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Texas Instruments SN74ALS645ADWR
- Part No.:
- SN74ALS645ADWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS645ADWR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,499
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Product details
Overview
SN74ALS645ADWR from Texas Instruments is an octal bus transceiver with 3-state outputs in a 20-pin SOIC (DW) package, designed for asynchronous bidirectional data transfer between A and B buses. It operates from 0°C to 70°C, supports 5 V supply, delivers 24 mA low-level output current, and features direction-control (DIR) and output-enable (OE) logic for bus isolation in industrial control backplanes.
For engineers reviewing the SN74ALS645ADWR datasheet, SN74ALS645ADWR pinout, SN74ALS645ADWR application, or SN74ALS645ADWR equivalent, this device serves as a TTL-compatible, high-density bus interface IC requiring precise timing control, bus contention avoidance, and 3-state drive capability in legacy 5 V digital systems.
Technical Context
This ALS-family transceiver implements true bipolar TTL logic with Schottky-clamped inputs and outputs, enabling compatibility with standard 74LS/74ALS systems. Its DIR input selects data flow direction (A→B or B→A), while OE independently disables all outputs into high-impedance state-critical for shared-bus arbitration.
Propagation delays are specified at 3–10 ns (tPLH/tPHL) under 50 pF load, with enable/disable times (tPZH/tPLZ) as fast as 2–20 ns. The device meets ANSI/IEEE Std 91-1984 logic symbol conventions and is characterized for 4.5 V to 5.5 V VCC operation with guaranteed VIH ≥ 2 V and VIL ≤ 0.8 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across industrial 5 V rail tolerances without brownout or overvoltage risk. |
| IOL (max) | 24 mA - Supports driving standard TTL loads (up to 10 LS-TTL inputs) without external buffering. |
| tPLH / tPHL | 3 ns to 10 ns - Enables reliable 100+ MHz bus handshaking in synchronous backplane designs. |
| VOH / VOL | ≥2.4 V / ≤0.4 V - Guarantees noise margins >0.4 V in mixed-logic environments with 5 V CMOS/TTL interfaces. |
| Operating Temp | 0°C to 70°C - Qualified for commercial-grade embedded controllers, test equipment, and industrial PLC I/O modules. |
| Package | SOIC-20 (DW) - Surface-mount footprint compatible with automated assembly; 7.5 mm × 12.8 mm body, 1.27 mm pitch. |
| 3-State Enable | Active-low OE with 2–20 ns disable/enable - Allows dynamic bus release during DMA cycles or multi-master arbitration. |
Pinout & Package
SN74ALS645ADWR uses a 20-pin SOIC (DW) package per JEDEC MS-013, with 1.27 mm lead pitch, 2.65 mm max height, and Q1 pin-1 orientation in tape-and-reel delivery.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow - Determines real-time bus traffic direction without reset or configuration. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines tied to one bus segment; internally buffered with 3-state drivers controlled by OE/DIR. |
| 10 (GND) | Ground Reference | Primary signal return path; must be low-inductance connection to minimize ground bounce during 24 mA switching. |
| 11–18 (B1–B8) | Port B I/O Terminals | Second bidirectional port; electrically isolated from A-side when OE is high, enabling dual-bus domain separation. |
| 19 (OE) | Output Enable Input | Active-low global 3-state control - Drives all A/B outputs to high-Z simultaneously, essential for bus sharing. |
| 20 (VCC) | Power Supply | +5 V supply pin; requires local 0.1 µF ceramic decoupling within 5 mm to suppress switching noise on internal drivers. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Data Flow | Single DIR pin configures full-duplex A↔B transfer without external multiplexers or routing logic. |
| True TTL Logic Compatibility | Meets 74ALS voltage thresholds (VIH ≥ 2 V, VIL ≤ 0.8 V) and fanout specs - interoperable with legacy 74LS/ALS systems. |
| High-Density SOIC Packaging | DW package reduces PCB area by ~60% vs. PDIP-20 while maintaining identical pinout and thermal performance. |
| Fast 3-State Switching | tPHZ/tPLZ ≤ 10 ns ensures minimal bus contention window during enable/disable transitions in time-critical applications. |
| Robust Absolute Ratings | Withstands 7 V VCC and 5.5 V I/O stress - protects against transient overvoltage during hot-swap or power sequencing events. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extender |
|---|---|
|
Use Scenario: Interfacing microcontroller local bus to a multi-slot ISA-style backplane carrying sensor data and actuator commands. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B (CPU-to-peripheral) and B→A (peripheral-to-CPU) transfers under DIR control, with OE used for slot arbitration. Use Value: Eliminates need for discrete direction logic and buffers; enables deterministic 10 ns-level timing control for cycle-accurate peripheral access. |
Use Scenario: Upgrading aging 74LS245-based subsystems where board space is constrained but electrical compatibility must be preserved. IC Role / Device Role / Timing Role: Pin-compatible drop-in replacement for 74LS245 with improved speed (3–10 ns vs. 15–25 ns) and lower power consumption. Use Value: Maintains existing PCB layout and firmware while delivering faster data throughput and reduced thermal load in dense rack-mounted systems. |
| Test Equipment Data Mux | Programmable Logic I/O Bridge |
|
Use Scenario: Routing DUT signals between multiple instrument channels (e.g., oscilloscope, logic analyzer, pattern generator) in automated test fixtures. IC Role / Device Role / Timing Role: Isolating and steering parallel data paths using OE for channel selection and DIR for signal direction reversal during calibration sequences. Use Value: Provides sub-10 ns signal routing latency and <0.4 V VOL - critical for preserving signal integrity in high-speed digital stimulus/response testing. |
Use Scenario: Connecting FPGA I/O banks to external memory or peripheral ASICs operating at different voltage or timing domains. IC Role / Device Role / Timing Role: Level-shifting and bus-isolation interface between 3.3 V FPGA I/O and 5 V legacy peripherals via controlled 3-state enable timing. Use Value: Enables safe bidirectional communication without level translators; OE timing aligns with FPGA output register clocks to prevent metastability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245N | Identical ALS logic family, same 20-pin PDIP package, but lacks DIR pin - unidirectional only (A→B only). | Requires external direction logic or two devices for bidirectional use; higher component count and board area. | Select when system design mandates fixed-direction data flow and cost-sensitive through-hole assembly is preferred. |
| SN74AS645DWR | AS-family variant: faster propagation (2–9.5 ns), higher IOL (48 mA), but higher ICC (62–97 mA) and stricter VIH (2 V min). | Better suited for high-speed, low-latency applications; less tolerant of marginal input rise times or noisy 5 V rails. | Choose for performance-critical paths where timing margin is tight and power budget allows +30% increase over ALS. |
Compared with SN74ALS645ADWR, SN74ALS245N sacrifices bidirectionality for simplicity and cost, while SN74AS645DWR trades power efficiency for speed and drive strength - making SN74ALS645ADWR optimal for balanced legacy-system upgrades requiring minimal redesign.
Availability
SN74ALS645ADWR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extenders, automated test equipment data muxing, and programmable logic I/O bridging requiring stable component supply across long-lifecycle production programs.
Supply support for SN74ALS645ADWR 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 with over 90 years of analog and logic innovation, serving automotive, industrial, and communications markets with high-reliability components.
The SN74ALS645ADWR belongs to TI's legacy 74ALS logic family, engineered for robust 5 V TTL interoperability, bus isolation, and backward compatibility in industrial control, instrumentation, and military-grade commercial systems.
FAQ
What is the maximum recommended output current for SN74ALS645ADWR?
The SN74ALS645ADWR is rated for a maximum low-level output current (IOL) of 24 mA per pin under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). This value is confirmed in the "Recommended Operating Conditions" table of the SDAS278 datasheet and supports direct drive of up to 10 LS-TTL loads without external buffering. Exceeding 24 mA risks VOL degradation or thermal overstress.
Does SN74ALS645ADWR support bidirectional data transfer without external logic?
Yes, SN74ALS645ADWR natively supports bidirectional data transfer using its dedicated DIR (direction-control) input pin. When DIR = Low, data flows from B bus to A bus; when DIR = High, data flows from A bus to B bus. This eliminates the need for external multiplexers or dual unidirectional transceivers, simplifying PCB layout and reducing component count in bus arbitration designs.
What is the function of the OE pin on SN74ALS645ADWR?
The OE (output-enable) pin on SN74ALS645ADWR is an active-low control that places all A1–A8 and B1–B8 outputs into high-impedance (3-state) mode when asserted high. This isolates both buses electrically, preventing contention during multi-master operations, DMA cycles, or power-down sequencing. OE timing (tPZH/tPLZ ≤ 10 ns) ensures rapid bus release for time-critical arbitration protocols.
Is SN74ALS645ADWR pin-compatible with SN74LS245?
SN74ALS645ADWR is functionally and pinout-compatible with SN74LS245 in the same SOIC-20 (DW) package, sharing identical pin assignments for VCC, GND, A/B ports, DIR, and OE. However, SN74ALS645ADWR offers faster propagation (3–10 ns vs. 15–25 ns), lower power consumption, and improved noise immunity due to ALS Schottky-clamped design - enabling drop-in performance upgrades without layout changes.
What package type and dimensions does SN74ALS645ADWR use?
SN74ALS645ADWR uses a 20-pin SOIC (DW) package per JEDEC MS-013, with 1.27 mm lead pitch, 7.5 mm body width, 12.8 mm body length, and 2.65 mm maximum height. It ships in tape-and-reel format (2000 units per reel) with Q1 pin-1 orientation, and is RoHS-compliant with NiPdAu lead finish and Level-1 moisture sensitivity rating for standard reflow processing.
SN74ALS645ADWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Logic Type:
- Transceiver, Non-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:
- 20-SOIC
SN74ALS645ADWR FAQ
1.How can I place an order for SN74ALS645ADWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS645ADWR 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 SN74ALS645ADWR reliable?
The price and inventory of SN74ALS645ADWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS645ADWR is usually 5 days.
3.What payment methods are accepted for SN74ALS645ADWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS645ADWR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS645ADWR?
SN74ALS645ADWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS645ADWR 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 SN74ALS645ADWR?
For technical support, including SN74ALS645ADWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS645ADWR requirements.
6.How does Aetrix verify that SN74ALS645ADWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS645ADWR 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 SN74ALS645ADWR meets industry standards.
7.What is the process for return or replacement of SN74ALS645ADWR?
All SN74ALS645ADWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS645ADWR, 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 SN74ALS645ADWR part is unused and in its original packaging.
Return procedure for SN74ALS645ADWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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