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Texas Instruments SN74ALS648ADWR
- Part No.:
- SN74ALS648ADWR
- Manufacturer:
- Texas Instruments
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS648ADWR.pdf
- Description:
- IC TXRX INVERT 5.5V 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,304
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Product details
Overview
SN74ALS648ADWR from Texas Instruments is an octal bus transceiver and register IC with 3-state outputs, inverting data path, and dual independent A/B bus registers. It operates at 0–40 MHz clock frequency, supports 5 V supply (4.5–5.5 V), delivers 24 mA low-level output current, and is housed in a 24-pin SOIC (DW) package for industrial bus isolation and real-time/stored data multiplexing in legacy control systems.
For engineers reviewing the SN74ALS648ADWR datasheet, SN74ALS648ADWR pinout, SN74ALS648ADWR application, or SN74ALS648ADWR equivalent, this device is selected for synchronous bidirectional bus management requiring glitch-free stored/transparent mode switching, direction-controlled 3-state drive, and register-retained data integrity across A↔B data paths in industrial backplanes and test equipment.
Technical Context
The SN74ALS648ADWR integrates eight D-type flip-flops per bus (A and B), dual clock inputs (CLKAB, CLKBA), and select-control logic (SAB, SBA) that eliminates decoding glitches during transitions between real-time and stored data modes. Its DIR input determines data flow direction while OE enables/disables 3-state outputs without disabling input capture.
It features independent storage registers for both buses, allowing simultaneous latching of A- and B-bus data on separate clock edges. The inverting output logic (per SN74ALS648A family specification) applies to all eight transceiver channels, distinguishing it from the true-output SN74ALS646A variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Octal bus transceiver with dual independent registers and 3-state outputs |
| Logic Type | Inverting data path - output complements input during transparent transfer |
| Max Clock Frequency | 40 MHz - supports high-speed synchronous bus arbitration in legacy TTL systems |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL rails; not 3.3 V tolerant |
| Output Drive | 24 mA low-level (IOL), –15 mA high-level (IOH) - drives standard TTL loads directly |
| Operating Temperature | 0°C to 70°C - commercial-grade rating suitable for non-military embedded control applications |
| Package | 24-pin SOIC (DW) - surface-mount, RoHS-compliant, 1.27 mm pitch, tape-and-reel (2000 pcs) |
Pinout & Package
SN74ALS648ADWR uses a 24-pin SOIC (DW) package with 300-mil body width and standard pinout per TI SDAS039F. Pin 1 is CLKAB; pin 12 is GND; pin 24 is VCC. NC pins (e.g., pins 4, 13, 14, 15, 25) are unconnected internally and must remain unconnected on PCB.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | CLKAB | Clock input for latching data from A bus into B-register on rising edge |
| 2 | SAB | Select control: chooses between real-time or stored B→A data when OE and DIR enable transfer |
| 3 | DIR | Direction control: low = B→A transfer; high = A→B transfer (when OE = low) |
| 4 | NC | No internal connection - must be left floating or grounded per layout best practice |
| 5–11 | A1–A8 | Input/output port for A-side bus - bidirectional I/O with 3-state control |
| 12 | GND | Ground reference for all logic and power domains |
| 13–14 | NC | No internal connection - no PCB trace or pad required |
| 15 | NC | No internal connection - unused terminal |
| 16–23 | B1–B8 | Input/output port for B-side bus - bidirectional I/O with 3-state control |
| 24 | VCC | +5 V supply input - requires local 0.1 µF ceramic decoupling adjacent to pin |
Key Features
| Feature | Design Value |
|---|---|
| Glitch-free multiplexing | SAB/SBA control logic prevents output glitches during real-time ↔ stored data mode transitions |
| Dual independent registers | Separate A- and B-bus storage enables asynchronous latching and hold operations on each bus |
| Inverting transceiver path | All eight channels invert data during transparent transfer - ensures signal polarity compatibility with legacy inverted bus protocols |
| 3-state output control | OE pin disables outputs without affecting input capture - allows shared bus arbitration with multiple drivers |
| Real-time + stored data selection | Combination of DIR, OE, SAB, and SBA enables four distinct bus-management functions per TI Figure 1 |
Applications
| Industrial Backplane Interface | Legacy Test Equipment Bus Control |
|---|---|
|
Use Scenario: Bidirectional data routing between CPU and peripheral modules on a 24-bit parallel backplane with timing-critical arbitration. IC Role / Device Role / Timing Role: SN74ALS648ADWR acts as a registered transceiver managing A↔B bus handshaking, storing command/status words while enabling real-time diagnostics via SAB/SBA-selectable paths. Use Value: Eliminates external latch + buffer combinations; reduces propagation delay variance vs. discrete solutions by integrating clocked register + transceiver in one 24-pin SOIC. |
Use Scenario: Isolating and synchronizing stimulus/response signals between pattern generator and DUT interface boards in automated test systems. IC Role / Device Role / Timing Role: SN74ALS648ADWR serves as a direction-controlled, clock-gated bus repeater with storage - capturing stimulus vectors on CLKAB and replaying them on CLKBA with precise edge alignment. Use Value: Enables deterministic timing for vector replay (±10 ns setup/hold) and eliminates bus contention during mode switching using OE and DIR coordination. |
| Programmable Logic Controller (PLC) I/O Module | Embedded Diagnostic Subsystem |
|
Use Scenario: Interfacing microcontroller GPIOs to isolated 8-bit sensor/actuator buses requiring noise-immune data retention during polling cycles. IC Role / Device Role / Timing Role: SN74ALS648ADWR buffers and registers sensor readings on the B bus while holding actuator commands on the A bus - updated only on valid clock edges to prevent metastability. Use Value: Provides hardware-level synchronization between slow microcontroller reads and fast peripheral updates, reducing firmware overhead for bus state management. |
Use Scenario: Capturing and forwarding real-time system status (e.g., watchdog timeout flags, voltage fault signals) alongside stored diagnostic logs in safety-critical embedded controllers. IC Role / Device Role / Timing Role: SN74ALS648ADWR stores diagnostic snapshots on CLKBA while passing live fault indicators transparently via SBA=H, enabling concurrent monitoring and logging without software intervention. Use Value: Supports fail-safe operation by guaranteeing atomic capture of time-correlated events across two independent buses with zero software latency. |
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 |
|---|---|---|---|
| SN74ALS646ADWR | True (non-inverting) output logic; otherwise identical pinout, timing, and register architecture | Used where signal polarity must be preserved end-to-end (e.g., direct replacement in non-inverted bus topologies) | Select SN74ALS646ADWR only if system-level signal inversion is unacceptable; verify bus driver/receiver compatibility before substitution. |
| SN74AS648DW | Faster max clock (90 MHz), higher drive (48 mA IOL), AS-family propagation delays (≤9 ns), but same pinout and function | Required for high-speed designs exceeding 40 MHz or needing stronger drive into capacitive loads (>50 pF) | Choose SN74AS648DW when timing budget or fanout demands exceed ALS648A limits; note higher ICC (120 mA vs. 88 mA) and tighter layout constraints. |
Compared with SN74ALS648ADWR, SN74ALS646ADWR preserves signal polarity but lacks inversion capability needed for certain legacy bus protocols, while SN74AS648DW offers superior speed and drive at the cost of increased power and reduced noise margin - making SN74ALS648ADWR optimal for cost-sensitive, timing-moderate industrial control interfaces.
Availability
SN74ALS648ADWR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy test equipment bus control, and programmable logic controller (PLC) I/O modules requiring stable component supply, long-lifecycle support, and RoHS-compliant SOIC packaging.
Supply support for SN74ALS648ADWR 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 founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and communications portfolio coverage.
The SN74ALS648ADWR belongs to TI's legacy ALS (Advanced Low-Power Schottky) logic family, designed specifically for high-reliability, moderate-speed bus interfacing in industrial control, instrumentation, and military-grade systems requiring TTL-compatible timing and drive.
FAQ
What is the primary function of the SN74ALS648ADWR in a digital system?
The SN74ALS648ADWR functions as an octal bus transceiver with dual independent registers and 3-state outputs. It enables bidirectional data transfer between two 8-bit buses (A and B), supports real-time or stored data selection via SAB/SBA controls, and provides synchronized latching on rising clock edges (CLKAB/CLKBA). Its inverting logic path makes it suitable for legacy TTL systems requiring signal complementation.
Does the SN74ALS648ADWR support 3.3 V operation?
No, the SN74ALS648ADWR does not support 3.3 V operation. Its recommended operating supply voltage is strictly 4.5 V to 5.5 V, and absolute maximum VCC is 7 V. Applying 3.3 V will result in undefined logic levels, insufficient noise margin, and failure to meet specified VOH/VOL thresholds. It is incompatible with mixed-voltage 3.3 V/5 V systems without level translation.
How does the SN74ALS648ADWR handle simultaneous data capture on both A and B buses?
The SN74ALS648ADWR supports simultaneous data capture: a rising edge on CLKAB latches data from the A bus into the B-register, while a rising edge on CLKBA latches data from the B bus into the A-register. These clocks operate independently, allowing concurrent storage - for example, capturing sensor values on B while loading actuator commands on A - with no internal conflict or arbitration required.
What is the significance of the "ADWR" suffix in SN74ALS648ADWR?
The "ADWR" suffix identifies the specific packaging and packaging format: "A" denotes the ALS648A revision (vs. original ALS648), "D" specifies SOIC (DW) package, and "WR" indicates tape-and-reel packaging with 2000 units per reel. This distinguishes it from tube-packaged variants like SN74ALS648ADW (25 pcs/tube) and confirms RoHS compliance and Level-1 moisture sensitivity rating.
Can the SN74ALS648ADWR replace the SN74ALS646ADWR in an existing design?
SN74ALS648ADWR cannot directly replace SN74ALS646ADWR without circuit validation because it implements inverting data transfer logic, whereas SN74ALS646ADWR is true (non-inverting). Swapping them would invert all eight data bits during transparent transfer, potentially corrupting protocol handshakes or data integrity. Functional replacement requires verifying whether system-level inversion is acceptable or compensated elsewhere in the signal chain.
SN74ALS648ADWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SOIC
SN74ALS648ADWR FAQ
1.How can I place an order for SN74ALS648ADWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS648ADWR 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 SN74ALS648ADWR reliable?
The price and inventory of SN74ALS648ADWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS648ADWR is usually 5 days.
3.What payment methods are accepted for SN74ALS648ADWR?
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4.How is shipping managed for SN74ALS648ADWR?
SN74ALS648ADWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS648ADWR 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 SN74ALS648ADWR?
For technical support, including SN74ALS648ADWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS648ADWR requirements.
6.How does Aetrix verify that SN74ALS648ADWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS648ADWR 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 SN74ALS648ADWR meets industry standards.
7.What is the process for return or replacement of SN74ALS648ADWR?
All SN74ALS648ADWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS648ADWR, 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 SN74ALS648ADWR part is unused and in its original packaging.
Return procedure for SN74ALS648ADWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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