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Texas Instruments SN74ALS641ANS
- Part No.:
- SN74ALS641ANS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS641ANS.pdf
- Description:
- IC TXRX INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,160
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Product details
Overview
SN74ALS641ANS from Texas Instruments is an octal bidirectional bus transceiver in a 20-pin plastic DIP (N) package, implementing true logic with direction-control (DIR) and output-enable (OE) inputs. It supports asynchronous two-way data transfer between A and B buses with 48 mA low-level output drive, 0°C to 70°C operation, and TTL-compatible voltage thresholds - used in legacy industrial backplane and memory expansion interfaces.
For engineers reviewing the SN74ALS641ANS datasheet, SN74ALS641ANS pinout, SN74ALS641ANS application, or SN74ALS641ANS equivalent, key selection criteria include its 48 mA IOL capability at VCC = 4.75–5.25 V, 3-state isolation timing (tPLH/tPHL ≤ 32 ns), 20-pin PDIP mechanical compatibility, and ALS family propagation delay vs. power trade-off.
Technical Context
The SN74ALS641ANS implements a dual-rail 3-state bus interface with independent DIR and OE control logic: DIR selects data flow direction (A→B or B→A), while OE disables all outputs to high-impedance. Its ALS bipolar transistor-transistor logic architecture delivers higher speed than standard LS but lower power than AS variants.
It operates strictly within 4.5 V to 5.5 V supply range, with VIH ≥ 2 V and VIL ≤ 0.8 V input thresholds, VOL ≤ 0.5 V at IOL = 48 mA, and ICC ≤ 47 mA (outputs low). Switching performance is specified under CL = 50 pF and RL = 680 Ω load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | Advanced Low-Power Schottky (ALS), TTL-compatible input/output levels |
| Bus Width | Octal (8-bit) bidirectional data path with A and B port symmetry |
| Output Drive | 48 mA low-level output current (IOL), enabling direct drive of multiple TTL loads |
| Propagation Delay | tPLH/tPHL ≤ 32 ns (DIR→A/B), ensuring sub-35 ns bus turnaround in synchronous systems |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V logic rails and tolerant of ±10% regulation |
| Operating Temperature | 0°C to 70°C - qualified for commercial/industrial ambient environments |
| Package Type | 20-pin plastic DIP (N), 300-mil width, through-hole mounting with 2.54 mm pitch |
Pinout & Package
SN74ALS641ANS uses a 20-pin plastic dual in-line package (PDIP-N), 300-mil body width, 2.54 mm lead pitch, and 3.94 mm maximum height per JEDEC MS-001. Pin 1 is located at the left end of the top row, identified by a beveled corner or notch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data transfer; High = A→B data transfer; TTL-compatible threshold |
| 2 (A1) | Port A Data I/O | Bi-directional terminal for bit 1 of A bus; 3-state when OE = High |
| 3–9 (A2–A8) | Port A Data I/O | Bi-directional terminals for bits 2–8 of A bus; share same DIR/OE control |
| 10 (GND) | Ground Reference | Power return for logic core and I/O drivers; must be low-impedance connection |
| 11–18 (B1–B8) | Port B Data I/O | Bi-directional terminals for bits 1–8 of B bus; electrically isolated from A when OE = High |
| 19 (VCC) | Supply Voltage | +5 V power rail; requires local 0.1 µF ceramic decoupling near pin |
| 20 (OE) | Output Enable Input | Low = active transceiver; High = all A/B pins in high-impedance state |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Bus Isolation | Independent DIR and OE control enables precise bus arbitration and prevents contention during hot-swap or multi-master operations |
| High-Drive Output Capability | 48 mA IOL allows driving up to 12 standard TTL inputs without external buffers, reducing component count on dense PCBs |
| ALS Speed-Power Optimization | 32 ns max propagation delay with 47 mA max ICC (low-output state) balances performance and thermal dissipation in legacy systems |
| TTL-Compatible Interface | VIH = 2 V / VIL = 0.8 V thresholds ensure interoperability with 74LS, 74F, and microcontroller GPIOs without level-shifting |
| Robust Absolute Ratings | 7 V max VCC and VI, −65°C to +150°C storage range support rework, burn-in, and extended field life |
Applications
| Industrial Backplane Interfacing | Legacy Memory Expansion |
|---|---|
Use Scenario: Connecting CPU local bus to peripheral expansion slots in programmable logic controllers (PLCs) and CNC motion controllers. IC Role / Device Role / Timing Role: Bidirectional data bridge isolating master and slave address/data lines during bus grant cycles. Use Value: 48 mA drive strength sustains signal integrity across 15 cm backplane traces loaded with 8+ TTL devices. | Use Scenario: Adding SRAM or EPROM modules to 8-bit microprocessor systems (e.g., Z80, 8085) with limited address/data bus fanout. IC Role / Device Role / Timing Role: Octal transceiver enabling shared data bus access between CPU and memory banks via DIR-controlled read/write direction. Use Value: Sub-35 ns propagation delay meets 4 MHz CPU bus timing budgets without wait states. |
| Test Equipment Bus Arbitration | Embedded Diagnostic Subsystem |
Use Scenario: Managing concurrent communication between FPGA-based test pattern generator and DUT interface boards in ATE systems. IC Role / Device Role / Timing Role: Directionally gated data conduit synchronized to test clock edges using DIR as phase-select signal. Use Value: OE-controlled 3-state isolation prevents bus contention during calibration or self-test sequences. | Use Scenario: Isolating diagnostic UART or JTAG debug port from main system bus during firmware updates in medical monitoring devices. IC Role / Device Role / Timing Role: Controlled bus gate that enables/disables debug interface only when system is in maintenance mode (OE asserted). Use Value: 0°C to 70°C rating ensures reliable operation inside sealed enclosures with passive thermal management. |
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 | SOIC-20 package (DW), same electrical specs, RoHS-compliant NIPDAU finish, tape-and-reel packaging | Suitable for automated SMT assembly; requires PCB redesign for surface-mount footprint and reflow profile | Select when migrating from through-hole to high-density SMT production or requiring volume tape-and-reel delivery |
| SN74ALS642ANS | Inverting logic function (vs. true logic in SN74ALS641ANS); identical pinout, timing, and drive capability | Requires complementary logic inversion in upstream/downstream circuitry to maintain functional equivalence | Select only if system-level logic already accommodates inverted data paths or simplifies control sequencing |
Compared with SN74ALS641ADWR, the SN74ALS641ANS offers drop-in replacement in legacy through-hole designs without layout changes; compared with SN74ALS642ANS, it eliminates need for external inverters in true-logic data paths, reducing component count and propagation delay.
Availability
SN74ALS641ANS is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy memory expansion, and embedded diagnostic subsystems requiring stable component supply over extended product lifecycles.
Supply support for SN74ALS641ANS 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 company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and communications portfolio coverage.
The SN74ALS641ANS belongs to TI's legacy 74ALS logic family, designed specifically for high-reliability, medium-speed bidirectional bus interfacing in commercial and industrial equipment where pin compatibility and long-term availability are critical.
FAQ
What is the maximum allowable supply voltage for SN74ALS641ANS?
The absolute maximum supply voltage (VCC) for SN74ALS641ANS is 7 V, but the recommended operating range is strictly 4.5 V to 5.5 V. Operation above 5.5 V risks permanent damage and violates TI's recommended conditions; sustained use at 7 V is prohibited. The SN74ALS641ANS is designed for nominal 5 V systems and does not support wide-input-voltage or mixed-supply operation.
Does SN74ALS641ANS support hot-swapping or live insertion into an energized bus?
SN74ALS641ANS is not rated for hot-swap operation. Its absolute maximum input voltage is 7 V, but no built-in bus-fault protection, current limiting, or power-up sequencing features are specified. Inserting SN74ALS641ANS into a live bus may cause transient contention, latch-up, or excessive ground bounce. System-level safeguards like series resistors or dedicated hot-swap controllers are required for such use cases.
How does the -1 suffix in SN74ALS641ANS relate to the IOL specification?
The "-1" designation in SN74ALS641ANS indicates the enhanced-output version: it guarantees 48 mA low-level output current (IOL) when VCC is maintained between 4.75 V and 5.25 V. Standard SN74ALS641A parts specify only 24 mA IOL. This higher drive capability is explicitly confirmed in the SDAS300 datasheet and applies to all package variants including the N-package SN74ALS641ANS.
Can SN74ALS641ANS be used interchangeably with SN74AS641N in the same PCB footprint?
No - SN74ALS641ANS and SN74AS641N are not interchangeable despite identical 20-pin PDIP packaging. SN74AS641N draws up to 136 mA ICC (vs. 47 mA for SN74ALS641ANS), has faster 7.5 ns tPHL, and requires stricter layout for noise control. Electrical differences in VIH/VIL, VOL, and power dissipation make direct substitution unsafe without full system validation.
What is the meaning of "true logic" in the context of SN74ALS641ANS functionality?
"True logic" means the SN74ALS641ANS passes data non-inverted between A and B ports: when DIR = Low, B1–B8 appear unchanged on A1–A8; when DIR = High, A1–A8 appear unchanged on B1–B8. This contrasts with the inverting SN74ALS642ANS, which complements all data bits. The SN74ALS641ANS truth table confirms identity mapping - no internal XOR or inversion logic is applied.
SN74ALS641ANS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- 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:
- -, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74ALS641ANS FAQ
1.How can I place an order for SN74ALS641ANS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS641ANS 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 SN74ALS641ANS reliable?
The price and inventory of SN74ALS641ANS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS641ANS is usually 5 days.
3.What payment methods are accepted for SN74ALS641ANS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS641ANS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS641ANS?
SN74ALS641ANS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS641ANS 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 SN74ALS641ANS?
For technical support, including SN74ALS641ANS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS641ANS requirements.
6.How does Aetrix verify that SN74ALS641ANS is sourced from the original manufacturer or authorized distributors?
All SN74ALS641ANS 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 SN74ALS641ANS meets industry standards.
7.What is the process for return or replacement of SN74ALS641ANS?
All SN74ALS641ANS units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS641ANS, 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 SN74ALS641ANS part is unused and in its original packaging.
Return procedure for SN74ALS641ANS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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