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Texas Instruments SN74AS640N
- Part No.:
- SN74AS640N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74AS640N.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,322
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Product details
Overview
SN74AS640N 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 package, ±15 mA high-level output current, 64 mA low-level output current, and operates from 0°C to 70°C.
For engineers reviewing the SN74AS640N datasheet, SN74AS640N pinout, SN74AS640N application, or SN74AS640N equivalent, this page delivers verified electrical specs, functional truth table, thermal limits, switching timing (tPLH/tPHL down to 2 ns), and precise package mechanical data - all critical for legacy system maintenance, industrial backplane design, and bus isolation validation.
Technical Context
The SN74AS640N implements dual-directional bus control via DIR input: low enables B→A transmission, high enables A→B transmission. Its 3-state outputs are fully disabled when OE is high, providing true bus isolation without leakage paths.
It uses AS (Advanced Schottky) logic technology, delivering faster propagation delays (tPLH/tPHL ≤ 7 ns at VCC = 5 V) and higher drive strength than ALS variants, while maintaining TTL voltage thresholds (VIH = 2 V, VIL = 0.8 V) and compatibility with standard 5-V digital systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures stable operation across standard 5-V supply tolerances in industrial and computing environments. |
| IOH / IOL | –15 mA / 64 mA - supports driving heavy capacitive loads or multiple TTL inputs without external buffers. |
| tPLH / tPHL | 2 ns / 6 ns (max) - enables reliable high-speed bus handshaking up to ~100 MHz in short-trace applications. |
| VIH / VIL | 2 V / 0.8 V - guarantees robust noise margin (≥0.4 V) against TTL-level signal degradation on shared buses. |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade embedded controllers, test equipment, and office automation hardware. |
| ICC (active) | 78 mA (max) - defines worst-case power budget per device in dense bus architectures. |
| 3-State Enable Delay | tPZH = 2 ns, tPLZ = 13 ns - determines minimum OE assertion time before valid data appears on bus. |
Pinout & Package
SN74AS640N uses a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is marked by a notch or dot at the top-left corner of the package body.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B bus data routed to A bus; High = A bus data routed to B bus. |
| 2–9 (A1–A8) | Input/Output Port A | Bidirectional I/O pins connected to A-side data 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) | Input/Output Port B | Bidirectional I/O pins connected to B-side data bus; isolated when OE = high. |
| 19 (OE) | Output Enable Input | Active-low control: Low enables transceiver function; High forces all A/B pins into high-impedance state. |
| 20 (VCC) | Power Supply | +5 V DC supply pin; requires local 0.1 µF ceramic decoupling capacitor near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Architecture | Ensures signal polarity consistency across bus segments, eliminating need for external inverters in matched-path designs. |
| 64 mA Sink Capability | Drives 20+ standard TTL loads directly, reducing component count in legacy backplane interfaces. |
| 2 ns Enable-to-Valid Delay | Minimizes bus turnaround latency in time-critical arbitration protocols like IEEE-488 or custom parallel handshakes. |
| TTL-Compatible Voltage Thresholds | Interoperates seamlessly with 74LS, 74ALS, and microcontroller GPIOs without level-shifting circuitry. |
| Full Bus Isolation | OE-high state guarantees <1 µA off-state leakage, preventing unintended loading or crosstalk between disconnected buses. |
Applications
| Industrial PLC Backplanes | Legacy Test Equipment Interfaces |
|---|---|
Use Scenario: Bidirectional data exchange between CPU module and I/O expansion cards in modular programmable logic controllers. IC Role / Device Role / Timing Role: Bus transceiver managing address/data multiplexing and direction control under microprocessor arbitration. Use Value: Enables hot-swappable I/O modules by isolating inactive slots and supporting 64 mA drive for long PCB traces. | Use Scenario: Interfacing DMM or oscilloscope mainframe with plug-in measurement modules requiring synchronized parallel data transfer. IC Role / Device Role / Timing Role: Direction-controlled data bridge between host controller and peripheral module buses. Use Value: Delivers sub-10 ns propagation delay and 2 ns enable timing to meet tight handshake windows in automated calibration sequences. |
| Computer Terminal Emulators | Avionics Data Concentrators |
Use Scenario: Emulating RS-232 or parallel printer interfaces using discrete logic and microcontrollers in ruggedized terminals. IC Role / Device Role / Timing Role: Level-translating and bus-isolating transceiver between UART peripherals and 8-bit data bus. Use Value: Provides TTL-compatible VIH/VIL margins and 0.35 V VOL at 64 mA to ensure reliable logic detection despite cable-induced noise. | Use Scenario: Aggregating sensor data from multiple analog-to-digital converters onto a central ARINC 429 or MIL-STD-1553 interface board. IC Role / Device Role / Timing Role: Isolating and routing parallel ADC output words to shared memory or FIFO buffers. Use Value: Guarantees bus contention avoidance during simultaneous read/write cycles via precise 3-state control timing. |
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 | ALS logic: lower IOL (24 mA), slower tPLH/tPHL (11/10 ns), reduced ICC (55 mA). | Suitable for lower-speed, lower-power legacy systems where 64 mA drive is unnecessary. | Select SN74ALS640BN only if power budget is constrained and bus capacitance is <30 pF. |
| 74F640PC | Fast logic: 64 mA IOL, but VIH = 2.0 V, VIL = 0.8 V, and tPLH/tPHL = 5/4 ns - slightly slower than AS but more widely available. | Used in mid-1990s PC add-in cards and telecom line cards where AS speed was over-specified. | Choose 74F640PC for cost-sensitive replacements where 5 ns delay is acceptable and RoHS compliance is required. |
Compared with SN74ALS640BN and 74F640PC, the SN74AS640N delivers the highest speed (2 ns min tPLH) and strongest drive (64 mA) among pin-compatible octal transceivers in PDIP, making it optimal for timing-critical bus arbitration in maintained legacy platforms.
Availability
SN74AS640N is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy test equipment interfaces, and computer terminal emulators requiring stable component supply and long-term obsolescence management.
Supply support for SN74AS640N 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 for industrial, automotive, and communications markets.
The SN74AS640N belongs to TI's Advanced Schottky TTL logic family, engineered for high-speed, high-drive bidirectional bus interfacing in commercial-grade computing and instrumentation systems.
FAQ
What is the maximum operating temperature range for the SN74AS640N?
The SN74AS640N is characterized for operation from 0°C to 70°C, meeting commercial-grade environmental requirements. This range is explicitly defined in the recommended operating conditions table of the SDAS122A datasheet and confirmed in TI's packaging addendum. Operation outside this range may result in parametric failure or accelerated aging. The SN74AS640N does not support extended or military temperature grades - those are fulfilled by the SN54AS640 variant.
Does the SN74AS640N support non-inverting data transfer?
No, the SN74AS640N implements inverting logic architecture - all data paths (A→B and B→A) invert the input signal. This is inherent to its internal gate structure and confirmed in the logic diagram and function table of the SDAS122A datasheet. For non-inverting operation, designers must use two cascaded SN74AS640N devices or select alternatives such as the SN74AS864N, which provides true non-inverting transceiver functionality.
What is the absolute maximum supply voltage rating for the SN74AS640N?
The absolute maximum supply voltage (VCC) for the SN74AS640N is 7 V, as specified in the "Absolute Maximum Ratings" section of the SDAS122A datasheet. Exceeding this voltage - even momentarily - risks permanent damage to internal junctions. Recommended operation remains strictly within 4.5 V to 5.5 V, and sustained operation above 5.5 V violates TI's reliability specifications and voids warranty coverage for the SN74AS640N.
Can the SN74AS640N be used with 3.3-V logic systems?
No, the SN74AS640N is a 5-V-only TTL device and is not 3.3-V tolerant. Its VIH minimum is 2.0 V and VIL maximum is 0.8 V, but input structures are designed for 5-V rail operation; applying 3.3-V signals may cause marginal switching or increased static current. Driving the SN74AS640N from 3.3-V sources requires level-shifting circuitry. The SN74AS640N itself must be powered at 5 V to meet its published IOL, VOH, and timing specifications.
Is the SN74AS640N pin-compatible with the SN74ALS640BN?
Yes, the SN74AS640N and SN74ALS640BN share identical 20-pin PDIP (N) packaging, pinout, and functional mapping - including DIR, OE, A1–A8, B1–B8, VCC, and GND assignments. Both comply with the same mechanical drawing and logic symbol per ANSI/IEEE Std 91-1984. However, they differ electrically: SN74AS640N offers higher speed and drive strength, while SN74ALS640BN consumes less power and has lower IOL. Direct substitution is possible only if timing and drive requirements align with the ALS variant's specifications.
SN74AS640N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- 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, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74AS640N FAQ
1.How can I place an order for SN74AS640N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS640N 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 SN74AS640N reliable?
The price and inventory of SN74AS640N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS640N is usually 5 days.
3.What payment methods are accepted for SN74AS640N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS640N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS640N?
SN74AS640N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS640N 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 SN74AS640N?
For technical support, including SN74AS640N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS640N requirements.
6.How does Aetrix verify that SN74AS640N is sourced from the original manufacturer or authorized distributors?
All SN74AS640N 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 SN74AS640N meets industry standards.
7.What is the process for return or replacement of SN74AS640N?
All SN74AS640N units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS640N, 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 SN74AS640N part is unused and in its original packaging.
Return procedure for SN74AS640N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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