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Texas Instruments SN74LS641NSR
- Part No.:
- SN74LS641NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74LS641NSR.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,579
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Product details
Overview
SN74LS641NSR from Texas Instruments is an octal bus transceiver with open-collector outputs, designed for bidirectional data transmission in TTL-level systems. It features 8-bit non-inverting data paths, active-low output-enable control (OE̅), and supports wired-AND bus interfacing. Typical use includes legacy industrial control backplanes and parallel I/O expansion in microprocessor-based systems operating at 0°C to 70°C.
For engineers reviewing the SN74LS641NSR datasheet, SN74LS641NSR pinout, SN74LS641NSR application, or SN74LS641NSR equivalent, key selection considerations include its open-collector output architecture, 20-pin SOP package, TTL-compatible input thresholds, and compatibility with 5-V-only bus environments requiring level translation or wired-logic aggregation.
Technical Context
This device implements dual 4-bit bidirectional transceivers in a single 20-pin package, with separate A- and B-side I/O terminals and shared directional control via OE̅. Each output can sink up to 24 mA while maintaining VOL ≤ 0.5 V, enabling direct connection to pull-up resistors or other open-collector nodes.
Input thresholds are standardized for LS-TTL logic families: VIH = 2.0 V min, VIL = 0.8 V max. Propagation delay is specified at tPLH/tPHL ≤ 25 ns (typical) under CL = 15 pF and VCC = 5 V, supporting synchronous bus rates up to ~20 MHz in controlled impedance layouts.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS - Low-power Schottky TTL, compatible with standard TTL and LSTTL interfaces |
| Function | Octal bidirectional bus transceiver with open-collector outputs, non-inverting data path |
| Supply Voltage | VCC = 4.75 V to 5.25 V - Requires stable 5-V rail; no internal regulation or wide-VCC support |
| Output Sink Current | IO(max) = 24 mA per pin - Enables direct drive of 4.7-kΩ pull-ups to 5 V with VOL ≤ 0.5 V |
| Propagation Delay | tPD = 25 ns (typ) at CL = 15 pF - Suitable for 20-MHz synchronous bus operation with margin |
| Operating Temperature | 0°C to +70°C - Commercial-grade rating; not qualified for extended or industrial temperature ranges |
| Package | SOP (NS) - 20-pin small-outline package, 0.300-inch body width, RoHS-compliant NIPDAU finish |
Pinout & Package
SOP (NS) package: 20-pin small-outline IC, 0.300-inch body width, 1.27-mm pitch, 8.4-mm A0 cavity length, 13.0-mm B0 cavity width, and Q1 pin-1 quadrant orientation in tape-and-reel delivery.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OE̅) | Output Enable (active low) | Global enable for all 8 outputs; high = high-impedance state, low = active open-collector drive |
| 2–9 (A1–A8) | Side-A data I/O | Input or output depending on direction; connected to local subsystem (e.g., CPU data bus) |
| 10 (GND) | Ground reference | Primary return path for all internal logic and output current sinking |
| 11–18 (B1–B8) | Side-B data I/O | Input or output depending on direction; connected to peripheral or memory bus segment |
| 19 (VCC) | Power supply | 5-V DC supply input; requires local 0.1-µF ceramic decoupling adjacent to pin |
| 20 (NC) | No connect | Internally unconnected; must remain floating or tied to GND per TI layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Open-collector outputs | Enable wired-AND bus arbitration and multi-drop line sharing without external diodes or logic |
| Bidirectional data flow | Single device replaces two unidirectional buffers, reducing board area and interconnect complexity |
| TTL-compatible inputs | VIH ≥ 2.0 V / VIL ≤ 0.8 V ensures reliable interfacing with 74LS, 74S, and standard TTL sources |
| 24-mA sink capability | Drives common 4.7-kΩ pull-ups to 5 V while maintaining VOL ≤ 0.5 V - eliminates need for external drivers |
| SOP packaging | Surface-mount NS package supports automated assembly and meets IPC-7351 land pattern standards |
Applications
| Industrial Backplane Interface | Legacy Microprocessor I/O Expansion |
|---|---|
Use Scenario: Interfacing multiple 8-bit peripheral modules to a central controller bus in factory automation PLC racks. IC Role / Device Role / Timing Role: Bidirectional bus transceiver enabling shared data exchange between CPU and distributed I/O cards using open-collector arbitration. Use Value: Eliminates discrete AND-gate logic for bus contention resolution and reduces component count by consolidating direction control into one IC. | Use Scenario: Adding parallel port capability to Z80- or 8085-based embedded controllers where space and BOM cost are constrained. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled data bridge between microprocessor data bus and external peripherals (e.g., ADCs, DACs, displays). Use Value: Provides TTL-compatible timing margins and 24-mA sink strength sufficient to drive LED indicators or optocoupler inputs directly. |
| Wired-AND Bus Arbitration | Parallel Printer Port Interface |
Use Scenario: Implementing priority-encoded interrupt lines across multiple slave devices sharing a common INT# signal. IC Role / Device Role / Timing Role: Open-collector output stage allows multiple SN74LS641NSR devices to share a single interrupt line with automatic OR-ing behavior. Use Value: Removes need for external diode-OR networks and guarantees monotonic voltage drop during simultaneous assertion. | Use Scenario: Connecting a microcontroller to a Centronics-style parallel printer requiring handshake signals and 8-bit data latching. IC Role / Device Role / Timing Role: Bidirectional data buffer managing data flow from MCU to printer and status feedback (BUSY, ACK) from printer to MCU. Use Value: Supports standard IEEE 1284-compliant timing with guaranteed tPLH/tPHL ≤ 25 ns and noise-immune open-collector handshaking. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | Tri-state (not open-collector) outputs; higher drive strength (35 mA); no built-in wired-AND capability | Requires external pull-up or bus-termination network for multi-drop use; better suited for point-to-point buffered buses | Select when tri-state isolation is preferred over wired-logic aggregation and higher fanout is needed |
| SN74LS642NSR | Same package and pinout; differs only in output configuration - SN74LS642NSR has 3-state outputs instead of open-collector | Cannot perform wired-AND; requires bus controller to manage direction and enable sequencing explicitly | Choose when system already uses centralized bus arbitration and avoids open-collector design constraints |
Compared with SN74LS245N and SN74LS642NSR, the SN74LS641NSR uniquely enables passive bus arbitration through open-collector outputs, making it irreplaceable in designs requiring hardware-level wired-AND logic without additional components or control overhead.
Availability
SN74LS641NSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor I/O expansion, wired-AND bus arbitration, and parallel printer port interfaces requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS641NSR 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, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.
The SN74LS641NSR belongs to TI's legacy 74LS logic family, engineered for reliability and interoperability in commercial-grade digital systems requiring robust TTL-level signal integrity and backward compatibility with 1970s–1990s equipment architectures.
FAQ
What is the maximum sink current per output pin on the SN74LS641NSR?
The SN74LS641NSR supports a maximum output sink current of 24 mA per pin under standard operating conditions (VCC = 5 V, TA = 25°C). This rating ensures reliable operation with typical 4.7-kΩ pull-up resistors while maintaining VOL ≤ 0.5 V. Exceeding this limit risks parametric shift or accelerated wear, especially at elevated temperatures.
Does the SN74LS641NSR support 3.3-V logic levels?
No, the SN74LS641NSR is strictly a 5-V TTL device. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output characteristics are specified only for VCC = 4.75 V to 5.25 V. Direct interface with 3.3-V systems requires level-shifting circuitry; the SN74LS641NSR itself does not tolerate 3.3-V supply or guarantee valid logic states at reduced voltages.
Is pin 20 (NC) on the SN74LS641NSR required to be left unconnected?
Yes, pin 20 is designated NC (no connect) in the official TI datasheet SDLS189. It is internally unconnected and must remain floating. TI recommends against tying it to VCC or GND, as doing so may introduce unintended coupling or violate package thermal/structural specifications. PCB layout should omit any trace or pad connection to this pin.
Can the SN74LS641NSR be used in place of the SN74LS642NSR?
No - the SN74LS641NSR and SN74LS642NSR are functionally distinct: SN74LS641NSR has open-collector outputs, while SN74LS642NSR has 3-state outputs. They share pinout and package but differ in electrical behavior. Substituting one for the other will cause bus contention or failure to achieve wired-AND functionality. Always verify output type before replacement.
What is the recommended decoupling for the SN74LS641NSR?
A minimum of one 0.1-µF ceramic capacitor placed as close as possible to pin 19 (VCC) and pin 10 (GND) is required for stable operation. TI further recommends adding a 4.7-µF tantalum or aluminum electrolytic capacitor near the power entry point of the board to suppress low-frequency ripple. Avoid shared decoupling across multiple ICs to prevent ground bounce during simultaneous switching.
SN74LS641NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- -, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74LS641NSR FAQ
1.How can I place an order for SN74LS641NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS641NSR 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 SN74LS641NSR reliable?
The price and inventory of SN74LS641NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS641NSR is usually 5 days.
3.What payment methods are accepted for SN74LS641NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS641NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS641NSR?
SN74LS641NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS641NSR 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 SN74LS641NSR?
For technical support, including SN74LS641NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS641NSR requirements.
6.How does Aetrix verify that SN74LS641NSR is sourced from the original manufacturer or authorized distributors?
All SN74LS641NSR 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 SN74LS641NSR meets industry standards.
7.What is the process for return or replacement of SN74LS641NSR?
All SN74LS641NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS641NSR, 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 SN74LS641NSR part is unused and in its original packaging.
Return procedure for SN74LS641NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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