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Texas Instruments SN74ALS240ADWR
- Part No.:
- SN74ALS240ADWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS240ADWR.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,897
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Product details
Overview
SN74ALS240ADWR 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 (tPLH/tPHL), and features pnp input structure to reduce DC loading on upstream logic.
For engineers reviewing the SN74ALS240ADWR datasheet, SN74ALS240ADWR pinout, SN74ALS240ADWR application, or SN74ALS240ADWR equivalent, this device is selected for high-fan-out 5-V bus buffering where fast enable/disable timing (tPZL = 18 ns max), low quiescent current (ICC = 14–25 mA), and industrial-temperature operation (0°C to 70°C) are required.
Technical Context
This device implements dual 4-bit noninverting buffers with independent active-low 3-state enable inputs (1OE, 2OE), allowing selective control of two groups of four outputs. Its ALS (Advanced Low-Power Schottky) logic family provides improved speed-power trade-offs over standard LS, with symmetrical OE/OE inputs enabling flexible bus arbitration schemes when paired with 'ALS241/'ALS244 devices.
The pnp input stage reduces input current draw (IIL = –0.1 mA max), while the totem-pole output stage supports bidirectional bus driving with guaranteed VOH ≥ 2.4 V at IOH = –15 mA and VOL ≤ 0.4 V at IOL = 24 mA - meeting TTL voltage thresholds across temperature and supply variations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - balances speed (9 ns propagation) and power (25 mA max ICC) better than LS. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V TTL rails; no regulation needed for nominal operation. |
| Output Drive | 24 mA low-level (IOL), –15 mA high-level (IOH) - drives 20+ TTL loads without external pull-ups. |
| Propagation Delay | 9 ns max (A→Y), 13 ns max (OE→Y disable) - enables sub-100 MHz bus cycles in synchronous designs. |
| 3-State Leakage | ±20 µA (IOZL/IOZH) - ensures minimal bus contention during output disable. |
| Operating Temp | 0°C to 70°C - qualified for commercial/industrial embedded systems, not extended or military grade. |
| Input Loading | IIL = –0.1 mA max - reduces loading on preceding gates, critical in high-fan-in address decode trees. |
Pinout & Package
SN74ALS240ADWR uses a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 1.27 mm pitch, 2.65 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE, 2OE | Active-low output enable | Independent control of Y1–Y4 (Group 1) and Y5–Y8 (Group 2); low = enabled, high = high-Z. |
| 1A1–1A4, 2A1–2A4 | Noninverting data inputs | Eight buffered inputs mapped 1:1 to outputs; pnp inputs minimize DC loading on source logic. |
| 1Y1–1Y4, 2Y1–2Y4 | 3-state noninverting outputs | Drive memory address buses or data lines; high-Z state isolates bus segments during arbitration. |
| VCC, GND | Power supply terminals | Single 5-V supply; decoupling required within 1 cm due to fast switching transients (di/dt). |
Key Features
| Feature | Design Value |
|---|---|
| High fan-out capability | Drives ≥20 TTL loads per output, reducing need for cascaded buffers in dense address decoding. |
| Symmetrical OE inputs | 1OE and 2OE share identical electrical specs, enabling balanced bus partitioning and clean timing margins. |
| pnp input structure | Reduces input current to ≤0.1 mA, preventing excessive loading on clock drivers or microcontroller port pins. |
| Fast 3-state transition | tPZL = 18 ns max and tPLZ = 12 ns max ensure rapid bus release for time-critical DMA or multiplexed memory access. |
| TTL-compatible voltage thresholds | VIH = 2.0 V min, VIL = 0.8 V max - interoperates seamlessly with legacy 74LS/74F and modern microcontrollers. |
Applications
| Memory Address Buffering | Bus Transceiver Interface |
|---|---|
Use Scenario: Driving 16-bit address bus between microprocessor and SRAM/ROM in industrial PLCs. IC Role / Device Role / Timing Role: Noninverting octal buffer isolating CPU address lines from memory load; 3-state enables shared bus with peripherals. Use Value: Prevents address skew via matched propagation delays (≤9 ns), and eliminates contention using independent OE control per 4-bit group. | Use Scenario: Bidirectional data bus isolation between FPGA and legacy parallel ADC/DAC in test equipment. IC Role / Device Role / Timing Role: Direction-controlled buffer with OE-synchronized enable; used as unidirectional leg in split-bus architecture. Use Value: Enables clean bus turn-around with 12–18 ns disable/enable times, avoiding metastability in handshaked transfers. |
| Clock Distribution Network | Legacy System Bus Expansion |
Use Scenario: Fan-out of system clock to multiple peripheral controllers in avionics subsystems. IC Role / Device Role / Timing Role: Low-skew clock driver with 3-state capability for dynamic clock gating during sleep modes. Use Value: Delivers 24 mA drive into 50-Ω traces, maintaining edge integrity; pnp inputs prevent clock tree loading degradation. | Use Scenario: Adding ISA-compatible I/O expansion to retro-computing platforms using Z80 or 8088 CPUs. IC Role / Device Role / Timing Role: Address latch interface and bus driver for 8-bit peripheral slots requiring TTL-level compatibility. Use Value: Matches vintage 74LS240 timing and voltage specs, ensuring drop-in replacement without layout changes. |
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 |
|---|---|---|---|
| SN74ALS240AN | Same ALS logic, PDIP-20 package; higher θJA (70°C/W vs. 58°C/W), no tape-and-reel option. | Preferred for prototyping or low-volume through-hole assembly; lacks automated placement support. | Select SN74ALS240AN only if manual soldering or socket-based validation is required. |
| SN74AS240ADWR | AS family: faster (6.5 ns max tPLH), higher drive (64 mA IOL), but 75 mA ICC - 3× power draw vs. ALS. | Better for high-speed backplanes (>25 MHz), but unsuitable for thermally constrained or battery-backed systems. | Choose SN74AS240ADWR only when propagation delay dominates over power and thermal budget. |
Compared with SN74ALS240AN and SN74AS240ADWR, the SN74ALS240ADWR offers optimal balance of speed (9 ns), power (25 mA ICC), and manufacturability (SOIC tape-and-reel), making it ideal for volume production of industrial control and instrumentation boards.
Availability
SN74ALS240ADWR is available at Aetrix Electronics and suitable for memory address buffering, bus transceiver interfaces, clock distribution networks, and legacy system bus expansion requiring stable component supply across long-lifecycle industrial programs.
Supply support for SN74ALS240ADWR 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 ICs, with decades of heritage in TTL and advanced logic families.
The SN74ALS240ADWR belongs to TI's legacy ALS logic portfolio, engineered specifically for high-density, low-power 3-state memory address and bus driver applications in commercial and industrial systems.
FAQ
What is the maximum recommended output current for SN74ALS240ADWR?
The SN74ALS240ADWR is rated for 24 mA low-level output current (IOL) under recommended conditions (VCC = 4.5 V, TA = 0°C to 70°C). This value is guaranteed per output and applies to the standard version - not the -1 variant (48 mA), which is not offered in the DW package. Exceeding 24 mA risks VOL degradation and thermal stress.
Does SN74ALS240ADWR support mixed-voltage interfacing with 3.3-V logic?
No, SN74ALS240ADWR is strictly a 5-V TTL device. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output swing (VOH ≥ 2.4 V, VOL ≤ 0.4 V) are specified only for 4.5–5.5 V operation. Direct connection to 3.3-V CMOS may cause overvoltage stress on inputs and undefined logic levels; level-shifting circuitry is required.
Can SN74ALS240ADWR replace SN74LS240 in existing designs?
Yes, SN74ALS240ADWR is a functional and pin-compatible upgrade to SN74LS240 in SOIC packages. It offers faster propagation (9 ns vs. 15 ns), lower ICC (25 mA vs. 35 mA), and reduced input loading (IIL = –0.1 mA vs. –0.4 mA), with identical pinout and voltage compatibility. No PCB changes are needed for drop-in replacement.
What is the thermal resistance (θJA) of the SN74ALS240ADWR package?
The SN74ALS240ADWR in SOIC (DW) package has a junction-to-ambient thermal resistance (θJA) of 58°C/W, as specified in the TI datasheet SDAS214E. This value assumes standard JEDEC 2-layer board conditions (1-inch² copper pad, 2 oz Cu). For sustained 24 mA per output, junction temperature rise remains within limits up to ~70°C ambient.
How does the pnp input structure benefit system design with SN74ALS240ADWR?
The pnp input structure in SN74ALS240ADWR reduces input current draw to ≤0.1 mA (vs. ~0.4 mA in LS), significantly lowering DC loading on upstream drivers such as microcontroller GPIOs or clock generators. This prevents voltage droop and timing margin erosion in high-fan-in address decode trees or clock distribution networks.
SN74ALS240ADWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm 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-SOIC
SN74ALS240ADWR FAQ
1.How can I place an order for SN74ALS240ADWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS240ADWR 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 SN74ALS240ADWR reliable?
The price and inventory of SN74ALS240ADWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS240ADWR is usually 5 days.
3.What payment methods are accepted for SN74ALS240ADWR?
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4.How is shipping managed for SN74ALS240ADWR?
SN74ALS240ADWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS240ADWR 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 SN74ALS240ADWR?
For technical support, including SN74ALS240ADWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS240ADWR requirements.
6.How does Aetrix verify that SN74ALS240ADWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS240ADWR 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 SN74ALS240ADWR meets industry standards.
7.What is the process for return or replacement of SN74ALS240ADWR?
All SN74ALS240ADWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS240ADWR, 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 SN74ALS240ADWR part is unused and in its original packaging.
Return procedure for SN74ALS240ADWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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