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Home > Products > Integrated Circuits (ICs) > Logic > Gates and Inverters

onsemi SN74LS38D

Name: SN74LS38D
Brand: onsemi
SKU: SN74LS38D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS38D

Manufacturer:: onsemi

Category:: Gates and Inverters

Package:: 14-SOIC (0.154", 3.90mm Width)

Datasheet:: SN74LS38D.pdf

Description:: IC GATE NAND 4CH 2-INP 14SOIC

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Product details

Overview

SN74LS38D from Texas Instruments is a quadruple 2-input positive-NAND buffer with open-collector outputs, designed for wired-AND logic interfacing and level translation in TTL-compatible digital systems. It operates over 0°C to 70°C, features 14-pin SOIC packaging, and delivers typical propagation delay of 15 ns at V_CC = 5 V with I_OL = 8 mA.

For engineers reviewing the SN74LS38D datasheet, pinout, applications, or equivalent options, key selection considerations include open-collector output drive capability, TTL input compatibility, fan-out capacity, and compatibility with legacy 74LS logic families in industrial control and instrumentation interfaces.

Technical Context

The SN74LS38D implements four independent 2-input NAND gates, each with an open-collector output stage enabling wired-AND bus configurations and voltage-level shifting. Its inputs are compatible with standard TTL logic thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), and outputs support up to 8 mA sink current at V_OL ≤ 0.4 V.

This device belongs to the 74LS family and shares identical logic function, timing, and DC electrical characteristics with SN74LS38N and SN74LS38DR, differing only in package type (SOIC vs. PDIP vs. SOIC tape-and-reel) and thermal rating - all operate within 0°C to 70°C ambient range.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Function	Quadruple 2-input positive-NAND with open-collector outputs - enables wired-AND bus arbitration and mixed-voltage interface design.
Propagation Delay	15 ns max (t_PLH/t_PHL) at V_CC = 5 V, R_L = 1.6 kΩ, C_L = 15 pF - ensures predictable timing in synchronous TTL subsystems.
Output Sink Current	8 mA max (I_OL) at V_OL ≤ 0.4 V - supports direct driving of LEDs, relays, or other 5 V logic loads without external pull-ups.
Input Thresholds	V_IL ≤ 0.8 V, V_IH ≥ 2.0 V - guarantees reliable recognition of standard TTL logic levels across temperature and supply variation.
Supply Voltage	4.75 V to 5.25 V - matches nominal 5 V TTL rail with ±5% tolerance, ensuring stable operation in regulated digital power domains.
Operating Temperature	0°C to 70°C - validated for commercial-grade applications including test equipment, data acquisition front-ends, and industrial PLC I/O modules.

Pinout & Package

SN74LS38D uses a 14-pin SOIC (Small Outline Integrated Circuit) package with 1.75 mm maximum height, 3.9 mm body width, and 1.27 mm lead pitch. Pin 1 is located at the top-left corner with a beveled edge or notch marking.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 4, 5, 8, 9, 11, 12	Input A/B per gate	Eight total inputs (two per NAND gate); TTL-compatible, high-impedance CMOS-like inputs with no internal pull-ups.
3, 6, 10, 13	Open-collector output	Four independent open-collector outputs requiring external pull-up resistors for logic HIGH assertion.
7	GND	Ground reference for all logic and output stages; must be low-impedance connection to minimize noise coupling.
14	V_CC	+5 V supply pin; decoupling capacitor (0.1 µF ceramic) required adjacent to pin for stable switching performance.

Key Features

Feature	Design Value
Wired-AND capability	Enables multiple SN74LS38D outputs to share a single pull-up resistor and bus line - simplifies interrupt arbitration and status aggregation.
TTL input compatibility	Accepts standard TTL output voltages directly without level-shifting circuitry - reduces BOM count in mixed-logic designs.
8 mA output sink	Sufficient to drive LEDs, small solenoids, or TTL inputs without external driver transistors - lowers system component count.
14-pin SOIC footprint	Standardized land pattern (JEDEC MS-012 AB) compatible with automated SMT assembly and IPC-7351 board layout guidelines.

Applications

Industrial Control Interface	Test Equipment Signal Conditioning
Use Scenario: Interfacing microcontroller GPIOs to 24 V PLC input modules via optocoupler drivers. IC Role / Device Role / Timing Role: SN74LS38D provides level-shifted, current-sinking NAND logic to enable/discharge optocoupler LEDs based on dual-control signals. Use Value: Eliminates need for discrete transistors or dedicated level shifters while maintaining precise timing alignment with controller clock domain.	Use Scenario: Generating synchronized strobe and enable signals for multi-channel ADC sampling in benchtop DMMs. IC Role / Device Role / Timing Role: SN74LS38D combines trigger and gate signals into a single wired-AND strobe output with sub-20 ns skew. Use Value: Ensures deterministic sampling window activation across channels without added propagation delay from active buffers.
Legacy System Bus Arbitration	Digital Panel Indicator Logic
Use Scenario: Managing shared interrupt lines among multiple peripheral cards in a backplane-based instrumentation rack. IC Role / Device Role / Timing Role: SN74LS38D acts as a wired-AND interrupt combiner, where any card pulling its output LOW asserts the global IRQ line. Use Value: Provides hardware-level priority resolution without software polling or additional arbitration ICs.	Use Scenario: Driving multiplexed LED displays in HVAC control panels using common-anode configuration. IC Role / Device Role / Timing Role: SN74LS38D sinks current from segment drivers controlled by microcontroller row/column select logic. Use Value: Delivers consistent 8 mA per segment with minimal voltage drop, ensuring uniform brightness across display digits.

Industrial Control Interface

Test Equipment Signal Conditioning

Use Scenario: Interfacing microcontroller GPIOs to 24 V PLC input modules via optocoupler drivers.

IC Role / Device Role / Timing Role: SN74LS38D provides level-shifted, current-sinking NAND logic to enable/discharge optocoupler LEDs based on dual-control signals.

Use Value: Eliminates need for discrete transistors or dedicated level shifters while maintaining precise timing alignment with controller clock domain.

Use Scenario: Generating synchronized strobe and enable signals for multi-channel ADC sampling in benchtop DMMs.

IC Role / Device Role / Timing Role: SN74LS38D combines trigger and gate signals into a single wired-AND strobe output with sub-20 ns skew.

Use Value: Ensures deterministic sampling window activation across channels without added propagation delay from active buffers.

Legacy System Bus Arbitration

Digital Panel Indicator Logic

Use Scenario: Managing shared interrupt lines among multiple peripheral cards in a backplane-based instrumentation rack.

IC Role / Device Role / Timing Role: SN74LS38D acts as a wired-AND interrupt combiner, where any card pulling its output LOW asserts the global IRQ line.

Use Value: Provides hardware-level priority resolution without software polling or additional arbitration ICs.

Use Scenario: Driving multiplexed LED displays in HVAC control panels using common-anode configuration.

IC Role / Device Role / Timing Role: SN74LS38D sinks current from segment drivers controlled by microcontroller row/column select logic.

Use Value: Delivers consistent 8 mA per segment with minimal voltage drop, ensuring uniform brightness across display digits.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NAND buffer applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS38DR	Same electrical specs and logic function; differs only in packaging (tape-and-reel vs. tube) and RoHS compliance (NIPDAU finish).	Identical use cases; preferred for high-volume SMT production due to 2500-unit reel quantity and automated placement compatibility.	Select SN74LS38DR when sourcing for volume manufacturing with pick-and-place assembly.
SN74LS38N	Same logic and timing; uses 14-pin PDIP package with through-hole mounting and wider 0.3" body width.	Used in prototyping, repair, and legacy through-hole PCBs; lacks surface-mount land pattern requirements.	Choose SN74LS38N for breadboarding, lab testing, or replacement in existing DIP-based designs.

Compared with SN74LS38DR and SN74LS38N, the SN74LS38D offers identical functional behavior but requires manual handling due to obsolete tube packaging - making it suitable only for low-volume legacy repair or niche qualification environments where SOIC form factor is mandated.

Availability

SN74LS38D is available at Aetrix Electronics and suitable for industrial control interface, test equipment signal conditioning, and legacy system bus arbitration requiring stable component supply and long-term obsolescence management.

Supply support for SN74LS38D 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 U.S.-based semiconductor company founded in 1930, specializing in analog and embedded processing technologies with broad industrial, automotive, and consumer product portfolios.

The SN74LS38D belongs to TI's legacy 74LS logic family, engineered for reliability and interoperability in commercial-grade digital systems where backward compatibility with 1970s–1980s TTL architectures remains critical.

FAQ

What is the maximum sink current supported by each output of the SN74LS38D?

Each open-collector output of the SN74LS38D supports a maximum sink current of 8 mA at V_OL ≤ 0.4 V under standard operating conditions (V_CC = 5 V, T_A = 25°C). This rating is confirmed in the SDLS105 datasheet and applies across the full 0°C to 70°C operating range. The SN74LS38D maintains this capability without thermal derating in typical PCB layouts with adequate copper pour.

Can the SN74LS38D be used as a direct replacement for SN7438 or SN74S38 in existing designs?

No - the SN74LS38D is not a direct replacement for SN7438 (standard TTL) or SN74S38 (Schottky TTL) due to differences in propagation delay (15 ns vs. 22 ns vs. 3 ns), input loading (2 LS-TTL units vs. 10 TTL units), and output drive strength. While pinout and logic function match, timing and fan-out behavior differ significantly; redesign validation is required before substitution.

Does the SN74LS38D require external pull-up resistors on its outputs?

Yes - all four outputs of the SN74LS38D are open-collector and require external pull-up resistors to define the HIGH logic state. Typical values range from 1.6 kΩ (for 5 V, 3 mA drive) to 10 kΩ (for reduced power consumption), selected based on rise time requirements and load capacitance. No internal pull-ups are present.

What is the recommended decoupling strategy for the SN74LS38D in high-speed digital layouts?

Place a 0.1 µF ceramic capacitor between V_CC (pin 14) and GND (pin 7) as close as possible to the SN74LS38D package - ideally within 3 mm trace length. For boards with multiple SN74LS38D devices, add one 4.7 µF tantalum or polymer capacitor per 5–10 ICs near the power entry point. Avoid shared vias between decoupling paths.

Is the SN74LS38D RoHS compliant?

No - the SN74LS38D is marked as non-RoHS compliant in TI's official packaging addendum, with lead finish specified as "Call TI" and no NIPDAU or Pb-free designation. For RoHS-compliant alternatives, consider SN74LS38DR (NIPDAU, Level-1 MSL) or SN74LS38NSR (NIPDAU, SOP package).

SN74LS38D Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: 74LS

Package/Case:: 14-SOIC (0.154", 3.90mm Width)

Packaging:: Tube

Product Status:: Obsolete

Logic Type:: NAND Gate

Number of Circuits:: 4

Number of Inputs:: 2

Features:: Open Collector

Voltage - Supply:: 4.75V ~ 5.25V

Current - Quiescent (Max):: 2 mA

Current - Output High, Low:: -, 24mA

Input Logic Level - Low:: 0.8V

Input Logic Level - High:: 2V

Max Propagation Delay @ V, Max CL:: 32ns @ 5V, 45pF

Operating Temperature:: 0°C ~ 70°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 14-SOIC

SN74LS38D FAQ

1.How can I place an order for SN74LS38D through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS38D 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 SN74LS38D reliable?

The price and inventory of SN74LS38D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS38D is usually 5 days.

3.What payment methods are accepted for SN74LS38D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS38D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS38D?

SN74LS38D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS38D 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 SN74LS38D?

For technical support, including SN74LS38D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS38D requirements.

6.How does Aetrix verify that SN74LS38D is sourced from the original manufacturer or authorized distributors?

All SN74LS38D 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 SN74LS38D meets industry standards.

7.What is the process for return or replacement of SN74LS38D?

All SN74LS38D units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS38D, 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 SN74LS38D part is unused and in its original packaging.

Return procedure for SN74LS38D:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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