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Texas Instruments SN74LS641-1N3
- Part No.:
- SN74LS641-1N3
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS641-1N3.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,141
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Product details
Overview
SN74LS641-1N from Texas Instruments is an octal bus transceiver with open-collector outputs, designed for bidirectional data flow control in TTL-level parallel bus systems. It features 8-bit non-inverting data paths, independent output-enable (OE) and direction (DIR) controls, and supports wired-AND logic implementation. It operates across 0°C to 70°C and is packaged in a 20-pin PDIP.
For engineers reviewing the SN74LS641-1N datasheet, SN74LS641-1N pinout, SN74LS641-1N application, or SN74LS641-1N equivalent, this device is selected for legacy industrial backplane interfaces, TTL-compatible level-shifting buses, and discrete logic-based address/data multiplexing where open-collector drive and bus arbitration are required.
Technical Context
The SN74LS641-1N implements two independent 4-bit bidirectional transceivers within a single 20-pin package, each with dedicated DIR and OE inputs. Its open-collector outputs allow direct connection to shared bus lines without external pull-ups when used in wired-AND configurations.
It uses standard LS-TTL circuitry with guaranteed 2.4 V minimum VOH at IOL = 8 mA per output, and supports fan-out of up to 20 LS-TTL loads. Propagation delay is specified at 25 ns max (tPLH/tPHL) under typical conditions, and it meets JEDEC JESD78 Class II latch-up immunity.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with legacy 74LS-series systems and predictable noise margins. |
| Data Width | 8-bit bidirectional - enables full byte-wide bus transfer between two subsystems using DIR control. |
| Output Type | Open-collector - permits wired-AND bus sharing, level translation, and active-low termination. |
| Supply Voltage | VCC = 4.75 V to 5.25 V - matches standard TTL rail tolerances and avoids marginal operation. |
| Operating Temperature | 0°C to 70°C - certified for commercial-grade embedded and instrumentation applications. |
| Propagation Delay | 25 ns max - sufficient for synchronous bus rates up to ~20 MHz in point-to-point or lightly loaded configurations. |
| Output Drive | IOL = 8 mA min at VO = 0.4 V - supports driving multiple LS-TTL inputs or 4.7 kΩ pull-up resistors on shared buses. |
Pinout & Package
SN74LS641-1N is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300" wide, with 0.100" lead pitch and through-hole mounting compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR A) | Direction control for A-side ports (A1–A4) | High = A→B transfer; Low = B→A transfer - enables independent bidirectional routing per 4-bit group. |
| 2 (OE A) | Output enable for A-side ports (A1–A4) | Low = outputs active; High = high-impedance - allows dynamic bus isolation during arbitration. |
| 3–6 (A1–A4) | Input/output terminals for A-side bus | Open-collector pins - require external pull-up for logic HIGH; support wired-AND bus topology. |
| 7 (GND) | Ground reference | Common return path for all internal logic and output current sinks. |
| 8–11 (B1–B4) | Input/output terminals for B-side bus | Open-collector pins - electrically identical to A-side; used for second 4-bit channel or extended bus segments. |
| 12 (OE B) | Output enable for B-side ports (B1–B4) | Low = outputs active; High = high-impedance - provides independent gating per channel. |
| 13 (DIR B) | Direction control for B-side ports (B1–B4) | High = B→A transfer; Low = A→B transfer - complements DIR A for full 8-bit bidirectional control. |
| 14 (VCC) | Positive supply | 5 V nominal power input - powers all internal gates and output drivers; decoupling recommended near pin. |
| 15–18 (A5–A8) | Input/output terminals for A-side upper nibble | Open-collector - extends A-side to full 8-bit width; shares OE A and DIR A with pins 3–6. |
| 19–20 (B5–B8) | Input/output terminals for B-side upper nibble | Open-collector - extends B-side to full 8-bit width; shares OE B and DIR B with pins 8–11. |
Key Features
| Feature | Design Value |
|---|---|
| Two independent 4-bit transceiver sections | Enables split-bus architectures - e.g., separate address and data lanes - with minimal IC count. |
| Separate DIR and OE per section | Allows asynchronous direction switching and selective bus release without disrupting adjacent channels. |
| Open-collector outputs with 8 mA sink capability | Supports direct interface to 5 V CMOS, NMOS, or other open-drain systems without level shifters. |
| Standard 20-pin PDIP footprint | Ensures drop-in replacement for SN74LS640/642/644/645 in existing through-hole designs. |
| Commercial temperature range (0°C to 70°C) | Validated for use in office equipment, test instruments, and non-military industrial controllers. |
Applications
| Industrial Backplane Interface | Legacy Microprocessor Bus Expansion |
|---|---|
|
Use Scenario: Interfacing a microcontroller's data bus to a multi-slot industrial backplane carrying sensor and actuator modules. IC Role / Device Role / Timing Role: Bidirectional data buffer and bus arbitrator, isolating master and slave devices via OE control while supporting shared interrupt lines via open-collector wiring. Use Value: Eliminates need for discrete AND/OR gates and pull-up networks; reduces board space and improves signal integrity over long traces. |
Use Scenario: Expanding Z80 or 8085 CPU address/data bus to external memory and peripheral chips in retro-computing or educational hardware. IC Role / Device Role / Timing Role: Level-translating and direction-controlled bus driver that synchronizes with CPU RD/WR strobes and maintains timing compliance under LS-TTL loading. Use Value: Maintains sub-25 ns propagation delay budget across 8-bit transfers, preserving original system timing margins. |
| TTL-Compatible Level Translation | Wired-AND Bus Arbitration |
|
Use Scenario: Connecting 5 V LS-TTL logic to older 12 V PMOS or NMOS peripherals requiring higher voltage thresholds. IC Role / Device Role / Timing Role: Open-collector interface element enabling safe voltage translation using external pull-up to 12 V while retaining TTL-compatible input thresholds. Use Value: Avoids dedicated level translators; leverages built-in 8 mA sink strength to drive higher-voltage rails directly. |
Use Scenario: Implementing priority-encoded interrupt request (IRQ) lines across multiple peripheral cards on a shared bus. IC Role / Device Role / Timing Role: Wired-AND combiner where any asserted low on A/B ports pulls the common line low, with DIR/OE managing contention resolution. Use Value: Enables hardware-prioritized interrupt handling without software polling or additional arbitration logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS642N | Features 3-state (not open-collector) outputs with complementary output polarity. | Suitable for tri-state bus architectures requiring high-impedance isolation instead of wired-AND logic. | Select SN74LS642N when bus sharing relies on high-Z disable rather than active-low wire-OR behavior. |
| SN74LS644N | Offers non-inverting 3-state outputs and separate A/B enable controls, but no direction control. | Used in unidirectional data paths (e.g., address latching) where direction reversal is handled externally. | Choose SN74LS644N for fixed-direction buffering with tighter output skew and lower quiescent current. |
Compared with SN74LS641-1N, SN74LS642N provides tri-state isolation ideal for modern bus-hold designs, while SN74LS644N simplifies unidirectional paths but lacks bidirectional flexibility - making SN74LS641-1N uniquely suited for legacy wired-AND bus arbitration and mixed-voltage interfacing.
Availability
SN74LS641-1N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor bus expansion, TTL-compatible level translation, and wired-AND bus arbitration requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS641-1N 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 and automotive reach.
The SN74LS641-1N belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-cost bidirectional bus interfacing in commercial-grade systems where reliability, pin compatibility, and backward design support are critical.
FAQ
What is the primary function of the SN74LS641-1N in a digital system?
The SN74LS641-1N functions as an octal bidirectional bus transceiver with open-collector outputs, enabling controlled data flow between two 8-bit buses. Its DIR and OE inputs allow real-time direction selection and output disabling, making it essential for bus arbitration, level translation, and legacy TTL system interconnection. The SN74LS641-1N is especially valued where wired-AND logic or shared bus lines are required.
Does the SN74LS641-1N support 3-state outputs?
No, the SN74LS641-1N does not provide 3-state outputs - it features open-collector outputs only. This means its outputs can actively drive LOW or float (high-impedance when disabled), but cannot actively drive HIGH. External pull-up resistors are required to establish logic HIGH states. For true 3-state functionality, consider SN74LS642N or SN74LS640N instead of the SN74LS641-1N.
Can the SN74LS641-1N be used as a direct replacement for SN74LS640N?
No - SN74LS641-1N and SN74LS640N are not functionally interchangeable. SN74LS640N has 3-state outputs and non-inverting data paths, whereas SN74LS641-1N uses open-collector outputs and supports bidirectional flow via DIR control. Substituting SN74LS641-1N for SN74LS640N would require redesigning pull-up networks and verifying bus timing, so the SN74LS641-1N must be selected intentionally for open-collector use cases.
What is the maximum sink current per output pin on the SN74LS641-1N?
Each output pin on the SN74LS641-1N is rated for a minimum sink current of 8 mA at VO = 0.4 V, per TI's SDLS189 datasheet. This specification ensures reliable driving of multiple LS-TTL inputs or standard 4.7 kΩ pull-up resistors. Exceeding this current may degrade VOH margin or cause thermal stress, so the SN74LS641-1N should be applied within this limit across all eight outputs simultaneously.
Is the SN74LS641-1N RoHS compliant?
Yes, the SN74LS641-1N is RoHS compliant, as confirmed by Texas Instruments' packaging addendum: "RoHS = Yes" and "Lead finish = NIPDAU" (nickel/palladium/gold). This applies to all active PDIP variants including SN74LS641-1N and SN74LS641-1N.A. The SN74LS641-1N meets EU Directive 2011/65/EU requirements for restricted hazardous substances.
SN74LS641-1N3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- 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:
- 100µA, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74LS641-1N3 FAQ
1.How can I place an order for SN74LS641-1N3 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS641-1N3 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 SN74LS641-1N3 reliable?
The price and inventory of SN74LS641-1N3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS641-1N3 is usually 5 days.
3.What payment methods are accepted for SN74LS641-1N3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS641-1N3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS641-1N3?
SN74LS641-1N3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS641-1N3 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 SN74LS641-1N3?
For technical support, including SN74LS641-1N3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS641-1N3 requirements.
6.How does Aetrix verify that SN74LS641-1N3 is sourced from the original manufacturer or authorized distributors?
All SN74LS641-1N3 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 SN74LS641-1N3 meets industry standards.
7.What is the process for return or replacement of SN74LS641-1N3?
All SN74LS641-1N3 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS641-1N3, 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 SN74LS641-1N3 part is unused and in its original packaging.
Return procedure for SN74LS641-1N3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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