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Texas Instruments SN74ALS540NE4
- Part No.:
- SN74ALS540NE4
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS540NE4.pdf
- Description:
- IC INVERTER DUAL 8-INPUT 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:195
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Product details
Overview
SN74ALS540NE4 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 output-enable inputs (OE1/OE2), pnp input structure for reduced DC loading, data flowthrough pinout (inputs on one side, outputs on the other), and operates at 4.5 V to 5.5 V supply voltage.
For engineers reviewing the SN74ALS540NE4 datasheet, SN74ALS540NE4 pinout, SN74ALS540NE4 application, or SN74ALS540NE4 equivalent, this device is selected for high-drive 3-state bus control in legacy industrial controllers, retro-computing peripherals, and embedded system backplanes requiring inverted logic-level buffering with 24 mA sink capability.
Technical Context
The SN74ALS540NE4 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 fanout in dense logic arrays.
It delivers true inverting logic function (A → Y̅) with propagation delays as low as 2 ns (tPHL) and 4 ns (tPLH) under loaded conditions (CL = 50 pF), and supports 3-state disable times down to 1 ns (tPHZ) - critical for glitch-free bus arbitration in synchronous memory interfaces.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting octal buffer with 3-state outputs (A → Y̅) |
| Supply Voltage (VCC) | 4.5 V to 5.5 V - compatible with standard 5 V TTL rails |
| Output Drive (IOL) | 24 mA max - sufficient to drive multiple TTL loads or terminated transmission lines |
| 3-State Enable Logic | 2-input NOR: OE1 or OE2 high disables all outputs - enables flexible bus arbitration |
| Propagation Delay (tPLH/tPHL) | 2–12 ns - ensures timing compliance in 25–50 MHz address/data strobe domains |
| Input Structure | pnp-based - reduces DC input current to ≤ –0.2 mA, lowering power and loading on upstream drivers |
Pinout & Package
SN74ALS540NE4 is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300-inch wide, with standard through-hole mounting and RoHS-compliant NiPdAu lead finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A1–A8 Inputs | Inverting data inputs; accept TTL-compatible logic levels (VIH ≥ 2 V, VIL ≤ 0.8 V) |
| 9 | GND | Ground reference for all internal circuitry and output stages |
| 10, 20 | VCC | Positive supply terminal; must be decoupled locally due to switching current transients |
| 11, 19 | OE1, OE2 | Active-low 3-state enable inputs - NOR logic: either high disables all outputs |
| 12, 13, 14, 15, 16, 17, 18, 20 | Y1–Y8 Outputs | Inverted, 3-state buffered outputs; capable of sinking 24 mA while maintaining VOL ≤ 0.4 V |
Key Features
| Feature | Design Value |
|---|---|
| Data flowthrough pinout | Inputs (A1–A8) on left side, outputs (Y1–Y8) on right side - simplifies PCB trace routing and minimizes crosstalk in parallel bus layouts |
| pnp input structure | Reduces input current to –0.2 mA max - increases effective fanout and eases drive requirements from preceding logic stages |
| Dual 3-state enable (OE1/OE2) | Enables hierarchical bus control: one enable can manage local subsystems while the other coordinates system-wide arbitration |
| High noise immunity | VIH = 2 V min, VIL = 0.8 V max - provides 0.4 V noise margin against ground bounce and supply ripple in industrial environments |
Applications
| Industrial PLC Backplane Interface | Retrocomputing Memory Expansion |
|---|---|
Use Scenario: Buffering and isolating CPU address bus signals to multiple I/O module slots in a DIN-rail mounted programmable logic controller. IC Role / Device Role / Timing Role: Inverting 3-state buffer that drives terminated 50 Ω traces with controlled slew and low ground bounce during address changes. Use Value: Enables hot-swap-capable slot addressing via OE1/OE2 gating, while pnp inputs reduce loading on aging microprocessor address pins. |
Use Scenario: Expanding RAM capacity in 1980s-era Z80 or 6502-based computers using bank-switched memory architectures. IC Role / Device Role / Timing Role: Address latch driver that inverts and buffers upper address bits before feeding them to memory chip select decoders. Use Value: Matches vintage TTL timing budgets (tPLH ≤ 12 ns) and drive strength, ensuring compatibility with original system timing margins and signal integrity. |
| Legacy Test Equipment Bus Controller | Avionics Data Acquisition Interface |
Use Scenario: Managing shared GPIB or IEEE-488 data bus lines between multiple instrument modules in rack-mounted test systems. IC Role / Device Role / Timing Role: Bidirectional bus driver with fast 3-state disable (tPZL ≤ 20 ns) to prevent bus contention during handshaking cycles. Use Value: Dual OE inputs allow independent control of read/write direction paths, supporting full-duplex protocol timing without external logic. |
Use Scenario: Interfacing ARINC 429 receiver outputs to a legacy flight management computer's discrete input monitoring circuitry. IC Role / Device Role / Timing Role: Level-shifting and current-boosting buffer for converting differential ARINC signals to single-ended TTL-compatible inputs. Use Value: 24 mA sink capability ensures reliable logic low assertion across long harness runs with contact resistance and EMI filtering. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS540N | No suffix 'E4'; same PDIP-N package, identical electrical specs, but non-lead-free finish (SnPb) | Not RoHS-compliant; restricted for new designs in EU/China markets | Select SN74ALS540NE4 for RoHS-conforming production; use SN74ALS540N only for legacy repair or exempt applications. |
| SN74ALS540-1N | '-1' version: rated for 48 mA IOL (vs. 24 mA), but only valid at VCC = 4.75–5.25 V | Higher drive needed for unterminated stubs or long traces; requires tighter VCC regulation | Choose SN74ALS540-1N when driving >10 TTL loads or >15 cm PCB traces; otherwise SN74ALS540NE4 suffices for standard bus loading. |
Compared with SN74ALS540N and SN74ALS540-1N, the SN74ALS540NE4 offers certified RoHS compliance and stable 24 mA drive across the full 4.5–5.5 V range - making it the preferred choice for new industrial and aerospace retro-fit designs where regulatory compliance and supply-chain continuity are prioritized over marginal current headroom.
Availability
SN74ALS540NE4 is available at Aetrix Electronics and suitable for industrial PLC backplanes, retrocomputing memory expansion, and avionics data acquisition interfaces requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ALS540NE4 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 deep heritage in TTL and advanced logic families.
The SN74ALS540NE4 belongs to the ALS (Advanced Low-Power Schottky) logic family - engineered for improved speed-power trade-offs in mid-1980s industrial and computing systems, emphasizing reliability, noise immunity, and backward compatibility.
FAQ
What is the logic function of the SN74ALS540NE4?
The SN74ALS540NE4 is an octal inverting buffer with 3-state outputs: each input An drives a corresponding inverted output Yn (i.e., Yn = An). When either OE1 or OE2 is high, all eight outputs enter high-impedance state. This function is confirmed in the logic diagram and truth table of the SDAS025D datasheet, and applies specifically to the SN74ALS540NE4 variant.
Does the SN74ALS540NE4 support 3.3 V operation?
No, the SN74ALS540NE4 is specified only for 4.5 V to 5.5 V operation per its recommended operating conditions. It lacks 3.3 V logic-level compatibility - VIH minimum is 2.0 V, but VCC must be ≥4.5 V for guaranteed performance. Using it below 4.5 V risks incorrect output states and increased propagation delay; SN74ALS540NE4 is not a mixed-voltage device.
What does the 'E4' suffix mean in SN74ALS540NE4?
The 'E4' suffix denotes a RoHS-compliant, lead-free finish (NiPdAu) on the PDIP-N package, per TI's packaging nomenclature. It indicates compliance with EU Directive 2011/65/EU and China RoHS II. The SN74ALS540NE4 shares identical electrical, thermal, and timing specifications with the non-E4 SN74ALS540N, differing only in lead finish and environmental certification.
Can SN74ALS540NE4 replace SN74ALS541NE4 in a design?
No - SN74ALS540NE4 provides inverted outputs (A → Y̅), while SN74ALS541NE4 provides true (non-inverting) outputs (A → Y). Swapping them without logic inversion elsewhere will invert all data paths, causing functional failure. Pinout and electrical specs are identical, but logic polarity is fundamentally different and not interchangeable without redesign.
What is the maximum capacitive load the SN74ALS540NE4 can drive reliably?
The SN74ALS540NE4 is characterized up to 50 pF load capacitance in its switching specifications (tPLH, tPHL, tPZH, etc.). While it may drive higher capacitance, timing parameters degrade beyond this value - tPLH increases to 17 ns at 50 pF, and further loading extends delays nonlinearly. For >50 pF, add series termination or consider a higher-drive variant like SN74ALS540-1NE4.
SN74ALS540NE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Logic Type:
- Buffer, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS540NE4 FAQ
1.How can I place an order for SN74ALS540NE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS540NE4 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 SN74ALS540NE4 reliable?
The price and inventory of SN74ALS540NE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS540NE4 is usually 5 days.
3.What payment methods are accepted for SN74ALS540NE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS540NE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS540NE4?
SN74ALS540NE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS540NE4 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 SN74ALS540NE4?
For technical support, including SN74ALS540NE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS540NE4 requirements.
6.How does Aetrix verify that SN74ALS540NE4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS540NE4 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 SN74ALS540NE4 meets industry standards.
7.What is the process for return or replacement of SN74ALS540NE4?
All SN74ALS540NE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS540NE4, 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 SN74ALS540NE4 part is unused and in its original packaging.
Return procedure for SN74ALS540NE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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