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Texas Instruments SN74ALS240ADB
- Part No.:
- SN74ALS240ADB
- Manufacturer:
- Texas Instruments
- Package:
- 20-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS240ADB.pdf
- Description:
- PROTOTYPE
- Quantity:
- Payment:
- Shipping:
Inventory:1,228
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Product details
Overview
SN74ALS240ADB 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.
For engineers reviewing the SN74ALS240ADB datasheet, SN74ALS240ADB pinout, SN74ALS240ADB application, or SN74ALS240ADB equivalent, key selection criteria include its 3-state bus-driving capability, ALS logic family speed-power tradeoff, SSOP-20 package footprint, and compatibility with legacy 74-series address/data path designs.
Technical Context
This device implements two independent 4-bit noninverting buffer sections, each controlled by a dedicated active-low output-enable (OE) input. Its pnp input structure lowers input current draw versus standard TTL, improving fan-in in dense address decoding networks.
Propagation delays are specified at 2–9 ns (tPLH/tPHL) under 50 pF load, with enable/disable times of 5–13 ns (tPZL/tPHZ). The 3-state outputs support high-impedance bus sharing, and absolute maximum ratings include 7 V supply voltage and –65°C to 150°C storage temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - balances speed (sub-10 ns) and power (ICC ≈ 14–25 mA) better than standard LS. |
| Supply Voltage | 4.5–5.5 V - compatible with standard 5 V TTL rails; not rated for 3.3 V operation. |
| Output Drive | IOL = 24 mA (min) - sufficient to drive multiple TTL inputs or short PCB traces without external buffering. |
| Input Structure | PNP input stage - reduces VIH/VIL input current, enabling higher fan-in (up to 20+ inputs per driver). |
| Propagation Delay | tPLH/tPHL ≤ 9 ns @ CL = 50 pF - suitable for address latching in sub-10 MHz bus systems. |
| Thermal Resistance | θJA = 70°C/W (SSOP-DB) - requires moderate PCB copper area for continuous operation near max IOL. |
Pinout & Package
SN74ALS240ADB uses a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm pitch, 7.4 mm × 5.3 mm body, and 2.0 mm max height. Pin 1 is located in quadrant Q1 per tape-and-reel orientation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE, 2OE | Active-low output-enable controls | Enable/disable respective 4-bit buffer groups independently; tied low to activate outputs. |
| 1A1–1A4, 2A1–2A4 | Noninverting data inputs | Eight buffered inputs; pnp structure minimizes loading on upstream drivers. |
| 1Y1–1Y4, 2Y1–2Y4 | 3-state noninverting outputs | Drive bidirectional buses or memory address lines; high-impedance when OE = high. |
| VCC (Pin 20) | Positive supply | 5 V nominal; must be decoupled locally due to transient current demands during switching. |
| GND (Pin 10) | Ground reference | Common return for all logic and output currents; critical for noise control in bus systems. |
Key Features
| Feature | Design Value |
|---|---|
| Octal 3-state buffering | Two independent 4-bit sections allow selective bus segment control without full-system disable. |
| PnP input architecture | Reduces input current to ≤0.1 mA, enabling direct connection to >20 LS-TTL outputs without loading issues. |
| ALS speed-power optimization | 9 ns max propagation delay at 24 mA drive - 3× faster than 74LS240 with comparable quiescent current. |
| Industrial temperature range | 0°C to 70°C operation - validated for commercial/industrial embedded control and instrumentation applications. |
Applications
| Memory Address Buffering | Bus Transceiver Interface |
|---|---|
Use Scenario: Driving 16-bit address bus from microprocessor to multiple memory ICs (SRAM, EPROM) in a shared-bus system. IC Role / Device Role / Timing Role: Noninverting buffer with 3-state outputs isolates address lines during DMA cycles or peripheral access. Use Value: 24 mA drive strength ensures clean signal edges across 10+ cm PCB traces; pnp inputs prevent address latch contention. | Use Scenario: Bidirectional data bus isolation between CPU and peripheral controllers (e.g., UART, ADC) in multi-master systems. IC Role / Device Role / Timing Role: Direction-controlled bus driver using separate OE pins for read/write arbitration. Use Value: Independent 1OE/2OE enables staggered enable timing to avoid bus contention during state transitions. |
| Clock Distribution Network | Legacy System Upgrade |
Use Scenario: Fan-out of system clock or strobe signals to multiple synchronous peripherals (e.g., timers, counters) in industrial PLCs. IC Role / Device Role / Timing Role: Low-skew, noninverting clock buffer with 3-state capability for dynamic clock gating. Use Value: 9 ns max tPHL/tPLH ensures <1 ns skew across 8 outputs; high-impedance mode eliminates clock loading during sleep states. | Use Scenario: Drop-in replacement for obsolete 74LS240 in field-upgraded avionics or test equipment where board space is constrained. IC Role / Device Role / Timing Role: Pin-compatible functional upgrade offering faster timing and lower input loading than LS variants. Use Value: SSOP-20 footprint matches legacy SOIC-20 layouts with minor trace adjustments; no logic redesign 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 |
|---|---|---|---|
| SN74ALS240ADW | SOIC-20 package (7.5 mm × 5.3 mm); θJA = 58°C/W vs. 70°C/W for DB; identical electrical specs. | Requires PCB land pattern change; better thermal performance but larger footprint than SSOP. | Choose for easier hand-soldering or higher thermal margin in non-space-constrained designs. |
| SN74AS240ADBR | AS family: faster (6.5 ns max tPHL), higher drive (64 mA IOL), but higher ICC (51–75 mA) and cost. | Not drop-in - increased power dissipation requires thermal redesign; suited for high-speed timing-critical paths. | Choose only when sub-7 ns propagation and 64 mA drive are mandatory; verify PSU and layout cooling. |
Compared with SN74ALS240ADW and SN74AS240ADBR, SN74ALS240ADB offers the smallest PCB footprint (SSOP), optimal balance of speed and power for legacy 5 V systems, and direct compatibility with tape-and-reel automated assembly - making it ideal for space-constrained industrial upgrades.
Availability
SN74ALS240ADB is available at Aetrix Electronics and suitable for memory address buffering, bus transceiver interfaces, clock distribution networks, and legacy system upgrades requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS240ADB 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.
SN74ALS240ADB belongs to TI's legacy 74ALS logic family, engineered for high-density, low-power 5 V TTL systems where fan-in, bus drive, and timing predictability are critical - especially in memory subsystems and control-plane interconnects.
FAQ
What is the maximum operating temperature range for SN74ALS240ADB?
The SN74ALS240ADB is rated for 0°C to 70°C ambient operating temperature. This industrial-grade specification ensures reliable operation in commercial and industrial control environments, including programmable logic controllers and instrumentation systems. Exceeding 70°C may cause timing violations or increased leakage; derating is recommended above 60°C.
Does SN74ALS240ADB support 3.3 V logic levels?
No, SN74ALS240ADB does not support 3.3 V logic operation. It requires a 4.5–5.5 V supply and is designed for 5 V TTL-compatible signaling. Input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output voltages (VOH ≥ 2.4 V, VOL ≤ 0.4 V) are specified only at VCC = 5 V. Interfacing with 3.3 V systems requires level-shifting circuitry.
Can SN74ALS240ADB replace SN74LS240 in existing designs?
Yes, SN74ALS240ADB is a functional and pin-compatible upgrade to SN74LS240, offering faster propagation (9 ns vs. 15 ns), higher output drive (24 mA vs. 8 mA), and lower input current. The SSOP-20 package requires minor PCB footprint adjustment, but logic behavior, pinout, and 5 V operation remain identical - simplifying legacy system refreshes.
What is the purpose of the pnp input structure in SN74ALS240ADB?
The pnp input structure in SN74ALS240ADB reduces input current (IIH ≤ 20 µA, IIL ≤ –0.1 mA) compared to standard TTL, enabling higher fan-in - up to 20+ upstream logic gates can drive a single SN74ALS240ADB input without exceeding voltage thresholds. This minimizes loading on address decoders and clock trees in dense digital systems.
Is SN74ALS240ADB RoHS compliant?
Yes, SN74ALS240ADB is RoHS compliant, with lead finish NIPDAU (Nickel/Palladium/Gold) and MSL Level-1 rating (260°C peak reflow). It meets JEDEC J-STD-020 moisture sensitivity requirements and is qualified for lead-free soldering processes, supporting modern environmental compliance mandates in industrial and medical electronics.
SN74ALS240ADB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SSOP (0.209", 5.30mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 20-SSOP
SN74ALS240ADB FAQ
1.How can I place an order for SN74ALS240ADB through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS240ADB 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 SN74ALS240ADB reliable?
The price and inventory of SN74ALS240ADB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS240ADB is usually 5 days.
3.What payment methods are accepted for SN74ALS240ADB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS240ADB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS240ADB?
SN74ALS240ADB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS240ADB 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 SN74ALS240ADB?
For technical support, including SN74ALS240ADB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS240ADB requirements.
6.How does Aetrix verify that SN74ALS240ADB is sourced from the original manufacturer or authorized distributors?
All SN74ALS240ADB 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 SN74ALS240ADB meets industry standards.
7.What is the process for return or replacement of SN74ALS240ADB?
All SN74ALS240ADB units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS240ADB, 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 SN74ALS240ADB part is unused and in its original packaging.
Return procedure for SN74ALS240ADB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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