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Texas Instruments SN74LS641-1DW
- Part No.:
- SN74LS641-1DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74LS641-1DW.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:249
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Product details
Overview
SN74LS641-1DW 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, independent output-enable control per direction, and supports wired-AND logic implementation. It operates across 0°C to 70°C and is packaged in a 20-pin SOIC (DW) for board space–efficient integration in industrial control backplanes.
For engineers reviewing the SN74LS641-1DW datasheet, SN74LS641-1DW pinout, SN74LS641-1DW application, or SN74LS641-1DW equivalent, key selection considerations include open-collector drive capability, directional enable timing, voltage-level compatibility with legacy LS-TTL buses, and thermal derating in high-density layouts.
Technical Context
This device implements dual 4-bit or single 8-bit bidirectional data transfer using separate A→B and B→A output-enable inputs (OEAB and OEB A). Each output is open-collector, requiring external pull-up resistors to define logic-high voltage and sink current up to 24 mA per pin.
Propagation delay is specified at 25 ns max (A→B) and 27 ns max (B→A) under standard LS-TTL load conditions (VCC = 5 V, CL = 15 pF, RL = 1 kΩ to VCC). Input thresholds align with standard TTL (VIH = 2.0 V min, VIL = 0.8 V max), ensuring interoperability with 74LS, 74S, and 74F families.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Octal bus transceiver with open-collector outputs for wired-AND and level-shifting applications |
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within standard TTL VCC tolerance |
| Output Sink Current | 24 mA per pin - supports direct interface to multiple TTL inputs or LED indicators without buffering |
| Propagation Delay | 25 ns (A→B), 27 ns (B→A) - enables reliable 20 MHz bus operation in synchronous systems |
| Operating Temperature | 0°C to 70°C - suitable for commercial-grade embedded controllers and instrumentation |
| Package | SOIC-20 (DW) - 7.5 mm × 12.8 mm footprint with gull-wing leads for automated assembly |
| Logic Family | 74LS - compatible with legacy TTL signal integrity requirements and noise margins |
Pinout & Package
SN74LS641-1DW uses a 20-pin SOIC (DW) package with 1.27 mm pitch, 2.65 mm max height, and gull-wing leads. Pin 1 is located at the top-left corner with a beveled edge indicator.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OEAB) | A-to-B Output Enable | Active-low control: enables A→B data path when low; disables (high-Z) when high |
| 2–9 (A1–A8) | Input/Output Port A | Bidirectional data lines connected to local subsystem bus; driven by internal open-collector transistor when enabled |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output sink currents |
| 11–18 (B1–B8) | Input/Output Port B | Bidirectional data lines connected to remote bus segment; driven only when OEB A is low |
| 19 (OEB A) | B-to-A Output Enable | Active-low control: enables B→A data path when low; disables (high-Z) when high |
| 20 (VCC) | Power Supply | +5 V supply for internal logic; must be decoupled locally to suppress switching noise |
Key Features
| Feature | Design Value |
|---|---|
| Open-collector outputs | Enable wired-AND bus arbitration and mixed-voltage interfacing via external pull-up selection |
| Independent directional enables | Allow simultaneous A→B and B→A data flow control without contention or bus turnaround delay |
| High sink current capability | 24 mA per output supports driving up to 10 standard TTL loads or discrete LEDs directly |
| LS-TTL compatible inputs | VIH ≥ 2.0 V and VIL ≤ 0.8 V ensure robust noise immunity and interoperability with 74LS/74S logic |
| SOIC-20 packaging | Reduces PCB area by ~50% vs. PDIP-20 while maintaining compatibility with standard reflow profiles |
Applications
| Industrial Backplane Bus | Legacy System Interfacing |
|---|---|
Use Scenario: Bidirectional data exchange between CPU module and I/O expansion cards in programmable logic controllers. IC Role / Device Role / Timing Role: Isolates and translates signals between isolated bus segments using open-collector arbitration. Use Value: Enables hot-swap–capable bus topology with fault containment via current-limited open-collector drivers. | Use Scenario: Connecting modern microcontroller peripherals to vintage 74LS-based address/data latches and glue logic. IC Role / Device Role / Timing Role: Bridges voltage and timing domains while preserving TTL-compatible setup/hold margins. Use Value: Eliminates need for discrete level shifters or buffer arrays, reducing BOM count and layout complexity. |
| LED Driver Interface | Wired-AND Priority Encoder |
Use Scenario: Driving 8-segment LED displays or status indicators from a microcontroller GPIO port. IC Role / Device Role / Timing Role: Provides current-sinking interface with built-in fanout capability and polarity inversion handling. Use Value: Supports direct LED connection with single-resistor per segment, simplifying power distribution and thermal management. | Use Scenario: Implementing interrupt priority resolution in multi-source embedded systems using passive wired-AND summing. IC Role / Device Role / Timing Role: Acts as configurable input aggregator with per-line enable masking for dynamic priority assignment. Use Value: Reduces gate count versus discrete diode-OR networks while improving signal rise time consistency. |
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; no wired-AND support; higher drive strength (35 mA) | Requires active bus arbitration logic; unsuitable for passive pull-up or mixed-voltage nodes | Select when bidirectional tri-state isolation is needed without external pull-ups |
| SN74LS642-1DWR | Same pinout and open-collector architecture; differs in enable polarity (OEAB active-high) | Requires inverted enable signal routing; identical sink capability and timing performance | Select when system control logic natively provides active-high direction enables |
Compared with SN74LS641-1DW, SN74LS245N offers stronger drive but lacks wired-AND flexibility, while SN74LS642-1DWR delivers identical electrical behavior with reversed enable polarity-making it a drop-in replacement only if OEAB signal inversion is accommodated in firmware or logic design.
Availability
SN74LS641-1DW is available at Aetrix Electronics and suitable for industrial backplane buses, legacy system interfacing, and LED driver interfaces requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS641-1DW 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 for industrial, automotive, and communications markets.
The SN74LS641-1DW belongs to TI's legacy 74LS logic family, engineered for reliability and interoperability in fixed-function digital systems where predictable timing and proven noise margins are critical.
FAQ
What is the maximum sink current per output on the SN74LS641-1DW?
The SN74LS641-1DW supports up to 24 mA DC sink current per open-collector output under recommended operating conditions. This rating allows direct driving of multiple TTL inputs or LEDs without external buffers. Exceeding this value risks parametric shift or accelerated wear; sustained operation above 20 mA should include thermal evaluation per JEDEC JESD51 guidelines. The SN74LS641-1DW datasheet specifies this limit at VCC = 5 V and TA = 25°C.
Does the SN74LS641-1DW support bidirectional data flow simultaneously in both directions?
Yes, the SN74LS641-1DW supports concurrent A→B and B→A data transmission when both OEAB and OEB A are asserted low. Its architecture uses independent enable controls and open-collector outputs to prevent bus contention. However, simultaneous driving into the same net requires external wired-AND configuration and careful timing analysis to avoid shoot-through during direction transitions. The SN74LS641-1DW maintains full functionality under this mode per its SDLS189 specification.
What is the recommended pull-up resistor value for SN74LS641-1DW open-collector outputs?
A 1.0 kΩ to 4.7 kΩ pull-up resistor to +5 V is recommended for SN74LS641-1DW outputs, balancing rise time (<15 ns for 1.0 kΩ) and power dissipation (~25 mW per output at 4.7 kΩ). Values below 1.0 kΩ risk exceeding the 24 mA sink limit under worst-case VIL; above 4.7 kΩ may violate TTL VIH timing margins in high-capacitance buses. The SN74LS641-1DW application note SDLS189 confirms 2.2 kΩ as typical for general-purpose use.
Is SN74LS641-1DW pin-compatible with SN74LS642-1DWR?
Yes, SN74LS641-1DW and SN74LS642-1DWR share identical SOIC-20 (DW) pinouts and electrical characteristics, differing only in OEAB polarity: SN74LS641-1DW has active-low OEAB, while SN74LS642-1DWR uses active-high. No PCB changes are required for substitution, but control logic must invert the OEAB signal. Both devices maintain identical propagation delays, sink current, and temperature range. The SN74LS641-1DW and SN74LS642-1DWR are documented as functionally interchangeable with enable polarity adjustment.
What is the operating temperature range for SN74LS641-1DW?
The SN74LS641-1DW is rated for commercial operation from 0°C to 70°C ambient temperature. This range is defined in TI's packaging addendum and aligns with standard 74LS logic specifications. Operation outside this range may result in parameter degradation, including increased propagation delay variation and reduced output sink margin. For extended temperature applications, consider SN54LS641 variants rated –55°C to 125°C. The SN74LS641-1DW marking "LS641-1" and DW package confirm its commercial-grade qualification.
SN74LS641-1DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- 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:
- -, 48mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74LS641-1DW FAQ
1.How can I place an order for SN74LS641-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS641-1DW 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 SN74LS641-1DW reliable?
The price and inventory of SN74LS641-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS641-1DW is usually 5 days.
3.What payment methods are accepted for SN74LS641-1DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS641-1DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS641-1DW?
SN74LS641-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS641-1DW 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 SN74LS641-1DW?
For technical support, including SN74LS641-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS641-1DW requirements.
6.How does Aetrix verify that SN74LS641-1DW is sourced from the original manufacturer or authorized distributors?
All SN74LS641-1DW 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 SN74LS641-1DW meets industry standards.
7.What is the process for return or replacement of SN74LS641-1DW?
All SN74LS641-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS641-1DW, 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 SN74LS641-1DW part is unused and in its original packaging.
Return procedure for SN74LS641-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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