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Texas Instruments CD74HC240E
- Part No.:
- CD74HC240E
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74HC240E.pdf
- Description:
- IC BUFFER INVERT 6V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,245
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Product details
Overview
CD74HC240E from Texas Instruments is an inverting octal buffer/line driver with three-state outputs and dual active-low output enables, operating across 2 V to 6 V. It delivers 8 ns typical propagation delay at 5 V/15 pF, supports ±25 mA bus-driver output current, and functions over –55℃ to 125℃ for industrial control backplane interfacing.
For engineers reviewing the CD74HC240E datasheet, CD74HC240E pinout, CD74HC240E application, or CD74HC240E equivalent, this page provides verified electrical characteristics, package-specific thermal data, functional block diagram alignment, three-state timing behavior (enable/disable), and direct comparison against HC241/HCT244 variants for bus isolation and bidirectional data path design.
Technical Context
The CD74HC240E implements two independent 4-bit inverting buffers, each controlled by its own active-low output enable (1OE, 2OE). All eight outputs enter high-impedance state when either enable is asserted, enabling shared-bus arbitration without external logic.
Its CMOS architecture ensures rail-to-rail output swing, buffered inputs for noise immunity, and fanout capability of 10 LSTTL loads per standard output or 15 per bus-driver output - validated under –55℃ to 125℃ operation with VIH/VIL thresholds defined at 30% and 70% of VCC.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting octal buffer with dual active-low 3-state enables (1OE, 2OE) |
| Propagation Delay | 8 ns typical at VCC = 5 V, CL = 15 pF, TA = 25℃ - enables ≤125 MHz bus toggling in low-load systems |
| Supply Voltage Range | 2 V to 6 V - supports mixed-voltage system interfacing and battery-backed operation down to 2 V |
| Output Drive | ±25 mA per output - sufficient to drive 15 LSTTL loads or terminate 50 Ω transmission lines |
| Operating Temperature | –55℃ to 125℃ - qualified for aerospace, automotive under-hood, and industrial motor control environments |
| Input Leakage | ±1 μA max at 6 V - minimizes static power in high-impedance input configurations |
| Three-State Leakage | ±10 μA max at 6 V - ensures reliable bus float during disable without pull-up/down contention |
Pinout & Package
CD74HC240E is supplied in a 20-pin PDIP (Plastic Dual In-line Package) with 25.40 mm × 6.35 mm body size and 2.54 mm lead pitch. The package is through-hole mountable, RoHS-compliant (NIPDAU finish), and rated for manual soldering up to 300℃ for 10 seconds.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 9 | Input A1–A4, B1–B4 | Eight buffered logic inputs; inverted at corresponding outputs Y1–Y4, Y1'–Y4' |
| 10, 19 | GND, VCC | Ground and positive supply pins - require local 0.1 μF bypass capacitor placement |
| 11, 18 | 1OE, 2OE | Active-low output enables - asserting either disables all four outputs in its group |
| 12, 13, 14, 15, 16, 17, 20, 8 | Y1–Y4, Y1'–Y4' | Eight inverting three-state outputs - high-impedance when respective OE is high |
Key Features
| Feature | Design Value |
|---|---|
| Inverting three-state logic | Enables bidirectional bus control using complementary enable signals without external inverters |
| High-noise-immunity inputs | NIH/NIL = 30% of VCC at 5 V - rejects >1.5 V common-mode noise on shared PCB traces |
| Wide supply range (2–6 V) | Eliminates level-shifting components when interfacing 3.3 V microcontrollers to 5 V peripherals |
| Low dynamic power dissipation | CPD = 38 pF - reduces switching current vs. LSTTL, critical for thermally constrained enclosures |
| Identical pinout with HC241/HCT244 | Allows drop-in replacement across inverting/non-inverting variants during prototyping or ECOs |
Applications
| Industrial PLC Backplane Interface | Legacy Bus Signal Conditioning |
|---|---|
|
Use Scenario: Isolating CPU address/data buses from noisy I/O modules in programmable logic controllers. IC Role / Device Role / Timing Role: Inverting buffer with three-state control acts as direction-controlled bus repeater between isolated voltage domains. Use Value: ±25 mA drive strength sustains signal integrity across 30 cm ribbon cables; –55℃ to 125℃ rating matches industrial enclosure thermal profiles. |
Use Scenario: Level-shifting and fanout expansion for TTL-era parallel printer ports connected to modern microcontrollers. IC Role / Device Role / Timing Role: Inverting buffer translates 3.3 V logic to 5 V while providing 15-LSTTL load drive for legacy peripherals. Use Value: 2 V to 6 V supply range allows direct 3.3 V or 5 V operation; 8 ns propagation delay preserves timing margins in 1 MHz parallel handshaking. |
| Automotive Sensor Hub Multiplexing | Test Equipment Signal Gating |
|
Use Scenario: Time-multiplexing analog sensor outputs (e.g., temperature, pressure) onto a shared ADC input channel. IC Role / Device Role / Timing Role: Three-state inverting buffer gates individual sensor signals under MCU GPIO control via 1OE/2OE. Use Value: Dual enables allow independent 4-bit group control; ±10 μA three-state leakage prevents crosstalk between unselected channels. |
Use Scenario: Enabling/disabling stimulus signals in automated test equipment during calibration sequences. IC Role / Device Role / Timing Role: Inverting buffer with precise enable timing isolates DUT inputs during setup/hold intervals. Use Value: 30 ns typical output enable/disable time (tPLZ/tPHZ) meets sub-100 ns gating requirements; rail-to-rail VOH/VOL ensures clean logic thresholds. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| CD74HCT240E | 5 V only (4.5–5.5 V); TTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2 V) | Required when interfacing directly to legacy 5 V TTL logic without level shifters | Select for strict LSTTL input compatibility; not suitable for 2–3.3 V systems |
| SN74HC240N | Same logic function and pinout; identical HC family specs but TI's commercial-grade variant (0℃ to 70℃) | Applicable in non-extended temperature commercial instrumentation where cost is prioritized | Choose for cost-sensitive, non-industrial designs with ambient temperature constraints |
Compared with CD74HC240E, CD74HCT240E trades wide-voltage flexibility for guaranteed TTL input compatibility, while SN74HC240N reduces temperature margin to lower cost - making CD74HC240E optimal for extended-range, mixed-supply industrial interfaces requiring robust noise immunity.
Availability
CD74HC240E is available at Aetrix Electronics and suitable for industrial PLC backplane interface, automotive sensor hub multiplexing, and test equipment signal gating requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HC240E 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, embedded processing, and connectivity solutions for industrial, automotive, and communications markets since 1930.
CD74HC240E belongs to TI's CD74HC high-speed CMOS logic family, engineered for low-power, wide-voltage, extended-temperature digital interfacing in harsh-environment control systems.
FAQ
What is the maximum output current per pin for CD74HC240E?
The CD74HC240E supports ±25 mA DC output current per pin under recommended operating conditions. This value is specified in the Electrical Characteristics table for VOL and VOH tests at 4.5 V and 6 V supply, ensuring reliable drive into 15 LSTTL loads or 50 Ω transmission lines without exceeding absolute maximum ratings.
Does CD74HC240E support 3.3 V operation?
Yes, CD74HC240E operates fully across 2 V to 6 V, including 3.3 V nominal supply. At 3.3 V, VIH is guaranteed ≥2.31 V and VIL ≤1.1 V (30% and 70% of VCC), and propagation delay increases to ~12 ns (typical) versus 8 ns at 5 V - confirmed in the HC-type switching characteristics tables.
How does the dual output enable (1OE/2OE) function in CD74HC240E?
In CD74HC240E, 1OE controls outputs Y1–Y4 and 2OE controls outputs Y1'–Y4'. Both enables are active-low: asserting either to logic low enables its respective 4-bit group, while pulling both high places all eight outputs in high-impedance state - enabling flexible bus arbitration without external logic.
Is CD74HC240E pin-compatible with CD74HC244E?
No - CD74HC240E is inverting, while CD74HC244E is non-inverting. Though both share identical 20-pin PDIP pinouts and dual active-low enables, their input-to-output polarity differs. Swapping them requires logic inversion elsewhere in the signal path to maintain functional correctness.
What thermal derating applies to CD74HC240E in PDIP package?
CD74HC240E in PDIP (N package) has RθJA = 84.6 °C/W. At 25℃ ambient and 6 V supply, maximum continuous power dissipation before junction temperature exceeds 150℃ is ~1.48 W - calculated as (150 – 25) / 84.6. Derate linearly above 25℃ ambient per the Thermal Information table.
CD74HC240E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- 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:
- 7.8mA, 7.8mA
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -55°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
CD74HC240E FAQ
1.How can I place an order for CD74HC240E through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HC240E 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 CD74HC240E reliable?
The price and inventory of CD74HC240E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HC240E is usually 5 days.
3.What payment methods are accepted for CD74HC240E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HC240E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HC240E?
CD74HC240E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HC240E 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 CD74HC240E?
For technical support, including CD74HC240E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HC240E requirements.
6.How does Aetrix verify that CD74HC240E is sourced from the original manufacturer or authorized distributors?
All CD74HC240E 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 CD74HC240E meets industry standards.
7.What is the process for return or replacement of CD74HC240E?
All CD74HC240E units undergo pre-shipment inspection (PSI). If there is an issue with CD74HC240E, 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 CD74HC240E part is unused and in its original packaging.
Return procedure for CD74HC240E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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