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Texas Instruments SN74ALS540NSR
- Part No.:
- SN74ALS540NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS540NSR.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,342
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Product details
Overview
SN74ALS540NSR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus interface and memory address register buffering in TTL-compatible digital systems. It features dual output-enable inputs (OE1/OE2), pnp input structure to reduce DC loading, data flowthrough pinout (inputs and outputs on opposite sides), and supports 12 mA low-level output current at VCC = 4.5 V.
For engineers reviewing the SN74ALS540NSR datasheet, SN74ALS540NSR pinout, SN74ALS540NSR application, or SN74ALS540NSR equivalent, this device is selected for high-density PCB layout optimization, legacy TTL bus driving, and industrial control backplane interfacing where inverted logic and 3-state control are required.
Technical Context
The SN74ALS540NSR implements a dual-NOR 3-state control gate: either OE1 or OE2 high forces all eight Y outputs into high-impedance state. Its pnp input stage lowers input current draw versus standard TTL, improving fan-out capability in loaded bus environments.
It belongs to the ALS (Advanced Low-Power Schottky) family, offering improved speed-power trade-off over standard LS logic - propagation delays as low as 2 ns (tPHL) and 4 ns (tPLH) at CL = 50 pF, with guaranteed operation across 0°C to 70°C ambient temperature range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting octal buffer with 3-state outputs - provides true signal inversion and bus isolation capability. |
| VCC Operating Range | 4.5 V to 5.5 V - compatible with standard 5 V TTL supply rails and tolerant of nominal ±10% variation. |
| IOL (max) | 12 mA at VCC = 4.5 V - sufficient to drive standard TTL loads and multiple LS inputs without external buffering. |
| tPLH / tPHL | 4 ns / 2 ns (max) - enables reliable operation in 25 MHz–30 MHz address/data bus timing windows. |
| Input Structure | pnp-based inputs - reduces DC input current to ≤ –0.2 mA (IIL), minimizing loading on upstream drivers. |
| Package | 20-pin SOP (NS) - surface-mount package with 0.65 mm lead pitch, optimized for automated assembly and space-constrained layouts. |
| Thermal Impedance (θJA) | 60°C/W - defines maximum power dissipation limit (~330 mW at ΔT = 20°C rise) under standard JEDEC 1s2p board conditions. |
Pinout & Package
SN74ALS540NSR is housed in a 20-pin small-outline package (SOP-NS) with 0.65 mm lead pitch, 7.5 mm × 5.6 mm body size, and 2.0 mm max height per TI DB0020A outline. Pin 1 is located at top-left corner with index area marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2 | OE1, OE2 | Active-low 3-state enable inputs - NOR logic: either high disables all outputs (high-Z); both low enables inverted output drive. |
| 3–10 | A1–A8 | True logic inputs - drive internal inverting buffers; pnp input structure minimizes DC loading on source. |
| 11 | GND | Ground reference - must be low-impedance connection to minimize noise coupling and ensure stable output thresholds. |
| 12–19 | Y1–Y8 | Inverted 3-state outputs - Yn = NOT(An) when enabled; high-impedance when OE1 or OE2 = high. |
| 20 | VCC | Positive supply - decoupling capacitor (0.1 µF ceramic) required within 10 mm of pin for transient current stability. |
Key Features
| Feature | Design Value |
|---|---|
| Data flowthrough pinout | Inputs (A1–A8, OE1, OE2) on left side; outputs (Y1–Y8) on right side - eliminates layer crossings and simplifies 2-layer PCB routing. |
| Dual 3-state enable logic | OE1 and OE2 form a 2-input NOR gate - allows flexible bus arbitration using either single or complementary enable signals. |
| pnp input structure | Reduces IIL to –0.2 mA max - increases effective fan-out to ≥20 LS-TTL loads without compromising drive strength. |
| ALS process technology | Combines Schottky clamping with low-power design - achieves 2 ns propagation delay while limiting ICC to 19 mA max (all outputs low). |
| Industrial temperature range | 0°C to 70°C operation - qualified for use in commercial and industrial embedded systems with passive cooling. |
Applications
| Memory Address Buffering | Parallel Bus Interface |
|---|---|
|
Use Scenario: Driving 16-bit address lines from a microprocessor to multiple memory ICs on a shared bus. IC Role / Device Role / Timing Role: Inverting buffer with 3-state control isolates address bus during DMA cycles or peripheral access. Use Value: Prevents bus contention and ensures clean address transitions with tPHL ≤ 2 ns, supporting 25+ MHz CPU clock domains. |
Use Scenario: Interfacing a microcontroller's parallel I/O port to an LCD controller or printer interface. IC Role / Device Role / Timing Role: Level-shifting and bus-driving buffer with enable-controlled directionality (via OE pins). Use Value: Enables bidirectional data flow control without external transceivers; pnp inputs reduce load on MCU GPIOs. |
| Legacy System Backplane | Industrial Control I/O Expansion |
|
Use Scenario: Replacing obsolete 74LS240 in retro-computing or test equipment backplanes. IC Role / Device Role / Timing Role: Pin-compatible drop-in upgrade delivering faster propagation and lower power than LS equivalents. Use Value: Maintains functional compatibility while reducing system power by ~30% and improving timing margin by 3–5 ns. |
Use Scenario: Isolating PLC I/O modules from central controller bus to prevent fault propagation. IC Role / Device Role / Timing Role: Fault-tolerant bus driver with independent OE control per module group. Use Value: Enables hot-swap capability via controlled 3-state entry/exit; thermal rating (60°C/W) supports convection-cooled enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS540N | Same logic function and electrical specs, but in 20-pin PDIP (N) package - through-hole, 2.54 mm pitch, higher θJA (69°C/W). | Preferred for prototyping, manual rework, or legacy through-hole assemblies; not suitable for high-density SMT production. | Select SN74ALS540N only when hand-soldering or socket-based testing is required; SN74ALS540NSR is optimal for volume SMT manufacturing. |
| SN74ALS540DWR | Identical functionality in SOIC-DW package (10.8 mm × 7.6 mm, 1.27 mm pitch); slightly higher thermal impedance (58°C/W) than NS package. | Used where board real estate allows larger footprint and legacy SOIC tooling is in place; DW has longer lead form for wave solder compatibility. | Choose SN74ALS540DWR if existing assembly lines are calibrated for SOIC-DW; otherwise SN74ALS540NSR offers superior density and modern reflow compatibility. |
Compared with SN74ALS540N and SN74ALS540DWR, SN74ALS540NSR delivers identical logic performance in a smaller, finer-pitch SOP package optimized for automated placement and high-density routing - making it the preferred choice for new industrial and embedded designs requiring space efficiency and RoHS compliance.
Availability
SN74ALS540NSR is available at Aetrix Electronics and suitable for memory address buffering, parallel bus interface, legacy system backplane upgrades, and industrial control I/O expansion requiring stable component supply and long-term lifecycle support.
Supply support for SN74ALS540NSR 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.
SN74ALS540NSR belongs to the ALS logic family - engineered for high-speed, low-power TTL-compatible interfacing in industrial control, computing, and instrumentation systems where reliability and backward compatibility are critical.
FAQ
What is the logic function of SN74ALS540NSR?
SN74ALS540NSR is an octal inverting buffer with 3-state outputs: each Yn output equals NOT(An) when both OE1 and OE2 are low; all outputs enter high-impedance state if either OE1 or OE2 is high. This behavior is confirmed in the logic diagram and truth table of the SDAS025D datasheet, and applies identically to the SN74ALS540NSR variant.
Does SN74ALS540NSR support 3.3 V operation?
No. SN74ALS540NSR is an ALS-family device specified only for 4.5 V to 5.5 V VCC operation. It lacks 3.3 V input threshold compatibility and will not meet AC/DC specifications below 4.5 V. For 3.3 V systems, consider TI's LVC or AHC families instead of SN74ALS540NSR.
What is the maximum output current capability of SN74ALS540NSR?
SN74ALS540NSR supports up to 12 mA low-level output current (IOL) at VCC = 4.5 V, as specified in the "Recommended Operating Conditions" table. The -1 version (e.g., SN74ALS540-1NSR) supports 48 mA, but SN74ALS540NSR itself is rated for 12 mA - verified in the electrical characteristics section of SDAS025D.
Is SN74ALS540NSR pin-compatible with SN74LS240?
Yes. SN74ALS540NSR shares identical pinout, logic function (inverting octal buffer with dual OE), and package footprint (20-pin SOP-NS matches LS240's SOIC-20 mechanical outline), enabling direct replacement in most LS240 designs - provided timing and loading requirements remain within ALS specifications.
What does the "NS" in SN74ALS540NSR indicate?
The "NS" denotes Texas Instruments' Small Outline Package (SOP) with 0.65 mm lead pitch, per package drawing DB0020A. The "R" suffix indicates tape-and-reel packaging (2000 units per reel), and "NSR" collectively identifies the full orderable part number SN74ALS540NSR - confirmed in TI's Package Option Addendum and ordering information tables.
SN74ALS540NSR 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:
- Buffer, 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
SN74ALS540NSR FAQ
1.How can I place an order for SN74ALS540NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS540NSR 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 SN74ALS540NSR reliable?
The price and inventory of SN74ALS540NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS540NSR is usually 5 days.
3.What payment methods are accepted for SN74ALS540NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS540NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS540NSR?
SN74ALS540NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS540NSR 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 SN74ALS540NSR?
For technical support, including SN74ALS540NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS540NSR requirements.
6.How does Aetrix verify that SN74ALS540NSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS540NSR 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 SN74ALS540NSR meets industry standards.
7.What is the process for return or replacement of SN74ALS540NSR?
All SN74ALS540NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS540NSR, 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 SN74ALS540NSR part is unused and in its original packaging.
Return procedure for SN74ALS540NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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