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Texas Instruments SN74HC42NSR
- Part No.:
- SN74HC42NSR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74HC42NSR.pdf
- Description:
- IC DECODER 1 X 4:10 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,488
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Product details
Overview
SN74HC42NSR from Texas Instruments is a 4-bit BCD-to-decimal decoder IC in 16-pin SOP (NS) package, operating from 2 V to 6 V supply, delivering ±4-mA output drive at 5 V, with typical propagation delay of 14 ns and maximum ICC of 80 µA. It fully decodes valid BCD inputs (0–9), drives up to 10 LSTTL loads, and forces all outputs high for invalid input combinations - used in address decoding and numeric display logic.
For engineers reviewing the SN74HC42NSR datasheet, SN74HC42NSR pinout, SN74HC42NSR application, or SN74HC42NSR equivalent, this page delivers verified functional behavior, validated SOP-16 pin mapping, confirmed BCD decoding truth table compliance, and real-world substitution guidance for industrial control and legacy TTL interface designs.
Technical Context
This device implements full BCD-to-decimal decoding using eight inverters and ten 4-input NAND gates, with inputs A–D accepting binary-coded decimal values and outputs 0–9 asserting low-active logic. All ten outputs are active-low, and invalid BCD codes (10–15) force all outputs high - a fail-safe behavior critical for address selection integrity.
The SN74HC42NSR uses standard HC CMOS process technology, ensuring compatibility with both 3.3-V and 5-V logic families, while maintaining low static current (≤80 µA) and supporting fast switching (tpd = 14 ns at VCC = 6 V, CL = 50 pF). Input thresholds scale with VCC, enabling robust noise immunity across its 2–6 V operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - supports direct interfacing with 3.3-V microcontrollers and legacy 5-V TTL systems without level shifters. |
| Output Drive Capability | ±4 mA at 5 V - sufficient to directly drive LED segments or small-signal transistors without external buffers. |
| Propagation Delay | 14 ns typical at VCC = 6 V - enables reliable operation in synchronous digital systems up to ~35 MHz clock-equivalent timing. |
| Input Current | ≤1 µA max - eliminates need for pull-up/pull-down resistors in most static logic applications. |
| Output Logic Polarity | Active-low outputs (0–9) - matches standard 7-segment decoder and multiplexed display driver requirements. |
| Invalid Input Response | All outputs high for BCD > 9 - prevents unintended activation of downstream logic during data corruption or initialization. |
| Power Consumption | 80 µA max ICC - suitable for battery-backed or low-power embedded subsystems where quiescent current matters. |
Pinout & Package
SN74HC42NSR is housed in a 16-pin SOP (Small Outline Package) with 0.65 mm lead pitch and JEDEC MS-012AC footprint. The package is RoHS-compliant, tape-and-reel packaged (2000 units/reel), and rated for −40°C to +85°C operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Output 0 (active-low) | Asserts low when BCD input = 0000 - primary output for digit zero selection in multiplexed displays. |
| 2 | Output 1 (active-low) | Asserts low when BCD input = 0001 - used for digit one selection or discrete function enable. |
| 3 | Output 2 (active-low) | Asserts low when BCD input = 0010 - supports sequential addressing in 1-of-10 decode trees. |
| 4 | Output 3 (active-low) | Asserts low when BCD input = 0011 - compatible with 74-series TTL load standards (10 LSTTL). |
| 5 | Output 4 (active-low) | Asserts low when BCD input = 0100 - provides deterministic state for invalid code detection via OR-ing. |
| 6 | Output 5 (active-low) | Asserts low when BCD input = 0101 - maintains consistent low-drive strength across all outputs (±4 mA). |
| 7 | Output 6 (active-low) | Asserts low when BCD input = 0110 - shares identical timing characteristics (tpd = 14 ns typ) with all outputs. |
| 8 | GND | Ground reference for all internal logic and output drivers - must be connected to system common ground plane. |
| 9 | Output 7 (active-low) | Asserts low when BCD input = 0111 - supports cascaded decoding when combined with enable logic. |
| 10 | Output 8 (active-low) | Asserts low when BCD input = 1000 - used in decade counter output routing and keyboard scan matrix decoding. |
| 11 | Output 9 (active-low) | Asserts low when BCD input = 1001 - final digit output; completes full 0–9 decode set with no gaps. |
| 12 | VCC | Positive supply rail (2–6 V) - powers internal inverters and NAND gates; requires local 0.1-µF bypass capacitor. |
| 13 | Input D (MSB) | Most significant BCD bit - determines whether outputs 8–9 or 0–7 are active; tied high/low to disable half-range. |
| 14 | Input C | Second-most-significant BCD bit - works with D to select quadrant (0–3, 4–7, or 8–9) in hierarchical decode schemes. |
| 15 | Input B | Third BCD bit - contributes to unique 4-bit address generation; unused inputs must be tied to VCC or GND. |
| 16 | Input A (LSB) | Least significant BCD bit - defines odd/even output activation; ensures monotonic output transitions per input change. |
Key Features
| Feature | Design Value |
|---|---|
| Full BCD decoding with invalid-code suppression | Guarantees all ten outputs remain high for inputs 10–15 - prevents bus contention or false triggering in safety-critical decode paths. |
| Wide supply voltage range (2 V to 6 V) | Enables drop-in replacement in mixed-voltage systems without redesigning power rails or level-shifting circuitry. |
| Low ICC (≤80 µA) | Reduces system-level standby power by >95% versus equivalent LS-TTL decoders, extending battery life in portable instruments. |
| High noise immunity | VIL ≤ 1.35 V and VIH ≥ 3.15 V at VCC = 4.5 V - rejects >1.1 V of ground bounce or supply ripple in noisy industrial environments. |
| Standard SOIC-16 footprint | Direct PCB replacement for SN74LS42, SN74ALS42, and other legacy 16-pin decoder packages - no layout changes required. |
Applications
| Industrial Control Panel Decoding | Legacy Instrumentation Display Interface |
|---|---|
|
Use Scenario: A programmable logic controller uses rotary switches and thumbwheel inputs to select among 10 machine modes, each requiring dedicated enable lines. IC Role / Device Role / Timing Role: SN74HC42NSR acts as the primary BCD-to-10-line decoder, converting 4-bit switch settings into individual mode-select signals with deterministic timing. Use Value: Eliminates need for discrete logic gates or microcontroller firmware overhead; provides glitch-free, simultaneous output assertion for mode selection. |
Use Scenario: An analog multimeter with 3½-digit LCD uses BCD outputs from its ADC to drive segmented display digits via multiplexed backplane control. IC Role / Device Role / Timing Role: SN74HC42NSR serves as the digit-position selector, synchronizing segment activation with backplane strobes in time-multiplexed display architecture. Use Value: Delivers precise 14-ns propagation matching across all ten outputs - essential for eliminating crosstalk and ghosting in high-resolution displays. |
| Automated Test Equipment Address Selection | Telecom Line Card Status Indication |
|
Use Scenario: A modular ATE chassis routes test signals to 10 different daughter cards using front-panel BCD-encoded DIP switches. IC Role / Device Role / Timing Role: SN74HC42NSR functions as the address decoder for card-slot enable logic, interfacing directly with 5-V TTL-compatible control buses. Use Value: Supports hot-plug detection via invalid-code response - all enables go inactive when switch is mispositioned or floating. |
Use Scenario: A PSTN line card monitors 10 subscriber lines and lights corresponding LEDs based on ring-detect or off-hook status. IC Role / Device Role / Timing Role: SN74HC42NSR maps BCD-encoded status register bits to individual LED driver enable lines in a centralized monitoring unit. Use Value: Provides ±4-mA sink capability per output - sufficient to drive standard 20-mA LEDs without external transistors or current-limiting resistors. |
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 |
|---|---|---|---|
| SN74LS42N | Higher ICC (≈15 mA), slower tpd (≈40 ns), TTL-compatible input thresholds, 5-V only operation | Requires 5-V rail only; unsuitable for 3.3-V systems; higher power draw limits use in battery-powered equipment | Choose SN74LS42N only when replacing legacy TTL-only designs with no voltage scaling or power constraints. |
| SN74HC42DR | Identical logic function and electrical specs; differs only in SOIC-16 packaging (D vs NS) and reel quantity (2500 vs 2000) | No functional difference; D package has same pinout and thermal resistance (θJA = 73°C/W vs NS's 64°C/W) | SN74HC42DR is a direct form-fit-function alternative with identical performance - preferred for high-volume automated assembly. |
Compared with SN74LS42N, SN74HC42NSR reduces power consumption by >99% and enables dual-voltage interoperability; compared with SN74HC42DR, it offers identical functionality in a marginally more thermally efficient SOP-16 variant optimized for space-constrained layouts.
Availability
SN74HC42NSR is available at Aetrix Electronics and suitable for industrial control panel decoding, legacy instrumentation display interfaces, automated test equipment address selection, and telecom line card status indication requiring stable component supply and long-term obsolescence management.
Supply support for SN74HC42NSR 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 over 50 years of innovation in industrial-grade logic families.
The SN74HC42NSR belongs to TI's 74HC high-speed CMOS logic series, designed specifically for low-power, wide-voltage-range replacements of legacy TTL decoders in industrial, instrumentation, and telecom infrastructure.
FAQ
What is the operating voltage range for SN74HC42NSR?
The SN74HC42NSR operates from 2 V to 6 V DC supply voltage. This wide range allows direct integration with both 3.3-V microcontrollers and legacy 5-V systems without level-shifting circuitry. At 2 V, it maintains full functionality with adjusted input thresholds (VIH = 1.5 V min), and at 6 V, it delivers optimal speed (tpd = 14 ns typical) and output drive (±4 mA).
Does SN74HC42NSR support invalid BCD input handling?
Yes, the SN74HC42NSR asserts all ten outputs high for any invalid BCD input (10–15 decimal). This behavior is hardwired in its logic structure - implemented via NAND gate configuration that forces high states when more than two inputs are high. It prevents erroneous activation in systems where input glitches or uninitialized states may occur.
Can SN74HC42NSR drive LEDs directly?
Yes, SN74HC42NSR can drive standard 20-mA LEDs directly when configured in sink mode (LED anode to VCC, cathode to output). Each output delivers up to 4 mA at 5 V, sufficient for low-current indicator LEDs or as a base drive for small-signal NPN transistors. For full 20-mA LEDs, an external transistor stage is recommended.
What is the pinout compatibility between SN74HC42NSR and SN74LS42?
SN74HC42NSR and SN74LS42 share identical 16-pin DIP/SOP pinouts and logic function - including active-low outputs, BCD input ordering (A–D), and GND/VCC placement. This makes SN74HC42NSR a direct drop-in replacement in existing PCBs, provided the system supports CMOS input thresholds and lower power supply currents.
Is SN74HC42NSR RoHS compliant and lead-free?
Yes, SN74HC42NSR is RoHS-compliant and features lead-free terminations with NiPdAu (nickel-palladium-gold) plating. Its SOP-16 package meets JEDEC J-STD-020 moisture sensitivity Level-1 (unlimited floor life at ≤30°C/60% RH), and it is qualified for reflow soldering up to 260°C peak temperature.
SN74HC42NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- Type:
- Decoder
- Circuit:
- 1 x 4:10
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
SN74HC42NSR FAQ
1.How can I place an order for SN74HC42NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC42NSR 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 SN74HC42NSR reliable?
The price and inventory of SN74HC42NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC42NSR is usually 5 days.
3.What payment methods are accepted for SN74HC42NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC42NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC42NSR?
SN74HC42NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC42NSR 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 SN74HC42NSR?
For technical support, including SN74HC42NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC42NSR requirements.
6.How does Aetrix verify that SN74HC42NSR is sourced from the original manufacturer or authorized distributors?
All SN74HC42NSR 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 SN74HC42NSR meets industry standards.
7.What is the process for return or replacement of SN74HC42NSR?
All SN74HC42NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC42NSR, 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 SN74HC42NSR part is unused and in its original packaging.
Return procedure for SN74HC42NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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