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Texas Instruments SN74LS641-1DWR
- Part No.:
- SN74LS641-1DWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74LS641-1DWR.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,721
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Product details
Overview
SN74LS641-1DWR from Texas Instruments is an octal bus transceiver with open-collector outputs, designed for bidirectional data flow control in TTL-level 8-bit parallel buses. It features active-low output-enable (OE̅), complementary A/B port direction control (DIR), and operates across 0°C to 70°C. Its 20-pin SOIC package supports legacy industrial backplane and memory expansion interfaces.
For engineers reviewing the SN74LS641-1DWR datasheet, SN74LS641-1DWR pinout, SN74LS641-1DWR application, or SN74LS641-1DWR equivalent, key selection criteria include open-collector drive capability, TTL-compatible input thresholds, bus-hold absence, and compatibility with LS-family timing budgets in legacy system upgrades.
Technical Context
This device implements eight independent bidirectional buffer channels, each with separate DIR and OE̅ controls enabling flexible data path routing. Output logic states are high-impedance (when OE̅ = HIGH) or LOW (when enabled and driven), requiring external pull-up resistors for HIGH-level assertion.
Propagation delay is specified at tPLH/tPHL ≤ 25 ns (VCC = 5 V, TA = 25°C), and input loading is 1 TTL unit per pin. The SN74LS641-1DWR shares pinout and functional behavior with SN74LS641, SN74LS642, and SN74LS644 within the same family but differs from 3-state variants like SN74LS640/645 by lacking internal totem-pole drivers.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS (Low-power Schottky TTL), ensuring compatibility with legacy LS-system timing and voltage thresholds. |
| Function | Octal bus transceiver with open-collector outputs - enables wired-AND bus sharing and level translation via external pull-ups. |
| Operating Temperature | 0°C to 70°C - suitable for commercial-grade embedded controllers and instrumentation, not extended/military range. |
| Supply Voltage | VCC = 4.75 V to 5.25 V - requires stable 5 V rail; no wide-VCC support or 3.3 V operation. |
| Output Type | Open-collector - mandates external pull-up resistors; supports mixed-voltage interfacing and bus arbitration. |
| Propagation Delay | tPD ≤ 25 ns - meets timing constraints of 20–25 MHz synchronous bus cycles in vintage microprocessor systems. |
| Input Loading | 1 TTL unit per input - minimal loading on upstream drivers, preserving fanout margins in daisy-chained configurations. |
Pinout & Package
SN74LS641-1DWR uses a 20-pin SOIC (DW) package, 7.5 mm wide, 2.65 mm max height, with 1.27 mm pitch and Q1 pin-1 orientation in tape-and-reel delivery.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Active-HIGH signal selecting data flow: A→B when HIGH, B→A when LOW. |
| 2–9 (A1–A8) | Port A Data I/O | Bidirectional TTL inputs/outputs tied to one bus segment; open-collector outputs sink current only. |
| 10 (GND) | Ground Reference | Signal return for all logic and output current paths; must be low-impedance for noise immunity. |
| 11–18 (B1–B8) | Port B Data I/O | Bidirectional TTL inputs/outputs tied to second bus segment; electrically identical to A-side pins. |
| 19 (OE̅) | Output Enable (Active-Low) | Disables all outputs to high-impedance state when HIGH; enables sinking when LOW. |
| 20 (VCC) | Power Supply | +5 V supply pin; decoupling capacitor required near pin for transient current handling. |
Key Features
| Feature | Design Value |
|---|---|
| Open-collector outputs | Enables wired-AND bus architectures and interface to higher-voltage rails using external pull-ups up to 15 V. |
| Independent DIR and OE̅ controls | Allows dynamic reconfiguration of data direction and selective channel disable without affecting other transceivers on shared buses. |
| Matched propagation delays | Ensures simultaneous enable/disable across all 8 channels, critical for glitch-free bus handshaking in synchronous designs. |
| TTL-compatible input thresholds | VIL ≤ 0.8 V and VIH ≥ 2.0 V guarantee reliable recognition of LS-family logic levels across temperature and voltage variation. |
| SOIC packaging with RoHS compliance | 20-pin DW package supports automated SMT assembly and meets modern environmental requirements while maintaining legacy footprint. |
Applications
| Industrial Backplane Interfacing | Legacy Microprocessor Bus Expansion |
|---|---|
|
Use Scenario: Connecting multiple CPU cards to a shared I/O backplane in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Bidirectional data isolation and bus contention prevention between master and slave modules using DIR-controlled flow and OE̅-gated arbitration. Use Value: Open-collector outputs allow multiple transceivers to share a single data line without hardware conflict, reducing board complexity versus discrete OR-ing solutions. |
Use Scenario: Extending Z80 or 8085 address/data buses to peripheral cards in retro-computing or test equipment. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled buffering between CPU bus and slower peripherals (e.g., UARTs, PIOs) with precise 25 ns timing alignment. Use Value: Matched propagation delay ensures setup/hold timing margins are preserved across all 8 bits, preventing data skew-induced read/write errors. |
| Memory-Mapped I/O Multiplexing | Parallel Printer Interface Logic |
|
Use Scenario: Sharing a single 8-bit data bus between RAM, ROM, and peripheral registers in resource-constrained embedded controllers. IC Role / Device Role / Timing Role: Enabling/disabling specific memory-mapped devices via OE̅ while DIR selects read (peripheral → CPU) or write (CPU → peripheral) paths. Use Value: Independent OE̅ per transceiver allows selective activation of memory banks or peripherals without software overhead or additional address decoding logic. |
Use Scenario: Driving Centronics-style parallel printer ports where handshake signals require wired-AND logic and bidirectional data transfer. IC Role / Device Role / Timing Role: Translating CPU-side TTL levels to printer-side open-drain signaling while supporting BUSY/ACK handshaking via shared lines. Use Value: Eliminates need for external diodes or MOSFETs in handshake line conditioning, simplifying PCB layout and improving reliability over discrete solutions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS642DWR | Same pinout and open-collector architecture, but DIR polarity inverted (DIR = LOW enables A→B). | Requires logic inversion of DIR signal in firmware/hardware; otherwise functionally interchangeable in static-direction systems. | Select SN74LS642DWR only if direction control is fixed and DIR inversion aligns with existing control logic. |
| SN74LS245N | 3-state (not open-collector) outputs, different pinout (20-pin PDIP only), no DIR pin - uses separate A→B/B→A control lines. | Cannot perform wired-AND; requires bus buffers instead of shared-line arbitration; incompatible pin mapping prevents drop-in replacement. | Choose SN74LS245N only when 3-state isolation suffices and board layout allows full redesign for its distinct pin assignment and control scheme. |
Compared with SN74LS641-1DWR, SN74LS642DWR offers identical electrical behavior with reversed DIR logic-ideal for design reuse where control polarity can be adjusted-while SN74LS245N provides higher drive strength and 3-state flexibility but sacrifices open-collector bus-sharing capability and requires mechanical redesign.
Availability
SN74LS641-1DWR is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy microprocessor bus expansion, memory-mapped I/O multiplexing, and parallel printer interface logic requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS641-1DWR 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 technologies with broad industrial and automotive portfolio coverage.
The SN74LS641-1DWR belongs to TI's legacy 74LS logic family, engineered for robustness and interoperability in vintage and retrofit digital systems where TTL-level timing, voltage, and drive characteristics remain essential.
FAQ
What is the maximum sink current per output pin on the SN74LS641-1DWR?
The SN74LS641-1DWR specifies IOL = 24 mA minimum per output at VOL = 0.5 V (VCC = 5 V, TA = 25°C). This rating ensures reliable driving of standard TTL loads and compatibility with common pull-up resistor values (e.g., 1–4.7 kΩ) used in wired-AND bus implementations. Exceeding this current may degrade VOL or cause thermal stress.
Does the SN74LS641-1DWR support hot-swap or live insertion?
No, the SN74LS641-1DWR does not support hot-swap operation. Its inputs lack protection against voltage overshoot during insertion, and the open-collector outputs can experience latch-up or excessive current if VCC is applied before ground or if bus voltages exceed VCC + 0.5 V. System-level hot-swap requires external protection circuitry and sequencing controls beyond the SN74LS641-1DWR's capabilities.
Can the SN74LS641-1DWR be used with 3.3 V logic systems?
The SN74LS641-1DWR is not 3.3 V compatible: it requires VCC = 4.75–5.25 V and has TTL input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). While 3.3 V outputs may meet VIH, they risk marginal noise immunity; direct connection risks damage if 3.3 V logic drives SN74LS641-1DWR inputs above absolute maximum ratings. Level-shifting circuitry is required for safe interfacing.
Is there a pin-compatible 3-state alternative to the SN74LS641-1DWR?
No direct pin-compatible 3-state alternative exists for the SN74LS641-1DWR. The SN74LS640 and SN74LS645 families offer 3-state outputs but use different pinouts (e.g., DIR replaced by separate A→B/B→A enables) and are not mechanically or electrically interchangeable. Migration requires PCB redesign and logic adaptation-not a drop-in replacement.
What is the recommended pull-up resistor value for SN74LS641-1DWR open-collector outputs?
For standard TTL loads and 5 V pull-ups, a 1.5 kΩ resistor is recommended: it limits output current to ~3.3 mA (well below the 24 mA IOL rating) while ensuring VOL ≤ 0.5 V and rise time < 100 ns with typical bus capacitance (< 50 pF). Values between 1 kΩ and 4.7 kΩ are acceptable depending on speed vs. power trade-offs and bus loading conditions.
SN74LS641-1DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-SOIC (0.295", 7.50mm 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:
- -, 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
SN74LS641-1DWR FAQ
1.How can I place an order for SN74LS641-1DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS641-1DWR 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 SN74LS641-1DWR reliable?
The price and inventory of SN74LS641-1DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS641-1DWR is usually 5 days.
3.What payment methods are accepted for SN74LS641-1DWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS641-1DWR transactions.
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4.How is shipping managed for SN74LS641-1DWR?
SN74LS641-1DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS641-1DWR 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 SN74LS641-1DWR?
For technical support, including SN74LS641-1DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS641-1DWR requirements.
6.How does Aetrix verify that SN74LS641-1DWR is sourced from the original manufacturer or authorized distributors?
All SN74LS641-1DWR 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 SN74LS641-1DWR meets industry standards.
7.What is the process for return or replacement of SN74LS641-1DWR?
All SN74LS641-1DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS641-1DWR, 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 SN74LS641-1DWR part is unused and in its original packaging.
Return procedure for SN74LS641-1DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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