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Texas Instruments SN74LS641DWR
- Part No.:
- SN74LS641DWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74LS641DWR.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,140
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Product details
Overview
SN74LS641DWR 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 (OE) and direction (DIR) controls, and operates over 0°C to 70°C. Used in legacy industrial control backplanes and parallel I/O expansion interfaces.
For engineers reviewing the SN74LS641DWR datasheet, SN74LS641DWR pinout, SN74LS641DWR application, or SN74LS641DWR equivalent, key selection criteria include open-collector drive capability, 20-pin SOIC packaging, TTL-compatible logic thresholds, and compatibility with LS-family bus loading requirements.
Technical Context
The SN74LS641DWR implements dual 4-bit or single 8-bit bidirectional data transfer using separate DIR and OE inputs. Its open-collector outputs allow wired-AND bus configurations and level translation to higher voltages via external pull-ups.
It belongs to the 74LS logic family, with typical propagation delay of 25 ns (max), output sink current of 24 mA per pin, and input thresholds aligned to standard TTL voltage levels (VIL ≤ 0.8 V, VIH ≥ 2.0 V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS - ensures compatibility with legacy TTL systems and predictable noise margins |
| Data Width | 8-bit bidirectional - supports full-byte parallel bus communication without external multiplexing |
| Output Type | Open-collector - enables wired-AND bus arbitration and interface to 5–15 V external pull-up rails |
| Propagation Delay | 25 ns max at VCC = 5 V - defines maximum clock rate for synchronous bus operation |
| Sink Current | 24 mA per output - determines minimum pull-up resistor value for reliable low-state voltage |
| Operating Temperature | 0°C to 70°C - validated for commercial-grade embedded control and instrumentation environments |
| Supply Voltage | 4.75 V to 5.25 V - matches standard TTL power rail tolerances and reduces need for regulation |
Pinout & Package
SN74LS641DWR is housed in a 20-pin SOIC (DW) package with 1.27 mm pitch, 7.5 mm body width, and 2.65 mm max height - compatible with standard surface-mount assembly processes and IPC-7351 land patterns.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High = A-to-B transfer; Low = B-to-A transfer - enables dynamic bus reversal without hardware reconfiguration |
| 2–9 (A1–A8) | Port A Data I/O | Input when DIR = 0 and OE = 0; output (open-collector) when DIR = 1 and OE = 0 - connects to microcontroller or CPU data bus |
| 10 (GND) | Ground Reference | Common return path for all logic and output currents - must be low-impedance for stable noise margin |
| 11–18 (B1–B8) | Port B Data I/O | Input when DIR = 1 and OE = 0; output (open-collector) when DIR = 0 and OE = 0 - interfaces to peripheral or memory bus |
| 19 (OE) | Output Enable Input | Low = outputs active; High = all outputs high-impedance - provides bus contention avoidance during multi-master arbitration |
| 20 (VCC) | Positive Supply | +5 V supply pin - requires local 0.1 µF ceramic decoupling adjacent to pin for transient current handling |
Key Features
| Feature | Design Value |
|---|---|
| Open-collector outputs | Supports wired-AND bus topologies and mixed-voltage interfacing via external pull-ups up to 15 V |
| Independent DIR and OE controls | Enables precise timing control - direction can change while outputs remain disabled, eliminating bus glitches |
| Standard 20-pin SOIC (DW) | Matches footprint of SN74LS245 and other octal transceivers - simplifies drop-in replacement in existing layouts |
| TTL-compatible input thresholds | VIL ≤ 0.8 V / VIH ≥ 2.0 V - ensures robust noise immunity and interoperability with 74LS/74F logic families |
| 24 mA output sink capability | Drives standard TTL loads (up to 20 units) or discrete LEDs directly without buffer stages |
Applications
| Industrial Backplane Bus | Legacy Microprocessor I/O Expansion |
|---|---|
Use Scenario: Bidirectional data routing between PLC CPU and distributed I/O modules over a shared 8-bit parallel bus. IC Role / Device Role / Timing Role: SN74LS641DWR acts as a direction-controlled bus isolator, enabling master-slave handshaking and preventing signal contention during read/write cycles. Use Value: Open-collector outputs tolerate voltage mismatches across modules; 25 ns propagation delay supports 20 MHz bus clocking in burst-mode transfers. | Use Scenario: Adding parallel port capability to Z80 or 8085-based embedded controllers with limited GPIO resources. IC Role / Device Role / Timing Role: SN74LS641DWR serves as a programmable data path extender, allowing software-controlled direction switching for shared address/data bus multiplexing. Use Value: Independent DIR/OE pins enable zero-wait-state I/O reads and writes; 24 mA sink current drives opto-isolators or relay drivers directly. |
| Test Equipment Signal Routing | EPROM Programming Adapter |
Use Scenario: Reconfigurable signal path switching in automated test fixtures where DUT interface voltage levels vary between 5 V and 12 V. IC Role / Device Role / Timing Role: SN74LS641DWR functions as a level-flexible bus coupler, with external 12 V pull-ups enabling TTL-to-12 V logic translation on B-side outputs. Use Value: Open-collector architecture eliminates level-shifter ICs; propagation delay consistency ensures deterministic timing across multiple DUT interfaces. | Use Scenario: Adapting vintage EPROM programmers to support different memory part numbers requiring inverted or non-inverted data bus polarity. IC Role / Device Role / Timing Role: SN74LS641DWR provides polarity-selectable data latching - DIR pin toggled to invert or pass-through data during programming verify cycles. Use Value: Non-inverting transfer mode ensures bit-for-bit data integrity; 0.8 V VIL threshold rejects noise during high-speed programming pulses. |
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 | 3-state (not open-collector) outputs; no built-in direction control - requires external DIR logic | Requires additional gates for direction management; unsuitable for wired-AND bus sharing | Choose when bus isolation without external pull-ups is required and direction is static |
| SN74LS642DWR | Same pinout and open-collector architecture, but includes inverting data paths on one port | Supports complemented bus protocols (e.g., differential signaling emulation); not functionally identical | Choose only if system design explicitly requires inverted data transfer on Port B |
Compared with SN74LS245N and SN74LS642DWR, the SN74LS641DWR uniquely combines open-collector outputs with integrated direction control in a single 20-pin SOIC package - eliminating external logic for dynamic bus reversal and enabling direct wired-AND implementation without redesign.
Availability
SN74LS641DWR is available at Aetrix Electronics and suitable for industrial backplane buses, legacy microprocessor I/O expansion, test equipment signal routing, and EPROM programming adapters requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS641DWR 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 SN74LS641DWR belongs to TI's legacy 74LS logic portfolio, engineered for reliability in fixed-function digital systems where deterministic timing, noise immunity, and long-lifecycle support are critical.
FAQ
What is the maximum sink current per output pin on the SN74LS641DWR?
The SN74LS641DWR supports a guaranteed 24 mA DC sink current per output pin under standard operating conditions (VCC = 5 V, TA = 25°C). This rating allows direct driving of TTL loads, LEDs, or optocouplers without external buffers. Exceeding this limit risks output transistor degradation and increased propagation delay. The SN74LS641DWR datasheet specifies this parameter in the "Electrical Characteristics" table under IOL.
Does the SN74LS641DWR support 3.3 V logic inputs?
No, the SN74LS641DWR is a 5 V-only TTL device with input thresholds defined for 74LS family compatibility (VIL ≤ 0.8 V, VIH ≥ 2.0 V). While a 3.3 V CMOS high may exceed VIH, it does not guarantee noise margin or reliable operation across temperature and voltage extremes. Interfacing with 3.3 V systems requires level-shifting circuitry. The SN74LS641DWR is not 3.3 V tolerant.
Can the SN74LS641DWR replace the SN74LS245 in an existing design?
The SN74LS641DWR cannot serve as a direct functional replacement for the SN74LS245 due to fundamental architectural differences: SN74LS641DWR has open-collector outputs and integrated direction control, whereas SN74LS245 uses 3-state outputs and requires external direction logic. Pin compatibility exists, but bus behavior, pull-up requirements, and control sequencing differ. Redesign validation is required before substitution.
What is the recommended pull-up resistor value for SN74LS641DWR open-collector outputs?
For SN74LS641DWR open-collector outputs driving a 5 V bus, a 1.2 kΩ pull-up resistor is recommended to ensure VOH ≥ 2.4 V at 24 mA sink while limiting power dissipation. For higher-voltage buses (e.g., 12 V), calculate RPULLUP = (VPU − VOL) / 24 mA, where VOL ≤ 0.4 V. The SN74LS641DWR datasheet provides VOL vs. IOL curves for precise selection.
Is the SN74LS641DWR RoHS compliant?
Yes, the SN74LS641DWR is RoHS compliant, as confirmed by Texas Instruments' packaging addendum: lead finish is NiPdAu (NIPDAU), and the "RoHS" column is marked "Yes". It meets EU Directive 2011/65/EU requirements for restricted substances. The SN74LS641DWR is supplied in tape-and-reel format (2000 pcs/reel) with MSL Level-1 rating for unlimited floor life at ≤30°C/60% RH.
SN74LS641DWR 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:
- 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:
- -, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74LS641DWR FAQ
1.How can I place an order for SN74LS641DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS641DWR 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 SN74LS641DWR reliable?
The price and inventory of SN74LS641DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS641DWR is usually 5 days.
3.What payment methods are accepted for SN74LS641DWR?
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4.How is shipping managed for SN74LS641DWR?
SN74LS641DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS641DWR 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 SN74LS641DWR?
For technical support, including SN74LS641DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS641DWR requirements.
6.How does Aetrix verify that SN74LS641DWR is sourced from the original manufacturer or authorized distributors?
All SN74LS641DWR 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 SN74LS641DWR meets industry standards.
7.What is the process for return or replacement of SN74LS641DWR?
All SN74LS641DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS641DWR, 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 SN74LS641DWR part is unused and in its original packaging.
Return procedure for SN74LS641DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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