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onsemi DM74AS240WM
- Part No.:
- DM74AS240WM
- Manufacturer:
- onsemi
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
DM74AS240WM.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,615
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Product details
Overview
DM74AS240WM from Fairchild Semiconductor is an advanced Schottky TTL octal 3-STATE inverting bus driver/receiver in a 20-pin SOIC package, featuring 4-channel enable-controlled inversion, ±15 mA high-level and 64 mA low-level output drive, and propagation delays as low as 2 ns, used for bidirectional memory and microprocessor bus interfacing.
For engineers reviewing the DM74AS240WM datasheet, pinout, applications, or equivalent options, key selection criteria include 3-STATE enable timing (tPZL ≤ 9 ns), CMOS-compatible VOH = VCC − 2 V interface capability, and 133 Ω transmission line drive strength under 5 V operation.
Technical Context
The DM74AS240WM implements two independent 4-bit inverting buffer groups, each with shared active-low 3-STATE enable (G̅), enabling bidirectional bus control when paired with complementary devices. Its oxide-isolated, ion-implanted Schottky process delivers improved speed-power trade-offs versus standard Schottky TTL.
It operates across 4.5–5.5 V supply with guaranteed logic thresholds (VIL = 0.8 V, VIH = 2.0 V), supports terminated line driving down to 133 Ω, and maintains high-impedance outputs (IOZH ≤ 50 µA, IOZL ≥ −50 µA) during disable-critical for multi-drop bus arbitration.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5–5.5 V - Ensures compatibility with standard 5 V TTL/CMOS systems and noise margin stability. |
| Propagation Delay (tPLH/tPHL) | 2–6.5 ns - Enables high-speed bus cycles up to ~150 MHz in point-to-point configurations. |
| Output Drive (IOL/IOH) | 64 mA / −15 mA - Sufficient to drive 50 Ω parallel-terminated lines or fan-out to ≥20 LS-TTL loads. |
| 3-STATE Enable Timing (tPZL/tPHZ) | 2–9 ns - Supports fast bus turnaround in time-multiplexed address/data architectures. |
| Input Thresholds (VIL/VIH) | 0.8 V / 2.0 V - Guarantees robust noise immunity and interoperability with 5 V CMOS and TTL families. |
| Operating Temperature | 0°C to +70°C - Qualified for commercial-grade embedded and industrial control applications. |
Pinout & Package
DM74AS240WM is housed in a 20-lead Small Outline Integrated Circuit (SOIC) package per JEDEC MS-013, 0.300-inch body width, with standard thermal pad layout and gull-wing leads for surface-mount assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 4, 5, 7, 8, 10, 11 | Inverting Input (A) | Eight buffered inputs accepting standard TTL logic levels; inverted at corresponding outputs. |
| 3, 6, 9, 12 | Active-Low Enable (G̅) | Four independent enables - pins 3/6 control outputs Y1–Y4; pins 9/12 control Y5–Y8. |
| 13–20 | Inverting Output (Y) | Eight 3-STATE outputs; driven low/high when respective G̅ = L, high-impedance when G̅ = H. |
| 10, 20 | Power (VCC/GND) | VCC on pin 20, GND on pin 10 - decoupling required within 1 cm for stable high-speed switching. |
Key Features
| Feature | Design Value |
|---|---|
| Advanced Schottky Process | Oxide-isolated, ion-implanted construction reduces propagation delay while lowering power vs. 74S/74LS equivalents. |
| CMOS Interface Compatibility | VOH specified at VCC − 2 V ensures reliable high-level recognition by 5 V CMOS inputs without level shifters. |
| Transmission Line Drive | Output impedance and current drive support direct connection to 133 Ω terminated buses without external series termination. |
| Pin Compatibility | Functional and pinout identical to 74LS240 and 74S240 - enables drop-in replacement in legacy designs. |
Applications
| Memory Bus Interface | Microprocessor Address Latch |
|---|---|
Use Scenario: Driving bidirectional data bus between CPU and SRAM/ROM in 8-bit embedded controllers. IC Role / Device Role / Timing Role: Inverting 3-STATE buffer providing direction-controlled data isolation and bus contention prevention. Use Value: 2 ns minimum propagation delay and 64 mA sink capability ensure setup/hold timing compliance with Z80 or 8085 bus cycles. | Use Scenario: Latching and buffering 16-bit address lines during multiplexed AD bus operation. IC Role / Device Role / Timing Role: Dual-group inverting driver enabling separate enable control for upper/lower address byte segments. Use Value: Independent G̅ pins (3/6 and 9/12) allow staggered address strobe timing without added glue logic. |
| Communications Backplane | Industrial I/O Expansion |
Use Scenario: Interfacing UART or parallel printer port signals across a 133 Ω-terminated backplane. IC Role / Device Role / Timing Role: Unidirectional line driver/receiver supporting hot-swappable module insertion. Use Value: High-impedance disable state (IOZL ≤ −50 µA) prevents signal corruption during module reconfiguration. | Use Scenario: Isolating PLC I/O modules from central controller bus under EMI-prone factory conditions. IC Role / Device Role / Timing Role: Noise-immune bus buffer with 0.8 V/2.0 V input thresholds rejecting common-mode transients. Use Value: Guaranteed operation from 0°C to +70°C and 5.5 V absolute max rating support long-term reliability in uncooled enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting 3-STATE bus driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS240N | Dual-in-line (PDIP) package; identical electrical specs and pinout; θJA = 57°C/W vs. 76°C/W for SOIC. | Better thermal performance in through-hole prototyping or low-volume manual assembly. | Prefer SN74AS240N for breadboarding or legacy PCBs with DIP footprints. |
| 74F240PC | Fast TTL family - faster tPLH/tPHL (1.5–4.5 ns), higher ICC (up to 95 mA), no VCC−2 V VOH guarantee. | Higher speed but reduced noise margin; requires tighter power integrity and decoupling. | Choose 74F240PC only when sub-5 ns delay is mandatory and CMOS interface is not required. |
Compared with SN74AS240N and 74F240PC, DM74AS240WM offers optimal balance of SOIC mountability, 76°C/W thermal resistance, guaranteed VCC−2 V output compatibility with CMOS, and proven reliability in commercial temperature bus systems.
Availability
DM74AS240WM is available at Aetrix Electronics and suitable for memory bus interface, microprocessor address latching, and industrial I/O expansion requiring stable component supply and long-lifecycle support.
Supply support for DM74AS240WM 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
Fairchild Semiconductor was a U.S.-based semiconductor company specializing in analog and mixed-signal ICs, acquired by ON Semiconductor in 2016; known for high-performance TTL, analog switches, and power management solutions.
The DM74AS240WM belongs to Fairchild's Advanced Schottky TTL bus interface product line, engineered for high-speed, low-noise bidirectional data transfer in memory and microprocessor systems operating at 5 V.
FAQ
What is the function of the DM74AS240WM in a digital system?
The DM74AS240WM functions as an octal inverting 3-STATE bus driver/receiver, providing bidirectional or unidirectional signal buffering with independent enable control per four-bit group. It isolates bus segments, prevents contention, and drives terminated transmission lines down to 133 Ω - critical for reliable data transfer in memory and microprocessor systems using the DM74AS240WM.
Does the DM74AS240WM support CMOS-level interfacing?
Yes, the DM74AS240WM specifies VOH = VCC − 2 V (minimum 2.4 V at VCC = 4.5 V), ensuring compatible high-level output voltage for standard 5 V CMOS inputs without external level-shifting circuitry - a verified design feature confirmed in its Electrical Characteristics table and explicitly called out in the Features section of the DM74AS240WM datasheet.
What is the maximum recommended operating temperature for the DM74AS240WM?
The DM74AS240WM is rated for a free-air operating temperature range of 0°C to +70°C, as defined in the Recommended Operating Conditions table. This commercial-grade specification aligns with typical requirements for industrial control panels, embedded computing, and communications equipment where ambient temperatures remain within this bound during DM74AS240WM deployment.
How does the DM74AS240WM differ from the DM74AS244?
The DM74AS240WM is an inverting octal buffer, whereas the DM74AS244 is non-inverting. Both share identical pinouts, 3-STATE enable architecture, and electrical specifications - making them functionally interchangeable only when inversion logic is accounted for in system design. The DM74AS240WM's inversion is fixed and cannot be disabled, distinguishing its use case from the DM74AS244 in signal polarity-sensitive paths.
Is the DM74AS240WM pin-compatible with older TTL families?
Yes, the DM74AS240WM is functionally and pin-compatible with 74LS240 and 74S240 devices, as stated in its Features section. This allows direct replacement in existing designs without PCB modification, preserving layout integrity while upgrading speed and reducing power - a key advantage confirmed across Fairchild's documentation for the DM74AS240WM.
DM74AS240WM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
DM74AS240WM FAQ
1.How can I place an order for DM74AS240WM through Aetrix?
Please submit a Request for Quotation (RFQ) for DM74AS240WM 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 DM74AS240WM reliable?
The price and inventory of DM74AS240WM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DM74AS240WM is usually 5 days.
3.What payment methods are accepted for DM74AS240WM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DM74AS240WM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DM74AS240WM?
DM74AS240WM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DM74AS240WM 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 DM74AS240WM?
For technical support, including DM74AS240WM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DM74AS240WM requirements.
6.How does Aetrix verify that DM74AS240WM is sourced from the original manufacturer or authorized distributors?
All DM74AS240WM 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 DM74AS240WM meets industry standards.
7.What is the process for return or replacement of DM74AS240WM?
All DM74AS240WM units undergo pre-shipment inspection (PSI). If there is an issue with DM74AS240WM, 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 DM74AS240WM part is unused and in its original packaging.
Return procedure for DM74AS240WM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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