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Texas Instruments SN74ALS640BDWRE4
- Part No.:
- SN74ALS640BDWRE4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640BDWRE4.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,066
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Product details
Overview
SN74ALS640BDWRE4 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, operating temperature range of 0°C to 70°C, and supports 12 mA low-level output current (IOL) with 2.4 V minimum VOH at –12 mA.
For engineers reviewing the SN74ALS640BDWRE4 datasheet, SN74ALS640BDWRE4 pinout, SN74ALS640BDWRE4 application, or SN74ALS640BDWRE4 equivalent, key selection criteria include direction-control (DIR) and output-enable (OE) timing behavior, 3-state isolation capability, bus loading compatibility with ALS logic families, and thermal derating for industrial board-level integration.
Technical Context
This device implements a dual-rail bidirectional bus interface using complementary control inputs: DIR selects data flow direction (A→B or B→A), while OE enables/disables all outputs into high-impedance state. Its internal architecture uses standard bipolar ALS circuitry with Schottky-clamped transistor stages to achieve fast propagation delays and low power consumption relative to earlier TTL families.
Electrical behavior is defined across VCC = 4.5–5.5 V, with guaranteed VOL ≤ 0.4 V at IOL = 12 mA and tPLH/tPHL ≤ 11 ns under CL = 50 pF load conditions. The -E4 suffix denotes TI's enhanced manufacturing flow with lead-free (NIPDAU) finish and Level-1 moisture sensitivity rating for standard reflow profiles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL/ALS supply rails without regulation overhead. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade embedded control and instrumentation applications. |
| IOL (max) | 12 mA - Supports direct drive of up to 10 standard TTL loads per output without external buffering. |
| tPLH / tPHL | ≤11 ns - Enables reliable operation in 20 MHz synchronous bus systems with margin for trace delay. |
| VOH (min) | 2.4 V at –12 mA - Maintains valid high-level logic margin when driving multiple ALS inputs. |
| VOL (max) | 0.4 V at 12 mA - Guarantees robust low-level noise immunity in electrically noisy industrial environments. |
| Package | SOIC-20 (DW) - Surface-mount footprint compatible with automated assembly and IPC-7351 land patterns. |
Pinout & Package
SN74ALS640BDWRE4 is housed in a 20-pin small-outline integrated circuit (SOIC) package with 1.27 mm pitch, 7.5 mm body width, and maximum height of 2.65 mm. Pin 1 is located at the top-left corner adjacent to the index notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data transfer; High = A→B data transfer - determines real-time bus flow polarity. |
| 2–9 (A1–A8) | Input/Output Port A | Bidirectional I/O pins connected to first data bus; internally isolated when OE = High. |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output currents; must be low-inductance connection. |
| 11–18 (B1–B8) | Input/Output Port B | Bidirectional I/O pins connected to second data bus; functionally mirrored to A-side ports. |
| 19 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter high-impedance state - enables bus sharing. |
| 20 (VCC) | Supply Voltage | +5 V nominal power rail; requires local 0.1 µF ceramic decoupling within 5 mm of this pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Architecture | Ensures signal phase consistency across bus segments when cascading multiple transceivers in series. |
| 3-State Output Isolation | Provides galvanic separation between A and B buses during OE = High, preventing contention and backfeeding. |
| ALS Family Compatibility | Matches input thresholds and output drive strength of SN74ALSxx devices, enabling seamless system-level integration. |
| Low Propagation Delay | Typical tPLH/tPHL = 7 ns allows use in high-speed address/data multiplexing without added wait states. |
| Standard SOIC Packaging | Enables drop-in replacement for legacy 20-pin DIP designs via adapter boards or layout reuse with minimal footprint change. |
Applications
| Industrial PLC Backplane Interface | Legacy Computer Memory Expansion Bus |
|---|---|
Use Scenario: Bidirectional data exchange between CPU module and I/O expansion cards in modular programmable logic controllers. IC Role / Device Role / Timing Role: Bus transceiver managing time-multiplexed address/data lines between main controller and peripheral slots. Use Value: Enables hot-swappable card insertion by isolating unpowered modules via OE control, reducing system downtime. |
Use Scenario: Interfacing 8-bit ISA-compatible memory expansion cards to older x86-based industrial PCs. IC Role / Device Role / Timing Role: Direction-controlled buffer for shared data bus between CPU and SRAM/ROM modules. Use Value: Provides clean signal integrity over 15 cm backplane traces with <11 ns skew, eliminating read/write timing violations. |
| Test Equipment Digital Pattern Generator | Automated Test Fixture Data Mux |
Use Scenario: Routing stimulus signals from pattern generator ASIC to DUT pins in boundary-scan test systems. IC Role / Device Role / Timing Role: Controlled-direction bus switch synchronizing test vector delivery with clock edges. Use Value: Achieves sub-12 ns setup/hold timing margins for 25 MHz digital test vectors, improving fault coverage accuracy. |
Use Scenario: Multiplexing sensor data streams from 8 parallel analog-to-digital converters onto a single microcontroller interface. IC Role / Device Role / Timing Role: Time-shared bidirectional data conduit managed by microcontroller GPIOs. Use Value: Reduces PCB layer count by consolidating eight independent data paths into one controlled bus segment. |
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 | Same electrical specs and logic function, but in 20-pin PDIP (N) package with through-hole mounting. | Suitable for prototyping, manual soldering, or legacy through-hole PCBs where SOIC rework is impractical. | Select when mechanical mounting method or hand-assembly requirements override surface-mount advantages. |
| SN74AS640N | Faster propagation delay (tPLH/tPHL ≤ 7 ns), higher IOL (48 mA), but increased ICC (up to 123 mA) and tighter VIH/VIL thresholds. | Better suited for high-speed bus arbitration or driving heavier capacitive loads (>100 pF), at cost of higher power and noise sensitivity. | Choose only if timing budget demands <8 ns delay and power budget permits >2× current draw versus SN74ALS640BDWRE4. |
Compared with SN74ALS640BN, SN74ALS640BDWRE4 offers superior thermal performance and smaller PCB area; compared with SN74AS640N, it trades speed for lower power and broader noise margin-making it optimal for cost-sensitive, thermally constrained commercial systems.
Availability
SN74ALS640BDWRE4 is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy computer expansion interfaces, and automated test fixture designs requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS640BDWRE4 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.
SN74ALS640BDWRE4 belongs to TI's legacy ALS logic family, engineered for reliable 5 V bus interfacing in cost-sensitive industrial control and instrumentation systems where speed-power balance matters more than extreme performance.
FAQ
What is the maximum recommended supply voltage for SN74ALS640BDWRE4?
The absolute maximum supply voltage (VCC) for SN74ALS640BDWRE4 is 7 V, but the recommended operating range is strictly 4.5 V to 5.5 V. Exceeding 5.5 V risks permanent damage and invalidates parametric guarantees; operation above 7 V may cause immediate latch-up or junction failure. Always use regulated 5 V ±5% supplies with local decoupling.
Does SN74ALS640BDWRE4 support non-inverting data transfer?
No, SN74ALS640BDWRE4 implements fixed inverting logic: data passed from A to B or B to A undergoes logical inversion. This is inherent to its ALS-family design and cannot be disabled or bypassed. For non-inverting operation, consider SN74ALS245 or SN74LS245 variants, which provide identical pinout and function without inversion.
Can SN74ALS640BDWRE4 drive standard TTL loads directly?
Yes, SN74ALS640BDWRE4 can drive up to 10 standard TTL inputs per output, based on its guaranteed IOL = 12 mA and VIH = 2.0 V minimum. Its VOH ≥ 2.4 V at –12 mA ensures sufficient margin above TTL's 2.0 V VIH threshold, and VOL ≤ 0.4 V stays well below TTL's 0.8 V VIL limit - satisfying both DC noise margin and fanout requirements.
What is the meaning of the "-E4" suffix in SN74ALS640BDWRE4?
The "-E4" suffix indicates Texas Instruments' enhanced manufacturing flow: RoHS-compliant lead-free finish (NIPDAU), moisture sensitivity level 1 (unlimited floor life at ≤30°C/60% RH), and qualification per JEDEC J-STD-020D reflow profile. It replaces older "-E" or no-suffix versions and is fully backward-compatible in form, fit, and function with SN74ALS640BDWR.
How does OE and DIR interact during simultaneous assertion in SN74ALS640BDWRE4?
When OE = Low, DIR controls data direction (A↔B); when OE = High, all A and B pins enter high-impedance regardless of DIR state. DIR has no effect during output disable - this priority logic prevents bus contention during mode transitions. The function table explicitly defines OE as the dominant control signal, verified in TI's SDAS122A datasheet Figure 1 timing waveforms.
SN74ALS640BDWRE4 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:
- Discontinued at Digi-Key
- 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
SN74ALS640BDWRE4 FAQ
1.How can I place an order for SN74ALS640BDWRE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BDWRE4 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 SN74ALS640BDWRE4 reliable?
The price and inventory of SN74ALS640BDWRE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BDWRE4 is usually 5 days.
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SN74ALS640BDWRE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BDWRE4 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 SN74ALS640BDWRE4?
For technical support, including SN74ALS640BDWRE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BDWRE4 requirements.
6.How does Aetrix verify that SN74ALS640BDWRE4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BDWRE4 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 SN74ALS640BDWRE4 meets industry standards.
7.What is the process for return or replacement of SN74ALS640BDWRE4?
All SN74ALS640BDWRE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BDWRE4, 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 SN74ALS640BDWRE4 part is unused and in its original packaging.
Return procedure for SN74ALS640BDWRE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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