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Texas Instruments SN74AS641N
- Part No.:
- SN74AS641N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74AS641N.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,560
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Product details
Overview
SN74AS641N from Texas Instruments is an octal bidirectional bus transceiver in a 20-pin PDIP package, designed for asynchronous two-way data communication between A and B buses. It features true logic (non-inverting), 64 mA low-level output drive, 5 V supply operation, and operates from 0°C to 70°C - used in legacy industrial backplane interfaces and board-to-board data routing.
For engineers reviewing the SN74AS641N datasheet, SN74AS641N pinout, SN74AS641N application, or SN74AS641N equivalent, key selection considerations include its 3-state bidirectional control via DIR/OE pins, high-current drive capability for TTL/LS bus loading, propagation delay under 22 ns, and compatibility with 5 V logic systems requiring robust bus isolation.
Technical Context
The SN74AS641N implements dual 8-bit bidirectional data paths controlled by separate direction (DIR) and output-enable (OE) inputs. Its architecture supports real-time bus arbitration: when OE is low, data flows either A→B (DIR = high) or B→A (DIR = low); when OE is high, all I/Os enter high-impedance state.
It uses advanced Schottky-clamped bipolar (AS) technology, delivering faster switching than ALS variants (e.g., tPHL down to 1 ns vs. 3–5 ns), higher IOL (64 mA vs. 24–48 mA), and elevated ICC (up to 136 mA) - optimized for driving heavy capacitive loads and legacy TTL bus stubs without signal degradation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Type | True (non-inverting) bidirectional transceiver - preserves signal polarity during A↔B transfer. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL/LS power rails and tolerant of nominal ±10% variation. |
| Low-Level Output Current | 64 mA - drives up to 16 standard TTL loads or long PCB traces with minimal VOL rise (≤0.55 V). |
| Propagation Delay | 1 ns to 22 ns - enables reliable operation in 25 MHz+ synchronous bus environments with tight timing margins. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems, instrumentation, and industrial control panels. |
| Input Voltage Thresholds | VIH = 2 V, VIL = 0.8 V - ensures noise-immune recognition of TTL-compatible logic levels. |
| Output Voltage Levels | VOH ≥ 5.5 V (with 0.1 mA load), VOL ≤ 0.55 V (at 64 mA) - maintains valid logic-high margin and low-voltage drop under full drive. |
Pinout & Package
SN74AS641N uses a 20-pin plastic DIP (N package), 300-mil width, with 0.1-inch lead pitch and through-hole mounting. Pin 1 is located at the top-left corner (notch-side indicator), and the package conforms to JEDEC MS-001.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: high = A→B transfer, low = B→A transfer - determines data flow path. |
| 2 | A1 | Bus A data terminal 1 - bidirectional I/O connected to A-side data bus. |
| 3–9 | A2–A8 | Bus A data terminals 2–8 - eight parallel I/O lines for A-bus connection. |
| 10 | GND | Ground reference - common return for all internal circuitry and I/O current paths. |
| 11–18 | B1–B8 | Bus B data terminals 1–8 - eight parallel I/O lines for B-bus connection. |
| 19 | VCC | Positive supply input - powers internal logic and output drivers (4.5–5.5 V). |
| 20 | OE | Output-enable input: low = active transceiver, high = 3-state isolation - disables all I/Os to prevent bus contention. |
Key Features
| Feature | Design Value |
|---|---|
| 64 mA Output Drive | Enables direct interface with multiple TTL loads or high-capacitance backplanes without external buffers. |
| Sub-10 ns Propagation Delay | Supports high-speed bus handshaking and minimizes setup/hold time violations in synchronous designs. |
| True Logic Configuration | Preserves signal integrity across bidirectional transfers - critical for address/data multiplexing in legacy CPU interfaces. |
| 3-State Bus Isolation | Prevents electrical contention when multiple transceivers share a common bus segment - essential for modular system architectures. |
| Commercial Temperature Range | Validated for stable operation in office, lab, and factory-floor environments without thermal derating. |
Applications
| Industrial Backplane Interface | Legacy CPU Data Bus Extension |
|---|---|
Use Scenario: Interfacing microcontroller-based I/O modules to a central PLC backplane using shared 8-bit data lanes. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between local module memory and main rack bus under DIR-controlled arbitration. Use Value: 64 mA drive sustains signal integrity over 15 cm backplane traces; 3-state isolation prevents conflict during hot-swap events. | Use Scenario: Extending Z80 or 8085 CPU data bus to off-board peripheral cards in test equipment chassis. IC Role / Device Role / Timing Role: True-logic transceiver synchronizing read/write cycles between CPU and expansion card memory or I/O registers. Use Value: Sub-10 ns delays align with 4–6 MHz CPU clock timing budgets; OE-controlled isolation avoids bus contention during DMA cycles. |
| Instrumentation Signal Routing | Modular Test System Data Switching |
Use Scenario: Routing sensor ADC outputs and DAC command signals between measurement front-end and processing unit in benchtop analyzers. IC Role / Device Role / Timing Role: Directionally configurable data conduit enabling simultaneous analog acquisition and digital control on shared bus infrastructure. Use Value: VIH/VIL thresholds reject noise from mixed-signal PCB sections; 0°C–70°C rating covers lab ambient variations. | Use Scenario: Dynamically reconfiguring signal paths among interchangeable test modules (e.g., power supply, DMM, waveform generator) in automated test racks. IC Role / Device Role / Timing Role: High-current bidirectional switch enabling firmware-directed data exchange between master controller and slave modules. Use Value: 64 mA sink capability handles worst-case stub loading from up to four modules; DIR/OE dual-control allows atomic bus reconfiguration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS641AN | Lower IOL (24 mA), slower tPHL (3–5 ns), lower ICC (max 47 mA) | Suitable for lighter bus loads and lower-frequency systems (<10 MHz) | Select when power efficiency and cost outweigh speed/current requirements. |
| SN74AS641DW | Same electrical specs, SOIC-20 surface-mount package (2.65 mm height) | Designed for automated SMT assembly; requires PCB layout revision | Choose for space-constrained or high-density boards where through-hole is impractical. |
Compared with SN74ALS641AN, SN74AS641N delivers 2.7× higher drive strength and ~5× faster turn-off, making it preferable for electrically demanding buses; versus SN74AS641DW, it offers identical performance in a through-hole form factor ideal for prototyping, repair, and low-volume industrial builds.
Availability
SN74AS641N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy CPU bus extensions, and instrumentation signal routing requiring stable component supply across extended production lifecycles.
Supply support for SN74AS641N 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 specializing in analog, embedded processing, and logic solutions, with decades of heritage in TTL and advanced bipolar logic families.
The SN74AS641N belongs to TI's 74AS logic series - engineered for high-speed, high-drive 5 V digital systems where legacy compatibility, noise immunity, and deterministic timing are critical.
FAQ
What is the maximum output current capability of the SN74AS641N?
The SN74AS641N supports a guaranteed low-level output current (IOL) of 64 mA per pin under recommended operating conditions (VCC = 4.5 V to 5.5 V). This rating enables direct drive of multiple TTL loads or high-capacitance bus segments without external buffering. The device maintains VOL ≤ 0.55 V at this current, ensuring valid logic-low margins even under full load. This specification is confirmed in the "Recommended Operating Conditions" and "Electrical Characteristics" tables of the SDAS300 datasheet.
Does the SN74AS641N support 3.3 V logic levels?
No, the SN74AS641N is a 5 V-only device and does not support 3.3 V logic interfacing. Its absolute maximum ratings specify VCC up to 7 V but require operation within 4.5–5.5 V, and input thresholds (VIH = 2 V, VIL = 0.8 V) are optimized for TTL/5 V CMOS levels. Applying 3.3 V signals to inputs may result in marginal or non-functional behavior, and VCC must remain at 5 V. For mixed-voltage systems, level-shifting circuitry or a 3.3 V–compatible transceiver such as the SN74LVC8T245 is required.
How is bus direction controlled on the SN74AS641N?
Bus direction on the SN74AS641N is controlled by the DIR pin (Pin 1): when DIR = high, data flows from the A bus (Pins 2–9) to the B bus (Pins 11–18); when DIR = low, data flows from B to A. This control operates only when OE (Pin 20) is low (active). When OE is high, all I/Os enter high-impedance state regardless of DIR state - enabling clean bus arbitration and preventing contention. This dual-control scheme is explicitly defined in the FUNCTION TABLE on page 1 of the SDAS300 datasheet.
What is the operating temperature range for the SN74AS641N?
The SN74AS641N is characterized for operation from 0°C to 70°C - the commercial temperature grade. This range is explicitly stated in the "Recommended Operating Conditions" table (page 5) and "Absolute Maximum Ratings" section (page 5) of the SDAS300 datasheet. It is not rated for extended industrial (−40°C to 85°C) or automotive temperature ranges. Designs intended for harsher environments require thermal validation or alternative devices such as the SN74AHCT245.
Can the SN74AS641N be used as a unidirectional buffer?
Yes, the SN74AS641N can be configured as a unidirectional buffer by fixing the DIR pin to a constant logic level (high for A→B, low for B→A) and using OE for enable/disable control. In this mode, it functions as an 8-bit non-inverting buffer with 64 mA drive strength and sub-22 ns propagation delay. However, unlike dedicated unidirectional buffers, it retains bidirectional I/O structure - meaning both A and B ports remain electrically connected and must be properly terminated to avoid floating nodes. This usage is supported by the functional description and timing diagrams in the SDAS300 datasheet.
SN74AS641N 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, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- Open Collector
- Current - Output High, Low:
- -, 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
SN74AS641N FAQ
1.How can I place an order for SN74AS641N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS641N 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 SN74AS641N reliable?
The price and inventory of SN74AS641N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS641N is usually 5 days.
3.What payment methods are accepted for SN74AS641N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS641N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS641N?
SN74AS641N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS641N 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 SN74AS641N?
For technical support, including SN74AS641N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS641N requirements.
6.How does Aetrix verify that SN74AS641N is sourced from the original manufacturer or authorized distributors?
All SN74AS641N 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 SN74AS641N meets industry standards.
7.What is the process for return or replacement of SN74AS641N?
All SN74AS641N units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS641N, 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 SN74AS641N part is unused and in its original packaging.
Return procedure for SN74AS641N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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