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Texas Instruments SN74ALS540NS
- Part No.:
- SN74ALS540NS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS540NS.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,342
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Product details
Overview
SN74ALS540NS from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus interfacing and memory address register buffering in TTL-compatible digital systems. It features dual 3-state enable inputs (OE1/OE2), pnp input structure for reduced DC loading, data flowthrough pinout (inputs and outputs on opposite package sides), and operates at 4.5–5.5 V supply voltage with IOL = 24 mA per output.
For engineers reviewing the SN74ALS540NS datasheet, SN74ALS540NS pinout, SN74ALS540NS application, or SN74ALS540NS equivalent, this device is selected for high-drive, low-input-current bus driving where inverted logic and 3-state control are required - especially in legacy industrial control, instrumentation, and memory subsystem designs.
Technical Context
The SN74ALS540NS implements a dual-NOR-gated 3-state control architecture: either OE1 or OE2 high forces all eight Y outputs into high-impedance state. Its pnp input stage reduces input current draw versus standard TTL, improving fan-out capability in dense logic systems.
It delivers true inverted data flow (A→Y inversion), supports 50-pF capacitive loads with propagation delays as low as 2 ns (tPHL) and 4 ns (tPLH), and maintains stable operation across 0°C to 70°C ambient temperature with thermal impedance of 60°C/W in its NS package.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting octal buffer with 3-state outputs - enables bidirectional bus control via active-low enable logic. |
| Supply Voltage (VCC) | 4.5 V to 5.5 V - compatible with standard 5-V TTL systems without level-shifting. |
| Output Drive (IOL) | 24 mA per output - sufficient to drive multiple TTL loads or terminated transmission lines. |
| Propagation Delay (tPLH/tPHL) | 2–12 ns - ensures timing predictability in synchronous bus architectures up to ~50 MHz. |
| Input Structure | pnp-based inputs - reduces DC input current to ≤ –0.2 mA (IIL), minimizing loading on upstream drivers. |
| Thermal Impedance (θJA) | 60°C/W (NS package) - defines maximum power dissipation limit under natural convection cooling. |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade industrial equipment and embedded control applications. |
Pinout & Package
SN74ALS540NS is housed in a 20-pin SOP (Small Outline Package) with 0.65 mm lead pitch, 7.5 mm × 5.6 mm body size, and 2.0 mm max height per JEDEC MO-150. The package is RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A1–A8 Inputs | Active-high data inputs; inverted logic passed to corresponding Y outputs when enabled. |
| 9 | GND | Ground reference for all internal circuitry and output stage return path. |
| 10, 20 | VCC | Primary 5-V supply connection; dual VCC pins reduce IR drop and improve noise immunity. |
| 11, 19 | OE1, OE2 | Active-high 3-state enable inputs; NOR logic - either high disables all outputs. |
| 12–18 | Y1–Y8 Outputs | Inverted buffered outputs; high-impedance when OE1 or OE2 is high; capable of 24 mA sink current. |
Key Features
| Feature | Design Value |
|---|---|
| Data flowthrough pinout | Inputs (A1–A8) on left side, outputs (Y1–Y8) on right side - simplifies PCB routing and minimizes trace crosstalk in bus layouts. |
| Dual 3-state enable (OE1/OE2) | NOR-gated control allows flexible bus arbitration using either enable signal independently - supports redundant or split-bus control schemes. |
| pnp input structure | Reduces input current to –0.2 mA (IIL) - increases fan-out to ≥20 LS-TTL loads without additional buffering. |
| High noise immunity | VIH = 2.0 V, VIL = 0.8 V - provides 0.4 V noise margin against ground bounce and supply ripple in noisy industrial environments. |
| Low quiescent current | ICC = 11–19 mA (all outputs disabled) - enables use in power-constrained legacy systems without thermal derating. |
Applications
| Industrial PLC Backplane Interface | Legacy Memory Address Buffering |
|---|---|
Use Scenario: Driving parallel address/data buses between microcontroller and discrete SRAM or EPROM in programmable logic controllers. IC Role / Device Role / Timing Role: Inverting buffer isolating CPU address lines while enabling/disabling bus access via OE signals during DMA cycles. Use Value: 24-mA drive strength ensures reliable signal integrity across 15-cm backplane traces; pnp inputs prevent loading of weak microcontroller outputs. |
Use Scenario: Buffering 8-bit address segments in vintage test equipment and diagnostic instruments using 74-series TTL logic. IC Role / Device Role / Timing Role: Octal inverting driver translating microprocessor address bits to memory chip select logic with precise 3-state timing control. Use Value: 2–12 ns propagation delay aligns with 74ALS timing budgets; dual OE inputs allow synchronized gating of multiple memory banks. |
| Test Equipment Signal Conditioning | Automated Manufacturing Controller I/O |
Use Scenario: Level-shifting and bus-driving in automated test fixtures interfacing FPGA-based pattern generators with DUTs requiring TTL-compatible inputs. IC Role / Device Role / Timing Role: Bidirectional bus interface element providing isolated, inverted data paths with controlled enable timing for stimulus/response sequencing. Use Value: 60°C/W θJA enables stable operation in enclosed test enclosures; 0.4 V noise margin prevents false triggering during ESD events. |
Use Scenario: Isolating and amplifying I/O signals between PLC CPU modules and field-mounted sensors/actuators in factory automation cabinets. IC Role / Device Role / Timing Role: Robust octal driver handling 24-VDC optocoupler inputs and driving LED status indicators or relay coils via external transistors. Use Value: High IOL supports direct connection to 10-mA indicator LEDs; pnp inputs tolerate leakage currents from aging sensor wiring. |
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 with 69°C/W θJA and no RoHS exemption. | Preferred for through-hole prototyping or legacy repair where SOP rework is impractical. | Select SN74ALS540N only if manual soldering, socketing, or thermal mass requirements favor DIP over surface-mount. |
| SN74LS240N | Non-inverting octal buffer with lower drive (IOL = 15 mA), higher ICC (22 mA disabled), and slower tPHL (15 ns typical). | Suitable for non-inverting bus applications where lower speed and cost outweigh need for inversion and higher drive. | Choose SN74LS240N only when system logic does not require A→Y inversion and thermal budget permits higher power dissipation. |
Compared with SN74ALS540N, the SN74ALS540NS offers superior thermal performance (60 vs. 69°C/W) and RoHS compliance, while SN74LS240N trades inversion capability and drive strength for broader legacy availability and lower unit cost in non-critical timing applications.
Availability
SN74ALS540NS is available at Aetrix Electronics and suitable for industrial PLC backplane interfaces, legacy memory subsystems, automated test equipment signal conditioning, and factory automation controller I/O requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS540NS 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 SN74ALS540NS belongs to TI's 74ALS advanced low-power Schottky logic family, engineered for high-speed, low-power bus interfacing in commercial-temperature industrial control and instrumentation systems.
FAQ
What logic function does the SN74ALS540NS implement?
The SN74ALS540NS implements an octal inverting buffer with 3-state outputs. Each input A1–A8 is inverted and presented at the corresponding Y1–Y8 output when both OE1 and OE2 are low. When either OE1 or OE2 is high, all Y outputs enter high-impedance state. This function is confirmed in the logic diagram and truth table of the SDAS025D datasheet.
Does the SN74ALS540NS support 3.3-V operation?
No, the SN74ALS540NS is specified only for 4.5 V to 5.5 V supply operation per its recommended operating conditions. It is not characterized for 3.3-V use, and VIH/VIL thresholds (2.0 V/0.8 V) are incompatible with standard 3.3-V CMOS logic levels. Using it at 3.3 V may result in undefined output states or excessive ICC.
What is the maximum output sink current per pin for SN74ALS540NS?
The maximum guaranteed low-level output current (IOL) for SN74ALS540NS is 24 mA per output at VCC = 4.5 V, as specified in the "recommended operating conditions" table. This value applies to the standard version - the -1 variant supports 48 mA, but SN74ALS540NS is not a -1 part.
How does the dual OE architecture of SN74ALS540NS improve system design?
The dual OE inputs (OE1 and OE2) are internally NOR-gated, so asserting either input high disables all eight outputs. This allows flexible bus arbitration - for example, OE1 can be tied to a master controller while OE2 connects to a watchdog timer, enabling fail-safe bus release without software intervention. This behavior is explicitly defined in the functional description of the SN74ALS540NS datasheet.
Is SN74ALS540NS pin-compatible with SN74ALS541NSR?
No - SN74ALS540NS and SN74ALS541NSR share identical pinouts and package (20-pin SOP), but differ in logic function: SN74ALS540NS provides inverted outputs (A→¬Y), while SN74ALS541NSR provides true outputs (A→Y). Swapping them without logic inversion elsewhere will cause functional failure. Pin compatibility does not imply functional interchangeability.
SN74ALS540NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- 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
SN74ALS540NS FAQ
1.How can I place an order for SN74ALS540NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS540NS 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 SN74ALS540NS reliable?
The price and inventory of SN74ALS540NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS540NS is usually 5 days.
3.What payment methods are accepted for SN74ALS540NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS540NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS540NS?
SN74ALS540NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS540NS 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 SN74ALS540NS?
For technical support, including SN74ALS540NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS540NS requirements.
6.How does Aetrix verify that SN74ALS540NS is sourced from the original manufacturer or authorized distributors?
All SN74ALS540NS 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 SN74ALS540NS meets industry standards.
7.What is the process for return or replacement of SN74ALS540NS?
All SN74ALS540NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS540NS, 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 SN74ALS540NS part is unused and in its original packaging.
Return procedure for SN74ALS540NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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