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Texas Instruments SN74ALS641A-1DW
- Part No.:
- SN74ALS641A-1DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS641A-1DW.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,878
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Product details
Overview
SN74ALS641A-1DW from Texas Instruments is an octal bidirectional bus transceiver in a 20-pin SOIC (DW) package, designed for asynchronous two-way data transfer between A and B buses. It features true logic, direction-control (DIR) and output-enable (OE) inputs, 48 mA low-level output current (IOL), and operates over 0°C to 70°C. It is used in legacy industrial backplane and board-to-board communication systems requiring robust TTL-compatible drive.
For engineers reviewing the SN74ALS641A-1DW datasheet, SN74ALS641A-1DW pinout, SN74ALS641A-1DW application, or SN74ALS641A-1DW equivalent, key selection criteria include its -1 version's enhanced 48 mA sink capability, SOIC-20 thermal and layout compatibility, DIR/OE dual-control timing behavior, and ALS family propagation delays (tPLH/tPHL ≤ 32 ns).
Technical Context
The SN74ALS641A-1DW implements a dual-rail, 3-state bidirectional bus interface with independent DIR and OE control logic: DIR selects data flow direction (A→B or B→A), while OE disables all outputs into high-impedance state. Its ALS bipolar technology delivers higher noise immunity and lower power than standard LS, with guaranteed operation at VCC = 4.5–5.5 V.
It supports hot-swap isolation via OE-driven tri-state control and exhibits defined VOL (≤0.5 V at IOL = 48 mA) and VIH/VIL thresholds (2.0 V / 0.8 V), ensuring interoperability with 5-V TTL and CMOS logic families in mixed-signal backplanes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across industrial 5-V rail tolerances without regulation. |
| IOL (max) | 48 mA - Enables direct driving of multiple TTL loads or termination resistors on dense backplanes. |
| tPLH/tPHL | ≤32 ns - Supports synchronous data rates up to ~15 MHz in point-to-point bus configurations. |
| Operating Temp | 0°C to 70°C - Qualified for commercial/industrial ambient environments, not extended or automotive. |
| VIL/VIH | 0.8 V / 2.0 V - Matches standard TTL input thresholds, eliminating level-shifting in legacy 5-V systems. |
| Package | SOIC-20 (DW) - 7.5 mm × 12.8 mm footprint with 1.27 mm pitch; compatible with standard reflow profiles (MSL Level-1). |
Pinout & Package
SN74ALS641A-1DW uses a 20-pin SOIC (DW) package per JEDEC MS-013, with 2.65 mm max height, 1.27 mm lead pitch, and gull-wing leads. Pin 1 is marked by a beveled corner and located in Quadrant Q1 per tape-and-reel orientation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow; controls internal bus switch path. |
| 2 (A1) | Port A I/O | Bidirectional data line connected to A bus; high-impedance when OE = High. |
| 3–9 (A2–A8) | Port A I/O | Seven additional bidirectional A-bus lines; all share same DIR/OE control. |
| 10 (GND) | Ground Reference | Primary signal return for all I/O and internal logic; must be low-inductance connection. |
| 11–18 (B1–B8) | Port B I/O | Eight bidirectional B-bus lines; electrically isolated from A side except during active transfer. |
| 19 (VCC) | Power Supply | +5 V supply for ALS logic core and output drivers; requires local 0.1 µF bypassing. |
| 20 (OE) | Output Enable Input | Low = enable transceiver; High = tri-state all A/B pins; overrides DIR state. |
Key Features
| Feature | Design Value |
|---|---|
| True Logic Configuration | Non-inverting data path ensures bit-for-bit signal integrity between A and B ports without polarity inversion. |
| -1 Version Output Drive | 48 mA IOL rating allows direct interface to unterminated stubs or multiple TTL inputs without external buffers. |
| Dual Independent Controls | Separate DIR and OE inputs enable precise sequencing: OE isolates buses first, then DIR sets direction before enabling. |
| ALS Bipolar Technology | Lower power than AS, higher noise margin than LS, and guaranteed 5-V operation without derating. |
| 3-State Bus Isolation | Simultaneous high-Z on all 16 I/O pins prevents bus contention during power-up, reset, or fault conditions. |
Applications
| Industrial Backplane Interconnect | Legacy System Data Bridge |
|---|---|
Use Scenario: Connecting CPU and peripheral modules across a 20-slot Eurocard backplane using parallel address/data buses. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A-bus (CPU side) ↔ B-bus (peripheral side) data flow under system controller DIR/OE signals. Use Value: Eliminates need for discrete direction-controlled buffers; 48 mA drive sustains signal integrity across 15 cm routed traces with 50 pF load. | Use Scenario: Retrofitting a discontinued 8-bit microcontroller development board with updated memory-mapped I/O expansion. IC Role / Device Role / Timing Role: Translating between the MCU's multiplexed AD bus and separate address/data latches on an expansion mezzanine card. Use Value: True logic preserves address/data bit alignment; SOIC-20 footprint matches original PCB land pattern without redesign. |
| Test Equipment Bus Interface | Programmable Logic Controller (PLC) I/O Module |
Use Scenario: Isolating DUT (device under test) digital stimulus/response lines from automated test equipment controller during self-test sequences. IC Role / Device Role / Timing Role: Controlled bus barrier that enables/disables communication paths based on test mode commands via OE and DIR. Use Value: Prevents signal corruption during test transitions; 3-state isolation guarantees no leakage current between test domains. | Use Scenario: Interfacing a PLC's central processor unit to distributed I/O modules over a parallel diagnostic bus. IC Role / Device Role / Timing Role: Synchronizing status register reads and command writes between master CPU and slave I/O banks using shared bus arbitration. Use Value: DIR-controlled flow direction supports half-duplex polling protocol; 0°C–70°C rating matches industrial enclosure thermal profile. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS641ADWR | No -1 suffix; rated IOL = 24 mA (not 48 mA); otherwise identical pinout, timing, and logic. | Suitable only where bus loading is light (<4 TTL loads) or where lower drive reduces EMI concerns. | Select SN74ALS641ADWR if legacy design validation confirms 24 mA suffices and cost optimization is prioritized. |
| SN74ALS642A-1DW | Inverting logic (vs. true); identical -1 drive (48 mA), package, and timing specs. | Requires complementary logic inversion in upstream/downstream circuitry; unsuitable for bit-transparent protocols. | Choose SN74ALS642A-1DW only when system architecture mandates inverted data path or when replacing existing inverting transceivers. |
Compared with SN74ALS641ADWR, the SN74ALS641A-1DW provides double the output sink current for heavier bus loads, while SN74ALS642A-1DW trades true logic for inversion-requiring signal-level redesign but retaining identical drive and packaging.
Availability
SN74ALS641A-1DW is available at Aetrix Electronics and suitable for industrial backplane interconnect, legacy system data bridging, and programmable logic controller (PLC) I/O modules requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS641A-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 specializing in analog, embedded processing, and logic solutions, with decades of heritage in TTL and advanced logic families.
The SN74ALS641A-1DW belongs to TI's legacy ALS (Advanced Low-Power Schottky) logic product line, engineered for high-speed, low-power 5-V digital systems where reliability and backward compatibility outweigh cutting-edge integration.
FAQ
What is the maximum output sink current specification for SN74ALS641A-1DW?
The SN74ALS641A-1DW is rated for a maximum low-level output current (IOL) of 48 mA per pin when VCC is between 4.75 V and 5.25 V. This is the defining feature of the "-1" suffix variant and exceeds the 24 mA rating of the standard SN74ALS641A. The 48 mA value is validated under recommended operating conditions and directly supports driving multiple TTL inputs or terminated transmission lines without external buffering.
Does SN74ALS641A-1DW support hot-swap or live insertion?
SN74ALS641A-1DW supports controlled hot-swap via its OE (output-enable) input: asserting OE = High places all 16 I/O pins in high-impedance state, preventing bus contention during insertion. However, it lacks built-in bus-hold or power-on reset circuitry, so external sequencing of VCC, OE, and DIR is required. The device itself does not implement hot-swap protection such as slew-rate limiting or current limiting on power-up.
Is SN74ALS641A-1DW pin-compatible with SN74AS641DW?
Yes, SN74ALS641A-1DW is pin-compatible with SN74AS641DW - both use the same 20-pin SOIC (DW) package and identical pin assignments for DIR, OE, A1–A8, B1–B8, VCC, and GND. However, they differ electrically: SN74AS641DW offers faster propagation (≤22 ns) and higher drive (64 mA), but consumes significantly more supply current (ICC up to 136 mA vs. 47 mA for SN74ALS641A-1DW).
What is the function of the DIR and OE inputs on SN74ALS641A-1DW?
On SN74ALS641A-1DW, DIR (pin 1) selects data direction: DIR = Low enables B→A transfer; DIR = High enables A→B transfer. OE (pin 20) is independent - OE = Low enables the transceiver; OE = High forces all A and B pins into high-impedance state regardless of DIR. This dual-control architecture allows safe bus isolation (via OE) before changing direction (via DIR), preventing transient contention.
Can SN74ALS641A-1DW operate at 3.3 V?
No, SN74ALS641A-1DW is not specified for 3.3 V operation. Its recommended VCC range is strictly 4.5 V to 5.5 V, and absolute maximum VCC is 7 V. At 3.3 V, the ALS bipolar process fails to meet VIH/VIL thresholds, output voltage levels, and switching performance. For 3.3-V systems, consider modern alternatives like SN74LVC245A or SN74ALVC164245, which are not pin-compatible but serve similar bidirectional functions.
SN74ALS641A-1DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- 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:
- -, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74ALS641A-1DW FAQ
1.How can I place an order for SN74ALS641A-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS641A-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 SN74ALS641A-1DW reliable?
The price and inventory of SN74ALS641A-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS641A-1DW is usually 5 days.
3.What payment methods are accepted for SN74ALS641A-1DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS641A-1DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS641A-1DW?
SN74ALS641A-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS641A-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 SN74ALS641A-1DW?
For technical support, including SN74ALS641A-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS641A-1DW requirements.
6.How does Aetrix verify that SN74ALS641A-1DW is sourced from the original manufacturer or authorized distributors?
All SN74ALS641A-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 SN74ALS641A-1DW meets industry standards.
7.What is the process for return or replacement of SN74ALS641A-1DW?
All SN74ALS641A-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS641A-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 SN74ALS641A-1DW part is unused and in its original packaging.
Return procedure for SN74ALS641A-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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