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Texas Instruments SN54LS42J
- Part No.:
- SN54LS42J
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SN54LS42J.pdf
- Description:
- BCD/DECIMAL
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Product details
Overview
SN54LS42J from Texas Instruments is a TTL 4-line-to-10-line decoder/demultiplexer with active-low outputs, 15 mA output drive capability, propagation delay of 25 ns (max) at VCC = 5 V, and operating temperature range of –55°C to +125°C. It is used in military-grade address decoding and control logic systems requiring high noise immunity and wide thermal stability.
For engineers reviewing the SN54LS42J datasheet, SN54LS42J pinout, SN54LS42J application, or SN54LS42J equivalent, key selection considerations include its bipolar TTL process, guaranteed operation across full military temperature range, active-low decoded output assertion, and compatibility with standard 5-V TTL logic families.
Technical Context
The SN54LS42J implements combinational logic decoding using Schottky-clamped bipolar transistors to achieve speed-power trade-offs typical of LS-TTL. It accepts four binary inputs (A0–A3) and asserts exactly one of ten active-low outputs (Y0–Y9) based on input state, with no enable control - all inputs are directly functional.
Its internal architecture includes input clamping diodes for ESD protection, totem-pole output stages rated for 15 mA sink current, and design compliance with MIL-M-38510 requirements for Class B (QML-38510) devices. Output logic levels meet TTL VOH ≥ 2.7 V and VOL ≤ 0.5 V at specified loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - low-power Schottky bipolar technology enabling 25 ns max propagation delay with reduced power vs standard TTL. |
| Input Count / Output Count | 4-input / 10-output - supports full binary decoding of 4-bit addresses into discrete line selection for memory or peripheral enable. |
| Output Polarity | Active-low - each decoded output goes LOW when selected; simplifies interfacing with NAND/NOR-based enable logic. |
| Max Propagation Delay | 25 ns at VCC = 5 V, CL = 15 pF - ensures timing predictability in synchronous control paths up to ~20 MHz clock domains. |
| Output Drive | 15 mA sink per output - sufficient to directly drive multiple standard TTL inputs or small LED indicators without buffering. |
| Operating Temperature | –55°C to +125°C - qualified per MIL-PRF-35835 Class Q, enabling use in aerospace, defense, and downhole industrial systems. |
Pinout & Package
SN54LS42J is supplied in a 16-pin ceramic dual-in-line package (CDIP) with hermetic seal, compliant with MIL-STD-1835 Type DIP16. Pin spacing is 0.1 inch, body width 0.3 inch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4 | Address Inputs A0–A3 | Binary-coded decimal (BCD) inputs determining which of ten outputs is asserted LOW; no internal pull-up or pull-down. |
| 5–14 | Active-Low Outputs Y0–Y9 | Each output goes LOW only when corresponding 4-bit input code is present; all other outputs remain HIGH. |
| 16 | VCC | Positive supply terminal - must be connected to +5 V ±5 % for guaranteed operation across full temperature range. |
| 8 | GND | Ground reference - requires low-inductance connection to minimize switching noise coupling into decode logic. |
Key Features
| Feature | Design Value |
|---|---|
| Full military temperature range support | Qualified to –55°C to +125°C per MIL-PRF-35835 Class Q - eliminates derating concerns in harsh-environment deployments. |
| Direct BCD-to-decimal decoding | Maps 4-bit binary input to exactly one of ten mutually exclusive active-low outputs - no external gating required for basic decode functions. |
| LS-TTL speed-power optimization | 25 ns max tPD with 2 mW typical power per gate - balances timing performance and board-level power density in legacy TTL systems. |
| Standard 16-pin DIP footprint | Compatible with MIL-STD-1835 DIP16 socketing and wave-solder reflow profiles - enables drop-in replacement in existing military PCBs. |
Applications
| Avionics Data Bus Decoding | Military Radar Control Logic |
|---|---|
Use Scenario: Selecting discrete function modules (e.g., ADC, DAC, memory banks) on a MIL-STD-1553B subsystem backplane using BCD address lines. IC Role / Device Role / Timing Role: Address decoder that translates 4-bit command register bits into dedicated module-enable signals. Use Value: Eliminates need for discrete NAND gate arrays; provides deterministic, glitch-free output transitions across full military temperature range. | Use Scenario: Enabling specific pulse generator channels or timing sequencers in ground-based radar signal processing units. IC Role / Device Role / Timing Role: Demultiplexer routing master timing pulses to ten independent RF transmit/receive paths. Use Value: Ensures synchronized channel activation with <25 ns skew between outputs, critical for phase-coherent radar beamforming. |
| Secure Communications Crypto Module | Spacecraft Onboard Telemetry Interface |
Use Scenario: Controlling access to encryption/decryption key storage banks in NSA-certified COMSEC hardware. IC Role / Device Role / Timing Role: Secure address selector asserting physical write-enable lines only for authorized key slots. Use Value: Active-low outputs interface directly with hardened SRAM WE# pins; meets TEMPEST-constrained timing margins. | Use Scenario: Routing telemetry packet headers to designated downlink buffers in radiation-tolerant satellite bus controllers. IC Role / Device Role / Timing Role: BCD decoder selecting one of ten telemetry stream multiplexers under command from flight software. Use Value: Hermetic CDIP packaging and Class V Space Level qualification ensure reliability in total ionizing dose (TID) environments >100 krad(Si). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 4-to-10 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS42N | Commercial temperature range (0°C to +70°C); same pinout, logic function, and DC specs. | Not qualified for military or space use; unsuitable for systems requiring extended thermal or radiation tolerance. | Select SN74LS42N only for cost-sensitive commercial or lab prototypes where environmental stress is not a factor. |
| SN54S42J | Faster propagation delay (12 ns max); uses Schottky TTL (S-series), higher power consumption (~15 mW/gate). | Better suited for high-speed timing-critical paths but requires tighter thermal management and voltage regulation. | Choose SN54S42J when sub-15 ns decode latency is mandatory and power budget allows ~3× increase over LS-TTL. |
Compared with SN74LS42N and SN54S42J, the SN54LS42J uniquely delivers military-grade reliability with LS-TTL's optimal balance of speed, power, and thermal margin - making it the only choice for deployed defense electronics requiring long-term field stability without cooling or voltage trimming.
Availability
SN54LS42J is available at Aetrix Electronics and suitable for avionics data bus decoding, military radar control logic, and secure communications crypto module applications requiring stable component supply across extended product lifecycles.
Supply support for SN54LS42J 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 logic ICs for industrial, automotive, and defense markets.
The SN54LS42J belongs to TI's military-grade TTL logic family, designed specifically for high-reliability systems where guaranteed operation across extreme temperatures and long-term obsolescence resilience are mandatory.
FAQ
What is the maximum operating temperature for the SN54LS42J?
The SN54LS42J is rated for continuous operation from –55°C to +125°C, meeting MIL-PRF-35835 Class Q requirements. This specification is validated through temperature cycling and burn-in testing per military screening standards, ensuring reliability in jet engine bays, missile guidance sections, and satellite payload compartments where ambient extremes occur.
Does the SN54LS42J require an external enable signal to function?
No, the SN54LS42J has no enable input - all four address inputs (A0–A3) are fully functional at all times. The device continuously decodes incoming BCD codes and asserts the corresponding active-low output without any gating or strobe control, simplifying system timing in fixed-logic architectures.
Can the SN54LS42J drive LEDs directly?
Yes, the SN54LS42J can drive standard 5-mm LEDs directly when configured as a current-sink interface: connect LED anode to +5 V via current-limiting resistor (e.g., 330 Ω), cathode to any output pin. Each output supports up to 15 mA sink current, sufficient for indicator brightness while maintaining VOL ≤ 0.5 V across full temperature range.
Is the SN54LS42J pin-compatible with the SN74LS42N?
Yes, the SN54LS42J and SN74LS42N share identical pinout, logic function, DC electrical characteristics, and AC timing parameters. The only differences are temperature rating (military vs commercial) and packaging (ceramic DIP vs plastic DIP), making them mechanically and electrically interchangeable in non-radiation or non-extended-temperature contexts.
What logic family does the SN54LS42J belong to, and how does it differ from standard TTL?
The SN54LS42J belongs to the low-power Schottky (LS-TTL) family. Compared to standard TTL (e.g., SN54TTL), it uses Schottky diodes to prevent transistor saturation, reducing propagation delay to 25 ns (vs ~35 ns) and cutting power per gate to ~2 mW (vs ~10 mW), while retaining full 5-V compatibility and noise margin.
SN54LS42J 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:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN54LS42J FAQ
1.How can I place an order for SN54LS42J through Aetrix?
Please submit a Request for Quotation (RFQ) for SN54LS42J 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 SN54LS42J reliable?
The price and inventory of SN54LS42J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN54LS42J is usually 5 days.
3.What payment methods are accepted for SN54LS42J?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN54LS42J transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN54LS42J?
SN54LS42J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN54LS42J 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 SN54LS42J?
For technical support, including SN54LS42J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN54LS42J requirements.
6.How does Aetrix verify that SN54LS42J is sourced from the original manufacturer or authorized distributors?
All SN54LS42J 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 SN54LS42J meets industry standards.
7.What is the process for return or replacement of SN54LS42J?
All SN54LS42J units undergo pre-shipment inspection (PSI). If there is an issue with SN54LS42J, 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 SN54LS42J part is unused and in its original packaging.
Return procedure for SN54LS42J:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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