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Texas Instruments SN74ALS640B-1DW
- Part No.:
- SN74ALS640B-1DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640B-1DW.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,545
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Product details
Overview
SN74ALS640B-1DW from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-compatible systems. It features inverting logic, 20-pin SOIC (DW) package, -1 version with 48 mA low-level output current (IOL), and operates from 0°C to 70°C. Used in legacy industrial control backplanes and memory expansion interfaces.
For engineers reviewing the SN74ALS640B-1DW datasheet, SN74ALS640B-1DW pinout, SN74ALS640B-1DW application, or SN74ALS640B-1DW equivalent, this page delivers verified electrical specs, functional timing behavior, package dimensions, real-world use cases, and validated alternative options - all specific to the SN74ALS640B-1DW variant with DW packaging and enhanced drive capability.
Technical Context
The SN74ALS640B-1DW implements dual-directional bus isolation using DIR (direction control) and OE (output enable) inputs, supporting A→B or B→A data flow under active-low OE. Its ALS logic family delivers improved speed-power tradeoff versus standard TTL, with propagation delays as low as 2 ns (tPLH/tPHL min) and enable/disable times down to 2 ns (tPHZ/tPLZ min).
It uses open-collector compatible totem-pole outputs with 3-state capability, enabling bus sharing without contention. The -1 suffix denotes a revised output stage allowing IOL = 48 mA at VCC = 4.75–5.25 V - a 100% increase over the base SN74ALS640B - while maintaining VIH = 2 V, VIL = 0.8 V, and VOL ≤ 0.5 V under full load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - supports standard 5 V TTL supply rails with ±10% tolerance. |
| IOL (–1 version) | 48 mA - enables direct driving of multiple TTL loads or resistive termination without external buffers. |
| tPLH / tPHL | 2 ns (min) to 11 ns (max) - ensures sub-12 ns bidirectional data path latency in high-speed backplane designs. |
| tPZH / tPZL | 4 ns (min) to 24 ns (max) - guarantees fast 3-state disable/enable for dynamic bus arbitration. |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade embedded systems and industrial control panels. |
| Package | SOIC-20 (DW) - 7.5 mm × 12.8 mm body, 1.27 mm pitch, surface-mount compatible with standard reflow profiles. |
| Logic Family | Advanced Low-Power Schottky (ALS) - provides 2× speed vs. LS-TTL at comparable power, with VIH = 2 V and VIL = 0.8 V. |
Pinout & Package
SN74ALS640B-1DW is housed in a 20-pin SOIC (DW) package per JEDEC MS-013, with 1.27 mm lead pitch, 7.5 mm width, and 2.65 mm max height. Pin 1 is located at the top-left corner with beveled edge marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: LOW enables B→A data flow; HIGH enables A→B data flow. |
| 2–9 | A1–A8 | Input/output port A - bidirectional data lines connected to one bus segment. |
| 10 | GND | Ground reference for all internal circuitry and I/O voltage levels. |
| 11–18 | B1–B8 | Input/output port B - bidirectional data lines connected to second bus segment. |
| 19 | OE | Output enable input: ACTIVE-LOW - disables all outputs into high-impedance state for bus isolation. |
| 20 | VCC | Positive supply terminal - must be decoupled locally with 0.1 µF ceramic capacitor. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Architecture | Ensures signal polarity consistency across bus segments without external inverters in daisy-chained configurations. |
| 48 mA IOL (–1 version) | Supports direct interface to 10+ standard TTL inputs or 20+ CMOS loads, eliminating need for buffer stages in dense backplanes. |
| Sub-12 ns Propagation Delay | Enables reliable operation in 80–100 MHz bus clock domains when combined with appropriate trace length and termination. |
| 3-State Output Control | Allows seamless integration into shared-bus architectures (e.g., ISA-like expansion slots) with no contention during idle cycles. |
| ALS Family Compatibility | Guarantees pin- and logic-compatible replacement for SN74LS640, SN74ALS640, and SN74AS640 in existing PCB layouts. |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
|
Use Scenario: Isolating CPU address/data bus from peripheral card slots in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B (CPU→card) and B→A (card→CPU) transfers under DIR/OE control. Use Value: Enables hot-swap-capable slot architecture via OE-controlled 3-state isolation, preventing bus contention during insertion/removal. |
Use Scenario: Extending 16-bit data bus between mainboard and add-on RAM modules in early PC/AT-style systems. IC Role / Device Role / Timing Role: Octal transceiver buffering and direction-switching for parallel memory read/write cycles. Use Value: Delivers 48 mA drive strength to overcome capacitive loading of long traces and multiple DRAM address latches. |
| Test Equipment Bus Arbitration | Automated Test Fixture Interfacing |
|
Use Scenario: Sharing a common GPIB or IEEE-488 bus among multiple instrument controllers in rack-mounted ATE systems. IC Role / Device Role / Timing Role: Directionally controlled bus repeater synchronizing data flow between master controller and slave instruments. Use Value: Sub-12 ns propagation delay ensures deterministic timing alignment across multi-instrument test sequences. |
Use Scenario: Interfacing microcontroller-based test jigs with DUTs requiring bidirectional digital stimulus/response on 8-bit parallel ports. IC Role / Device Role / Timing Role: Level-shifting and bus-isolation transceiver between 3.3 V MCU I/O and 5 V DUT logic. Use Value: ALS input thresholds (VIH = 2 V, VIL = 0.8 V) ensure robust noise margin when interfacing mixed-voltage subsystems. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640BDWR | Base version with IOL = 24 mA (not 48 mA); otherwise identical pinout, timing, and DC specs. | Suitable where lower drive strength suffices - e.g., short traces, low fanout, or buffered bus segments. | Select SN74ALS640BDWR only if system load does not exceed 24 mA per line; verify VOL remains ≤ 0.4 V under actual conditions. |
| SN74AS640N | AS-family variant: faster (tPLH/tPHL down to 6 ns), higher IOL = 64 mA, but consumes ~2× more ICC (78 mA vs. 55 mA). | Better for ultra-low-latency paths (e.g., real-time DSP interconnects), but requires tighter thermal management and decoupling. | Choose SN74AS640N only when propagation delay < 7 ns is mandatory and power budget allows +23 mA per device. |
Compared with SN74ALS640BDWR, the SN74ALS640B-1DW provides double the sink current for driving heavy bus loads; compared with SN74AS640N, it trades 3–4 ns of speed for significantly lower static power and better noise immunity in electrically noisy industrial environments.
Availability
SN74ALS640B-1DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion systems, automated test equipment bus arbitration, and microcontroller-to-DUT interfacing requiring stable component supply across extended production lifecycles.
Supply support for SN74ALS640B-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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.
The SN74ALS640B-1DW belongs to TI's legacy TTL-compatible logic portfolio, engineered specifically for robust, high-reliability bidirectional bus interfacing in commercial-temperature industrial control and instrumentation systems.
FAQ
What is the maximum output sink current for SN74ALS640B-1DW?
The SN74ALS640B-1DW supports a guaranteed low-level output current (IOL) of 48 mA per pin when VCC is maintained between 4.75 V and 5.25 V. This rating is exclusive to the "–1" version and exceeds the 24 mA capability of the standard SN74ALS640B. Exceeding this limit risks VOL degradation beyond 0.5 V or thermal overstress.
Does SN74ALS640B-1DW support non-inverting data transfer?
No, the SN74ALS640B-1DW implements inverting logic - meaning the output waveform is inverted relative to the input on both A and B ports. This is inherent to its ALS-family design and cannot be disabled. For non-inverting operation, external inverters or alternate devices like SN74ALS245 must be used.
Can SN74ALS640B-1DW operate at 3.3 V supply voltage?
No, the SN74ALS640B-1DW is specified only for VCC = 4.5 V to 5.5 V. Operation below 4.5 V violates recommended conditions and results in undefined VIH/VIL thresholds, increased propagation delay, and potential failure to meet 48 mA IOL guarantee. Use 3.3 V–compatible transceivers such as SN74LVC245 for modern low-voltage systems.
What is the thermal resistance (θJA) of the SN74ALS640B-1DW in SOIC-20 package?
Texas Instruments does not publish θJA for the SN74ALS640B-1DW in the SDAS122A datasheet. However, based on JEDEC-standard SOIC-20 (DW) thermal characterization, typical θJA is approximately 100°C/W on 1-inch² 2-layer board with 2 oz copper. For thermal design, assume worst-case power dissipation of 55 mA × 5.5 V = 303 mW and verify junction temperature stays below 125°C.
Is SN74ALS640B-1DW pin-compatible with SN74LS640?
Yes, the SN74ALS640B-1DW is pin-compatible and functionally compatible with SN74LS640 in SOIC-20 (DW) packaging. Both share identical pinout, DIR/OE control scheme, and 3-state behavior. However, SN74ALS640B-1DW offers faster timing (11 ns vs. 25 ns max tPLH), lower power, and 48 mA IOL versus 15 mA - making it a direct performance upgrade.
SN74ALS640B-1DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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:
- 20-SOIC
SN74ALS640B-1DW FAQ
1.How can I place an order for SN74ALS640B-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640B-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 SN74ALS640B-1DW reliable?
The price and inventory of SN74ALS640B-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640B-1DW is usually 5 days.
3.What payment methods are accepted for SN74ALS640B-1DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640B-1DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640B-1DW?
SN74ALS640B-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640B-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 SN74ALS640B-1DW?
For technical support, including SN74ALS640B-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640B-1DW requirements.
6.How does Aetrix verify that SN74ALS640B-1DW is sourced from the original manufacturer or authorized distributors?
All SN74ALS640B-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 SN74ALS640B-1DW meets industry standards.
7.What is the process for return or replacement of SN74ALS640B-1DW?
All SN74ALS640B-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640B-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 SN74ALS640B-1DW part is unused and in its original packaging.
Return procedure for SN74ALS640B-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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