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Texas Instruments SN74ALS640BNS
- Part No.:
- SN74ALS640BNS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS640BNS.pdf
- Description:
- PROTOTYPE
- Quantity:
- Payment:
- Shipping:
Inventory:3,879
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Product details
Overview
SN74ALS640BNS 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 PDIP (N) package, 0°C to 70°C operating temperature, and supports 12 mA low-level output current (IOL) at 5 V. It is used in legacy industrial control backplanes and board-to-board communication interfaces.
For engineers reviewing the SN74ALS640BNS datasheet, SN74ALS640BNS pinout, SN74ALS640BNS application, or SN74ALS640BNS equivalent, this device serves as a standard 8-bit bidirectional bus interface with direction-control (DIR) and output-enable (OE) inputs - critical for bus arbitration, memory-mapped I/O expansion, and legacy system interoperability where ALS logic family timing and drive strength are required.
Technical Context
The SN74ALS640BNS implements dual 8-bit bidirectional data paths controlled by DIR and OE inputs: when OE is low, data flows either A→B (DIR = high) or B→A (DIR = low); when OE is high, all outputs enter high-impedance state. Its ALS logic family delivers improved speed-power trade-offs over standard TTL, with propagation delays as low as 2 ns (tPLH/tPHL) and enable/disable times down to 2 ns (tPHZ/tPLZ).
It operates strictly within 4.5 V–5.5 V supply range and is characterized for 0°C to 70°C ambient. Input thresholds (VIH = 2 V, VIL = 0.8 V) and output voltage levels (VOH = 2.4 V min at IOH = –12 mA, VOL = 0.4 V max at IOL = 12 mA) ensure robust noise margin and compatibility with other 5-V TTL/ALS devices in mixed-logic systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - enables lower power consumption than standard TTL while maintaining compatible voltage thresholds and drive capability. |
| Bus Width | 8-bit bidirectional - supports simultaneous transfer of one byte between two independent data buses. |
| Propagation Delay | 2–11 ns (tPLH/tPHL) - ensures fast data handshaking in high-speed backplane and microprocessor peripheral interfaces. |
| Output Drive | IOL = 12 mA / IOH = –12 mA - sufficient to drive multiple TTL loads or short PCB traces without buffering. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems, test equipment, and industrial controllers. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with regulated 5-V rails; tolerates typical power-supply ripple and dropout. |
| Package Type | PDIP-20 (N) - through-hole mounting for prototyping, repair, and legacy production; 300-mil width, 0.1-inch pin pitch. |
Pinout & Package
SN74ALS640BNS is supplied in a 20-pin plastic dual in-line package (PDIP-N), with 300-mil body width and 0.1-inch lead pitch. The package is RoHS-compliant, lead-finished with NiPdAu, and rated for standard reflow profiles.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: high enables A→B data flow; low enables B→A data flow. |
| 2–9 | A1–A8 | Input/output port A: bidirectional data lines connected to first bus segment. |
| 10 | GND | Ground reference for logic and power return path. |
| 11–18 | B1–B8 | Input/output port B: bidirectional data lines connected to second bus segment. |
| 19 | OE | Output-enable active-low input: low enables transceiver; high places all A/B pins in high-impedance state. |
| 20 | VCC | Positive supply input: must be decoupled locally to minimize switching noise on shared 5-V rail. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting logic architecture | Ensures signal polarity consistency across bus segments without external inversion, simplifying timing analysis in synchronous designs. |
| 3-state outputs with dual control | Independent DIR and OE inputs allow precise bus arbitration - enabling dynamic direction switching and complete isolation during idle or conflict periods. |
| ALS-family speed-power optimization | Delivers 10 ns typical propagation delay with ICC ≈ 27–55 mA (depending on output state), reducing thermal load vs. standard TTL equivalents. |
| TTL-compatible voltage thresholds | VIH = 2 V min and VIL = 0.8 V max guarantee interoperability with legacy 5-V microcontrollers, FPGAs, and peripheral ICs without level-shifting. |
| High noise immunity | Input hysteresis and 0.4 V guaranteed VOL support >0.4 V noise margin under worst-case loading, critical for noisy industrial environments. |
Applications
| Industrial Backplane Interface | Microcontroller I/O Expansion |
|---|---|
|
Use Scenario: Interfacing multiple 8-bit microcontrollers to a shared parallel backplane in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing time-multiplexed access to common address/data lines, synchronized via external clock and handshake signals. Use Value: Enables deterministic bus arbitration using DIR/OE control, eliminating contention and supporting hot-swap-capable modular I/O cards. |
Use Scenario: Expanding GPIO count of an 8-bit MCU (e.g., 8051 derivative) to drive LED arrays, keypad scanners, and sensor multiplexers. IC Role / Device Role / Timing Role: Level-shifting and buffering interface between MCU port and peripheral subsystems, operating at same 5-V domain with no added latency. Use Value: Provides 12 mA per output - sufficient to directly drive LEDs or CMOS inputs without external drivers, reducing BOM count and layout area. |
| Legacy Test Equipment Data Bus | Memory-Mapped Peripheral Bridge |
|
Use Scenario: Connecting DUT (device under test) parallel data ports to automated test system controller in benchtop ATE platforms. IC Role / Device Role / Timing Role: Isolating and routing 8-bit data between tester and DUT during functional test sequences, controlled by FPGA-based sequencer. Use Value: High-impedance disable mode prevents back-driving during test setup or fault conditions, protecting both DUT and tester hardware. |
Use Scenario: Bridging an 8-bit microprocessor's data bus to external SRAM, EPROM, or ASIC peripherals in embedded instrumentation. IC Role / Device Role / Timing Role: Synchronizing read/write cycles between processor and memory-mapped peripherals using OE as chip-select proxy and DIR for write-enable mapping. Use Value: Eliminates need for discrete bus switches or latches, simplifying timing closure and reducing propagation skew across 8-bit data path. |
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 and pinout; differs only in packaging - PDIP tube (20 pcs) vs. tape-and-reel (2000 pcs) for SN74ALS640BNSR. | No functional difference; suitable for manual assembly or small-batch prototyping where reel handling is unnecessary. | Select SN74ALS640BN for low-volume builds or lab use; SN74ALS640BNSR preferred for automated SMT line integration. |
| SN74AS640N | AS-family variant: faster propagation (2–7 ns), higher drive (IOL = 48 mA), but increased ICC (78 mA active) and tighter VIH/VIL (2.0 V/0.8 V). | Better suited for high-speed timing-critical paths; less tolerant of marginal input noise or degraded VCC. | Choose SN74AS640N only if sub-8 ns delay is mandatory and power budget allows +40% active current; otherwise SN74ALS640BNS offers superior noise margin and thermal stability. |
Compared with SN74ALS640BN, SN74ALS640BNS offers identical functionality in tape-and-reel format for automated placement - while SN74AS640N trades noise immunity and power efficiency for raw speed, making it appropriate only in validated high-performance subsystems where ALS timing margins are insufficient.
Availability
SN74ALS640BNS is available at Aetrix Electronics and suitable for industrial control backplanes, microcontroller I/O expansion, legacy test equipment, and memory-mapped peripheral bridging requiring stable component supply across long-lifecycle programs.
Supply support for SN74ALS640BNS 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, delivering reliable, high-volume production components for industrial, automotive, and communications markets.
The SN74ALS640BNS belongs to TI's legacy 74ALS logic family - engineered for robust 5-V TTL interoperability, low static power, and predictable timing in mission-critical embedded systems where long-term part availability and design stability are essential.
FAQ
What is the maximum operating temperature range for the SN74ALS640BNS?
The SN74ALS640BNS is characterized for operation from 0°C to 70°C - the commercial temperature grade. This range is confirmed in the "recommended operating conditions" table of the SDAS122A datasheet and applies specifically to all SN74xxx variants including SN74ALS640BNS. It is not rated for extended industrial or military temperature ranges.
Does the SN74ALS640BNS support non-inverting data transfer?
No, the SN74ALS640BNS implements inverting logic per its function table and logic diagram - all data paths invert signal polarity during transmission. This is inherent to the ALS640B design and cannot be disabled or bypassed. For non-inverting operation, alternative transceivers such as SN74ALS245 must be evaluated.
What are the absolute maximum ratings for VCC and input voltage on the SN74ALS640BNS?
The SN74ALS640BNS has an absolute maximum VCC rating of 7 V and absolute maximum input voltage of 7 V on control inputs (DIR, OE) and 5.5 V on I/O ports (A1–A8, B1–B8). Exceeding these values risks permanent damage, as stated in the SDAS122A datasheet Section "Absolute Maximum Ratings".
Can the SN74ALS640BNS be used as a direct replacement for SN74LS640?
No - the SN74ALS640BNS is not a drop-in replacement for SN74LS640. While both are octal 3-state transceivers, ALS logic has different propagation delay (faster), output drive (higher), and input thresholds (VIH = 2.0 V vs. LS's 2.0 V but with distinct IIL/IIH behavior). Board-level validation is required due to timing and loading differences.
What is the recommended decoupling strategy for the SN74ALS640BNS VCC pin?
TI recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC pin (Pin 20) and GND (Pin 10) of the SN74ALS640BNS, with short, low-inductance traces. For boards with multiple transceivers, add a bulk 4.7 µF–10 µF tantalum or aluminum electrolytic capacitor near the power entry point to suppress low-frequency ripple.
SN74ALS640BNS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.209", 5.30mm 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-SO
SN74ALS640BNS FAQ
1.How can I place an order for SN74ALS640BNS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BNS 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 SN74ALS640BNS reliable?
The price and inventory of SN74ALS640BNS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BNS is usually 5 days.
3.What payment methods are accepted for SN74ALS640BNS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640BNS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640BNS?
SN74ALS640BNS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BNS 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 SN74ALS640BNS?
For technical support, including SN74ALS640BNS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BNS requirements.
6.How does Aetrix verify that SN74ALS640BNS is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BNS 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 SN74ALS640BNS meets industry standards.
7.What is the process for return or replacement of SN74ALS640BNS?
All SN74ALS640BNS units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BNS, 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 SN74ALS640BNS part is unused and in its original packaging.
Return procedure for SN74ALS640BNS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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