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Texas Instruments SN74ALS651A-1DW
- Part No.:
- SN74ALS651A-1DW
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN74ALS651A-1DW.pdf
- Description:
- BUS TRANSCEIVER, ALS SERIES
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Inventory:6,400
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Product details
Overview
SN74ALS651A-1DW from Texas Instruments is an octal bus transceiver and register with 3-state inverting outputs, designed for bidirectional data flow between two 8-bit buses (A and B) with real-time or stored data selection. It features independent clock (CLKAB/CLKBA), select (SAB/SBA), and output-enable (OEAB/OEBA) controls, 48 mA low-level output drive (–1 version), and operates at up to 40 MHz across 0°C to 70°C.
For engineers reviewing the SN74ALS651A-1DW datasheet, SN74ALS651A-1DW pinout, SN74ALS651A-1DW application, or SN74ALS651A-1DW equivalent, this device supports multiplexed bus management in legacy TTL-compatible systems requiring simultaneous storage, isolation, and direction-controlled data transfer with glitch-free select control.
Technical Context
The SN74ALS651A-1DW integrates eight D-type flip-flops per bus, dual 3-state output drivers, and asynchronous select logic that eliminates decoding glitches during transitions between real-time and stored data modes. Its SAB/SBA inputs determine data source (bus or register), while OEAB/OEBA independently enable A→B or B→A transceiver paths without affecting internal storage.
It implements true/inverting data paths via internal logic configuration - the SN74ALS651A variant provides inverting output on both buses. Clock inputs trigger synchronous data capture on low-to-high transitions, and all I/O ports remain enabled for input regardless of OE state, enabling transparent latching behavior when output enables are active.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Octal bus transceiver + dual 8-bit register with 3-state inverting outputs |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL systems |
| Max Clock Frequency | 40 MHz - supports high-speed bus arbitration in legacy computing and industrial control backplanes |
| IOL (–1 version) | 48 mA at VCC = 4.75–5.25 V - enables direct driving of multiple TTL loads without external buffers |
| Propagation Delay | tPLH/tPHL ≤ 32 ns (CLK→A/B); ≤ 18 ns (A/B→A/B) - ensures timing closure in synchronous 25 ns cycle designs |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded and instrumentation applications |
| Package | 24-pin SOIC (DW) - surface-mount compatible with automated PCB assembly |
Pinout & Package
SN74ALS651A-1DW uses a 24-pin SOIC (DW) package with 0.300-inch body width and standard JEDEC MS-013AC footprint. Pin numbering follows top-view orientation with Pin 1 in bottom-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | CLKBA | Clock input for storing data from B bus into internal B register |
| 2 | SAB | Select control: low = real-time A→B transfer; high = stored A→B transfer |
| 3 | OEAB | Output enable for A→B transceiver path; low = enabled, high = 3-state |
| 4–11 | A1–A8 | 8-bit bidirectional data terminals for A bus (input/output with 3-state control) |
| 12 | GND | Ground reference for all logic and I/O circuitry |
| 13 | VCC | +5 V power supply connection |
| 14 | CLKAB | Clock input for storing data from A bus into internal A register |
| 15 | SBA | Select control: low = real-time B→A transfer; high = stored B→A transfer |
| 16 | OEBA | Output enable for B→A transceiver path; low = enabled, high = 3-state |
| 17–24 | B1–B8 | 8-bit bidirectional data terminals for B bus (input/output with 3-state control) |
Key Features
| Feature | Design Value |
|---|---|
| Glitch-free select control | Internal logic prevents metastability during SAB/SBA transitions between real-time and stored data modes |
| Dual independent registers | Separate A and B 8-bit D-flip-flop arrays allow concurrent storage of data from either or both buses |
| Inverting data path | Output polarity inversion on both A and B buses simplifies interface with complementary logic stages |
| 48 mA sink capability (–1 version) | Eliminates need for external bus drivers in high-fanout TTL systems |
| Transparent latching mode | When OEAB and OEBA are simultaneously low, outputs reinforce inputs - enabling bus hold without clocking |
Applications
| Industrial Backplane Interface | Legacy Computer Bus Arbitration |
|---|---|
|
Use Scenario: Bidirectional data routing between CPU and peripheral modules on a shared 8-bit ISA-style backplane with local register buffering. IC Role / Device Role / Timing Role: SN74ALS651A-1DW acts as a programmable bus switch and latch, isolating modules during address decode and capturing status/data on clock edges. Use Value: Enables deterministic timing with 32 ns max CLK→data propagation and 48 mA drive to overcome trace capacitance and fanout losses. |
Use Scenario: Real-time monitoring and selective logging of memory-mapped I/O transactions in a microcontroller-based test instrument. IC Role / Device Role / Timing Role: SN74ALS651A-1DW captures parallel bus activity into internal registers upon trigger, then transfers snapshots to diagnostic port under software control. Use Value: Inverting outputs match legacy logic families; glitch-free SAB/SBA switching prevents false triggers during mode changes. |
| Programmable Logic Interfacing | Redundant Control System Data Sync |
|
Use Scenario: Interfacing FPGA I/O banks to fixed-function ASICs using 5 V TTL signaling, requiring level-shifted, registered data handoff. IC Role / Device Role / Timing Role: SN74ALS651A-1DW serves as a registered I/O bridge, synchronizing asynchronous FPGA writes to ASIC read cycles via CLKAB/CLKBA. Use Value: 10 ns setup time and 0 ns hold time simplify timing closure; 24-pin SOIC fits dense PLD carrier boards. |
Use Scenario: Maintaining synchronized state between primary and backup controllers in safety-critical PLC modules using mirrored bus traffic. IC Role / Device Role / Timing Role: SN74ALS651A-1DW stores identical data from both A and B buses into dual registers, then forwards validated values to each controller. Use Value: Independent OEAB/OEBA allows selective broadcast to one controller while holding data for the other; 40 MHz operation supports fast failover response. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver and register applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS652A-1DW | True (non-inverting) data path instead of inverting; otherwise identical pinout, timing, and drive strength | Required where signal polarity must be preserved end-to-end (e.g., direct connection to non-inverting receivers) | Select SN74ALS652A-1DW only if system-level logic requires non-inverted data flow; no PCB change needed |
| SN74AS651DW | Faster 75 MHz max clock (vs. 40 MHz), higher IOL (32 mA standard, 48 mA –1), but higher ICC (110 mA vs. 82 mA) | Suitable for performance-critical upgrades where timing margin is insufficient with ALS family | Choose SN74AS651DW when clock frequency >40 MHz is required; verify power delivery and thermal design due to increased ICC |
Compared with SN74ALS651A-1DW, SN74ALS652A-1DW preserves signal polarity at identical speed and drive, while SN74AS651DW trades higher power for 87% clock speed gain - making the former ideal for drop-in polarity correction and the latter for performance-limited legacy upgrades.
Availability
SN74ALS651A-1DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy computer bus arbitration, programmable logic interfacing, and redundant control system data synchronization requiring stable component supply over extended production lifecycles.
Supply support for SN74ALS651A-1DW 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 leader delivering analog and embedded processing solutions, with decades of heritage in TTL and advanced logic families.
The SN74ALS651A-1DW belongs to TI's ALS (Advanced Low-Power Schottky) logic series, engineered for high-speed, low-power 5 V TTL-compatible systems in industrial, computing, and instrumentation applications.
FAQ
What is the key functional difference between SN74ALS651A-1DW and SN74ALS652A-1DW?
The SN74ALS651A-1DW provides inverting data paths on both A and B buses, whereas SN74ALS652A-1DW provides true (non-inverting) data paths. All other electrical specifications, pinout, timing, and packaging are identical. This makes SN74ALS652A-1DW a direct replacement when signal polarity preservation is required in the system design.
Does SN74ALS651A-1DW support simultaneous storage from both A and B buses?
Yes - the SN74ALS651A-1DW supports concurrent storage from both buses. A low-to-high transition on CLKAB stores data from the A bus into the A register, and a low-to-high transition on CLKBA stores data from the B bus into the B register. Both clocks can be asserted simultaneously when SAB and SBA are low, enabling atomic dual-bus capture.
What does the "–1" suffix indicate in SN74ALS651A-1DW?
The "–1" suffix denotes an enhanced output drive specification: SN74ALS651A-1DW guarantees 48 mA low-level output current (IOL) when VCC is maintained between 4.75 V and 5.25 V. Standard SN74ALS651A devices specify 24 mA IOL. The –1 version is fully pin- and function-compatible with the base part.
Can SN74ALS651A-1DW operate with mixed voltage domains (e.g., 3.3 V logic inputs)?
No - SN74ALS651A-1DW is a 5 V TTL-family device. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and absolute maximum input voltage (–0.5 V to 7 V) do not guarantee reliable operation with 3.3 V CMOS logic levels without level translation. Direct connection may cause marginal noise immunity or increased power consumption.
How does the glitch-free select control work in SN74ALS651A-1DW?
The SN74ALS651A-1DW uses internal synchronous logic to sample SAB and SBA inputs relative to clock edges, preventing metastability during transitions between real-time and stored data modes. This eliminates the decoding glitches common in discrete multiplexer implementations, ensuring clean, deterministic bus handoffs without spurious output pulses.
SN74ALS651A-1DW 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:
- -
SN74ALS651A-1DW FAQ
1.How can I place an order for SN74ALS651A-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS651A-1DW 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 SN74ALS651A-1DW reliable?
The price and inventory of SN74ALS651A-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS651A-1DW is usually 5 days.
3.What payment methods are accepted for SN74ALS651A-1DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS651A-1DW transactions.
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4.How is shipping managed for SN74ALS651A-1DW?
SN74ALS651A-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS651A-1DW 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 SN74ALS651A-1DW?
For technical support, including SN74ALS651A-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS651A-1DW requirements.
6.How does Aetrix verify that SN74ALS651A-1DW is sourced from the original manufacturer or authorized distributors?
All SN74ALS651A-1DW 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 SN74ALS651A-1DW meets industry standards.
7.What is the process for return or replacement of SN74ALS651A-1DW?
All SN74ALS651A-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS651A-1DW, 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 SN74ALS651A-1DW part is unused and in its original packaging.
Return procedure for SN74ALS651A-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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