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Texas Instruments SN74ALS640B-1N
- Part No.:
- SN74ALS640B-1N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS640B-1N.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,150
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Product details
Overview
SN74ALS640B-1N 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, -1 version IOL rating of 48 mA at VCC = 4.75–5.25 V, and operates across 0°C to 70°C. It is used in legacy industrial control backplanes and memory expansion interfaces.
For engineers reviewing the SN74ALS640B-1N datasheet, SN74ALS640B-1N pinout, SN74ALS640B-1N application, or SN74ALS640B-1N equivalent, this page delivers verified electrical specs, functional timing behavior, package dimensions, real-world use cases, and validated alternative options for system-level bus interface design.
Technical Context
The SN74ALS640B-1N implements dual-directional 8-bit data routing controlled by DIR (direction) and OE (output enable) inputs. Its inverting logic architecture ensures signal polarity inversion during transmission, and its 3-state outputs provide high-impedance isolation when OE is high. The -1 suffix denotes enhanced low-level output drive capability.
It complies with ALS (Advanced Low-Power Schottky) logic family characteristics: propagation delays as low as 2 ns (tPLH/tPHL), enable/disable times under 25 ns (tPZH/tPLZ), and guaranteed operation at VCC = 4.5–5.5 V. All 16 I/O pins (A1–A8, B1–B8) support bidirectional current-sinking up to 48 mA per pin in the -1 variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL power rails and tolerates supply ripple without functional degradation. |
| IOL (–1 version) | 48 mA - Enables direct driving of heavier loads (e.g., multiple TTL inputs or short PCB traces) without external buffers. |
| tPLH / tPHL | 2 ns (min) to 11 ns (max) - Supports high-speed bus arbitration in legacy computing and instrumentation systems operating up to ~90 MHz effective throughput. |
| VOH / VOL | VOH ≥ 2.4 V @ IOH = –12 mA; VOL ≤ 0.35 V @ IOL = 48 mA - Guarantees robust noise margins (>0.4 V) against TTL input thresholds. |
| Operating Temp | 0°C to 70°C - Qualified for commercial-grade embedded systems, including industrial HMIs and test equipment mainboards. |
| Package | PDIP-20 (N package) - Through-hole mounting compatible with wave soldering and manual prototyping; 300-mil width, 0.100" lead pitch. |
| Logic Family | ALS (Advanced Low-Power Schottky) - Delivers lower power than standard LS while maintaining speed comparable to AS, with typical ICC = 28 mA (disabled). |
Pinout & Package
SN74ALS640B-1N uses a 20-pin plastic dual in-line package (PDIP-N) with 300-mil body width and 0.100" lead spacing. Pin 1 is located at the top-left corner (notch-side left), with leads numbered counter-clockwise.
| 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 | First 8-bit bidirectional bus port - connects to local subsystem (e.g., CPU data bus or peripheral controller). |
| 10 | GND | Ground reference for all internal logic and I/O circuits - must be low-impedance connection to minimize ground bounce. |
| 11–18 | B1–B8 | Second 8-bit bidirectional bus port - interfaces to remote subsystem (e.g., memory module or I/O expansion bus). |
| 19 | OE | Output enable input: LOW activates transceiver; HIGH places all A/B pins in high-impedance state for bus isolation. |
| 20 | VCC | +5 V supply input - requires local 0.1 µF ceramic decoupling capacitor placed within 10 mm of pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting bidirectional logic | Signal polarity inversion on both A→B and B→A paths simplifies level-shifting in mixed-logic systems without external inverters. |
| 48 mA low-level output drive (–1 version) | Eliminates need for external bus drivers in high-fanout applications such as ISA-bus peripherals or multi-slot backplanes. |
| 3-state output isolation | OE-controlled high-impedance mode prevents bus contention during DMA cycles or processor reset sequences. |
| ALS-family speed/power balance | Propagation delay <11 ns with typical ICC = 28 mA (disabled) - optimizes performance-per-watt for legacy 5 V digital systems. |
| Standard 20-pin DIP footprint | Enables drop-in replacement of SN74LS640, SN74ALS640, and SN74AS640 in existing through-hole designs without layout changes. |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
|
Use Scenario: Interfacing a microcontroller-based PLC CPU board to a modular I/O backplane carrying discrete sensor/actuator signals. IC Role / Device Role / Timing Role: Bidirectional data bridge between CPU address/data bus and isolated slot-addressed peripheral modules; DIR toggled per command cycle, OE synchronized to slot-select strobes. Use Value: 48 mA IOL supports direct termination of unterminated 12-inch ribbon-cable runs with up to 8 parallel modules, eliminating repeater ICs. |
Use Scenario: Adding external SRAM or EPROM to an 8088/80286-based embedded controller where address/data multiplexing requires bus separation. IC Role / Device Role / Timing Role: Isolates CPU AD[0–7] bus from memory data bus during read/write cycles; DIR set statically, OE gated by memory enable (MEMEN#). Use Value: Sub-12 ns propagation delay ensures setup/hold compliance with 8 MHz CPU clock domains without added wait states. |
| Test Equipment Data Bus Arbiter | Instrumentation Signal Router |
|
Use Scenario: Routing measurement data between multiple ADC/DAC modules and a central DSP in automated test systems. IC Role / Device Role / Timing Role: Time-shared bidirectional conduit between DSP data bus and configurable analog front-end banks; DIR controlled by sequencer, OE managed per channel group. Use Value: 3-state isolation prevents cross-talk between active and idle channels, enabling deterministic latency under concurrent multi-channel acquisition. |
Use Scenario: Reconfigurable signal path switching in benchtop oscilloscopes or spectrum analyzers requiring dynamic probe-to-ADC routing. IC Role / Device Role / Timing Role: Logic-level bus transceiver implementing programmable input multiplexing; DIR selects source bank, OE enables/disables entire path. Use Value: ALS family's low ICC (28 mA disabled) minimizes thermal drift in precision analog signal chains adjacent to digital sections. |
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 | Standard version: IOL = 24 mA (not 48 mA); identical pinout, timing, and voltage specs. | Lower drive strength limits use in long-trace or high-fanout scenarios where SN74ALS640B-1N's 48 mA is required. | Select SN74ALS640BN only if load capacitance is ≤30 pF per line and trace length <4 inches. |
| SN74AS640N | AS family: faster tPLH/tPHL (2–7 ns), higher IOL (64 mA), but higher ICC (78 mA disabled) and stricter VIH/VIL thresholds. | Requires tighter VCC regulation and cleaner signal integrity; not drop-in due to increased power dissipation and noise sensitivity. | Choose SN74AS640N only when sub-8 ns propagation is mandatory and thermal management allows +50% quiescent power. |
Compared with SN74ALS640BN and SN74AS640N, the SN74ALS640B-1N uniquely balances enhanced drive (48 mA), moderate power (28 mA disabled), and proven robustness in noisy industrial environments - making it optimal for cost-sensitive, field-deployed systems where reliability trumps peak speed.
Availability
SN74ALS640B-1N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion subsystems, and test equipment data bus arbitration requiring stable component supply over extended production lifecycles.
Supply support for SN74ALS640B-1N 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, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS640B-1N belongs to TI's legacy TTL logic portfolio, engineered specifically for reliable, pin-compatible upgrades in 5 V bus-oriented systems where backward compatibility and long-term manufacturability are critical.
FAQ
What is the maximum sink current per output pin for SN74ALS640B-1N?
The SN74ALS640B-1N 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 specification is explicitly defined for the "-1" version in the SDAS122A datasheet and applies to all 16 I/O pins (A1–A8, B1–B8) under valid operating conditions. Exceeding this current risks parametric shift or accelerated wear.
Does SN74ALS640B-1N support non-inverting data transfer?
No, the SN74ALS640B-1N implements fixed inverting logic: data transmitted from A to B or B to A undergoes polarity inversion. This behavior is inherent to its ALS-family gate architecture and cannot be disabled or bypassed. For non-inverting operation, designers must pair it with external inverters or select alternate parts like SN74ABT640.
Can SN74ALS640B-1N operate at 3.3 V supply voltage?
No, the SN74ALS640B-1N is specified only for VCC = 4.5 V to 5.5 V. Operation below 4.5 V violates recommended conditions and results in undefined output states, degraded noise margins, and potential failure to meet timing specs. For 3.3 V systems, consider TI's SN74LVC640A or similar LVC-family devices.
What is the thermal resistance (θJA) of the SN74ALS640B-1N in PDIP package?
The datasheet does not publish θJA for SN74ALS640B-1N in PDIP (N) package. However, based on TI's generic PDIP-20 thermal characterization, typical θJA is ~70°C/W on 1-inch² FR-4 board with 2 oz copper. Actual junction temperature must be calculated using measured power dissipation (ICC × VCC) and ambient conditions - no derating guidance is provided for extended temperature operation beyond 70°C.
Is SN74ALS640B-1N RoHS compliant?
Yes, SN74ALS640B-1N is RoHS compliant, as confirmed in TI's Package Option Addendum: "RoHS = Yes", with lead finish "NIPDAU" (Nickel/Palladium/Gold). It meets EU Directive 2011/65/EU and associated exemptions, and is suitable for commercial electronics manufacturing without hazardous substance restrictions.
SN74ALS640B-1N 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
SN74ALS640B-1N FAQ
1.How can I place an order for SN74ALS640B-1N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640B-1N 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-1N reliable?
The price and inventory of SN74ALS640B-1N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640B-1N is usually 5 days.
3.What payment methods are accepted for SN74ALS640B-1N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640B-1N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640B-1N?
SN74ALS640B-1N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640B-1N 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-1N?
For technical support, including SN74ALS640B-1N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640B-1N requirements.
6.How does Aetrix verify that SN74ALS640B-1N is sourced from the original manufacturer or authorized distributors?
All SN74ALS640B-1N 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-1N meets industry standards.
7.What is the process for return or replacement of SN74ALS640B-1N?
All SN74ALS640B-1N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640B-1N, 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-1N part is unused and in its original packaging.
Return procedure for SN74ALS640B-1N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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