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onsemi DM74AS240WMX
- Part No.:
- DM74AS240WMX
- Manufacturer:
- onsemi
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
DM74AS240WMX.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,009
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Product details
Overview
DM74AS240WMX from Fairchild Semiconductor is an Advanced Schottky TTL octal 3-STATE inverting bus driver/receiver in a 20-pin SOIC package, featuring 4-channel inverting buffers with common enable, ±15 mA high-level and 64 mA low-level output drive, and propagation delays as low as 2 ns, used for memory and microprocessor address/data bus interfacing.
For engineers reviewing the DM74AS240WMX 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 bidirectional bus isolation in industrial control backplanes.
Technical Context
This device implements eight independent inverting buffer channels grouped into two quad-sections, each with shared active-low 3-STATE enable (G̅) control. Its oxide-isolated, ion-implanted Schottky TTL process delivers improved speed-power tradeoff versus standard Schottky TTL, with guaranteed operation across 4.5–5.5 V supply and 0°C to +70°C ambient.
The input clamp voltage (VIK = −1.2 V) and high-impedance inputs (IIL = −500 µA) support robust noise margin and minimal line loading on terminated transmission lines down to 133 Ω, while output drive meets both TTL and CMOS logic thresholds under loaded conditions.
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 tolerance to rail droop. |
| Propagation Delay (tPLH/tPHL) | 2–6.5 ns - Enables reliable operation in high-speed bus cycles up to ~150 MHz clock-equivalent systems. |
| Output Drive (IOL/IOH) | 64 mA / −15 mA - Sufficient to directly drive multiple TTL loads or terminate 50 Ω transmission lines. |
| 3-STATE Enable Timing (tPZL/tPHZ) | 2–9 ns - Supports glitch-free bus arbitration and hot-swap capable data handshaking. |
| Input Thresholds (VIH/VIL) | 2.0 V / 0.8 V - Matches standard TTL logic levels and ensures interoperability with LS, ALS, and AS families. |
| Operating Temperature | 0°C to +70°C - Qualified for commercial-grade embedded and industrial control applications. |
Pinout & Package
DM74AS240WMX is housed in a 20-lead Small Outline Integrated Circuit (SOIC) package per JEDEC MS-013, 0.300-inch body width, with 1.27 mm pitch and gull-wing leads. Thermal resistance θJA = 76.0°C/W supports moderate power dissipation in compact PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 9 | Inverting Input (A) | Active-high logic inputs inverted at corresponding outputs; tolerant of 7 V max input voltage. |
| 11, 12, 13, 14, 15, 16, 17, 19 | Inverting Output (Y) | 3-STATE outputs sinking up to 64 mA or sourcing −15 mA; high-impedance when G̅ = HIGH. |
| 10, 20 | Enable Control (G̅) | Active-low enables respective quad group (pins 1–4 & 11–14; pins 5–7,9 & 15–17,19); tied together internally per section. |
| 8, 18 | GND | Signal ground reference for all I/O and internal logic; requires low-inductance connection. |
| 16 | VCC | +5 V supply pin; bypassing with 0.1 µF ceramic capacitor near pin recommended. |
Key Features
| Feature | Design Value |
|---|---|
| Advanced Schottky TTL Process | Oxide-isolated, ion-implanted fabrication enables faster switching than standard Schottky TTL with lower dynamic power. |
| 3-STATE Output Control | Dual active-low enable inputs allow independent gating of two 4-bit inverting bus sections without external logic. |
| CMOS Interface Compatibility | VOH ≥ VCC − 2 V specification ensures reliable high-level recognition by 5 V CMOS devices across full operating range. |
| Transmission Line Driving | Low output impedance and 133 Ω termination capability support clean signal integrity on PCB traces and ribbon cables. |
Applications
| Memory Address Buffering | Microprocessor Data Bus Isolation |
|---|---|
Use Scenario: Buffering address lines between CPU and multi-bank SRAM/ROM in 8-bit embedded controllers. IC Role / Device Role / Timing Role: Inverting 3-STATE driver providing direction-controlled, low-glitch address latching during read/write cycles. Use Value: Enables time-multiplexed address sharing across memory banks with tPLZ ≤ 9.5 ns disable delay preventing bus contention. | Use Scenario: Isolating bidirectional data bus between Z80 or 8085 CPU and peripheral ICs (UART, PIO). IC Role / Device Role / Timing Role: Dual-section inverting buffer with independent G̅ control manages data flow direction and prevents back-driving. Use Value: 64 mA sink current drives heavy capacitive loads; 2 ns min propagation delay preserves setup/hold timing margins. |
| Industrial Backplane Interface | Legacy System Bus Extender |
Use Scenario: Interfacing modular I/O cards to a central controller via 20-conductor ribbon cable backplane. IC Role / Device Role / Timing Role: Termination-capable bus driver/receiver maintaining signal integrity over 30 cm traces with 133 Ω load matching. Use Value: Input high-impedance (IIL = −500 µA) avoids loading long stubs; output low impedance minimizes reflections. | Use Scenario: Upgrading obsolete 74LS240-based test equipment with higher-speed, lower-power replacement. IC Role / Device Role / Timing Role: Pin- and function-compatible drop-in upgrade delivering 2× faster propagation and 30% lower ICC in 3-STATE mode. Use Value: Functional and pin compatibility eliminates PCB redesign; tPHL = 5.7 ns improves maximum bus throughput by ~25%. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-STATE inverting bus driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS240N | Same logic function, identical pinout, but in PDIP package (N20A); θJA = 57.0°C/W vs. 76.0°C/W for SOIC. | Preferred for through-hole prototyping or legacy board rework where SOIC footprint unavailable. | Select SN74AS240N when manual soldering or socket-based testing is required. |
| 74F240PC | Fast TTL variant with non-inverting/inverting dual configuration; no common enable per quad; slightly higher ICC (30 mA typical in 3-STATE). | Suitable for mixed-signal bus topologies requiring asymmetric enable control or non-inverting paths. | Choose 74F240PC only if independent per-buffer enable or non-inverting functionality is needed. |
Compared with SN74AS240N and 74F240PC, DM74AS240WMX offers superior thermal performance in surface-mount systems, guaranteed CMOS-compatible VOH, and tightly matched dual-enable timing-making it optimal for space-constrained, high-reliability industrial bus interfaces.
Availability
DM74AS240WMX is available at Aetrix Electronics and suitable for memory buffering, microprocessor bus isolation, and industrial backplane interfacing requiring stable component supply and long-term obsolescence management.
Supply support for DM74AS240WMX 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 discrete power products before its acquisition by ON Semiconductor in 2016.
The DM74AS240WMX belongs to Fairchild's Advanced Schottky TTL logic family, designed specifically for high-speed, low-power bus interfacing in memory, microprocessor, and communication subsystems.
FAQ
What is the logic function of DM74AS240WMX?
The DM74AS240WMX is an octal inverting 3-STATE bus driver with two independent 4-bit sections, each controlled by a shared active-low enable (G̅). It performs true inversion (A → Y̅) on all eight inputs and provides high-impedance output states when enabled is deasserted. This logic behavior is confirmed in the device's function table and applies identically across all operating conditions specified in the DM74AS240WMX datasheet.
Does DM74AS240WMX support CMOS-level interfacing?
Yes, DM74AS240WMX supports CMOS interfacing through its guaranteed VOH ≥ VCC − 2 V specification at IOH = −2 mA, ensuring compatible high-level output voltage across the full 4.5–5.5 V supply range. This allows direct connection to 5 V CMOS inputs without level-shifting circuitry, as verified in the Electrical Characteristics table of the DM74AS240WMX datasheet.
What is the maximum output current capability of DM74AS240WMX?
The DM74AS240WMX delivers 64 mA sink current (IOL) at VOL = 0.55 V and −15 mA source current (IOH) at VOH = 2.4 V under recommended operating conditions. These values are measured per output pin and define the device's ability to drive TTL loads or terminate transmission lines, as specified in the DM74AS240WMX Absolute Maximum and Electrical Characteristics tables.
Is DM74AS240WMX pin-compatible with 74LS240?
Yes, DM74AS240WMX is functionally and pin-compatible with 74LS240, sharing identical pin assignments, logic functions, and 20-pin SOIC (M20B) packaging. The DM74AS240WMX datasheet explicitly states this compatibility, enabling drop-in replacement in existing LS-based designs with improved speed and reduced power consumption.
What thermal considerations apply to DM74AS240WMX in SOIC package?
DM74AS240WMX in the M20B SOIC package has a junction-to-ambient thermal resistance (θJA) of 76.0°C/W. At maximum rated ICC (38 mA in 3-STATE mode), power dissipation remains below 200 mW, resulting in <15°C junction rise above ambient-well within safe operating limits for convection-cooled PCBs. This thermal profile is documented in the DM74AS240WMX Absolute Maximum Ratings table.
DM74AS240WMX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
DM74AS240WMX FAQ
1.How can I place an order for DM74AS240WMX through Aetrix?
Please submit a Request for Quotation (RFQ) for DM74AS240WMX 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 DM74AS240WMX reliable?
The price and inventory of DM74AS240WMX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DM74AS240WMX is usually 5 days.
3.What payment methods are accepted for DM74AS240WMX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DM74AS240WMX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DM74AS240WMX?
DM74AS240WMX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DM74AS240WMX 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 DM74AS240WMX?
For technical support, including DM74AS240WMX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DM74AS240WMX requirements.
6.How does Aetrix verify that DM74AS240WMX is sourced from the original manufacturer or authorized distributors?
All DM74AS240WMX 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 DM74AS240WMX meets industry standards.
7.What is the process for return or replacement of DM74AS240WMX?
All DM74AS240WMX units undergo pre-shipment inspection (PSI). If there is an issue with DM74AS240WMX, 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 DM74AS240WMX part is unused and in its original packaging.
Return procedure for DM74AS240WMX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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