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Texas Instruments SN74ALS240AN
- Part No.:
- SN74ALS240AN
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS240AN.pdf
- Description:
- IC BUFFER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:397
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Product details
Overview
SN74ALS240AN from Texas Instruments is an octal noninverting buffer/driver with 3-state outputs, designed for memory address driving and bus interfacing in TTL-compatible systems. It operates at 4.5–5.5 V, delivers 24 mA low-level output current (IOL), features pnp inputs to reduce DC loading, and supports 0°C to 70°C industrial temperature range in a 20-pin PDIP package.
For engineers reviewing the SN74ALS240AN datasheet, SN74ALS240AN pinout, SN74ALS240AN application, or SN74ALS240AN equivalent, this page provides verified electrical specs, functional timing behavior, thermal characteristics, real-world use cases in address buffering and clock distribution, and validated alternative options for legacy system redesigns.
Technical Context
The SN74ALS240AN implements dual 4-bit noninverting buffers with independent 3-state enable controls (1OE and 2OE), each managing four outputs (Y1–Y4). Its ALS (Advanced Low-Power Schottky) logic family delivers improved speed-power trade-offs over standard LS, with typical propagation delays of 2–9 ns (tPLH/tPHL) and enable/disable times as low as 2–13 ns (tPZH/tPLZ).
Input structure uses pnp-based circuitry to minimize input current draw (IIL = –0.1 mA max), while output stages support high fan-out and symmetrical active-low OE control. The device is not pin-compatible with AS-series variants due to differing IOL ratings and switching performance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL/ALS logic rails and noise margin stability. |
| Low-Level Output Current | 24 mA - Supports direct drive of multiple TTL inputs or moderate-capacitance buses without external amplification. |
| Propagation Delay | 2–9 ns - Enables reliable operation in high-speed address/data paths up to ~100 MHz system timing budgets. |
| 3-State Enable Time | 5–13 ns - Allows precise bus arbitration and avoids contention during multi-driver shared-bus transitions. |
| Input Loading | –0.1 mA max IIL - Reduces loading on upstream drivers, critical for cascaded address register chains. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial/industrial embedded applications with no derating required. |
| Package Type | 20-pin PDIP (N) - Through-hole mounting compatible with legacy prototyping, repair, and MIL-STD-883-referenced test fixtures. |
Pinout & Package
SN74ALS240AN is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300" wide, with standard 0.1" pin pitch and JEDEC MS-001 compliant footprint. Thermal resistance θJA is 70°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE | Output Enable (Group 1) | Active-low control for Y1–Y4 outputs; asserts high-impedance state when high. |
| 1A1–1A4 | Input Group 1 | Noninverting data inputs driving Y1–Y4 respectively; pnp-coupled for low DC loading. |
| 2OE | Output Enable (Group 2) | Independent active-low control for Y1–Y4 of second buffer section. |
| 2A1–2A4 | Input Group 2 | Noninverting inputs for second buffer set; electrically isolated from Group 1. |
| 1Y1–1Y4, 2Y1–2Y4 | 3-State Outputs | Buffered noninverting outputs; tri-state capable with <0.5 V VOL at 24 mA sink. |
| VCC | Power Supply | +5 V supply pin; requires local 0.1 µF ceramic decoupling per device. |
| GND | Ground Reference | Signal and power return; must be low-impedance connection to minimize ground bounce. |
Key Features
| Feature | Design Value |
|---|---|
| Octal noninverting buffering | Two independent 4-bit sections enable flexible partitioning of address/data buses without inversion logic. |
| pnp input structure | Reduces input current to ≤0.1 mA, minimizing loading on preceding registers or counters in memory subsystems. |
| 3-state output control | Dual OE pins allow selective disabling of either buffer group-critical for bidirectional bus management and conflict avoidance. |
| ALS logic family | Combines Schottky-clamped speed (sub-10 ns delays) with lower power than standard LS, improving density in board-constrained designs. |
| Industrial temperature range | 0°C to 70°C rating ensures stable operation across uncontrolled environments like factory automation panels and telecom line cards. |
Applications
| Memory Address Buffering | Bus Transceiver 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: Noninverting octal buffer providing level translation, fan-out expansion, and bus isolation via 3-state control. Use Value: Eliminates need for discrete transistor arrays; enables clean address strobing with <9 ns delay and <0.5 V VOL at full load. | Use Scenario: Interfacing between two asynchronous subsystems sharing a common data bus (e.g., CPU and DMA controller). IC Role / Device Role / Timing Role: Bidirectional bus driver with independent OE control per group to prevent contention during handshaking. Use Value: Dual OE pins allow precise timing of bus release and acquisition, reducing arbitration latency by up to 40% vs single-OE alternatives. |
| Clock Distribution Network | Legacy System Repair & Replacement |
Use Scenario: Distributing a system clock signal to multiple synchronous peripherals (e.g., UARTs, timers) with matched skew. IC Role / Device Role / Timing Role: Low-skew noninverting buffer ensuring simultaneous edge delivery across all eight outputs. Use Value: Propagation delay matching within ±2 ns across channels maintains setup/hold timing integrity for parallel peripherals. | Use Scenario: Replacing obsolete SN74LS240 or SN74S240 in fielded military or industrial equipment. IC Role / Device Role / Timing Role: Pin- and function-compatible drop-in upgrade offering lower power and higher drive strength. Use Value: Direct replacement with identical pinout, voltage levels, and logic behavior-no PCB or firmware changes required. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS240AN | Higher drive (64 mA IOL), faster switching (1.2–6.5 ns delays), but higher ICC (51–75 mA) and tighter VIL (0.4 V). | Better suited for high-speed backplanes or low-capacitance loads; less tolerant of marginal input thresholds. | Select SN74AS240AN only if system demands sub-7 ns timing and can support increased power dissipation. |
| SN74LS240N | Lower drive (24 mA IOL same), slower (15–35 ns delays), higher input loading (–0.4 mA IIL), identical pinout and voltage specs. | Compatible with legacy LS-only designs where timing slack exists and power budget is constrained. | Choose SN74LS240N for cost-sensitive repairs where ALS speed is unnecessary and LS stock is available. |
Compared with SN74AS240AN and SN74LS240N, the SN74ALS240AN delivers optimal balance: 24 mA drive matches LS compatibility while delivering ALS-speed advantages (2–9 ns), making it ideal for upgrading aging LS-based systems without redesigning timing margins or power delivery.
Availability
SN74ALS240AN is available at Aetrix Electronics and suitable for memory address buffering, bus transceiver interfaces, clock distribution networks, and legacy system repair requiring stable component supply across long-lifecycle industrial programs.
Supply support for SN74ALS240AN 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 specializing in analog, embedded processing, and logic solutions, with decades of heritage in TTL and advanced logic families.
The SN74ALS240AN belongs to TI's legacy Advanced Low-Power Schottky (ALS) logic portfolio, engineered specifically to enhance performance and density in memory address drivers, clock buffers, and bus-oriented receivers/transmitters for industrial and computing systems.
FAQ
What is the maximum recommended output current for SN74ALS240AN?
The SN74ALS240AN is rated for a maximum low-level output current (IOL) of 24 mA per output under recommended operating conditions (VCC = 4.5–5.5 V, TA = 0°C to 70°C). This value applies to the standard version; the -1 variant supports 48 mA but is not represented by the SN74ALS240AN part number. Exceeding 24 mA risks VOL degradation and thermal stress.
Is SN74ALS240AN pin-compatible with SN74LS240N?
Yes, SN74ALS240AN is fully pin-compatible with SN74LS240N: identical 20-pin PDIP package, matching pin functions (1OE, 1A1–1A4, 1Y1–1Y4, etc.), and compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V). No PCB layout changes are needed when upgrading from LS to ALS for improved speed and reduced power.
Does SN74ALS240AN support mixed-voltage interfacing?
No, SN74ALS240AN is strictly a 5 V TTL/ALS device with VCC range 4.5–5.5 V and input thresholds referenced to 5 V rails. It does not support 3.3 V or other voltage domain interfacing without level-shifting circuitry. Input voltages above 5.5 V or below 0 V violate absolute maximum ratings and may cause permanent damage.
What is the thermal resistance (θJA) of SN74ALS240AN in its PDIP package?
The SN74ALS240AN in the 20-pin PDIP (N) package has a junction-to-ambient thermal resistance (θJA) of 70°C/W, as specified in the official Texas Instruments datasheet SDAS214E. This value assumes standard JEDEC test conditions (single device on 1-inch² FR-4 board with 2 oz copper); actual board-level θJA will vary with layout and airflow.
Can SN74ALS240AN drive a 50 pF load with guaranteed timing?
Yes, SN74ALS240AN switching characteristics-including tPLH (2–9 ns), tPHL (2–9 ns), and tPZH (5–13 ns)-are explicitly characterized at CL = 50 pF, R1 = R2 = 500 Ω, and VCC = 4.5–5.5 V. These values are guaranteed across the full operating temperature range (0°C to 70°C), making it suitable for standard digital bus loading conditions.
SN74ALS240AN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Buffer, Inverting
- Number of Elements:
- 2
- Number of Bits per Element:
- 4
- 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:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS240AN FAQ
1.How can I place an order for SN74ALS240AN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS240AN 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 SN74ALS240AN reliable?
The price and inventory of SN74ALS240AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS240AN is usually 5 days.
3.What payment methods are accepted for SN74ALS240AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS240AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS240AN?
SN74ALS240AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS240AN 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 SN74ALS240AN?
For technical support, including SN74ALS240AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS240AN requirements.
6.How does Aetrix verify that SN74ALS240AN is sourced from the original manufacturer or authorized distributors?
All SN74ALS240AN 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 SN74ALS240AN meets industry standards.
7.What is the process for return or replacement of SN74ALS240AN?
All SN74ALS240AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS240AN, 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 SN74ALS240AN part is unused and in its original packaging.
Return procedure for SN74ALS240AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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