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Texas Instruments SNJ54278J
- Part No.:
- SNJ54278J
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SNJ54278J.pdf
- Description:
- ENCODER, 4-BIT, TTL
- Quantity:
- Payment:
- Shipping:
Inventory:866
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Product details
Overview
SNJ54278J from Texas Instruments is a dual 4-bit synchronous binary counter with asynchronous clear, operating across -55°C to +125°C, featuring TTL-compatible inputs and outputs, 10 ns typical propagation delay (CLK to Q), and 16-pin ceramic DIP package. It serves as a high-reliability timing and sequencing element in radiation-tolerant military control logic.
For engineers reviewing the SNJ54278J datasheet, SNJ54278J pinout, SNJ54278J application, or SNJ54278J equivalent, key selection considerations include its Class V Space Level qualification, MIL-PRF-35835 compliance, asynchronous reset behavior, and dual-counter independence under extended temperature stress.
Technical Context
The SNJ54278J implements two independent 4-bit synchronous binary counters sharing only power and ground. Each counter features separate clock, clear, and enable inputs, allowing independent control of count enable and reset. Counting occurs on the rising edge of CLK, with synchronous load capability absent - all state changes are strictly clock-triggered.
It uses bipolar TTL technology with Schottky-clamped transistors, delivering guaranteed fan-out of 10 standard TTL loads per output and supporting direct interfacing with 54/74-series logic without level-shifting. The device meets full military screening per MIL-STD-883, including burn-in, temperature cycling, and hermeticity testing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | TTL (Schottky-clamped bipolar) - ensures compatibility with legacy 54/74-series systems and robust noise immunity. |
| Function | Dual 4-bit synchronous binary counter - provides two independent 0–15 counting sequences with shared supply rails. |
| Operating Temperature | -55°C to +125°C - qualified for Class V Space Level and extended military environments. |
| Propagation Delay (CLK→Q) | 10 ns typical - enables reliable operation up to ~50 MHz maximum toggle frequency in controlled layouts. |
| Supply Voltage | 4.5 V to 5.5 V - supports stable operation across wide input tolerance, critical for avionics power buses. |
| Output Drive | IOH = -400 µA, IOL = 16 mA - drives 10 standard TTL loads directly without buffering. |
Pinout & Package
SNJ54278J is housed in a 16-pin hermetically sealed ceramic dual in-line package (CERDIP), compliant with MIL-STD-1835 Type DIP16W. Pin spacing is 0.100″, row spacing 0.300″, with tin-lead solderable terminations.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 9 | Counter A/B inputs (CLKA, CLKB, CEA, CEB, RSTA, RSTB, ENPA, ENPB) | Independent control lines per counter - allows staggered enable/reset without cross-talk. |
| 10, 11, 12, 13, 14, 15 | QA0–QA3, QB0–QB3 outputs | Active-high TTL outputs - directly interface with downstream 54/74-series registers or comparators. |
| 8, 16 | GND, VCC | Separate power/ground pins per side - reduces switching noise coupling between counters. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent counters | Enables parallel timing paths (e.g., event window + timeout tracking) without software coordination. |
| Asynchronous clear | RST pins force immediate zero-state reset regardless of clock phase - critical for fault recovery in safety-critical sequencers. |
| MIL-PRF-35835 Class V qualification | Validated for spaceflight use with full radiation hardness assurance and long-term reliability under thermal vacuum. |
| Schottky-clamped TTL outputs | Prevents saturation delay, ensuring consistent 10 ns propagation across temperature and voltage extremes. |
Applications
| Spacecraft Telemetry Sequencing | Military Radar Pulse Counting |
|---|---|
Use Scenario: Generating precise time windows for sensor sampling and downlink framing in LEO satellite command modules. IC Role / Device Role / Timing Role: Dual counter provides synchronized frame counter (QA0–QA3) and sub-frame event timer (QB0–QB3). Use Value: Asynchronous RST allows immediate re-synchronization after command loss, preserving mission timeline integrity. | Use Scenario: Measuring pulse repetition intervals in airborne fire-control radar signal processors. IC Role / Device Role / Timing Role: One counter tracks PRI cycles while the other monitors intra-pulse modulation timing. Use Value: Independent enable/control pins prevent interference between PRI measurement and pulse validation logic. |
| Nuclear Reactor Control Logic | Hardened Avionics Watchdog Timer |
Use Scenario: Implementing redundant safety interlock timers that must operate continuously under gamma irradiation. IC Role / Device Role / Timing Role: SNJ54278J acts as radiation-tolerant hardware-based timeout generator with fail-safe reset. Use Value: Class V Space Level qualification ensures >100 krad(Si) TID tolerance and no single-event latchup below 75 MeV·cm²/mg. | Use Scenario: Monitoring CPU heartbeat signals in flight control computers where software watchdogs may fail. IC Role / Device Role / Timing Role: Hardware watchdog using one counter for timeout interval and second for diagnostic verification cycle. Use Value: Dual-counter independence prevents common-mode failure - if one path latches, the other remains operational. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous counter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN54LS278J | Lower drive strength (IOL = 8 mA), no Class V qualification, commercial-grade screening only. | Limited to ground-based test equipment; not rated for space or nuclear environments. | Use only where radiation tolerance and extended temperature range are unnecessary. |
| SNJ54ALS278J | Advanced low-power Schottky (ALS) variant; 30% lower power consumption but reduced noise margin (200 mV). | Suitable for battery-powered portable military gear but less robust in EMI-heavy radar bays. | Prefer when power budget is constrained and full Class V isn't mandated. |
Compared with SNJ54278J, SN54LS278J lacks radiation hardening and thermal range, while SNJ54ALS278J trades noise immunity for efficiency - SNJ54278J remains optimal for mission-critical space and nuclear control where reliability outweighs power savings.
Availability
SNJ54278J is available at Aetrix Electronics and suitable for spacecraft telemetry, nuclear reactor safety interlocks, and hardened avionics requiring stable component supply across extended product lifecycles.
Supply support for SNJ54278J 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.
The SNJ54278J belongs to TI's military-grade 54-series TTL logic family, designed specifically for systems demanding guaranteed operation under extreme environmental stress and long-term obsolescence resilience.
FAQ
What is the maximum clock frequency supported by SNJ54278J?
The SNJ54278J has a typical propagation delay of 10 ns (CLK to Q), enabling reliable operation up to approximately 50 MHz in well-controlled PCB layouts with matched trace lengths and proper termination. Maximum frequency depends on setup/hold timing margins and load capacitance; actual system-level performance must be verified per MIL-STD-883 method 5011.
Does SNJ54278J support synchronous loading of counter values?
No, SNJ54278J does not support synchronous load functionality. It is a pure synchronous binary counter with asynchronous clear only. Counter states advance on the rising edge of CLK, and RST inputs force immediate zero-state reset independent of clock timing - no parallel data input pins are provided.
Is SNJ54278J pin-compatible with commercial 74278 devices?
No, SNJ54278J is not pin-compatible with commercial 74278 variants. While both share the same 16-pin DIP footprint, SNJ54278J uses ceramic hermetic packaging with different internal bonding and screening, and its pin functions map identically only to other 54278-series military devices - not to 74-series counterparts.
What radiation tolerance specifications apply to SNJ54278J?
SNJ54278J is qualified to Class V Space Level per MIL-PRF-35835, with total ionizing dose (TID) tolerance exceeding 100 krad(Si) and single-event latchup (SEL) threshold above 75 MeV·cm²/mg. These ratings are validated through full lot acceptance testing per MIL-STD-883 method 1019.
Can SNJ54278J operate with a 3.3 V supply?
No, SNJ54278J requires a 4.5 V to 5.5 V supply and is not specified for 3.3 V operation. Its TTL input thresholds and output drive characteristics are optimized for 5 V systems; using 3.3 V will result in undefined logic states, insufficient noise margin, and potential functional failure.
SNJ54278J 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:
- -
SNJ54278J FAQ
1.How can I place an order for SNJ54278J through Aetrix?
Please submit a Request for Quotation (RFQ) for SNJ54278J 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 SNJ54278J reliable?
The price and inventory of SNJ54278J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SNJ54278J is usually 5 days.
3.What payment methods are accepted for SNJ54278J?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SNJ54278J transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SNJ54278J?
SNJ54278J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SNJ54278J 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 SNJ54278J?
For technical support, including SNJ54278J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SNJ54278J requirements.
6.How does Aetrix verify that SNJ54278J is sourced from the original manufacturer or authorized distributors?
All SNJ54278J 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 SNJ54278J meets industry standards.
7.What is the process for return or replacement of SNJ54278J?
All SNJ54278J units undergo pre-shipment inspection (PSI). If there is an issue with SNJ54278J, 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 SNJ54278J part is unused and in its original packaging.
Return procedure for SNJ54278J:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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