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Texas Instruments SN74ALS640B-1DWR
- Part No.:
- SN74ALS640B-1DWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640B-1DWR.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,476
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Product details
Overview
SN74ALS640B-1DWR 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, 20-pin SOIC (DW) package, 48 mA low-level output current (IOL), and operates from 0°C to 70°C. It is used in legacy industrial control backplanes and board-to-board communication interfaces requiring bus isolation.
For engineers reviewing the SN74ALS640B-1DWR datasheet, SN74ALS640B-1DWR pinout, SN74ALS640B-1DWR application, or SN74ALS640B-1DWR equivalent, key selection criteria include its -1 version's enhanced 48 mA sink capability, 3-state enable/disable timing (tPZH/tPLZ ≤ 21 ns), bidirectional direction control (DIR), and compatibility with 5 V TTL logic families in space-constrained SOIC layouts.
Technical Context
This device implements a dual-rail bidirectional bus interface using complementary TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V) and active-low 3-state control via OE. Its DIR input determines data flow direction-low enables B→A transmission, high enables A→B-while OE independently disables all outputs into high-impedance state.
The -1 suffix denotes a specific performance variant: only SN74ALS640B-1 versions support IOL = 48 mA at VCC = 4.75–5.25 V, distinguishing it from standard SN74ALS640B (IOL = 24 mA). Propagation delays (tPLH/tPHL ≤ 11 ns) and enable/disable times (tPZH/tPLZ ≤ 21 ns) are specified under CL = 50 pF, R1/R2 = 500 Ω conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures stable operation across standard 5 V TTL supply tolerances. |
| IOL (–1 version) | 48 mA - supports driving heavier capacitive loads or multiple TTL inputs without external buffers. |
| tPLH / tPHL | ≤11 ns - enables high-speed bus arbitration in real-time control systems with tight timing budgets. |
| tPZH / tPLZ | ≤21 ns - guarantees fast output disable/enable for dynamic bus sharing and hot-swap isolation. |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade embedded systems, not extended or military temperature ranges. |
| Logic Family | TTL-compatible ALS - provides lower power than standard TTL while maintaining pin-level compatibility with 74LS/74ALS systems. |
| Package | SOIC-20 (DW) - surface-mount footprint (7.5 mm × 12.8 mm) suitable for automated PCB assembly. |
Pinout & Package
SN74ALS640B-1DWR uses a 20-pin SOIC (DW) package with 1.27 mm pitch, 2.65 mm max height, and Q1 pin-1 orientation per JEDEC MS-013. Pin 1 is located at top-left corner when notch faces up.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow; determines bus traffic direction synchronously. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to A-side bus; driven or received based on DIR and OE states. |
| 10 (GND) | Ground Reference | Primary signal return path; must be low-inductance connection to minimize switching noise. |
| 11–18 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to B-side bus; functionally identical to A-port but electrically isolated. |
| 19 (OE) | Output Enable Input | Active-low control: Low = outputs enabled; High = all A/B pins enter high-impedance state for bus isolation. |
| 20 (VCC) | Power Supply | +5 V supply rail; requires local 0.1 µF ceramic decoupling capacitor near pin 20. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Architecture | Ensures signal polarity consistency across cascaded ALS devices without external inversion logic. |
| 48 mA Sink Capability (–1 version) | Enables direct drive of up to 12 standard TTL loads (IIL = –1.6 mA each) without fanout buffers. |
| 3-State Output Isolation | OE-controlled high-Z state prevents bus contention during multi-master arbitration or power sequencing. |
| 20-Pin SOIC Packaging | Reduces PCB area by ~60% vs. equivalent PDIP, supporting higher-density backplane and controller board layouts. |
| ALS Technology | Delivers 1/3 the power consumption of standard 74LS at comparable speed, extending thermal margin in sealed enclosures. |
Applications
| Industrial Backplane Interface | Legacy System Bus Expansion |
|---|---|
Use Scenario: Interfacing a microcontroller-based master module to multiple slave I/O cards over a shared 8-bit parallel bus in factory automation PLC racks. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow direction and isolating segments during configuration or fault recovery. Use Value: DIR and OE allow dynamic reconfiguration of bus topology without hardware changes; 48 mA IOL drives long traces and multiple receivers reliably. | Use Scenario: Extending address/data bus between CPU board and peripheral expansion slot in vintage test equipment or medical imaging subsystems. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled repeater enabling modular upgrades while preserving original timing budgets. Use Value: Sub-12 ns propagation delay maintains setup/hold margins across added trace length; SOIC package fits constrained expansion connector areas. |
| Board-to-Board Communication Link | TTL-Compatible Data Multiplexer |
Use Scenario: Connecting two separate PCBs carrying parallel sensor data streams in aerospace avionics chassis with EMI-sensitive analog sections. IC Role / Device Role / Timing Role: Electrically isolating buses via 3-state control during power-up sequencing or fault shutdown. Use Value: Fast tPLZ/tPHZ (≤21 ns) enables deterministic bus release within 100 ns; GND/VCC pin placement minimizes ground bounce in mixed-signal zones. | Use Scenario: Selecting between two 8-bit data sources (e.g., ADC and memory) feeding a single processing unit in embedded instrumentation. IC Role / Device Role / Timing Role: Direction-controlled multiplexer where DIR selects source and OE gates output to processor bus. Use Value: Inverting logic simplifies control logic design; ALS family compatibility avoids level translation components in all-TTL designs. |
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 with IOL = 24 mA (not 48 mA); otherwise identical pinout, timing, and electrical specs. | Suitable for lighter bus loads (<6 TTL inputs) or where lower drive strength suffices. | Select SN74ALS640BDWR only if verified load capacitance and fanout requirements do not exceed 24 mA sink capability. |
| SN74AS640N | AS-family variant: faster tPLH/tPHL (≤7 ns), higher IOL (64 mA), but higher ICC (78 mA typical) and incompatible VIH/VIL thresholds (VIH = 2 V, VIL = 0.8 V same, but AS has stricter noise margin). | Used in high-speed digital test systems requiring sub-8 ns propagation; not drop-in due to increased power and layout sensitivity. | Choose SN74AS640N only when timing budget demands <8 ns delay and power supply can support >2× ICC; verify noise immunity in target environment. |
Compared with SN74ALS640BDWR, SN74ALS640B-1DWR delivers double the output sink current for robust bus driving, while SN74AS640N trades power efficiency for raw speed-making SN74ALS640B-1DWR optimal for cost-sensitive, thermally constrained commercial systems needing reliable 48 mA drive in SOIC format.
Availability
SN74ALS640B-1DWR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus expansion, and board-to-board communication links requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS640B-1DWR 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.
The SN74ALS640B-1DWR belongs to TI's legacy 74ALS logic family, engineered for low-power, high-noise-immunity TTL-compatible digital interfacing in commercial-grade embedded systems and retrofitted industrial controllers.
FAQ
What is the maximum sink current supported by SN74ALS640B-1DWR?
The SN74ALS640B-1DWR supports a guaranteed low-level output current (IOL) of 48 mA when VCC is between 4.75 V and 5.25 V. This is a defining feature of the "–1" suffix variant and exceeds the 24 mA rating of the standard SN74ALS640B. The value is validated per TI's SDAS122A datasheet Section "Recommended Operating Conditions" and applies only under those voltage constraints.
Is SN74ALS640B-1DWR pin-compatible with SN74ALS640BDWR?
Yes, SN74ALS640B-1DWR is pin-compatible with SN74ALS640BDWR: both use identical SOIC-20 (DW) packages, share identical pin functions (DIR, OE, A1–A8, B1–B8, VCC, GND), and match in physical dimensions and solder pad layout. However, SN74ALS640B-1DWR delivers higher IOL (48 mA vs. 24 mA), making it a functional upgrade without PCB changes.
Does SN74ALS640B-1DWR support operation outside the 0°C to 70°C range?
No, SN74ALS640B-1DWR is characterized and qualified only for the commercial temperature range of 0°C to 70°C. Military-grade variants (e.g., SN54ALS640B) operate from –55°C to 125°C but use different packages (CDIP-J) and are not interchangeable with SN74ALS640B-1DWR due to packaging and qualification differences.
What logic family does SN74ALS640B-1DWR belong to, and how does it compare to 74LS?
SN74ALS640B-1DWR belongs to the Advanced Low-Power Schottky (ALS) logic family. Compared to standard 74LS, it consumes approximately one-third the power at similar speeds and offers improved noise immunity due to tighter VIH/VIL thresholds (2.0 V / 0.8 V). It maintains pin compatibility with 74LS and 74ALS devices but is not compatible with CMOS families without level shifting.
Can SN74ALS640B-1DWR be used with 3.3 V systems?
No, SN74ALS640B-1DWR is strictly a 5 V TTL-compatible device. Its absolute maximum VCC is 7 V, but recommended operation is 4.5–5.5 V. Input thresholds (VIH = 2.0 V, VIL = 0.8 V) and output levels (VOH ≥ 2.4 V, VOL ≤ 0.5 V) are defined for 5 V operation. Direct connection to 3.3 V logic requires level-shifting circuitry to prevent damage or incorrect logic interpretation.
SN74ALS640B-1DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm 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-SOIC
SN74ALS640B-1DWR FAQ
1.How can I place an order for SN74ALS640B-1DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640B-1DWR 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-1DWR reliable?
The price and inventory of SN74ALS640B-1DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640B-1DWR is usually 5 days.
3.What payment methods are accepted for SN74ALS640B-1DWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640B-1DWR transactions.
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4.How is shipping managed for SN74ALS640B-1DWR?
SN74ALS640B-1DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640B-1DWR 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-1DWR?
For technical support, including SN74ALS640B-1DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640B-1DWR requirements.
6.How does Aetrix verify that SN74ALS640B-1DWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS640B-1DWR 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-1DWR meets industry standards.
7.What is the process for return or replacement of SN74ALS640B-1DWR?
All SN74ALS640B-1DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640B-1DWR, 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-1DWR part is unused and in its original packaging.
Return procedure for SN74ALS640B-1DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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