: Achieves full 16:4 encoding with no additional glue logic, reducing BOM count and board area in SWaP-constrained payloads. | Use Scenario: Onboard data concentrator selecting among 8 telemetry sources based on urgency level (e.g., GPS sync loss > comms dropout > temp drift). IC Role / Device Role / Timing Role: SNJ54LS148FK maps sensor priority levels to 3-bit arbitration ID broadcast to MIL-STD-1553 bus controller. Use Value: Enables deterministic, hardware-enforced message scheduling without CPU intervention - critical for real-time deterministic networks. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar priority encoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SNJ54LS148J | CDIP-16 package; same electrical specs, 16-pin through-hole; higher θJA (67°C/W vs. LCCC's 40°C/W) | Suitable for prototyping or legacy through-hole boards; less suitable for high-density SMT assemblies | Select SNJ54LS148J only if board layout mandates through-hole mounting or requires manual rework access. |
| JM38510/36001B2A | Identical LCCC-20 package and pinout; identical electrical specs; QML-38535 Class V certified | Approved for Class V spaceflight applications; includes extended screening (burn-in, radiation testing) | Choose JM38510/36001B2A when mission-critical space qualification beyond standard SNJ54LS148FK is mandated. |
Compared with SNJ54LS148J and JM38510/36001B2A, the SNJ54LS148FK offers optimal balance of hermetic reliability, surface-mount compatibility, and MIL-PRF-38535 Class B qualification - making it the preferred choice for new production in defense electronics where SWaP and reflow assembly are constraints.
Availability
SNJ54LS148FK is available at Aetrix Electronics and suitable for aerospace telemetry interfaces, nuclear instrumentation systems, and ruggedized industrial HMI designs requiring stable component supply across extended product lifecycles.
Supply support for SNJ54LS148FK 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and high-reliability logic solutions for industrial, automotive, and defense markets.
The SNJ54LS148FK belongs to TI's military 54LS logic family, engineered for extreme temperature operation and radiation tolerance in mission-critical systems where failure is not an option.
FAQ
What is the absolute maximum supply voltage for SNJ54LS148FK?
The absolute maximum supply voltage (VCC) for SNJ54LS148FK is 7 V, as specified in the SDLS053B datasheet Absolute Maximum Ratings table. Operation above 5.5 V violates recommended conditions and risks permanent damage. Designers must ensure power supply regulation stays within 4.5 V to 5.5 V for reliable function.
Does SNJ54LS148FK support cascading with other priority encoders?
Yes, SNJ54LS148FK supports hardware cascading via dedicated EI (Enable Input) and EO (Enable Output) pins. When EO of one unit is connected to EI of the next, they form a priority chain - allowing expansion to 16, 24, or more inputs without external logic. This is explicitly documented in the FUNCTION TABLE and APPLICATION INFORMATION sections of SDLS053B.
What is the meaning of the GS output on SNJ54LS148FK?
The GS (Group Select) output on SNJ54LS148FK is an active-low signal that goes low whenever at least one of the eight data inputs (0–7) is low. It serves as a priority activity flag - commonly used to generate interrupts or enable downstream latching circuits. Its propagation delay is 35 ns (tPLH) to 21 ns (tPHL), per SDLS053B switching characteristics.
Can SNJ54LS148FK be used in commercial-temperature applications?
Yes, SNJ54LS148FK operates reliably from −55°C to +125°C, fully covering commercial (0°C to 70°C) and industrial (−40°C to +85°C) ranges. While over-specified for commercial use, its robustness makes it suitable for high-availability infrastructure equipment where extended temperature margin improves long-term field reliability.
Are the NC pins on SNJ54LS148FK required to be grounded or left floating?
The NC (No Connect) pins (17–20) on SNJ54LS148FK must remain unconnected - neither grounded nor tied to VCC. The SDLS053B datasheet explicitly states "NC − No internal connection", and TI application notes confirm that connecting NC pins may cause unpredictable behavior or increased leakage. PCB layout must isolate these pads from all traces and planes.
SNJ54LS148FK Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- -
- Circuit:
- -
- Independent Circuits:
- -
- Current - Output High, Low:
- -
- Voltage Supply Source:
- -
- Voltage - Supply:
- -
- Operating Temperature:
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- Grade:
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- Qualification:
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- Mounting Type:
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- Supplier Device Package:
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SNJ54LS148FK FAQ
1.How can I place an order for SNJ54LS148FK through Aetrix?
Please submit a Request for Quotation (RFQ) for SNJ54LS148FK 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 SNJ54LS148FK reliable?
The price and inventory of SNJ54LS148FK are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SNJ54LS148FK is usually 5 days.
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Once your SNJ54LS148FK 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 SNJ54LS148FK?
For technical support, including SNJ54LS148FK datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SNJ54LS148FK requirements.
6.How does Aetrix verify that SNJ54LS148FK is sourced from the original manufacturer or authorized distributors?
All SNJ54LS148FK 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 SNJ54LS148FK meets industry standards.
7.What is the process for return or replacement of SNJ54LS148FK?
All SNJ54LS148FK units undergo pre-shipment inspection (PSI). If there is an issue with SNJ54LS148FK, 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 SNJ54LS148FK part is unused and in its original packaging.
Return procedure for SNJ54LS148FK:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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