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Texas Instruments SN74ALS29821NT
- Part No.:
- SN74ALS29821NT
- Manufacturer:
- Texas Instruments
- Category:
- Flip Flops
- Package:
- 24-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS29821NT.pdf
- Description:
- IC FF D-TYPE SNGL 10BIT 24DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,820
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Product details
Overview
SN74ALS29821NT from Texas Instruments is a 10-bit edge-triggered D-type flip-flop with 3-state outputs, designed for driving high-capacitance or low-impedance bus loads. It operates at 5 V supply, supports 48 mA sink / −24 mA source output drive, features power-up high-impedance state, and delivers 10 ns typical propagation delay (CL = 50 pF) in industrial temperature range (0°C to 70°C). It is used in wide I/O port expansion and parity-enabled bidirectional bus driver applications.
For engineers reviewing the SN74ALS29821NT datasheet, SN74ALS29821NT pinout, SN74ALS29821NT application, or SN74ALS29821NT equivalent, key selection criteria include 3-state timing behavior under OE control, undershoot-protection circuitry on outputs, buffered input loading reduction, and compatibility with ALS logic family voltage thresholds and drive strength.
Technical Context
This device implements ten independent D-type latches synchronized to the rising edge of CLK, with each Q output mirroring its corresponding D input only when OE is low. The 3-state outputs are fully decoupled from internal latch operation-OE asserts high-impedance without affecting data retention or clocked updates.
It uses bipolar ALS (Advanced Low-Power Schottky) technology, delivering higher speed than standard LS while maintaining TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V) and robust output drive (IOL = 48 mA). Undershoot-protection diodes on all outputs prevent negative transients from damaging the device during bus contention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky), TTL-compatible input/output levels |
| Supply Voltage (VCC) | 4.75 V to 5.25 V - ensures stable operation within industrial rail tolerance |
| Output Drive (IOL / IOH) | 48 mA sink / −24 mA source - sufficient to drive 50-pF bus lines without external buffers |
| Propagation Delay (tPLH/tPHL) | 2 ns to 10 ns (CL = 50 pF) - enables reliable timing in 100-MHz-class address/data paths |
| Setup/Hold Time (tsu/th) | 4 ns setup / 2 ns hold - tight timing window compatible with fast microprocessor bus cycles |
| Operating Temperature | 0°C to 70°C - qualified for commercial/industrial embedded systems, not extended/military grade |
| 3-State Enable Delay (tPZH/tPLZ) | 1 ns to 14 ns (CL = 50 pF) - fast bus turnaround critical for bidirectional data arbitration |
Pinout & Package
SN74ALS29821NT is supplied in a 24-pin plastic dual-in-line package (PDIP), 300-mil width, with standard through-hole mounting and JEDEC MO-058 AA compliance. Pin spacing is 0.100 inch (2.54 mm), row spacing 0.300 inch (7.62 mm).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | OE (Output Enable) | Active-low 3-state control; buffered to reduce DC loading on upstream drivers |
| 2–11 | 1D–10D | Data inputs for ten D-type flip-flops; TTL-compatible thresholds (VIH = 2 V, VIL = 0.8 V) |
| 12 | GND | Ground reference for all logic and output stages |
| 13 | VCC | +5 V supply for ALS logic core and output drivers |
| 14–23 | 1Q–10Q | True outputs with 3-state capability; include undershoot-protection diodes |
| 24 | CLK | Positive-edge-triggered clock input; synchronizes all ten flip-flops simultaneously |
Key Features
| Feature | Design Value |
|---|---|
| Power-Up High-Impedance State | Outputs default to Z-state at power-on, preventing bus contention during system boot |
| Undershoot-Protection Circuitry | Integrated clamping diodes on all Q outputs suppress negative transients below −1.2 V |
| Buffered Control Inputs | OE input has reduced DC loading (IIL ≤ −0.5 mA), easing fanout from CMOS or microcontroller GPIOs |
| 10-Bit Bus Width Extension | Provides extra data/parity bits for 16-bit or wider address/data buses without discrete glue logic |
| ALS Speed-Power Optimization | Delivers 10 ns propagation delay at 115 mA ICC - faster than LS with lower power than standard Schottky |
Applications
| Memory Interface Buffering | Parity-Enabled Data Bus Driver |
|---|---|
|
Use Scenario: Expanding microprocessor data bus width to support 16-bit memory access with parity checking. IC Role / Device Role / Timing Role: Latches and drives 10-bit parity + auxiliary address bits synchronized to CPU clock edge. Use Value: Eliminates need for discrete AND/OR gates and pull-ups; 48 mA drive handles loaded memory bus directly. |
Use Scenario: Bidirectional data transfer between CPU and peripheral with real-time parity validation. IC Role / Device Role / Timing Role: Provides 10-bit 3-state data path with OE-controlled direction switching and glitch-free bus release. Use Value: Fast tPZL (≤14 ns) enables sub-100 ns bus turnaround; undershoot protection prevents damage during hot-swap events. |
| I/O Port Expansion | Legacy System Bus Isolation |
|
Use Scenario: Adding parallel I/O capability to an 8-bit microcontroller-based industrial controller. IC Role / Device Role / Timing Role: Acts as 10-bit output latch and input buffer, interfacing MCU GPIOs to external sensors/actuators. Use Value: Buffered OE and CLK inputs reduce loading on MCU pins; high-impedance state isolates peripherals during reset. |
Use Scenario: Isolating legacy ISA or VME bus segments to prevent signal integrity degradation across backplane traces. IC Role / Device Role / Timing Role: Serves as repeater/latch between bus segments, regenerating timing-critical address/data signals. Use Value: 2 ns minimum pulse width (tw) and 4 ns setup time ensure compatibility with 8-MHz ISA timing budgets. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 10-bit 3-state D-flip-flop applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS29821DW | Same die, SOIC-24 package; RoHS-compliant NiPdAu lead finish; MSL Level-1 | Surface-mount assembly required; no through-hole footprint compatibility | Select for automated PCB assembly where board space and reflow compatibility are priorities. |
| AM29821 (AMD) | Functionally equivalent per TI documentation; identical pinout, timing, and electrical specs | No TI-specific quality or traceability documentation; limited current availability | Consider only if legacy AMD-sourced boards require exact second-source replacement with no redesign. |
Compared with SN74ALS29821NT, the DW variant offers modern packaging and RoHS compliance but requires layout change, while AM29821 provides functional drop-in replacement only where original AMD qualification remains mandatory.
Availability
SN74ALS29821NT is available at Aetrix Electronics and suitable for memory interface buffering, parity-enabled data bus driver, and I/O port expansion applications requiring stable component supply and long-term industrial lifecycle support.
Supply support for SN74ALS29821NT 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 global semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs for industrial, automotive, and communications markets.
The SN74ALS29821NT belongs to TI's legacy ALS logic product line, engineered for high-speed, low-power bus interface and register applications in commercial and industrial systems.
FAQ
What is the operating temperature range for the SN74ALS29821NT?
The SN74ALS29821NT is rated for operation from 0°C to 70°C, qualifying it for commercial and industrial environments but excluding extended military or automotive under-hood use. This range aligns with the SN74 prefix designation and is verified in the recommended operating conditions table of the SDAS145B datasheet.
Does the SN74ALS29821NT support true bidirectional data flow?
The SN74ALS29821NT does not implement automatic bidirectional control; it provides 10-bit unidirectional D-to-Q latching with independent 3-state output enable (OE). Bidirectional bus operation requires external direction control logic coordinating OE with data flow direction - a common implementation in ISA/VME-style systems using this device.
What is the maximum capacitive load the SN74ALS29821NT can drive reliably?
The SN74ALS29821NT is characterized up to 300 pF load capacitance, with specified tPLH/tPHL delays of ≤21 ns (SN74 version). At 50 pF, propagation delay drops to ≤10 ns. Its 48 mA output sink current ensures stable logic transitions even under heavy bus loading typical in backplane or multi-drop configurations.
Is the SN74ALS29821NT pin-compatible with the SN54ALS29821JT?
Yes - both SN74ALS29821NT and SN54ALS29821JT share identical 24-pin DIP pinout, terminal functions, and logic behavior. The difference lies solely in temperature rating (0°C–70°C vs −55°C–125°C) and package material (plastic vs ceramic), not pin assignment or electrical interface.
How does the undershoot-protection circuitry in the SN74ALS29821NT function?
The SN74ALS29821NT integrates internal clamping diodes on each Q output, limiting negative voltage excursions to −1.2 V (VIK) under transient conditions. This protects the output stage during bus contention or hot-plug events, eliminating need for external Schottky clamps in most industrial backplane designs.
SN74ALS29821NT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 24-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Standard
- Type:
- D-Type
- Output Type:
- Tri-State, Non-Inverted
- Number of Elements:
- 1
- Number of Bits per Element:
- 10
- Clock Frequency:
- -
- Max Propagation Delay @ V, Max CL:
- 16ns @ 5V, 300pF
- Trigger Type:
- Positive Edge
- Current - Output High, Low:
- 24mA, 48mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Current - Quiescent (Iq):
- 115 mA
- Input Capacitance:
- -
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 24-PDIP
SN74ALS29821NT FAQ
1.How can I place an order for SN74ALS29821NT through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS29821NT 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 SN74ALS29821NT reliable?
The price and inventory of SN74ALS29821NT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS29821NT is usually 5 days.
3.What payment methods are accepted for SN74ALS29821NT?
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4.How is shipping managed for SN74ALS29821NT?
SN74ALS29821NT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS29821NT 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 SN74ALS29821NT?
For technical support, including SN74ALS29821NT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS29821NT requirements.
6.How does Aetrix verify that SN74ALS29821NT is sourced from the original manufacturer or authorized distributors?
All SN74ALS29821NT 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 SN74ALS29821NT meets industry standards.
7.What is the process for return or replacement of SN74ALS29821NT?
All SN74ALS29821NT units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS29821NT, 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 SN74ALS29821NT part is unused and in its original packaging.
Return procedure for SN74ALS29821NT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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