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Texas Instruments SN74ALS640B-1NSR
- Part No.:
- SN74ALS640B-1NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS640B-1NSR.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,673
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Product details
Overview
SN74ALS640B-1NSR 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-1NSR datasheet, SN74ALS640B-1NSR pinout, SN74ALS640B-1NSR application, or SN74ALS640B-1NSR equivalent, key selection considerations include its -1 version's enhanced IOL rating, SOP-20 package compatibility, 0°C to 70°C commercial temperature range, and strict adherence to ALS logic family timing and voltage thresholds.
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.
Timing is characterized with CL = 50 pF and R1/R2 = 500 Ω, delivering tPLH/tPHL ≤ 11 ns and enable/disable times (tPZH/tPLZ) ≤ 24 ns under recommended conditions (VCC = 4.5–5.5 V). The -1 suffix specifically denotes increased IOL capability-48 mA vs. 24 mA in standard SN74ALS640B-without altering propagation delay or voltage thresholds.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL power rails and noise margin stability |
| IOL (–1 version) | 48 mA - enables direct drive of heavier capacitive loads or multiple TTL inputs without external buffers |
| tPLH / tPHL | ≤ 11 ns - supports high-speed bus arbitration in legacy microprocessor systems up to ~90 MHz effective toggle rate |
| VIH / VIL | 2.0 V / 0.8 V - defines unambiguous logic-high/low recognition thresholds for reliable interfacing with 5 V CMOS and TTL sources |
| VOH / VOL | ≥ 2.4 V / ≤ 0.4 V - guarantees robust noise immunity and fanout of ≥20 LS-TTL loads under full IOL conditions |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade embedded control, instrumentation, and office equipment environments |
| Package | SOP-20 (NS) - surface-mount variant with 1.27 mm pitch, 8.4 mm × 13.0 mm footprint, RoHS-compliant NIPDAU finish |
Pinout & Package
SOP-20 (NS) package: 8.4 mm × 13.0 mm body, 1.27 mm lead pitch, 2.65 mm max height, gull-wing leads, pin 1 quadrant Q1 per tape orientation standard.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction control input | High enables A→B data flow; low enables B→A; referenced to VCC/GND, TTL-compatible threshold |
| 2–9 (A1–A8) | Port A bidirectional I/O | Transmit/receive data lines tied to A bus; internally buffered with 3-state drivers |
| 10 (GND) | Ground reference | Primary signal return path; must be low-inductance connection for noise-sensitive bus operation |
| 11–18 (B1–B8) | Port B bidirectional I/O | Transmit/receive data lines tied to B bus; electrically identical to A-port pins |
| 19 (OE) | Output-enable input | Active-low control: low enables transceiver; high places all A/B pins in high-Z state for bus isolation |
| 20 (VCC) | Power supply | +5 V supply pin; requires local 0.1 µF ceramic decoupling adjacent to pin for switching noise suppression |
Key Features
| Feature | Design Value |
|---|---|
| Inverting logic architecture | Ensures predictable phase relationship between input and output signals during enabled data transfer, critical for synchronous bus handshaking |
| 48 mA low-level output drive (–1 version) | Eliminates need for external driver stages when interfacing with high-capacitance backplanes or multiple TTL loads |
| Independent DIR and OE controls | Allows dynamic bus direction reversal without disrupting isolation state-enables flexible time-multiplexed bus sharing |
| TTL-compatible voltage thresholds | Guarantees interoperability with legacy 74LS, 74ALS, and 74AS logic families without level-shifting circuitry |
| 20-pin SOP (NS) packaging | Reduces PCB area vs. DIP while maintaining mechanical robustness and reflow compatibility for automated assembly |
Applications
| Industrial Backplane Interface | Legacy Microprocessor Expansion |
|---|---|
Use Scenario: Isolating and routing address/data between CPU module and peripheral cards in modular PLC chassis. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A/B port arbitration under control of system DIR and OE signals. Use Value: Enables hot-swap-safe bus segmentation with 48 mA drive strength to overcome chassis trace capacitance up to 150 pF. | Use Scenario: Extending Z80 or 8086 data bus across multi-board computer systems with independent memory and I/O modules. IC Role / Device Role / Timing Role: Octal transceiver synchronizing data flow direction and enabling/disabling per bus cycle via CPU-generated control lines. Use Value: Meets sub-12 ns propagation delay requirement for 4 MHz CPU bus timing while supporting full 8-bit parallel transfer. |
| Memory Subsystem Buffering | Test Equipment Bus Coupling |
Use Scenario: Interfacing EPROM/RAM banks to processor bus in embedded controllers where memory access direction changes dynamically. IC Role / Device Role / Timing Role: Direction-controlled data conduit between processor and memory array, with OE used for chip-select gating. Use Value: 0.4 V VOL at 48 mA ensures valid logic-low recognition even under worst-case VCC droop and trace IR drop. | Use Scenario: Coupling GPIB or IEEE-488 bus signals to internal test instrument logic in benchtop analyzers. IC Role / Device Role / Timing Role: Level-translating and isolating bidirectional handshake lines (DAV, NRFD, NDAC) between controller and peripherals. Use Value: TTL-compatible VIH/VIL thresholds prevent false triggering during noisy lab environment operation with long cable runs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640BDWR | Standard version (24 mA IOL); SOIC-20 (DW) package; identical timing and logic function | Lacks enhanced drive strength; suitable where load capacitance < 75 pF or fanout ≤ 10 | Select SN74ALS640BDWR only if 48 mA drive is unnecessary and DW package is preferred for layout continuity |
| SN74AS640N | AS-family variant; 64 mA IOL; faster tPLH/tPHL (≤7 ns); PDIP-20 package; higher ICC (78 mA) | Better speed but higher power; incompatible with ALS-level input thresholds (VIL = 0.8 V vs. 0.7 V) | Choose SN74AS640N only when sub-8 ns propagation is mandatory and power budget allows +50% ICC increase |
Compared with SN74ALS640BDWR, SN74ALS640B-1NSR delivers double the output sink current without timing penalty; versus SN74AS640N, it trades 4 ns speed gain for 30% lower static power and guaranteed ALS-family compatibility in mixed-logic systems.
Availability
SN74ALS640B-1NSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor expansions, memory subsystem buffering, test equipment bus coupling, and embedded controller bus isolation requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS640B-1NSR 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, automotive, and consumer reach.
SN74ALS640B-1NSR belongs to TI's legacy ALS (Advanced Low-Power Schottky) logic family, engineered for high-speed, low-power bidirectional bus communication in 1980s–1990s computing and industrial control systems.
FAQ
What is the maximum output sink current supported by SN74ALS640B-1NSR?
The SN74ALS640B-1NSR supports a maximum low-level output current (IOL) of 48 mA when VCC is maintained between 4.75 V and 5.25 V. This rating is specific to the "–1" version and exceeds the 24 mA capability of the standard SN74ALS640B. The 48 mA drive enables direct interfacing with high-capacitance buses or multiple TTL loads without external buffering. Always verify voltage compliance and thermal derating in high-current continuous operation.
Does SN74ALS640B-1NSR support non-inverting data transfer?
No, SN74ALS640B-1NSR implements inverting logic: data appearing at A1–A8 appears inverted at B1–B8 (and vice versa) when the transceiver is enabled and directionally configured. This behavior is inherent to the ALS640B design and cannot be disabled or bypassed. System-level inversion must be compensated in firmware or upstream logic. The device does not offer selectable polarity or non-inverting mode.
What is the operating temperature range for SN74ALS640B-1NSR?
SN74ALS640B-1NSR is characterized for commercial operation from 0°C to 70°C ambient temperature. It is not rated for extended industrial (–40°C to 85°C) or military (–55°C to 125°C) ranges. This specification aligns with the SN74ALS640B family designation and is validated per TI's SDAS122A datasheet revision. Operation outside this range may result in parametric failure or reduced reliability.
Can SN74ALS640B-1NSR be used as a direct replacement for SN74ALS640BN?
SN74ALS640B-1NSR is functionally compatible with SN74ALS640BN but not mechanically pin-to-pin due to differing packages: NS (SOP-20) vs. N (PDIP-20). While electrical characteristics-including 48 mA IOL, timing, and logic behavior-are identical, PCB layout modification is required to accommodate the surface-mount SOP footprint, smaller pad pitch (1.27 mm vs. 2.54 mm), and absence of through-hole mounting. No schematic change is needed.
What are the absolute maximum ratings for SN74ALS640B-1NSR?
The absolute maximum ratings for SN74ALS640B-1NSR are: supply voltage (VCC) ≤ 7 V; input voltage (VI) ≤ 7 V on control pins, ≤ 5.5 V on I/O ports; operating free-air temperature = –55°C to 125°C (stress rating only); storage temperature = –65°C to 150°C. Exceeding any of these limits-even momentarily-may cause permanent damage. Functional operation is only guaranteed within the recommended conditions: VCC = 4.5–5.5 V and TA = 0°C–70°C.
SN74ALS640B-1NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74ALS640B-1NSR FAQ
1.How can I place an order for SN74ALS640B-1NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640B-1NSR 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-1NSR reliable?
The price and inventory of SN74ALS640B-1NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640B-1NSR is usually 5 days.
3.What payment methods are accepted for SN74ALS640B-1NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640B-1NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640B-1NSR?
SN74ALS640B-1NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640B-1NSR 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-1NSR?
For technical support, including SN74ALS640B-1NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640B-1NSR requirements.
6.How does Aetrix verify that SN74ALS640B-1NSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS640B-1NSR 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-1NSR meets industry standards.
7.What is the process for return or replacement of SN74ALS640B-1NSR?
All SN74ALS640B-1NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640B-1NSR, 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-1NSR part is unused and in its original packaging.
Return procedure for SN74ALS640B-1NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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