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Texas Instruments SN74ALS640B-1N3
- Part No.:
- SN74ALS640B-1N3
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS640B-1N3.pdf
- Description:
- IC TXRX INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,320
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Product details
Overview
SN74ALS640B-1N3 from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-compatible systems. It features inverting logic, direction control (DIR), output-enable (OE), and supports 48 mA low-level output current at VCC = 4.75–5.25 V. Used in legacy industrial backplanes and memory expansion interfaces.
For engineers reviewing the SN74ALS640B-1N3 datasheet, SN74ALS640B-1N3 pinout, SN74ALS640B-1N3 application, or SN74ALS640B-1N3 equivalent, this page delivers verified electrical specs, package mapping to PDIP-20, functional timing behavior, and direct alternatives for bus isolation and level-shifting upgrades in 5-V digital systems.
Technical Context
This device implements a dual-rail bidirectional bus interface using active-low 3-state control: OE disables all outputs to high-impedance, while DIR selects A→B (high) or B→A (low) data flow. Its inverting logic architecture means input transitions produce inverted output transitions on enabled paths.
It operates strictly within 4.5–5.5 V supply range and is characterized for 0°C to 70°C ambient. The "-1" suffix denotes enhanced IOL capability (48 mA vs. standard 24 mA), confirmed only under tight VCC regulation (4.75–5.25 V), with no change to propagation delay (tPLH/tPHL ≤ 11 ns) or enable/disable timing (tPZH/tPLZ ≤ 24 ns).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Must be regulated; -1 version requires 4.75–5.25 V for full 48 mA IOL rating. |
| IOL (max) | 48 mA - Enables direct drive of multiple TTL loads or termination-resistor networks without external buffers. |
| tPLH / tPHL | ≤ 11 ns - Supports >45 MHz bus toggle rates in point-to-point configurations with CL = 50 pF. |
| VOH / VOL | ≥ 2.4 V / ≤ 0.4 V - Guarantees TTL-compatible logic thresholds across temperature and load. |
| Operating Temp | 0°C to 70°C - Qualified for commercial-grade embedded control and instrumentation applications. |
| Package | PDIP-20 (N) - Through-hole mounting; 300-mil width; compatible with standard DIP sockets and wave-solder processes. |
| Logic Type | Inverting - Output polarity is inverted relative to input on enabled data paths; affects bus arbitration timing. |
Pinout & Package
SN74ALS640B-1N3 uses a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard DIP pin spacing (2.54 mm). Pin 1 is marked by a notch or dot at the top-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High enables A→B data flow; low enables B→A; referenced to GND, TTL-compatible thresholds. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines tied to A bus; internally connected to transceiver core via controlled impedance paths. |
| 10 (GND) | Ground Reference | Primary signal return; must be low-inductance connection to minimize ground bounce during 48 mA switching. |
| 11–18 (B1–B8) | Port B I/O Terminals | Bidirectional data lines tied to B bus; electrically isolated from A when OE is high. |
| 19 (OE) | Output Enable Input | Active-low; drives all A/B outputs to high-impedance when high; critical for bus arbitration and hot-swap isolation. |
| 20 (VCC) | Power Supply | +5 V supply; requires local 0.1 µF ceramic decoupling adjacent to pin to suppress switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting bidirectional logic | Ensures deterministic phase relationship between control signals and data edges-critical for synchronous bus handshaking. |
| 48 mA sink capability (-1 version) | Eliminates need for external bus drivers in high-fanout backplane designs, reducing component count and layout area. |
| 3-state output isolation | Provides galvanic separation between A and B buses when OE is asserted, preventing contention and signal corruption. |
| 11 ns max propagation delay | Enables reliable operation in 20-MHz clock domains with margin for trace skew and setup/hold timing. |
| TTL-compatible voltage thresholds | Guarantees interoperability with legacy 74LS/74ALS logic families without level translation circuitry. |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
Use Scenario: Isolating CPU address/data bus from peripheral card slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B (CPU→card) and B→A (card→CPU) transfers under DIR/OE control. Use Value: 48 mA drive strength sustains signal integrity across 15 cm backplane traces loaded with 10+ TTL inputs. |
Use Scenario: Extending 8-bit data bus between Z80 CPU and SRAM/ROM modules on retro-computing motherboards. IC Role / Device Role / Timing Role: Direction-controlled data conduit enabling shared memory access between processor and storage banks. Use Value: Inverting logic aligns with Z80's RD/WR timing protocol; 11 ns delay preserves 4 MHz bus cycle timing margins. |
| Test Equipment Bus Arbitration | Industrial I/O Module Isolation |
Use Scenario: Enabling multi-instrument communication over GPIB-like parallel control bus in automated test systems. IC Role / Device Role / Timing Role: 3-state-enabled bus transceiver allowing one instrument to drive while others tri-state their outputs. Use Value: OE-controlled isolation prevents bus contention during instrument switching; meets IEEE 488.1 DC loading limits. |
Use Scenario: Interfacing microcontroller GPIOs to 24 V industrial sensors/actuators via opto-isolated 5 V logic side. IC Role / Device Role / Timing Role: Level-shifting buffer translating between MCU I/O and isolated bus transceivers in PLC I/O racks. Use Value: TTL-compatible VIH/VIL ensures robust noise immunity in electrically noisy factory environments (≥400 mV noise margin). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640BN | No "-1" suffix; rated for 24 mA IOL (not 48 mA); otherwise identical pinout, timing, and logic function. | Suitable where fanout ≤ 8 TTL loads; insufficient for high-current backplane termination or long-trace driving. | Select SN74ALS640BN only if legacy design validation confirms 24 mA suffices and VCC regulation is looser than ±2.5%. |
| SN74AS640N | Faster (tPLH/tPHL ≤ 7 ns), higher IOL (64 mA), but increased ICC (78 mA active vs. 55 mA for ALS); non-inverting logic. | Better for high-speed timing-critical paths; incompatible with existing inverting-control firmware or timing diagrams. | Choose SN74AS640N only when upgrading for speed and drive strength, and redesigning DIR logic polarity and timing margins. |
Compared with SN74ALS640BN and SN74AS640N, SN74ALS640B-1N3 uniquely balances enhanced 48 mA drive with proven ALS power efficiency and inverting compatibility-making it the optimal drop-in upgrade for aging 74ALS-based systems requiring higher bus loading capacity without logic inversion changes.
Availability
SN74ALS640B-1N3 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion, test equipment bus arbitration, and industrial I/O module isolation requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ALS640B-1N3 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 for industrial, automotive, and communications markets.
SN74ALS640B-1N3 belongs to TI's 74ALS advanced low-power Schottky logic family, engineered for reliable 5-V TTL interoperability with reduced power consumption versus standard LS-targeting cost-sensitive, thermally constrained industrial control systems.
FAQ
What is the maximum output current rating for SN74ALS640B-1N3?
The SN74ALS640B-1N3 is rated for 48 mA low-level output current (IOL) when VCC is maintained between 4.75 V and 5.25 V. This is double the 24 mA rating of the standard SN74ALS640BN. Exceeding the voltage window invalidates the 48 mA guarantee per TI's SDAS122A specification.
Is SN74ALS640B-1N3 pin-compatible with SN74ALS640BN?
Yes, SN74ALS640B-1N3 is fully pin-compatible with SN74ALS640BN-same PDIP-20 package, identical pinout, and identical logic function. The only difference is the enhanced IOL rating; all control timing, voltage thresholds, and thermal specs remain aligned.
Does SN74ALS640B-1N3 support non-inverting data transfer?
No. SN74ALS640B-1N3 implements inverting logic: data appearing at A1 appears inverted at B1 when DIR = H and OE = L. This is inherent to its internal gate structure and cannot be disabled. Non-inverting behavior requires SN74AS640N or redesign with external inverters.
What is the operating temperature range for SN74ALS640B-1N3?
SN74ALS640B-1N3 is characterized for commercial operation from 0°C to 70°C ambient. It is not rated for extended temperature ranges; for –55°C to 125°C operation, the military-grade SN54ALS640BJ (CDIP) must be used instead.
Can SN74ALS640B-1N3 be used with 3.3 V logic systems?
No. SN74ALS640B-1N3 requires a 4.5–5.5 V supply and has TTL input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). Direct connection to 3.3 V systems risks undriven inputs and marginal noise immunity. Level-shifting circuitry or a 3.3 V–compatible transceiver like SN74LVC8T245 is required.
SN74ALS640B-1N3 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, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 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
SN74ALS640B-1N3 FAQ
1.How can I place an order for SN74ALS640B-1N3 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640B-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 SN74ALS640B-1N3 reliable?
The price and inventory of SN74ALS640B-1N3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640B-1N3 is usually 5 days.
3.What payment methods are accepted for SN74ALS640B-1N3?
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SN74ALS640B-1N3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640B-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 SN74ALS640B-1N3?
For technical support, including SN74ALS640B-1N3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640B-1N3 requirements.
6.How does Aetrix verify that SN74ALS640B-1N3 is sourced from the original manufacturer or authorized distributors?
All SN74ALS640B-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 SN74ALS640B-1N3 meets industry standards.
7.What is the process for return or replacement of SN74ALS640B-1N3?
All SN74ALS640B-1N3 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640B-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 SN74ALS640B-1N3 part is unused and in its original packaging.
Return procedure for SN74ALS640B-1N3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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