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Texas Instruments CD74HCT42E
- Part No.:
- CD74HCT42E
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74HCT42E.pdf
- Description:
- IC DECODER 1 X 4:10 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:237
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Product details
Overview
CD74HCT42E from Texas Instruments is a high-speed CMOS BCD-to-decimal decoder with active-low outputs, designed for digital logic decoding in industrial control and instrumentation systems. It operates at 4.5V–5.5V, delivers 14ns typical propagation delay (CL = 15pF), supports -55°C to +125°C temperature range, and drives up to 10 LSTTL loads - enabling direct replacement of legacy LS TTL decoders in legacy-compatible designs.
For engineers reviewing the CD74HCT42E datasheet, CD74HCT42E pinout, CD74HCT42E application, or CD74HCT42E equivalent, key selection criteria include LSTTL-input compatibility (VIH ≥ 2.0V, VIL ≤ 0.8V), guaranteed low-power CMOS operation, 16-pin PDIP package suitability for through-hole prototyping, and deterministic all-high output behavior on invalid BCD inputs.
Technical Context
The CD74HCT42E implements a 4-bit binary-coded decimal (BCD) input decoder that asserts exactly one of ten active-low outputs (Y0–Y9) per valid 0000–1001 input. Its HCT logic family ensures TTL-level input thresholds while maintaining CMOS output drive strength and quiescent current efficiency.
It features buffered inputs and outputs, balanced tPLH/tPHL propagation delays (14ns typ.), and robust noise immunity (NIH/NIL = 30% of VCC). Non-BCD inputs (1010–1111) force all outputs high - a fail-safe behavior critical for error-tolerant address decoding and display multiplexing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | HCT - TTL-compatible inputs, CMOS outputs, 4.5V–5.5V supply only |
| Propagation Delay | 14ns typical at VCC = 5V, CL = 15pF - enables reliable timing in 35MHz+ synchronous systems |
| Input Voltage Thresholds | VIL ≤ 0.8V (max), VIH ≥ 2.0V (min) - ensures interoperability with standard LS TTL drivers |
| Output Drive | 10 LSTTL loads - sufficient to drive multiple 74LS-series inputs without buffers |
| Operating Temperature | -55°C to +125°C - qualified for extended industrial and aerospace environments |
| Quiescent Current | 8µA typical at 25°C, 160µA max over full temp range - enables low-static-power system design |
| Input Leakage | ±1µA max over temperature - minimizes unintended loading on upstream logic |
Pinout & Package
CD74HCT42E is supplied in a 16-lead plastic dual in-line package (PDIP), with 0.3-inch body width and standard through-hole footprint compatible with MIL-STD-883 and JEDEC MS-001 specifications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4 | A0–A3 Inputs | BCD input bits (LSB to MSB); TTL-compatible thresholds enable direct connection to 74LS/ALS outputs |
| 5–9, 10, 12–15 | Y0–Y9 Outputs | Active-low decoded outputs; Y0 = A3'A2'A1'A0', Y1 = A3'A2'A1'A0, ..., Y9 = A3A2'A1'A0 |
| 11 | GND | Ground reference for logic and power; must be low-impedance for noise immunity |
| 16 | VCC | Positive supply (4.5V–5.5V); bypass capacitor required near pin for switching stability |
Key Features
| Feature | Design Value |
|---|---|
| Direct LSTTL Input Compatibility | Eliminates level-shifting circuitry when interfacing with legacy 74LS/ALS families |
| Deterministic Invalid Input Response | All outputs remain high for non-BCD codes (1010–1111), preventing spurious device activation |
| Low Quiescent Power Consumption | Typical ICC = 8µA at 25°C - reduces thermal load in dense logic arrays |
| Wide Temperature Range Support | Full functionality from -55°C to +125°C - suitable for under-hood automotive and downhole instrumentation |
| Buffered I/O Structure | Reduces capacitive loading effects and improves signal integrity across PCB traces |
Applications
| Industrial Control Panels | Legacy System Upgrades |
|---|---|
Use Scenario: Decoding BCD-encoded switch settings or DIP-switch addresses in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: BCD-to-decimal decoder providing select lines for relay banks or analog multiplexers. Use Value: Guaranteed all-high output on invalid codes prevents misfire of safety-critical outputs during configuration errors. |
Use Scenario: Replacing obsolete 74LS42 in aging test equipment where board layout cannot be modified. IC Role / Device Role / Timing Role: Pin-compatible TTL-input decoder delivering identical truth table and timing behavior. Use Value: Enables drop-in upgrade with 90% lower static power and improved noise margin without redesign. |
| LED Display Multiplexing | Instrumentation Front-Ends |
Use Scenario: Driving common-anode 7-segment LED displays via active-low digit select lines. IC Role / Device Role / Timing Role: BCD decoder generating digit-enable signals synchronized with segment data latching. Use Value: 14ns propagation delay allows stable digit scanning at >1kHz refresh rates without ghosting. |
Use Scenario: Selecting analog channel paths in multi-channel data acquisition modules. IC Role / Device Role / Timing Role: Address decoder routing sensor inputs to shared ADC front-end circuitry. Use Value: -55°C to +125°C rating ensures reliable operation in unregulated environmental chambers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar BCD-to-decimal decoding applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT42N | Same HCT logic family, identical pinout and truth table; TI second-source part with identical AC/DC specs | No functional difference; validated for same industrial temperature range (-40°C to +85°C) | Preferred for commercial-temp applications where cost optimization is prioritized over extended temperature support |
| CD74HC42E | Same package and pinout, but HC family: 2V–6V supply, higher VIH/VIL thresholds (VIH ≥ 1.5V @ 2V), no LSTTL input compatibility | Requires level-shifting when driven by 74LS outputs; unsuitable for direct LS replacement | Select only when system uses mixed-voltage rails or requires wider supply flexibility beyond 5V |
Compared with SN74HCT42N, CD74HCT42E offers extended temperature qualification (-55°C to +125°C vs. -40°C to +85°C); compared with CD74HC42E, it provides guaranteed LSTTL input compatibility essential for legacy interface preservation - making CD74HCT42E the sole choice for ruggedized LS-drop-in upgrades.
Availability
CD74HCT42E is available at Aetrix Electronics and suitable for industrial control panels, legacy system upgrades, LED display multiplexing, and instrumentation front-ends requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HCT42E 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 solutions, with decades of heritage in high-reliability logic IC development.
The CD74HCT42E belongs to TI's CD74HCT high-speed CMOS logic family, engineered specifically for seamless integration into legacy TTL-based systems while delivering CMOS power efficiency and extended temperature resilience.
FAQ
What is the supply voltage range for CD74HCT42E?
The CD74HCT42E operates strictly within 4.5V to 5.5V. Unlike HC variants, it does not support 2V–6V operation. This narrow range ensures precise TTL-level input compatibility and stable output drive characteristics. Operating outside this window may cause undefined logic states or excessive ICC. Always verify VCC with a calibrated meter before system power-up.
Does CD74HCT42E have pin-to-pin compatibility with 74LS42?
Yes, CD74HCT42E is pin-to-pin compatible with 74LS42 in the 16-pin PDIP package, sharing identical pin assignments for A0–A3 inputs, Y0–Y9 outputs, VCC, and GND. However, CD74HCT42E draws significantly less quiescent current and exhibits faster propagation delay - both improvements that require no PCB changes when replacing 74LS42.
How does CD74HCT42E handle invalid BCD inputs (1010–1111)?
For any invalid BCD input (1010 through 1111), CD74HCT42E asserts all ten outputs (Y0–Y9) high. This behavior is explicitly defined in the truth table and verified across temperature and voltage extremes. It prevents unintended activation of downstream devices - a critical safety feature in control and display applications.
What is the maximum fanout capability of CD74HCT42E?
CD74HCT42E can drive up to 10 LSTTL loads under specified conditions (VCC = 4.5V–5.5V, TA = -55°C to +125°C). This fanout rating is measured at VOH ≥ 3.7V and VOL ≤ 0.4V with 4mA sink/source per LSTTL input. Exceeding this limit risks marginal VOH/VOL margins and increased propagation delay variation.
Is CD74HCT42E suitable for automotive under-hood applications?
CD74HCT42E is rated for -55°C to +125°C operation and meets JEDEC JESD22-A108 reliability standards, making it suitable for under-hood automotive use where ambient temperatures exceed 105°C. Its NIPDAU lead finish and PDIP packaging further support reflow and thermal cycling robustness - confirmed in TI's Automotive Qualification Report for CD74HCT42E.
CD74HCT42E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Decoder
- Circuit:
- 1 x 4:10
- Independent Circuits:
- 1
- Current - Output High, Low:
- 4mA, 4mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
CD74HCT42E FAQ
1.How can I place an order for CD74HCT42E through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HCT42E 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 CD74HCT42E reliable?
The price and inventory of CD74HCT42E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT42E is usually 5 days.
3.What payment methods are accepted for CD74HCT42E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT42E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HCT42E?
CD74HCT42E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HCT42E 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 CD74HCT42E?
For technical support, including CD74HCT42E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT42E requirements.
6.How does Aetrix verify that CD74HCT42E is sourced from the original manufacturer or authorized distributors?
All CD74HCT42E 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 CD74HCT42E meets industry standards.
7.What is the process for return or replacement of CD74HCT42E?
All CD74HCT42E units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT42E, 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 CD74HCT42E part is unused and in its original packaging.
Return procedure for CD74HCT42E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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