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Texas Instruments SN74ALS240ADBR
- Part No.:
- SN74ALS240ADBR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS240ADBR.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:831
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Product details
Overview
SN74ALS240ADBR 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), supports 9 ns typical propagation delay (tPHL), and features pnp inputs to reduce DC loading on upstream logic.
For engineers reviewing the SN74ALS240ADBR datasheet, SN74ALS240ADBR pinout, SN74ALS240ADBR application, or SN74ALS240ADBR equivalent, this device is selected for high-fan-out 5 V bus buffering where fast enable/disable timing (tPZL = 18 ns max), low quiescent ICC (14 mA max when disabled), and SSOP-20 packaging for space-constrained PCB layouts are critical.
Technical Context
This device implements dual 4-bit noninverting buffers with independent active-low 3-state enable controls (1OE and 2OE). Each buffer pair shares a common enable signal but drives separate output groups (Y1–Y4 and Y1'–Y4'), enabling selective bus segmentation. The ALS family uses advanced Schottky-clamped bipolar technology to achieve higher speed and lower power than standard LS logic.
Input structure includes pnp-based input stages that minimize input current draw (IIL = –0.1 mA max), reducing loading on preceding drivers. Output stage design supports symmetrical drive capability-24 mA sink and 15 mA source-with guaranteed VOH ≥ 2.4 V and VOL ≤ 0.4 V under full load, ensuring robust noise margins in mixed-logic systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5–5.5 V - Compatible with standard 5 V TTL/ALS logic rails; no external regulation required. |
| Low-Level Output Current | 24 mA - Sustains reliable logic-low drive into 50 Ω transmission lines or multiple TTL inputs. |
| Propagation Delay | 9 ns max (tPHL) - Enables operation in high-speed address/data paths up to ~60 MHz clock domains. |
| 3-State Disable Time | 18 ns max (tPZL) - Ensures clean bus release before next driver activation, preventing bus contention. |
| Input Loading | –0.1 mA max IIL - Reduces fan-out burden on preceding gates, supporting >20 LS-TTL loads per input. |
| Quiescent Supply Current | 14 mA max (ICC, outputs disabled) - Low standby power enables use in power-sensitive backplane interfaces. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade embedded and industrial control applications. |
Pinout & Package
SN74ALS240ADBR is housed in a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch, 7.4 mm × 5.3 mm body size, and 2.0 mm maximum height - optimized for high-density PCB layouts requiring fine-pitch surface-mount assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE | Group 1 Output Enable (active low) | Controls Y1–Y4; asserts 3-state when high, enables buffer when low. |
| 1A1–1A4 | Group 1 Inputs | Noninverting data inputs for first four buffers; pnp structure minimizes input current. |
| 2Y1–2Y4 | Group 2 Outputs | Noninverting buffered outputs driven by 2A1–2A4; 24 mA sink capability. |
| GND | Ground Reference | Power return path; must be low-inductance connection to minimize switching noise. |
| VCC | Positive Supply | +5 V supply rail; requires local 0.1 µF ceramic decoupling adjacent to pin. |
| 2OE | Group 2 Output Enable (active low) | Independent control of Y1'–Y4'; enables asynchronous bus partitioning. |
| 1Y1–1Y4 | Group 1 Outputs | Noninverting outputs for A1–A4; electrically identical to 2Yx outputs. |
| 2A1–2A4 | Group 2 Inputs | Second set of noninverting inputs; allows dual-bus or mirrored address routing. |
Key Features
| Feature | Design Value |
|---|---|
| 3-State Dual-Enable Architecture | Separate 1OE/2OE pins allow independent control of two 4-bit output groups - essential for bidirectional bus arbitration and memory bank selection. |
| pnp Input Stage | Reduces input current to ≤0.1 mA, lowering loading on microcontroller port pins or address latches without external pull-ups. |
| ALS Logic Family Performance | Combines LS power efficiency with AS speed: 9 ns tPHL and 14 mA ICC (disabled) - superior to standard 74LS240. |
| SSOP-20 Packaging | 0.65 mm pitch, 7.4 × 5.3 mm footprint - saves >40% board area vs. SOIC-20 while maintaining reflow compatibility. |
| Guaranteed Bus-Hold Margin | VOL ≤ 0.4 V at 24 mA ensures >0.4 V noise immunity against crosstalk in dense backplane traces. |
Applications
| Memory Address Buffering | ISA Bus Interface |
|---|---|
Use Scenario: Driving 20-bit address bus from microprocessor to multiple SRAM/ROM chips in legacy PC architecture. IC Role / Device Role / Timing Role: Noninverting octal buffer providing fan-out expansion and 3-state isolation during DMA cycles. Use Value: Enables clean address hold during bus grant with tPZL ≤ 18 ns, preventing memory access corruption. | Use Scenario: Interfacing 8-bit data/address signals between ISA slot and peripheral controller ASIC. IC Role / Device Role / Timing Role: Bidirectional bus driver with independent OE control for read/write direction management. Use Value: Dual-enable architecture allows simultaneous control of upper/lower byte lanes without external logic. |
| Industrial PLC Backplane | Legacy Test Equipment Bus |
Use Scenario: Distributing I/O address decoding signals across modular rack-mounted I/O cards. IC Role / Device Role / Timing Role: High-reliability 3-state buffer isolating card-specific address lines from shared backplane. Use Value: 24 mA drive strength maintains signal integrity over 15 cm ribbon cable runs at 5 V. | Use Scenario: Replacing obsolete 74LS240 in automated test system mainframe bus repeaters. IC Role / Device Role / Timing Role: Drop-in compatible buffer with improved speed/power for aging ATE hardware upgrades. Use Value: Pinout and logic function match enables direct replacement without PCB revision. |
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 |
|---|---|---|---|
| SN74ALS240ADWR | Same ALS240 core, SOIC-20 package (1.27 mm pitch, larger footprint) | Preferred for through-hole prototyping or legacy SOIC assembly lines | Select when board layout lacks SSOP-20 land pattern or requires manual rework accessibility. |
| SN74AS240ADBR | AS-family variant: faster (6.5 ns tPHL), higher drive (64 mA IOL), but higher ICC (51 mA active) | Better suited for ultra-high-speed bus repeaters where power budget allows | Choose only if timing margin is insufficient with ALS version and thermal design accommodates +37 mA extra dissipation. |
Compared with SN74ALS240ADWR and SN74AS240ADBR, SN74ALS240ADBR delivers optimal balance of speed, power, and density for modern space-constrained industrial control boards - offering 30% smaller footprint than SOIC while consuming 65% less active power than the AS variant.
Availability
SN74ALS240ADBR is available at Aetrix Electronics and suitable for memory address buffering, ISA bus interfacing, industrial PLC backplanes, and legacy test equipment upgrades requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ALS240ADBR 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 delivering analog and embedded processing solutions, with over 90 years of innovation in logic, power, and signal chain technologies.
The SN74ALS240ADBR belongs to TI's legacy ALS (Advanced Low-Power Schottky) logic family, engineered specifically for high-density, high-fan-out 5 V bus driving in memory subsystems and industrial control backplanes.
FAQ
What is the maximum recommended operating temperature for SN74ALS240ADBR?
The SN74ALS240ADBR is rated for commercial operation from 0°C to 70°C ambient temperature. This range is validated per TI's SDAS214E datasheet and applies to continuous operation under specified supply (4.5–5.5 V) and load conditions. Exceeding 70°C may degrade parametric performance, particularly propagation delay and output drive strength.
Does SN74ALS240ADBR support true bidirectional data flow?
No, SN74ALS240ADBR is a unidirectional noninverting buffer - it does not support automatic direction sensing or internal bus transceivers. Data flows strictly from A-inputs to Y-outputs. Bidirectional operation requires external control logic coordinating 1OE/2OE with system direction signals, as used in ISA bus implementations.
Can SN74ALS240ADBR replace SN74LS240 in existing designs?
Yes, SN74ALS240ADBR is a functional and pin-compatible upgrade to SN74LS240, offering faster propagation delay (9 ns vs. 15 ns), lower ICC (14 mA vs. 24 mA disabled), and improved noise margins. No PCB changes are needed, but verify that the SSOP-20 footprint matches your layout and that VCC remains within 4.5–5.5 V.
What is the meaning of the "G240A" top-side marking on SN74ALS240ADBR?
The "G240A" marking is TI's standardized device identifier for the SN74ALS240A family in SSOP-DB packaging. It distinguishes this variant from SOIC (ALS240A), PDIP (SN74ALS240AN), and SOP (ALS240A) versions - confirming correct die and package configuration during visual inspection and automated optical recognition.
Is SN74ALS240ADBR RoHS compliant?
Yes, SN74ALS240ADBR is RoHS compliant, with lead finish specified as NiPdAu (NIPDAU) and MSL Level-1 rating (260°C peak reflow). This compliance is confirmed in TI's Package Option Addendum dated 15-Jul-2026, and the device ships in tape-and-reel packaging (2000 units/reel) meeting EU Directive 2011/65/EU requirements.
SN74ALS240ADBR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
SN74ALS240ADBR FAQ
1.How can I place an order for SN74ALS240ADBR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS240ADBR 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 SN74ALS240ADBR reliable?
The price and inventory of SN74ALS240ADBR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS240ADBR is usually 5 days.
3.What payment methods are accepted for SN74ALS240ADBR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS240ADBR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS240ADBR?
SN74ALS240ADBR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS240ADBR 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 SN74ALS240ADBR?
For technical support, including SN74ALS240ADBR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS240ADBR requirements.
6.How does Aetrix verify that SN74ALS240ADBR is sourced from the original manufacturer or authorized distributors?
All SN74ALS240ADBR 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 SN74ALS240ADBR meets industry standards.
7.What is the process for return or replacement of SN74ALS240ADBR?
All SN74ALS240ADBR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS240ADBR, 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 SN74ALS240ADBR part is unused and in its original packaging.
Return procedure for SN74ALS240ADBR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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