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Texas Instruments SN74ALS648-1DW
- Part No.:
- SN74ALS648-1DW
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN74ALS648-1DW.pdf
- Description:
- BUS TRANSCEIVER, ALS SERIES
- Quantity:
- Payment:
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Inventory:394
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Product details
Overview
SN74ALS648-1DW from Texas Instruments is an octal bus transceiver with 3-state outputs and active-low output enable, designed for bidirectional data transmission in TTL-compatible systems. It features 8-bit data flow control, 5.5V absolute maximum supply voltage, -40°C to +85°C operating temperature range, and typical propagation delay of 12 ns at VCC = 5V. It is used in industrial backplane bus interfaces requiring level-shifted bidirectional communication.
For engineers reviewing the SN74ALS648-1DW datasheet, SN74ALS648-1DW pinout, SN74ALS648-1DW application, or SN74ALS648-1DW equivalent, key selection factors include its 3-state bidirectional capability, ALS logic family speed-power trade-off, TTL input compatibility, and SOIC-24 package footprint constraints.
Technical Context
The SN74ALS648-1DW implements dual-function 8-bit bus transceivers with separate transmit (DIR) and output-enable (OE̅) controls. Its internal architecture includes complementary BJT-based ALS circuitry enabling faster switching than standard LS while maintaining TTL input thresholds and output drive strength.
It supports true bidirectional data transfer without external direction logic: DIR high enables A-to-B transmission; DIR low enables B-to-A transmission. OE̅ must be low for either direction to be active; when high, both A and B ports enter high-impedance state.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - balances speed (12 ns tPD) and power (19 mA ICC max) better than LS. |
| Data Width | 8-bit bidirectional - supports parallel byte-wide bus transfer between two subsystems. |
| Supply Voltage | VCC = 4.5V to 5.5V - compatible with standard 5V TTL rails; no 3.3V operation. |
| Propagation Delay | 12 ns typical (VCC = 5V, CL = 15 pF) - determines maximum synchronous bus clock rate. |
| Output Drive | IOH = -15 mA, IOL = 24 mA - sufficient to drive 20+ TTL loads or one LSTTL load. |
| Operating Temp | -40°C to +85°C - qualified for extended industrial environments, not automotive or military grade. |
Pinout & Package
SN74ALS648-1DW is housed in a 24-pin SOIC (Small Outline Integrated Circuit) package with 300-mil body width and standard 1.27 mm pitch. Pin numbering follows JEDEC MS-013AC, with Pin 1 marked by notch or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A1–A8 | Input/Output port A | Left-side bidirectional data terminals; connected to local subsystem bus. |
| B1–B8 | Input/Output port B | Right-side bidirectional data terminals; connected to remote subsystem or backplane. |
| DIR | Direction control input | Active-high signal: high = A→B, low = B→A; requires pull-up/down for deterministic startup. |
| OE̅ | Output enable (active-low) | Enables transceiver function only when low; high forces both ports into high-Z. |
| GND | Ground reference | Signal and power return for all logic and I/O; must be low-inductance connection. |
| VCC | Positive supply | 5V ±5% DC supply; decoupling capacitor (0.1 µF ceramic) required per device. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 8-bit data path | Eliminates need for separate transmitter/receiver ICs and direction logic gates in bus interface designs. |
| 3-state outputs on both ports | Allows multiple SN74ALS648-1DW devices to share common bus segments without contention. |
| TTL-compatible inputs | Accepts standard TTL voltage thresholds (VIH ≥ 2.0V, VIL ≤ 0.8V), enabling direct interfacing with legacy 74LS/74S logic. |
| ALS speed-power optimization | Delivers 12 ns propagation delay at 19 mA ICC - ~30% faster than 74LS648 with comparable power draw. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Connecting CPU module to I/O expansion cards across a 200-mm backplane with stub lengths up to 15 cm. IC Role / Device Role / Timing Role: Bidirectional data repeater buffering and isolating signals between mismatched impedance zones. Use Value: Maintains signal integrity at 8 MHz bus clock rates using ALS timing margins and controlled drive strength. | Use Scenario: Upgrading a 1980s PLC rack with new analog I/O modules while retaining original 74LS-based controller backplane. IC Role / Device Role / Timing Role: Logic-level translator and bus driver ensuring compatibility between newer ALS and older LS subsystems. Use Value: Matches 74LS input thresholds and output loading specs while improving propagation delay by 3.5 ns. |
| Test Equipment Data Bus | Embedded Controller Debug Port |
Use Scenario: Routing parallel test vectors between FPGA pattern generator and DUT socket in automated test equipment. IC Role / Device Role / Timing Role: Configurable-direction bus switch synchronized to test clock edge for deterministic data capture. Use Value: DIR and OE̅ pins allow precise timing control over data flow direction and bus release within 12 ns window. | Use Scenario: Exposing microcontroller internal registers via 8-bit parallel debug port accessible through front-panel header. IC Role / Device Role / Timing Role: Isolating debug bus from main system bus during normal operation using OE̅ control. Use Value: Prevents debug port contention during runtime; enables hot-plug diagnostics without system reset. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS648N | Slower (15 ns tPD), higher ICC (28 mA), same pinout and logic function. | Valid where lower speed and higher power are acceptable; lacks ALS speed advantage. | Choose SN74LS648N only if existing board layout uses DIP-24 and thermal budget allows +9 mA extra supply current. |
| SN74F648N | Faster (8 ns tPD), higher ICC (45 mA), TTL-compatible but not ALS-family matched. | Used in high-speed test fixtures where propagation delay dominates over power or noise immunity. | Prefer SN74F648N only when system timing closure requires sub-10 ns delay and fanout > 10 is not needed. |
Compared with SN74LS648N and SN74F648N, the SN74ALS648-1DW delivers optimal balance of speed, power, and noise margin for industrial backplane and legacy upgrade applications - neither the slowest nor fastest, but best suited for thermally constrained 5V systems needing reliable 8-MHz bus operation.
Availability
SN74ALS648-1DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system upgrades, and test equipment data buses requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ALS648-1DW 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 company founded in 1930, specializing in analog, embedded processing, and logic ICs for industrial, automotive, and communications markets.
The SN74ALS648-1DW belongs to TI's 74ALS logic family, developed in the early 1980s to improve speed-power efficiency over 74LS for industrial control and instrumentation systems.
FAQ
What is the maximum clock frequency supported by the SN74ALS648-1DW in a synchronous bus application?
The SN74ALS648-1DW does not include internal clocking; its usable bus clock frequency depends on propagation delay and system setup/hold timing. With 12 ns typical tPD and conservative board trace delays, it reliably supports 8 MHz synchronous bus operation. For 10 MHz, verify timing margins using worst-case 15 ns tPD and actual load capacitance in your layout. The SN74ALS648-1DW datasheet specifies no minimum pulse width or clock frequency limit.
Can the SN74ALS648-1DW operate from a 3.3V supply?
No, the SN74ALS648-1DW is strictly a 5V-only device. Its absolute maximum VCC is 5.5V and minimum recommended VCC is 4.5V. Operation below 4.5V violates the ALS family's input threshold and output drive specifications. Using 3.3V will result in undefined logic states and insufficient output voltage swing. For 3.3V systems, consider level-shifting solutions or modern 3.3V-compatible transceivers instead of the SN74ALS648-1DW.
Is the SN74ALS648-1DW pin-compatible with the SN74LS648N?
Yes, the SN74ALS648-1DW is pin-compatible with the SN74LS648N in SOIC-24 and DIP-24 packages respectively - same pin functions, ordering, and terminal assignments. However, the SN74ALS648-1DW uses SOIC-24 (DW suffix), while SN74LS648N uses PDIP-24 (N suffix). Physical mounting differs, but PCB layout adaptation is minimal when migrating from through-hole to surface-mount.
Does the SN74ALS648-1DW support hot-swap or live-insertion on a powered bus?
No, the SN74ALS648-1DW has no built-in hot-swap protection. Applying power or signals before VCC stabilization may cause latch-up or excessive current draw. Its inputs are not overvoltage tolerant beyond VCC + 0.5V. To implement safe live insertion, external series resistors, TVS diodes, and controlled power sequencing are required - the SN74ALS648-1DW itself provides no inherent hot-swap capability.
What is the meaning of the '-1' in SN74ALS648-1DW?
The '-1' in SN74ALS648-1DW denotes a specific revision or process variant defined by Texas Instruments' internal manufacturing coding. It indicates compliance with a particular wafer fabrication lot control and test specification, not a functional difference from SN74ALS648DW. All documented electrical and timing parameters for SN74ALS648-1DW match those of SN74ALS648DW per TI's official datasheet - the SN74ALS648-1DW is a fully functional equivalent.
SN74ALS648-1DW 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:
- -
SN74ALS648-1DW FAQ
1.How can I place an order for SN74ALS648-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS648-1DW 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 SN74ALS648-1DW reliable?
The price and inventory of SN74ALS648-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS648-1DW is usually 5 days.
3.What payment methods are accepted for SN74ALS648-1DW?
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4.How is shipping managed for SN74ALS648-1DW?
SN74ALS648-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS648-1DW 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 SN74ALS648-1DW?
For technical support, including SN74ALS648-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS648-1DW requirements.
6.How does Aetrix verify that SN74ALS648-1DW is sourced from the original manufacturer or authorized distributors?
All SN74ALS648-1DW 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 SN74ALS648-1DW meets industry standards.
7.What is the process for return or replacement of SN74ALS648-1DW?
All SN74ALS648-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS648-1DW, 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 SN74ALS648-1DW part is unused and in its original packaging.
Return procedure for SN74ALS648-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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