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Texas Instruments SN74ALS240ANSR
- Part No.:
- SN74ALS240ANSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS240ANSR.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,768
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Product details
Overview
SN74ALS240ANSR 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 SOP-NS package.
For engineers reviewing the SN74ALS240ANSR datasheet, SN74ALS240ANSR pinout, SN74ALS240ANSR application, or SN74ALS240ANSR equivalent, this device serves as a legacy-compatible, high-fan-out bus driver for memory subsystems, address latching, and bidirectional data path control where TTL-level voltage thresholds and 3-state bus arbitration are required.
Technical Context
This device implements dual 4-bit noninverting buffers with independent active-low 3-state enable controls (1OE and 2OE), enabling selective bus isolation per half-section. Its ALS logic family delivers improved speed-power trade-offs over standard TTL, with typical propagation delays of 2–9 ns (tPLH/tPHL) and fast 3-state transition times (tPZL/tPHZ down to 3–10 ns).
The input structure uses pnp-based circuitry to minimize dc input current (IIL ≤ –0.1 mA), reducing loading on upstream drivers. Output stages support symmetrical drive capability (IOH = –15 mA, IOL = 24 mA) and maintain defined VOH ≥ 2.4 V and VOL ≤ 0.4 V under full load, ensuring robust noise margins in dense bus environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | Advanced Low-Power Schottky (ALS), TTL-compatible input/output voltage thresholds |
| Supply Voltage (VCC) | 4.5 V to 5.5 V - ensures compatibility with 5 V TTL/CMOS mixed-signal systems |
| Output Drive (IOL) | 24 mA - sufficient to drive 20+ TTL loads or terminate short stubs on parallel buses |
| Propagation Delay (tPLH/tPHL) | 2 ns (min) to 9 ns (max) - enables reliable operation in sub-100 MHz address/data strobe timing windows |
| 3-State Enable Time (tPZL) | 5 ns (min) to 18 ns (max) - allows rapid bus release for time-multiplexed shared resource access |
| Input Loading (IIL) | –0.1 mA max - reduces cumulative fan-in burden on clock/address generators |
| Operating Temperature | 0°C to 70°C - qualified for commercial/industrial embedded control and computing applications |
Pinout & Package
SOP-NS (Small Outline Package, narrow body), 20-pin, 0.65 mm pitch, 7.4 mm × 8.2 mm footprint, 2.0 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1 (260°C reflow compatible).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE | Active-low output enable (Group 1) | Controls Y1–Y4 outputs; low enables, high places in high-impedance state |
| 1A1–1A4 | Noninverting input group 1 | Directly drives corresponding Y1–Y4 outputs when 1OE is asserted |
| 2OE | Active-low output enable (Group 2) | Controls Y1–Y4 outputs of second buffer set; independent of 1OE |
| 2A1–2A4 | Noninverting input group 2 | Drives second set of outputs (labeled 2Y1–2Y4 on logic diagram) |
| 1Y1–1Y4, 2Y1–2Y4 | 3-state buffered outputs | Each pair (e.g., 1Y1/2Y1) shares physical pin location but belongs to separate functional groups |
| VCC, GND | Power supply terminals | Single 5 V supply; decoupling required near pins 10 (GND) and 20 (VCC) per layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Octal noninverting buffering with dual 3-state enables | Enables independent control of two 4-bit data lanes on shared bus infrastructure |
| pnp input structure | Reduces input current draw to ≤0.1 mA, minimizing loading on preceding address generators or latches |
| High fan-out capability (24 mA IOL) | Drives up to 20 standard TTL inputs without external buffering, simplifying memory interface design |
| TTL-compatible voltage thresholds | VIH = 2.0 V min, VIL = 0.8 V max - ensures interoperability with legacy 74-series and microprocessor address/data buses |
| Fast 3-state switching (tPZL ≤ 18 ns) | Minimizes bus contention window during enable/disable transitions in time-critical memory cycles |
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 architecture. IC Role / Device Role / Timing Role: Noninverting buffer with 3-state control isolates CPU address lines during DMA or peripheral access. Use Value: Prevents address bus contention while maintaining TTL-level signal integrity across 15 cm traces with ≤9 ns propagation delay. |
Use Scenario: Bidirectional data path control between microcontroller and peripheral ASIC using single 8-bit data bus. IC Role / Device Role / Timing Role: Dual-enable octal driver acts as direction-controlled bus switch, synchronized with RD/WR strobes. Use Value: Enables clean bus turn-around with ≤18 ns disable time, eliminating need for external direction logic or pull-ups. |
| Clock Distribution Network | Legacy System Bus Expansion |
|
Use Scenario: Fan-out of system clock or chip-select signals to multiple peripheral devices in industrial controller backplane. IC Role / Device Role / Timing Role: Low-skew buffer replicating clock edges with matched tPLH/tPHL to minimize inter-device skew. Use Value: Delivers 24 mA drive into 50 Ω loads, supporting ≤2 ns skew across 8 outputs for synchronous peripheral timing. |
Use Scenario: Adding ISA-compatible I/O expansion slots to retro-computing or test equipment with vintage bus protocols. IC Role / Device Role / Timing Role: Pin-compatible replacement for obsolete 74LS240 in address latch and I/O port driver positions. Use Value: Maintains identical pinout and electrical behavior while improving power efficiency and thermal margin over LS variants. |
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 | SOIC-DW package (300 mil width, 1.27 mm pitch); same electrical specs and pinout | Requires PCB redesign for wider SOIC footprint; better thermal dissipation (θJA = 58°C/W vs 60°C/W) | Select when board layout accommodates wider SOIC and higher-volume tape-and-reel procurement is preferred. |
| SN74AS240ANSR | Faster propagation (6.5 ns max vs 9 ns), higher drive (64 mA IOL), increased ICC (75 mA vs 23 mA) | Higher speed suits tighter timing budgets but demands stricter power delivery and layout for noise control | Choose for performance-critical upgrades where ALS timing margin is insufficient and AS family qualification is acceptable. |
Compared with SN74ALS240ANSR, SN74ALS240ADWR offers identical functionality in a different SOP variant with slightly better thermal performance, while SN74AS240ANSR trades higher power consumption for significantly faster switching-making it suitable only where the 3 ns timing improvement justifies the 3× ICC increase.
Availability
SN74ALS240ANSR is available at Aetrix Electronics and suitable for memory subsystem design, industrial bus interface development, and legacy system repair requiring stable component supply with long-term traceable sourcing.
Supply support for SN74ALS240ANSR 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 with over 90 years of analog and logic innovation, delivering high-reliability components for industrial, automotive, and computing markets.
The SN74ALS240ANSR belongs to TI's legacy 74ALS logic family, engineered specifically to enhance density and performance of 3-state memory address drivers and bus-oriented receivers in 5 V TTL systems.
FAQ
What is the maximum recommended output current for SN74ALS240ANSR?
The SN74ALS240ANSR 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 is specified in the "Recommended Operating Conditions" table of the SDAS214E datasheet and reflects sustained DC drive capability into resistive loads without exceeding thermal limits or degrading VOL performance.
Does SN74ALS240ANSR support mixed-voltage interfacing with 3.3 V logic?
No, SN74ALS240ANSR is not designed for direct 3.3 V logic interfacing. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output voltage levels (VOH ≥ 2.4 V, VOL ≤ 0.4 V at 24 mA) are specified for 5 V TTL systems. Driving it from 3.3 V sources may result in marginal VIH margin, and connecting its 5 V outputs to 3.3 V inputs risks overvoltage damage unless level-shifting circuitry is used.
What is the thermal resistance (θJA) of the SN74ALS240ANSR SOP-NS package?
The junction-to-ambient thermal resistance (θJA) for SN74ALS240ANSR in the SOP-NS package is 60°C/W, as documented in the "Absolute Maximum Ratings" section of the SDAS214E datasheet. This value assumes standard JEDEC-defined PCB mounting conditions (two-layer board, 1 in² copper area) and is critical for calculating maximum allowable power dissipation at elevated ambient temperatures.
Can SN74ALS240ANSR be used as a drop-in replacement for SN74LS240N?
SN74ALS240ANSR is functionally and electrically compatible with SN74LS240 but is not a mechanical drop-in replacement due to differing packages: SN74LS240N uses PDIP-20 (600 mil width), while SN74ALS240ANSR uses SOP-NS (150 mil width, 0.65 mm pitch). Electrical behavior-including VIH/VIL, VOH/VOL, and timing-is improved in ALS, but PCB layout must be revised to accommodate the smaller SOP footprint and pitch.
How does the pnp input structure in SN74ALS240ANSR improve system design?
The pnp input structure in SN74ALS240ANSR reduces input current (IIL ≤ –0.1 mA) compared to standard TTL inputs, lowering cumulative dc loading on upstream drivers such as microprocessor address pins or latch outputs. This allows more devices to be driven from a single source without violating fan-out limits, simplifies termination design, and improves overall power efficiency in large memory or I/O subsystems.
SN74ALS240ANSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (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-SO
SN74ALS240ANSR FAQ
1.How can I place an order for SN74ALS240ANSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS240ANSR 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 SN74ALS240ANSR reliable?
The price and inventory of SN74ALS240ANSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS240ANSR is usually 5 days.
3.What payment methods are accepted for SN74ALS240ANSR?
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS240ANSR?
SN74ALS240ANSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS240ANSR 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 SN74ALS240ANSR?
For technical support, including SN74ALS240ANSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS240ANSR requirements.
6.How does Aetrix verify that SN74ALS240ANSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS240ANSR 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 SN74ALS240ANSR meets industry standards.
7.What is the process for return or replacement of SN74ALS240ANSR?
All SN74ALS240ANSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS240ANSR, 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 SN74ALS240ANSR part is unused and in its original packaging.
Return procedure for SN74ALS240ANSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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