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Texas Instruments SN74ALS640BN
- Part No.:
- SN74ALS640BN
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS640BN.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,365
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Product details
Overview
SN74ALS640BN 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 packaging, operating temperature range of 0°C to 70°C, and supports 12 mA low-level output current (IOL) at VCC = 4.5 V - used in legacy industrial backplane and memory expansion interfaces.
For engineers reviewing the SN74ALS640BN datasheet, SN74ALS640BN pinout, SN74ALS640BN application, or SN74ALS640BN equivalent, this page delivers verified electrical specs (VOH = 2.4 V min, VOL = 0.4 V max), timing parameters (tPLH = 11 ns max), package dimensions (PDIP-20, 0.300" width), and direct alternatives for bus isolation upgrades in legacy 5 V digital systems.
Technical Context
This device implements dual-directional 8-bit data routing controlled by DIR (direction) and OE (output enable) inputs, with true 3-state output behavior enabling bus contention avoidance. Its inverting logic architecture means input-to-output polarity inversion occurs regardless of direction mode.
It operates strictly within 4.5 V–5.5 V supply range and is characterized only for commercial temperature (0°C to 70°C). Unlike the -1 variant, SN74ALS640BN specifies IOL = 12 mA (not 48 mA) and does not support military-grade operation or SOIC/SOP packages - confirmed by TI's official packaging addendum.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - defines strict 5 V ±5% supply tolerance; operation outside invalidates timing and drive capability. |
| Logic Type | Inverting - all data paths invert signal polarity; requires complementary logic handling in system design. |
| IOL (max) | 12 mA at VCC = 4.5 V - determines minimum pull-down strength for driving TTL loads or stub lines. |
| tPLH / tPHL (max) | 11 ns / 10 ns - sets maximum propagation delay for A→B or B→A transfers under CL = 50 pF load. |
| Operating Temp | 0°C to 70°C - restricts use to commercial environments; excludes extended industrial or automotive deployment. |
| Output State | 3-state (high-impedance) - enables shared-bus architectures without external bus buffers or arbitration logic. |
| Package | PDIP-20 (N), 0.300" width - standard through-hole footprint compatible with legacy PCB tooling and manual assembly. |
Pinout & Package
SN74ALS640BN uses a 20-pin plastic dual in-line package (PDIP-N) with standard 0.300" body width and 0.100" lead pitch. Pin 1 is located at top-left corner when notch faces upward.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction control input | Low = B→A data flow; High = A→B data flow; determines bus traffic direction unidirectionally. |
| 2–9 (A1–A8) | Port A I/O terminals | Bidirectional data pins connected to A-side bus; high-impedance when OE = High. |
| 10 (GND) | Ground reference | Primary return path for all internal logic and output currents; must be low-inductance connection. |
| 11–18 (B1–B8) | Port B I/O terminals | Bidirectional data pins connected to B-side bus; functionally identical to A-port but electrically isolated. |
| 19 (OE) | Output enable input | Low = outputs active; High = all A/B pins enter high-impedance state - critical for bus isolation. |
| 20 (VCC) | Power supply | +5 V supply input; bypass capacitor (0.1 µF) required near pin for noise suppression during switching. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 8-bit data path | Enables single-chip interconnection between two independent 8-bit buses without external direction logic. |
| True 3-state outputs | Provides full electrical isolation (Z-state) when OE is high - eliminates need for external bus switches or gate arrays. |
| Inverting logic architecture | Guarantees signal inversion on all data paths, simplifying interface with non-inverting peripherals via consistent polarity mapping. |
| TTL-compatible voltage thresholds | VIH = 2.0 V min and VIL = 0.8 V max ensure reliable interfacing with standard 5 V TTL families (e.g., 74LS, 74F). |
| Commercial temperature grade | Validated for 0°C to 70°C operation - suitable for office equipment, test instrumentation, and non-harsh industrial control panels. |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
|
Use Scenario: Connecting CPU address/data bus to peripheral card slots in modular PLC chassis using passive backplane wiring. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between main controller and add-on I/O modules; DIR selects module read/write direction. Use Value: Eliminates discrete buffer ICs per line - reduces component count and layout complexity while maintaining TTL-level signal integrity over 15 cm traces. |
Use Scenario: Extending 8-bit data bus between microcontroller and external SRAM/ROM chips on retro-computing development boards. IC Role / Device Role / Timing Role: Isolating memory bus segments during DMA cycles; OE synchronized with memory enable strobes to prevent contention. Use Value: Enables zero-wait-state memory access with tPLH ≤ 11 ns - meets timing budgets for 8 MHz Z80 or 6502-based systems. |
| Test Equipment Bus Arbitration | Legacy Industrial Controller Interfacing |
|
Use Scenario: Sharing a common diagnostic bus among multiple DUT (device-under-test) handlers in automated test fixtures. IC Role / Device Role / Timing Role: Direction-controlled bus repeater allowing master controller to send commands (A→B) and receive responses (B→A) over same physical lines. Use Value: Reduces fixture cabling by 50% versus unidirectional solutions; DIR toggling enables half-duplex communication without protocol overhead. |
Use Scenario: Interfacing 8-bit parallel output from legacy PLC CPU module to field I/O rack with separate input/output bus segments. IC Role / Device Role / Timing Role: Level-shifting and isolating control signals between isolated power domains; OE tied to watchdog timeout signal for fail-safe shutdown. Use Value: Prevents cross-talk-induced spurious I/O activation during power-up/down sequences - improves system reliability in noisy factory environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640B-1N | Higher IOL rating (48 mA vs. 12 mA); otherwise identical pinout, logic, and timing. | Supports heavier capacitive loads (e.g., >100 pF buses) and longer trace lengths without signal degradation. | Select SN74ALS640B-1N when driving >5 TTL loads or >20 cm traces; SN74ALS640BN remains optimal for light-load, space-constrained designs. |
| SN74AS640N | Faster propagation (tPLH = 7 ns max vs. 11 ns); higher IOL (48 mA); AS-series logic family with stricter VIH/VIL thresholds. | Requires tighter input voltage margins (VIH = 2.0 V, VIL = 0.8 V) and higher drive capability - unsuitable for marginal TTL sources. | Choose SN74AS640N only when system demands sub-8 ns timing and has robust 5 V drive sources; SN74ALS640BN offers broader noise margin compatibility. |
Compared with SN74ALS640B-1N and SN74AS640N, SN74ALS640BN provides the most relaxed input voltage thresholds and lowest power consumption (ICC = 55 mA max), making it ideal for cost-sensitive, noise-prone legacy systems where speed is secondary to robustness.
Availability
SN74ALS640BN is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion subsystems, and test equipment bus arbitration requiring stable component supply across long-lifecycle embedded programs.
Supply support for SN74ALS640BN 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, embedded processing, and logic devices with global manufacturing and quality certification infrastructure.
SN74ALS640BN belongs to TI's 74ALS advanced low-power Schottky logic family, engineered for high-speed, low-power 5 V TTL-compatible digital systems in industrial and computing applications.
FAQ
What is the maximum operating temperature for SN74ALS640BN?
The SN74ALS640BN is rated for operation from 0°C to 70°C only. This commercial-grade specification is explicitly defined in TI's SDAS122A datasheet and confirmed in the Package Option Addendum. It is not qualified for extended temperature ranges like –40°C to 85°C or military –55°C to 125°C - those apply only to SN54ALS640B variants. Always maintain ambient PCB temperature within this window during continuous operation.
Does SN74ALS640BN support non-inverting data transfer?
No, SN74ALS640BN implements fixed inverting logic on all data paths - A1 to B1, A2 to B2, etc., each invert signal polarity regardless of DIR or OE state. This behavior is inherent to its ALS-family design and documented in the logic diagram and function table of the SDAS122A datasheet. System-level inversion must be handled externally if non-inverting operation is required.
Can SN74ALS640BN be used with 3.3 V logic systems?
No, SN74ALS640BN requires a 4.5 V–5.5 V supply and is not 3.3 V tolerant. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output levels (VOH ≥ 2.4 V, VOL ≤ 0.4 V) are specified only for 5 V operation. Direct connection to 3.3 V controllers risks undervoltage lockout or unreliable switching - level-shifting circuitry is mandatory for interoperability.
What is the recommended bypass capacitor for SN74ALS640BN?
A 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 20) and GND (pin 10) pins is required for stable operation. This value is derived from TI's application guidance for ALS-series devices and ensures adequate high-frequency decoupling during output transitions, preventing supply rail collapse that could cause timing violations or false outputs in the SN74ALS640BN.
Is SN74ALS640BN pin-compatible with SN74AS640N?
Yes, SN74ALS640BN and SN74AS640N share identical PDIP-20 pinouts, terminal functions, and mechanical dimensions - both follow the same N-package outline. However, they differ electrically: SN74AS640N has faster timing (7 ns vs. 11 ns) and higher drive (48 mA vs. 12 mA), but stricter input thresholds. Direct substitution may require validation of timing margins and noise immunity in the target system.
SN74ALS640BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- 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:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS640BN FAQ
1.How can I place an order for SN74ALS640BN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BN 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 SN74ALS640BN reliable?
The price and inventory of SN74ALS640BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BN is usually 5 days.
3.What payment methods are accepted for SN74ALS640BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640BN?
SN74ALS640BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BN 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 SN74ALS640BN?
For technical support, including SN74ALS640BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BN requirements.
6.How does Aetrix verify that SN74ALS640BN is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BN 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 SN74ALS640BN meets industry standards.
7.What is the process for return or replacement of SN74ALS640BN?
All SN74ALS640BN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BN, 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 SN74ALS640BN part is unused and in its original packaging.
Return procedure for SN74ALS640BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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