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Texas Instruments SN74ALS640BNSR
- Part No.:
- SN74ALS640BNSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS640BNSR.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,132
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Product details
Overview
SN74ALS640BNSR 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 operates over 0°C to 70°C with 5 V supply. Used in legacy industrial backplanes and memory expansion interfaces.
For engineers reviewing the SN74ALS640BNSR datasheet, SN74ALS640BNSR pinout, SN74ALS640BNSR application, or SN74ALS640BNSR equivalent, key selection factors include its 20-pin SOP (NS) package, 12 mA low-level output drive, 11 ns max propagation delay, 3-state isolation timing, and compatibility with ALS logic families in space-constrained board designs.
Technical Context
This device implements a dual-rail bidirectional bus interface using active-low DIR and OE controls. Its internal architecture supports simultaneous A→B or B→A data flow based on DIR state, while OE independently disables all outputs into high-impedance mode - enabling bus sharing without contention.
Electrical behavior follows standard ALS TTL thresholds: VIH = 2 V, VIL = 0.8 V, VOH ≥ 2.4 V at –12 mA, VOL ≤ 0.4 V at 12 mA. Switching performance is specified under CL = 50 pF, R1/R2 = 500 Ω, with tPLH/tPHL ≤ 11 ns and enable/disable times (tPZH/tPLZ) ≤ 24 ns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS TTL - ensures compatibility with legacy 74ALS systems and predictable noise margins |
| Supply Voltage | 4.5 V to 5.5 V - requires stable 5 V rail; not 3.3 V compatible |
| Operating Temperature | 0°C to 70°C - commercial-grade rating; excludes extended/military ranges |
| Output Drive | IOL = 12 mA / IOH = –12 mA - sufficient for driving 10–15 TTL loads per line |
| Propagation Delay | tPLH/tPHL ≤ 11 ns - enables reliable operation up to ~45 MHz bus toggle rates |
| Package | SOP-20 (NS) - surface-mount, 0.300" width, 1.27 mm pitch, RoHS-compliant NIPDAU finish |
| 3-State Enable Time | tPZH ≤ 10 ns - fast bus release critical for time-multiplexed shared-bus protocols |
Pinout & Package
SOP-20 (NS) package: 12.6 mm × 7.5 mm body, 2.65 mm max height, gull-wing leads, pin 1 marked by beveled corner. Lead finish: NIPDAU, MSL Level-1, reflow peak 260°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: LOW enables B→A transfer; HIGH enables A→B transfer |
| 2–9 | A1–A8 | Input/output port A - bidirectional I/O pins tied to local bus segment |
| 10 | GND | Ground reference - must be low-impedance connection to minimize switching noise |
| 11–18 | B1–B8 | Input/output port B - bidirectional I/O pins tied to remote bus segment |
| 19 | OE | Output-enable input: LOW activates transceiver; HIGH forces all A/B pins to high-Z |
| 20 | VCC | Positive supply - bypass with 0.1 µF ceramic capacitor near pin for noise suppression |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Architecture | Ensures signal polarity consistency across bus segments without external inverters |
| Independent DIR and OE Controls | Allows dynamic bus direction switching and selective isolation without affecting other channels |
| ALS-Compatible Input Thresholds | VIH = 2 V / VIL = 0.8 V - matches legacy 74ALS logic levels for seamless integration |
| Low Propagation Skew | Max tPLH–tPHL difference < 3 ns - maintains data integrity across all 8 lines in parallel transfers |
| High Noise Immunity | VNK ≥ 0.4 V (typical) - suppresses false triggering from EMI in industrial environments |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
Use Scenario: Interfacing microcontroller local bus to multi-slot ISA-style backplane with daisy-chained peripherals. IC Role / Device Role / Timing Role: Bidirectional bus buffer managing address/data flow between CPU and peripheral cards; DIR toggled per transaction phase. Use Value: Enables clean separation of A and B bus domains while maintaining ALS-level timing compliance and noise rejection. | Use Scenario: Adding SRAM or EPROM modules to vintage 8-bit embedded controllers (e.g., Z80, 8085) with limited address/data bus drive capability. IC Role / Device Role / Timing Role: Octal transceiver isolating main CPU bus from memory module bus during read/write cycles; OE synchronized to memory enable signals. Use Value: Provides required 12 mA drive per line and sub-12 ns delay to meet strict memory access timing windows. |
| Test Equipment Bus Arbitration | Programmable Logic Interface |
Use Scenario: Sharing GPIB or IEEE-488 control lines among multiple instrument controllers in automated test racks. IC Role / Device Role / Timing Role: Direction-controlled bus coupler allowing master/slave role reversal; OE used for hot-swap isolation during reconfiguration. Use Value: Prevents bus contention during dynamic topology changes while supporting TTL-level signaling integrity. | Use Scenario: Connecting FPGA I/O banks to external TTL logic subsystems requiring level-shifted, direction-aware data paths. IC Role / Device Role / Timing Role: Protocol-transparent bridge between programmable logic and fixed-function TTL peripherals; DIR driven by FPGA state machine. Use Value: Eliminates need for discrete direction logic and pull-up networks, reducing component count and layout complexity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245N | Non-inverting logic; identical ALS specs, same 20-pin PDIP package but different pinout | Requires PCB redesign due to DIR/OE pin relocation and A/B port ordering change | Select only if non-inverting signal path is required and layout revision is feasible |
| SN74AS640N | Faster AS-family: tPLH/tPHL ≤ 7 ns, IOL = 48 mA, higher ICC (78 mA vs 55 mA) | Higher power consumption and cost; suitable only where speed >11 ns is mandatory | Prefer SN74ALS640BNSR for power-sensitive or cost-driven legacy upgrades |
Compared with SN74ALS245N and SN74AS640N, the SN74ALS640BNSR offers optimal balance of ALS compatibility, SOP packaging, moderate speed, and low static current - making it the preferred choice for drop-in replacement in space-constrained, thermally managed commercial systems.
Availability
SN74ALS640BNSR is available at Aetrix Electronics and suitable for industrial backplanes, legacy memory expansion, test equipment bus arbitration, and programmable logic interfaces requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS640BNSR 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 and automotive reach.
The SN74ALS640BNSR belongs to TI's legacy 74ALS logic family, engineered for robustness and interoperability in commercial-grade digital systems requiring TTL-compatible voltage levels and timing.
FAQ
What is the maximum clock frequency supported by SN74ALS640BNSR?
The SN74ALS640BNSR does not operate on a clock; it is an asynchronous transceiver. Its usable data rate depends on propagation delay and system setup/hold timing. With tPLH/tPHL ≤ 11 ns and tPZH/tPLZ ≤ 24 ns, it supports reliable bus toggle rates up to approximately 45 MHz in well-designed layouts with matched trace lengths and proper termination.
Is SN74ALS640BNSR pin-compatible with SN74ALS245N?
No, SN74ALS640BNSR is not pin-compatible with SN74ALS245N. Although both are 20-pin octal transceivers, their pinouts differ significantly: DIR and OE positions are swapped, and A/B port assignments are reordered. Direct substitution requires PCB modification and signal routing changes.
Does SN74ALS640BNSR support 3.3 V operation?
No, SN74ALS640BNSR is rated for 4.5 V to 5.5 V supply only. It is not 3.3 V tolerant - applying 3.3 V to VCC will result in undefined logic thresholds and insufficient output drive. For 3.3 V systems, consider modern alternatives like SN74LVC245A with appropriate level-shifting.
What is the thermal resistance (θJA) of the SN74ALS640BNSR SOP-20 package?
The official datasheet does not specify θJA for SN74ALS640BNSR in SOP-20 (NS) package. Based on TI's generic NS package characterization and JEDEC standards, typical θJA is ~120°C/W on 1-inch² 2-layer board with 2 oz copper. Actual value depends heavily on PCB layout, copper area, and airflow.
Can SN74ALS640BNSR be used in place of SN74ALS640BN?
Yes, SN74ALS640BNSR is a direct functional replacement for SN74ALS640BN, differing only in package: NS (SOP-20) vs N (PDIP-20). Electrical specifications, timing, and logic behavior are identical. Migration requires adapting footprint and reflow profile but no schematic or firmware changes.
SN74ALS640BNSR 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
SN74ALS640BNSR FAQ
1.How can I place an order for SN74ALS640BNSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BNSR 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 SN74ALS640BNSR reliable?
The price and inventory of SN74ALS640BNSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BNSR is usually 5 days.
3.What payment methods are accepted for SN74ALS640BNSR?
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640BNSR?
SN74ALS640BNSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BNSR 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 SN74ALS640BNSR?
For technical support, including SN74ALS640BNSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BNSR requirements.
6.How does Aetrix verify that SN74ALS640BNSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BNSR 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 SN74ALS640BNSR meets industry standards.
7.What is the process for return or replacement of SN74ALS640BNSR?
All SN74ALS640BNSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BNSR, 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 SN74ALS640BNSR part is unused and in its original packaging.
Return procedure for SN74ALS640BNSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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