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Texas Instruments SN74ALS640BDWG4
- Part No.:
- SN74ALS640BDWG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640BDWG4.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,871
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Product details
Overview
SN74ALS640BDWG4 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, 0°C to 70°C operating temperature, and supports 12 mA low-level output current (IOL) at VCC = 4.5 V. Used in legacy industrial control backplanes and memory expansion interfaces.
For engineers reviewing the SN74ALS640BDWG4 datasheet, SN74ALS640BDWG4 pinout, SN74ALS640BDWG4 application, or SN74ALS640BDWG4 equivalent, key selection criteria include 3-state bus isolation timing (tPZH ≤ 21 ns), DIR/OE dual-control logic, ALS family propagation delay (tPLH/tPHL ≤ 11 ns), and compatibility with 5-V TTL signal levels and legacy PCB layouts.
Technical Context
This device implements a dual-rail bidirectional bus interface using complementary output drivers controlled by DIR (direction) and OE (output enable) inputs. Its inverting logic architecture ensures signal polarity consistency across both transmission directions (A→B and B→A), while the 3-state outputs provide high-impedance isolation when OE is high.
Designed for TTL-system integration, it operates strictly within 4.5–5.5 V supply range and meets ALS-family specifications: VIH = 2 V min, VIL = 0.8 V max, VOH = 2.4 V min at IOH = –12 mA, and VOL = 0.4 V max at IOL = 12 mA - all verified over 0°C to 70°C ambient.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Octal bidirectional bus transceiver with 3-state outputs and inverting logic |
| Supply Voltage (VCC) | 4.5 V to 5.5 V - ensures compatibility with standard 5-V TTL power rails |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded and industrial control applications |
| Propagation Delay (tPLH/tPHL) | ≤11 ns max at CL = 50 pF - enables reliable operation in sub-100-MHz synchronous bus environments |
| Output Drive (IOL) | 12 mA min at VOL ≤ 0.4 V - sufficient to drive 10 TTL loads or terminate short stubs on parallel buses |
| 3-State Enable Time (tPZH) | ≤21 ns max - guarantees fast bus release for time-critical arbitration protocols |
| Input Thresholds (VIH/VIL) | VIH ≥ 2 V, VIL ≤ 0.8 V - provides noise margin >0.4 V against TTL-level interference |
Pinout & Package
SN74ALS640BDWG4 uses a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 1.27 mm pitch, 2.65 mm max height, RoHS-compliant NiPdAu lead finish, and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction control input | Low = B→A data flow; High = A→B data flow - determines bus transmission direction |
| 2–9 (A1–A8) | Port A I/O terminals | Bidirectional data lines connected to primary bus segment; internally inverted |
| 10 (GND) | Ground reference | Signal and power return path for all internal logic and output drivers |
| 11–18 (B1–B8) | Port B I/O terminals | Bidirectional data lines connected to secondary bus segment; internally inverted |
| 19 (OE) | Output enable input | Low = active transceiver; High = 3-state isolation of both A and B ports |
| 20 (VCC) | Power supply | +5 V DC supply for logic core and output drivers; requires local 0.1 µF bypass |
Key Features
| Feature | Design Value |
|---|---|
| Inverting bidirectional logic | Ensures consistent signal polarity regardless of DIR state - eliminates external inversion in symmetric bus architectures |
| Dual independent control (DIR + OE) | Enables precise timing separation: DIR sets direction before OE enables, preventing bus contention during state transitions |
| ALS-family speed-power balance | 11 ns max propagation delay with 28 mA typical ICC (outputs disabled) - optimized for low-noise, medium-speed backplane use |
| TTL-compatible voltage thresholds | VIH = 2 V min / VIL = 0.8 V max - interoperable with 74LS, 74F, and microcontroller GPIO without level-shifting |
| 20-pin SOIC (DW) footprint | Standardized land pattern per IPC-7351 - supports automated placement and reflow in legacy SMT lines |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
Use Scenario: Isolating CPU address/data bus from peripheral card slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B (CPU→card) and B→A (card→CPU) transfers under DIR-controlled direction and OE-gated enable. Use Value: Prevents bus contention during hot-swap events via fast 3-state disable (tPLZ ≤ 15 ns) and maintains signal integrity across 15 cm traces. | Use Scenario: Extending 8-bit data bus between Z80 CPU and SRAM/ROM modules on retro-computing motherboards. IC Role / Device Role / Timing Role: Octal transceiver synchronizing read/write cycles between CPU and memory banks using DIR-driven direction switching and OE-based cycle gating. Use Value: Delivers 11 ns propagation delay and 12 mA drive strength - sufficient for 4 MHz Z80 bus timing with 50 pF load. |
| Test Equipment Bus Arbitration | Automated Test Fixture Control |
Use Scenario: Managing shared GPIB or IEEE-488 data lines among multiple instrument controllers in ATE racks. IC Role / Device Role / Timing Role: Isolating test head controller from DUT interface bus using OE-driven 3-state control and DIR-based channel routing. Use Value: Enables deterministic bus ownership handoff with <21 ns tPZH - critical for sub-microsecond handshake protocols. | Use Scenario: Interfacing FPGA I/O banks to 5-V sensor arrays and actuator drivers in production line test fixtures. IC Role / Device Role / Timing Role: Level-translating and buffering bidirectional control signals (e.g., SPI MISO/MOSI) between 3.3-V FPGA and 5-V peripherals. Use Value: Provides TTL-compatible thresholds and 12 mA sink capability - eliminates need for discrete pull-up networks on open-drain lines. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640BN | Same ALS logic, identical electrical specs, but in 20-pin PDIP (N) package - through-hole mounting, no reflow requirements | Preferred for prototyping, repair, or wave-soldered legacy assemblies where SOIC placement is impractical | Select when manual assembly, socketing, or thermal cycling robustness outweighs board space constraints |
| SN74AS640N | AS-family variant: faster propagation (7 ns max), higher drive (64 mA IOL), but increased ICC (78 mA typical) and tighter VIH (2 V min) | Suitable for high-speed bus extensions requiring sub-10 ns timing, but demands stricter power delivery and layout | Choose only if system timing budget requires <8 ns delay and power supply can support 2× ICC increase |
Compared with SN74ALS640BN and SN74AS640N, SN74ALS640BDWG4 offers optimal balance of SOIC manufacturability, 11 ns timing, and 28 mA quiescent current - making it the preferred choice for cost-sensitive, volume-produced commercial backplanes where layout density and reflow compatibility are critical.
Availability
SN74ALS640BDWG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion systems, test equipment bus arbitration, and automated test fixture control requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS640BDWG4 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 U.S.-based semiconductor company founded in 1930, specializing in analog ICs, embedded processors, and logic devices with broad industrial, automotive, and aerospace qualification.
The SN74ALS640BDWG4 belongs to TI's legacy ALS (Advanced Low-Power Schottky) logic family, engineered specifically for reliable 5-V TTL bus interfacing in commercial-temperature industrial control and computing systems.
FAQ
What is the maximum operating temperature range for SN74ALS640BDWG4?
The SN74ALS640BDWG4 is characterized for operation from 0°C to 70°C, meeting commercial-grade temperature specifications. This range is confirmed in the "recommended operating conditions" table of the SDAS122A datasheet, and applies specifically to the SN74ALS640B variant in DW package. It does not support extended or military temperature ranges like the SN54ALS640B.
Does SN74ALS640BDWG4 support pin-to-pin replacement with SN74ALS640BN?
Yes, SN74ALS640BDWG4 and SN74ALS640BN share identical pinout, logic function, and electrical specifications - differing only in package type (SOIC vs. PDIP). The DW and N packages maintain the same 20-pin arrangement and terminal assignments, enabling direct PCB footprint substitution with layout modification for mounting method.
What is the guaranteed low-level output current (IOL) for SN74ALS640BDWG4 at VCC = 4.5 V?
At VCC = 4.5 V, SN74ALS640BDWG4 guarantees IOL ≥ 12 mA with VOL ≤ 0.4 V, as specified in the "electrical characteristics" table for SN74ALS640B. This value is distinct from the -1 version (48 mA), and applies to the standard SN74ALS640B part including SN74ALS640BDWG4.
How does the DIR input control data flow direction in SN74ALS640BDWG4?
In SN74ALS640BDWG4, the DIR input selects bidirectional data path: DIR = Low enables B→A transmission (data from Port B appears on Port A), while DIR = High enables A→B transmission (data from Port A appears on Port B). This control is active only when OE = Low; if OE = High, both ports enter high-impedance state regardless of DIR.
Is SN74ALS640BDWG4 RoHS compliant and what is its moisture sensitivity level?
Yes, SN74ALS640BDWG4 is RoHS compliant with NiPdAu lead finish and carries MSL Level-1 (unlimited floor life at ≤30°C/60% RH), as documented in TI's Package Option Addendum. This allows indefinite storage and standard reflow processing without baking, simplifying manufacturing for commercial electronics producers.
SN74ALS640BDWG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- 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
SN74ALS640BDWG4 FAQ
1.How can I place an order for SN74ALS640BDWG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BDWG4 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 SN74ALS640BDWG4 reliable?
The price and inventory of SN74ALS640BDWG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BDWG4 is usually 5 days.
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SN74ALS640BDWG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BDWG4 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 SN74ALS640BDWG4?
For technical support, including SN74ALS640BDWG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BDWG4 requirements.
6.How does Aetrix verify that SN74ALS640BDWG4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BDWG4 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 SN74ALS640BDWG4 meets industry standards.
7.What is the process for return or replacement of SN74ALS640BDWG4?
All SN74ALS640BDWG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BDWG4, 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 SN74ALS640BDWG4 part is unused and in its original packaging.
Return procedure for SN74ALS640BDWG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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