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Texas Instruments SN74ALS641A-1N
- Part No.:
- SN74ALS641A-1N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS641A-1N.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,856
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Product details
Overview
SN74ALS641A-1N from Texas Instruments is an octal bidirectional bus transceiver in a 20-pin PDIP package, implementing true (non-inverting) logic with direction-control (DIR) and output-enable (OE) inputs. It supports asynchronous two-way data flow between A and B buses, delivers 48 mA low-level output current (IOL), and operates across 0°C to 70°C for industrial bus isolation applications.
For engineers reviewing the SN74ALS641A-1N datasheet, SN74ALS641A-1N pinout, SN74ALS641A-1N application, or SN74ALS641A-1N equivalent, key selection criteria include its -1 version's enhanced 48 mA IOL rating, 5 V TTL-compatible operation, 3-state bidirectional control architecture, and PDIP-20 mechanical compatibility with legacy board layouts.
Technical Context
The SN74ALS641A-1N implements a dual-rail 3-state bidirectional buffer with independent DIR and OE control logic: DIR selects data path direction (A↔B), while OE disables all outputs to high-impedance state. Its ALS (Advanced Low-Power Schottky) process ensures propagation delays of 3–32 ns under 50 pF load conditions.
It features TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V), guaranteed VOL ≤ 0.5 V at IOL = 48 mA, and absolute maximum ratings including 7 V supply and input voltage tolerance - enabling robust interfacing with mixed-voltage bus systems without level-shifting circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Type | True (non-inverting) octal bus transceiver with 3-state outputs |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL bus rails |
| IOL (Max) | 48 mA at VCC = 4.75–5.25 V - supports driving heavy capacitive loads or multiple TTL inputs |
| Propagation Delay | 3–32 ns (tPHL/tPLH) - enables reliable timing in 20–30 MHz bus systems with 50 pF loading |
| Operating Temperature | 0°C to 70°C - qualified for commercial/industrial ambient environments |
| Package | PDIP-20 (300-mil) - through-hole mounting with 2.54 mm pitch, compatible with legacy PCB tooling |
| VOL @ IOL=48mA | ≤ 0.5 V - ensures valid low-level logic margin when sourcing full output current |
Pinout & Package
SN74ALS641A-1N uses a 20-pin plastic dual in-line package (PDIP, 300-mil width) with standard 2.54 mm lead pitch and 0.33 mm lead thickness. Pin 1 is marked by a notch or dot on the package body.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Determines data flow: DIR = L → B-to-A; DIR = H → A-to-B |
| 2 (A1) | Port A Data I/O | Bi-directional terminal for first bit of A bus; high-impedance when OE = H |
| 3–9 (A2–A8) | Port A Data I/O | Remaining seven A-bus terminals; identical electrical behavior to A1 |
| 10 (GND) | Ground Reference | Power return path for all internal logic and output drivers |
| 11–18 (B1–B8) | Port B Data I/O | Eight bi-directional B-bus terminals; functionally symmetric to A-port |
| 19 (VCC) | Positive Supply | 5 V nominal supply input; decoupling capacitor required near pin |
| 20 (OE) | Output Enable Input | Active-low control: OE = L → outputs enabled; OE = H → all outputs high-Z |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Data Flow | Single DIR pin configures eight parallel channels for A→B or B→A transfer without external routing logic |
| Enhanced Drive Strength | 48 mA IOL (−1 version) sustains valid logic levels into 50 Ω transmission lines or >10 TTL loads |
| 3-State Isolation | Simultaneous high-impedance disable of all 16 I/Os via OE eliminates bus contention during arbitration or power-down |
| TTL-Compatible Interface | VIH/VIL thresholds and VOL/VOH specs ensure direct connection to standard 5 V TTL and CMOS logic families |
| ALS Process Technology | Combines Schottky-clamped bipolar transistors with low-power design for speed/power balance (ICC ≤ 47 mA max) |
Applications
| Industrial Backplane Bus | Legacy System Upgrade Interface |
|---|---|
Use Scenario: Interfacing microcontroller peripherals to a shared 8-bit ISA-style backplane with multiple slot devices. IC Role / Device Role / Timing Role: Bidirectional bus transceiver isolating CPU address/data bus from peripheral slots while supporting hot-insertion sequencing via OE control. Use Value: Enables deterministic bus arbitration using DIR and OE signals, with 48 mA drive ensuring signal integrity over 15 cm backplane traces. | Use Scenario: Replacing obsolete 74LS245 in aging test equipment requiring extended temperature range support. IC Role / Device Role / Timing Role: Drop-in functional replacement providing identical pinout and true logic, with improved IOL and thermal margin. Use Value: Eliminates need for redesign or requalification by maintaining identical timing (tPLH/tPHL ≤ 32 ns) and DC specs within legacy footprint. |
| Microcontroller Expansion Bridge | Multi-Processor Memory Sharing |
Use Scenario: Connecting an 8-bit MCU's data bus to external SRAM or I/O expanders operating at different timing domains. IC Role / Device Role / Timing Role: Synchronizing asynchronous memory access cycles via DIR-controlled direction switching and OE-gated bus release. Use Value: Prevents bus contention during read/write transitions, leveraging 3-state isolation to decouple timing-critical paths. | Use Scenario: Enabling shared memory access between two 8-bit processors in a redundant control system. IC Role / Device Role / Timing Role: Arbitrating bidirectional data movement between processor A and processor B memory spaces using DIR as master/slave selector. Use Value: Supports lock-step operation with <32 ns propagation delay, ensuring coherency in sub-100 ns memory cycle windows. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS641AN | Standard version with 24 mA IOL (vs. 48 mA in −1N); otherwise identical pinout, timing, and logic | Lower drive capability limits use in high-capacitance or multi-load bus segments | Select SN74ALS641AN only if load capacitance < 30 pF and fanout ≤ 6 TTL units |
| SN74AS641N | Faster propagation (1–22 ns vs. 3–32 ns) but higher ICC (up to 136 mA) and 64 mA IOL; same PDIP-20 package | Higher speed suits 40+ MHz bus systems but requires more aggressive power delivery and thermal management | Choose SN74AS641N when timing budget demands <20 ns delay and power/thermal constraints allow |
Compared with SN74ALS641AN, the SN74ALS641A-1N provides double the output drive for noise-immune bus operation; versus SN74AS641N, it trades 10–15 ns speed reduction for 60% lower quiescent current and better thermal stability in dense layouts.
Availability
SN74ALS641A-1N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system upgrades, microcontroller expansion bridges, and multi-processor memory sharing requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ALS641A-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 company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and communications portfolio coverage.
The SN74ALS641A-1N belongs to TI's legacy 74ALS logic family, designed specifically for high-reliability, medium-speed bidirectional bus interfacing in commercial and industrial systems where power efficiency and noise immunity are prioritized over maximum frequency.
FAQ
What is the maximum output current capability of the SN74ALS641A-1N?
The SN74ALS641A-1N supports up to 48 mA low-level output current (IOL) when VCC is between 4.75 V and 5.25 V - a key enhancement over the standard SN74ALS641AN (24 mA). This rating is validated per TI's SDAS300 datasheet and enables reliable driving of heavy capacitive loads or multiple TTL inputs without signal degradation. The SN74ALS641A-1N maintains this performance across its full 0°C to 70°C operating range.
Is the SN74ALS641A-1N pin-compatible with other 74-series transceivers?
Yes, the SN74ALS641A-1N shares the same 20-pin PDIP footprint and pin assignments as SN74ALS641AN, SN74ALS642A-1N, and SN74AS641N - including identical DIR, OE, A1–A8, B1–B8, VCC, and GND locations. However, SN74ALS642A-1N implements inverting logic, so functional substitution requires logic inversion in the system design. The SN74ALS641A-1N retains true (non-inverting) behavior matching the original 74LS245 interface.
Does the SN74ALS641A-1N require external pull-up resistors on its I/O pins?
No, the SN74ALS641A-1N does not require external pull-up resistors on A or B port pins because it features active push-pull outputs in both high and low states. Its 3-state outputs enter high-impedance mode only when OE is high; otherwise, they actively drive logic-high or logic-low levels. Pull-ups would conflict with the device's designed output structure and risk excessive current draw or logic contention. The SN74ALS641A-1N operates correctly with direct connection to TTL/CMOS loads.
What is the recommended decoupling strategy for the SN74ALS641A-1N?
TI recommends placing a 0.1 µF ceramic capacitor between VCC (pin 19) and GND (pin 10) as close as possible to the SN74ALS641A-1N package - ideally within 5 mm. For systems with multiple transceivers or high-frequency switching, add a bulk 4.7 µF–10 µF electrolytic capacitor near the power entry point. This decoupling prevents VCC droop during simultaneous 48 mA output transitions and suppresses noise coupling into adjacent logic. The SN74ALS641A-1N's ALS process benefits from low-inductance local bypassing to maintain timing stability.
Can the SN74ALS641A-1N operate reliably at 4.5 V supply voltage?
Yes, the SN74ALS641A-1N is fully specified down to 4.5 V VCC per its recommended operating conditions. At 4.5 V, it guarantees VOL ≤ 0.5 V at IOL = 48 mA, VIH ≥ 2 V, and tPLH/tPHL ≤ 32 ns with 50 pF load - meeting all key timing and DC parameters. This makes the SN74ALS641A-1N suitable for systems with marginal 5 V rails or brown-out conditions where supply may dip to 4.5 V without functional failure.
SN74ALS641A-1N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- 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:
- -, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS641A-1N FAQ
1.How can I place an order for SN74ALS641A-1N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS641A-1N 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-1N reliable?
The price and inventory of SN74ALS641A-1N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS641A-1N is usually 5 days.
3.What payment methods are accepted for SN74ALS641A-1N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS641A-1N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS641A-1N?
SN74ALS641A-1N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS641A-1N 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-1N?
For technical support, including SN74ALS641A-1N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS641A-1N requirements.
6.How does Aetrix verify that SN74ALS641A-1N is sourced from the original manufacturer or authorized distributors?
All SN74ALS641A-1N 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-1N meets industry standards.
7.What is the process for return or replacement of SN74ALS641A-1N?
All SN74ALS641A-1N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS641A-1N, 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-1N part is unused and in its original packaging.
Return procedure for SN74ALS641A-1N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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