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Texas Instruments SN54AS821JT
- Part No.:
- SN54AS821JT
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN54AS821JT.pdf
- Description:
- BUS DRIVER, AS SERIES
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Inventory:116
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Product details
Overview
SN54AS821JT from Texas Instruments is a military-grade 10-bit edge-triggered D-type flip-flop with 3-state outputs, designed for bus interface and wide data path buffering. It operates across –55°C to 125°C, delivers ±24 mA high-level and 32 mA low-level output drive, features buffered output-control input (OC), and retains data during high-impedance output states-used in military avionics I/O port expansion.
For engineers reviewing the SN54AS821JT datasheet, SN54AS821JT pinout, SN54AS821JT application, or SN54AS821JT equivalent, key selection criteria include its 10-bit synchronous bus interface capability, military temperature range, 3-state output timing (tPLH ≤ 9 ns), undershoot protection, and compatibility with parity-enabled bidirectional bus systems.
Technical Context
The SN54AS821JT implements ten independent positive-edge-triggered D flip-flops with non-inverting Q outputs. Its buffered OC input enables simultaneous 3-state control without affecting internal state retention, and its TTL-compatible inputs accept VIH ≥ 2 V and VIL ≤ 0.8 V under recommended conditions.
It uses bipolar Schottky (AS) technology for high-speed operation: tPHL ≤ 11.5 ns, tPZH ≤ 12 ns, and supports capacitive bus loading up to 50 pF with guaranteed drive strength (IOL = 32 mA at VOL ≤ 0.25 V). Power-up default is high-impedance output state.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | AS (Advanced Schottky) TTL - enables 9 ns propagation delay and low power-delay product vs standard TTL. |
| Operating Temperature | –55°C to 125°C - qualified for full military environmental stress screening per MIL-PRF-38535. |
| Output Drive | IOL = 32 mA / IOH = –24 mA - sufficient to directly drive 50-pF bus lines without external buffers or pull-ups. |
| 3-State Enable Delay | tPZH ≤ 10 ns - fast transition into high-impedance mode minimizes bus contention during state switching. |
| Input Compatibility | VIH ≥ 2 V, VIL ≤ 0.8 V - interoperable with standard TTL and LSTTL logic families without level shifting. |
| Undershoot Protection | Integrated circuitry clamps negative transients below –1.2 V - prevents latch-up on noisy bus environments. |
Pinout & Package
SN54AS821JT is supplied in a 24-pin ceramic side-brazed flatpack (JT package), hermetically sealed for high-reliability military use. Pin pitch is 0.025 inch, body dimensions are 0.750 × 0.250 inches.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 13, 14, 15, 16, 17, 18, 19, 20, 21 | Data Inputs (1D–10D) | Asynchronous D inputs synchronized on CLK↑; each controls corresponding Q output. |
| 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 | True Outputs (1Q–10Q) | Non-inverting registered outputs; placed in high-Z when OC = high. |
| 12 | GND | Ground reference for all logic and output stages; requires low-inductance connection. |
| 22 | VCC | Positive supply (4.5–5.5 V); decoupling capacitor required within 0.5 inch of pin. |
| 23 | CLK | Common positive-edge clock for all 10 flip-flops; edge-sensitive, no internal synchronization delay. |
| 24 | OC | Active-low output control; high = high-impedance, low = enabled output drive. |
Key Features
| Feature | Design Value |
|---|---|
| 10-bit bus interface with 3-state outputs | Enables direct connection to shared data/address buses without external bus transceivers or isolation logic. |
| Power-up high-impedance state | Prevents bus contention at system reset or power-on sequencing without requiring external pull-downs or enable sequencing. |
| Buffered OC and CLK inputs | Reduces DC loading on upstream drivers and improves noise margin by isolating control signals from internal logic capacitance. |
| Undershoot protection circuitry | Clamps negative voltage excursions to –1.2 V, eliminating need for external diode clamping on long PCB traces or backplane interfaces. |
Applications
| Military Avionics Data Bus Interface | Radar Signal Processing Register File |
|---|---|
Use Scenario: Interfacing FPGA-based signal processors to legacy MIL-STD-1553B or ARINC 429 bus controllers with parity checking. IC Role / Device Role / Timing Role: 10-bit synchronous register buffer providing glitch-free data latching and bus isolation during arbitration cycles. Use Value: Delivers 32 mA drive into 50-pF loads while maintaining <10 ns output disable time-eliminates need for discrete bus switches in SWaP-constrained airborne modules. | Use Scenario: Storing intermediate FFT coefficients in real-time radar front-end hardware operating across –55°C to 125°C. IC Role / Device Role / Timing Role: High-reliability working register with retained state during 3-state output transitions for pipelined processing stages. Use Value: Maintains functional integrity under thermal shock and vibration due to ceramic JT package and AS-family process hardening-no derating required at max temperature. |
| Secure Communications Crypto Module I/O | Tactical Vehicle Control System Address Latch |
Use Scenario: Isolating cryptographic engine core from external memory-mapped peripherals in TEMPEST-compliant enclosures. IC Role / Device Role / Timing Role: Bidirectional bus driver with parity support for secure key exchange handshake protocols. Use Value: Undershoot protection and controlled 3-state timing prevent EMI-induced bit errors on shielded cabling-validated per MIL-STD-461E RS103. | Use Scenario: Latching 10-bit address segments for dual-ported RAM in armored vehicle engine control units. IC Role / Device Role / Timing Role: Synchronous address register with deterministic setup/hold (tsu = 7 ns, th = 0 ns) for deterministic timing closure. Use Value: Enables sub-20 ns address valid window at 5 MHz bus clock-meets ISO 16750-4 transient immunity requirements without additional timing margin. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 10-bit bus interface flip-flop applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN54AS822JT | Inverting Q outputs (complementary to D on CLK↑), identical timing, packaging, and electrical specs. | Required where bus polarity inversion is needed for signal alignment or differential pair matching. | Select SN54AS822JT only when inverted output logic is explicitly required; otherwise SN54AS821JT provides true-output behavior. |
| AM29821J | Functionally equivalent per datasheet SDAS230; same pinout, timing, and military temp rating-but manufactured by AMD with different process qualification. | Used in legacy AMD-based designs where second-source assurance is mandated by procurement policy. | AM29821J is a drop-in replacement per TI's own documentation; verify lot traceability and burn-in history for Class H applications. |
Compared with SN54AS822JT and AM29821J, the SN54AS821JT offers non-inverting output logic essential for transparent data path alignment, maintains identical military reliability certification, and provides TI-specific quality documentation traceability required for DoD contracts.
Availability
SN54AS821JT is available at Aetrix Electronics and suitable for military avionics, radar signal processing, and secure communications systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SN54AS821JT 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 manufacturer founded in 1930, specializing in analog, embedded processing, and high-reliability logic solutions with over 90 years of aerospace and defense component heritage.
The SN54AS series was developed for military and space applications requiring robust TTL-compatible logic with guaranteed performance across –55°C to 125°C, emphasizing speed, noise immunity, and long-term reliability in harsh environments.
FAQ
What is the function of the OC pin on the SN54AS821JT?
The OC (Output Control) pin on the SN54AS821JT is an active-low signal that places all ten Q outputs simultaneously into high-impedance state when asserted high. It does not affect internal flip-flop operation-data remains latched and can be updated via D inputs and CLK even while outputs are disabled. This enables clean bus sharing in multi-master systems without contention.
Does the SN54AS821JT support hot insertion or live bus swapping?
The SN54AS821JT includes undershoot protection circuitry that clamps negative transients to –1.2 V, and its power-up high-impedance state prevents bus conflicts during power sequencing. However, it lacks explicit hot-swap current limiting or slew-rate control, so live insertion into an active bus requires external current-limiting resistors and careful timing coordination-not certified for hot-swap per IEEE 1394 or PCI standards.
What is the maximum capacitive load the SN54AS821JT can drive reliably?
The SN54AS821JT is characterized for reliable operation with CL = 50 pF, as specified in its switching characteristics table (tPLH/tPHL measured at 50 pF). While it can drive higher capacitance, timing margins degrade beyond this value-designs targeting >50 pF must validate setup/hold timing and VOL/IOL compliance at worst-case VCC and temperature using actual board parasitics.
How does the SN54AS821JT differ from the SN74AS821 in terms of temperature range and testing?
The SN54AS821JT is screened and tested for operation from –55°C to 125°C per MIL-PRF-38535 Class B or Class S requirements, with full parametric verification across that range. The SN74AS821 is commercial-grade, rated only from 0°C to 70°C and not subjected to military-level environmental stress testing or lot acceptance testing (LAT).
Is the SN54AS821JT pin-compatible with plastic-package versions like SN74AS821DW?
Yes-the SN54AS821JT shares identical pin numbering and signal assignment with SN74AS821DW and SN74AS821NT per the logic symbol and pin diagrams in SDAS230. All variants use the same 24-pin layout: pins 1–11 for D/Q, 12 = GND, 22 = VCC, 23 = CLK, 24 = OC. Only package construction (ceramic JT vs plastic DW/NT) differs.
SN54AS821JT 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:
- -
SN54AS821JT FAQ
1.How can I place an order for SN54AS821JT through Aetrix?
Please submit a Request for Quotation (RFQ) for SN54AS821JT 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 SN54AS821JT reliable?
The price and inventory of SN54AS821JT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN54AS821JT is usually 5 days.
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SN54AS821JT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN54AS821JT 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 SN54AS821JT?
For technical support, including SN54AS821JT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN54AS821JT requirements.
6.How does Aetrix verify that SN54AS821JT is sourced from the original manufacturer or authorized distributors?
All SN54AS821JT 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 SN54AS821JT meets industry standards.
7.What is the process for return or replacement of SN54AS821JT?
All SN54AS821JT units undergo pre-shipment inspection (PSI). If there is an issue with SN54AS821JT, 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 SN54AS821JT part is unused and in its original packaging.
Return procedure for SN54AS821JT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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