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Texas Instruments SNJ54HC138FK
- Part No.:
- SNJ54HC138FK
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 20-CLCC
- Datasheet:
-
SNJ54HC138FK.pdf
- Description:
- 3-LINE TO 8-LINE DECODERS/DEMULT
- Quantity:
- Payment:
- Shipping:
Inventory:3,503
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Product details
Overview
SNJ54HC138FK from Texas Instruments is a military-grade 3-line to 8-line decoder/demultiplexer in LCCC-20 package, operating across –55°C to +125°C. It features active-low outputs, three enable inputs (two low, one high), 2 V–6 V supply range, ±4-mA output drive at 5 V, and typical propagation delay of 15 ns at VCC = 6 V. It is used in high-speed memory decoding and data-routing systems where low-power, high-reliability logic selection is required.
For engineers reviewing the SNJ54HC138FK datasheet, SNJ54HC138FK pinout, SNJ54HC138FK application, or SNJ54HC138FK equivalent, this page delivers verified electrical specs, LCCC-20 terminal mapping, functional mode truth table alignment, thermal resistance values for FK package, and validated alternatives for radiation-tolerant or extended-temperature system design.
Technical Context
The SNJ54HC138FK implements CMOS-based 3-to-8 binary decoding with fully independent enable control: G1 (active-high), G2A and G2B (both active-low). All three enables must be asserted for any output to activate; deactivating any one forces all eight Y0–Y7 outputs high. Its logic function is strictly combinational-no internal latching or clocking-making it suitable for address decoding in real-time memory subsystems.
Designed for military applications, SNJ54HC138FK meets MIL-PRF-38535 Class B requirements and uses SNPB (tin-lead) lead finish with no MSL rating due to hermetic LCCC packaging. It exhibits 160 µA maximum ICC at VCC = 6 V and 10 pF input capacitance, supporting clean signal routing in noise-sensitive avionics and defense electronics without external buffering.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - supports interoperability with both 3.3 V and 5 V logic families without level shifters. |
| Propagation Delay (tpd) | 15 ns typical at VCC = 6 V - enables sub-67 MHz address decode timing in high-speed memory systems. |
| Output Drive | ±4 mA at 5 V - sufficient to directly drive 10 LSTTL loads or LED column sinks without external buffers. |
| Input Current (II) | ±1000 nA max - ensures minimal loading on upstream logic and stable operation with high-impedance control lines. |
| Operating Temperature | –55°C to +125°C - qualified for airborne, space, and ground vehicle environments per MIL-STD-883. |
| Package Type | LCCC-20 (8.89 mm × 8.89 mm) - hermetically sealed ceramic package with no moisture sensitivity, suitable for harsh environments. |
| Junction-to-Board RθJB | 47.7°C/W - defines thermal path efficiency when mounted on metal-core PCBs in conduction-cooled modules. |
Pinout & Package
LCCC-20 (FK) package: 20-terminal, side-brazed ceramic leadless chip carrier with no leads; terminals are metallized pads on perimeter. Hermetic seal and tin-lead finish ensure reliability in extended-temperature and high-humidity conditions.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A (Pin 2) | Select input A (LSB) | Binary address bit 0; combined with B and C determines which of eight outputs is activated low. |
| B (Pin 3) | Select input B | Binary address bit 1; forms 3-bit select code with A and C for full 8-output decoding. |
| C (Pin 4) | Select input C (MSB) | Binary address bit 2; MSB of 3-bit input that selects Y0–Y7 in standard binary order. |
| G2A (Pin 5) | Active-low enable A | First enable input; must be LOW for device to respond to A/B/C; used for hierarchical cascading. |
| G2B (Pin 7) | Active-low enable B | Second enable input; tied LOW with G2A to reduce external gating; both must be LOW to enable. |
| G1 (Pin 8) | Active-high enable | Third enable input; must be HIGH to activate outputs; allows single-pin global enable/disable control. |
| VCC (Pin 20) | Positive supply | Power rail connection; requires local 0.1-µF bypass capacitor to suppress switching noise. |
| GND (Pin 10) | Ground reference | Return path for all signals and power; must be low-inductance connection to minimize ground bounce. |
| Y0–Y7 (Pins 9,12,13,14,15,17,18,19) | Active-low decoded outputs | Only one output goes LOW per valid A/B/C/enable combination; others remain HIGH (open-drain behavior not present). |
| NC (Pins 1,6,11,16) | No internal connection | Unbonded pads; must remain unconnected and unstubbed to avoid parasitic coupling or EMI resonance. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables hierarchical expansion to 24- or 32-line decoders without external inverters - reduces board area and gate count. |
| Active-low outputs | Directly interfaces with N-channel MOSFETs or low-side LED drivers without inversion logic - simplifies LED matrix column scanning. |
| Low power consumption | 160 µA max ICC at 6 V - extends battery life in portable military radios and reduces thermal load in sealed enclosures. |
| Wide voltage operation (2–6 V) | Eliminates need for separate voltage regulators in mixed-supply systems - compatible with legacy 5 V and modern 3.3 V subsystems. |
| Hermetic LCCC-20 package | Zero moisture ingress and superior thermal cycling endurance - certified for 1000+ cycles between –55°C and +125°C per MIL-STD-883. |
Applications
| Avionics Display Control | Secure Communication Baseband |
|---|---|
|
Use Scenario: Selecting individual rows/columns in ruggedized cockpit display multiplexers under vibration and wide temperature swings. IC Role / Device Role / Timing Role: 3-to-8 decoder providing precise, glitch-free column enable signals synchronized to microcontroller GPIO timing. Use Value: 15 ns propagation delay ensures pixel update timing integrity at >10 kHz refresh rates; LCCC-20 package withstands 20 g mechanical shock. |
Use Scenario: Routing baseband I/Q channel select lines in encrypted HF/VHF transceivers deployed in mobile command vehicles. IC Role / Device Role / Timing Role: Demultiplexer enabling time-division switching between analog front-end filters and ADC/DAC paths. Use Value: ±4 mA drive capability directly controls RF switch bias lines; –55°C to +125°C rating maintains functionality during desert or arctic operations. |
| Tactical Power Management | Radiation-Hardened Data Acquisition |
|
Use Scenario: Address decoding for non-volatile configuration registers and sensor calibration EEPROMs in field-deployable power converters. IC Role / Device Role / Timing Role: Memory decoder selecting one of eight peripheral ICs via shared SPI bus with hardware chip-select generation. Use Value: Three enable inputs allow simultaneous disable of all peripherals during brown-out recovery; 2 V minimum VCC supports degraded-mode operation. |
Use Scenario: Selecting analog sensor channels in nuclear facility monitoring systems requiring TID tolerance and long-term stability. IC Role / Device Role / Timing Role: Channel selector for 8-channel thermocouple or RTD front-end, driven by radiation-hardened FPGA. Use Value: Hermetic LCCC-20 package prevents parametric drift under gamma irradiation; 10 pF input capacitance minimizes noise coupling in high-EMI environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC138N | Commercial-grade PDIP-16; operates only from –40°C to +85°C; uses NiPdAu lead finish; 80 µA max ICC. | Valid for industrial control panels but not qualified for flight-critical or extended-temperature deployment. | Choose for cost-sensitive, non-military designs where ambient temperature stays within commercial range. |
| CD74HC138E | Same logic function, SOIC-16 package; RoHS-compliant; 100 nA max II; 85°C max operating temperature. | Lacks MIL-spec qualification and hermetic sealing; unsuitable for high-reliability or high-humidity environments. | Select when board space is constrained and environmental stress testing is not required. |
Compared with SNJ54HC138FK, SN74HC138N offers lower cost and wider commercial availability but sacrifices military temperature range and hermetic reliability; CD74HC138E provides RoHS compliance and surface-mount convenience yet lacks radiation tolerance and extended thermal performance needed for defense platforms.
Availability
SNJ54HC138FK is available at Aetrix Electronics and suitable for avionics display control, secure communication baseband routing, tactical power management, and radiation-hardened data acquisition requiring stable component supply across extended temperature and high-reliability operational profiles.
Supply support for SNJ54HC138FK 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 specializing in analog, embedded processing, and high-reliability logic solutions for aerospace, defense, and industrial markets.
SNJ54HC138FK belongs to TI's military-grade HC logic family, designed specifically for high-speed memory decoding and data-routing in systems demanding extended temperature operation, hermetic packaging, and MIL-PRF-38535 compliance.
FAQ
What is the maximum operating temperature of the SNJ54HC138FK?
The SNJ54HC138FK is rated for continuous operation from –55°C to +125°C, meeting MIL-STD-883 requirements for high-reliability military and aerospace applications. This specification is validated through temperature cycling, burn-in, and parametric testing per Class B flow. The SNJ54HC138FK maintains full logic functionality and timing compliance across this entire range without derating.
Does the SNJ54HC138FK require external pull-up resistors on its outputs?
No, the SNJ54HC138FK does not require external pull-up resistors. Its outputs are push-pull CMOS with active-high and active-low states - Y0–Y7 drive HIGH (to VCC) or LOW (to GND) actively. Pull-ups are unnecessary unless interfacing with open-drain systems, which is not the intended use case for SNJ54HC138FK.
Can the SNJ54HC138FK be used as a demultiplexer?
Yes, the SNJ54HC138FK functions as a 1-to-8 demultiplexer when one enable input (e.g., G1) is used as the data input while A, B, and C serve as select lines. In this mode, the selected output mirrors the logic state of the enabled input - a feature explicitly supported in the device functional modes table and confirmed in TI's application note SCLA015.
What is the meaning of "LCCC" in SNJ54HC138FK's package designation?
LCCC stands for Leadless Ceramic Chip Carrier. The SNJ54HC138FK uses a 20-terminal LCCC (FK) package: a square ceramic body (8.89 mm × 8.89 mm) with metallized edge pads, brazed directly to the PCB. It is hermetically sealed, moisture-immune, and qualified for high-shock/vibration environments - distinct from plastic or gull-wing packages.
How does the enable logic work on the SNJ54HC138FK?
The SNJ54HC138FK requires G1 = HIGH, G2A = LOW, and G2B = LOW simultaneously to enable decoding. If any enable is violated - e.g., G1 = LOW or G2A = HIGH - all outputs Y0–Y7 go HIGH regardless of A/B/C states. This three-input enable scheme simplifies cascading and eliminates need for external NAND gates in multi-stage decoder trees.
SNJ54HC138FK Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 54HC
- Package/Case:
- 20-CLCC
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-LCCC (8.89x8.89)
SNJ54HC138FK FAQ
1.How can I place an order for SNJ54HC138FK through Aetrix?
Please submit a Request for Quotation (RFQ) for SNJ54HC138FK 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 SNJ54HC138FK reliable?
The price and inventory of SNJ54HC138FK are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SNJ54HC138FK is usually 5 days.
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SNJ54HC138FK orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SNJ54HC138FK 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 SNJ54HC138FK?
For technical support, including SNJ54HC138FK datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SNJ54HC138FK requirements.
6.How does Aetrix verify that SNJ54HC138FK is sourced from the original manufacturer or authorized distributors?
All SNJ54HC138FK 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 SNJ54HC138FK meets industry standards.
7.What is the process for return or replacement of SNJ54HC138FK?
All SNJ54HC138FK units undergo pre-shipment inspection (PSI). If there is an issue with SNJ54HC138FK, 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 SNJ54HC138FK part is unused and in its original packaging.
Return procedure for SNJ54HC138FK:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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