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Home > Products > Integrated Circuits (ICs) > Logic > Signal Switches, Multiplexers, Decoders

Texas Instruments SN74LS348NSR

Name: SN74LS348NSR
Brand: Texas Instruments
SKU: SN74LS348NSR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS348NSR

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: 16-SOIC (0.209", 5.30mm Width)

Datasheet:: SN74LS348NSR.pdf

Description:: IC PRIORITY ENCODER 1 X 8:3 16SO

Quantity:: RFQ Add To RFQ list

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Product details

Overview

SN74LS348NSR from Texas Instruments is a TTL-compatible 8-line to 3-line priority encoder with active-low inputs, 3-state outputs, and cascading capability for system-level encoding. It operates at V_CC = 4.75–5.25 V, supports propagation delay t_pd ≤ 30 ns (typ), and functions across 0°C to 70°C ambient temperature. It is used in keyboard scanning, interrupt request encoding, and address compression circuits.

For engineers reviewing the SN74LS348NSR datasheet, SN74LS348NSR pinout, SN74LS348NSR application, or SN74LS348NSR equivalent, key selection criteria include input priority logic behavior, 3-state output control timing, enable/cascade signal compatibility, and PDIP-16 mechanical fit in legacy industrial control panels.

Technical Context

The SN74LS348NSR implements priority encoding using standard TTL bipolar transistor-transistor logic, where the highest-order active-low input (I₀ to I₇) determines the 3-bit binary output (Y₀, Y₁, Y₂). Its GS (Group Select) and EO (Enable Output) pins support daisy-chained multi-encoder systems.

Output enable (EI) controls all three outputs in high-impedance state, and the GS output indicates whether any input is active. All inputs and outputs are TTL-compatible with V_IL ≤ 0.8 V, V_IH ≥ 2.0 V, and I_OH/I_OL rated per TTL loading standards.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.75 V to 5.25 V - Ensures stable operation under standard TTL power rail tolerances.
Propagation Delay	t_pd ≤ 30 ns (typ) - Enables reliable encoding in sub-33 MHz synchronous control cycles.
Input Voltage Levels	V_IL ≤ 0.8 V, V_IH ≥ 2.0 V - Guarantees noise margin compatibility with LS-TTL and standard TTL logic families.
Output Drive	I_OL = 8 mA, I_OH = –0.4 mA - Supports direct fan-out to 10 LS-TTL loads without buffering.
Operating Temperature	0°C to +70°C - Validated for commercial-grade embedded control and instrumentation applications.
Cascading Support	GS and EO pins - Allow hierarchical encoding of up to eight 8-line inputs using multiple SN74LS348NSR devices.

Pinout & Package

SN74LS348NSR is supplied in a 16-pin plastic dual in-line package (PDIP), with 0.3-inch body width and through-hole mounting. Pin spacing is 0.1 inch, compatible with standard 0.1"-grid protoboards and PCB footprints.

Pin/Terminal	Circuit Role	Design Meaning
I₀–I₇	Active-low data inputs	Highest-priority input (I₇) dominates; encodes first asserted low input into 3-bit binary output.
Y₀–Y₂	3-state encoded outputs	Active-low 3-bit binary code; tri-stated when EI = HIGH or device disabled.
EI	Enable Input	Active-low; disables all outputs (forces high-Z) when HIGH; must be LOW for encoding operation.
GS	Group Select Output	Active-low; indicates at least one input is active (I₀–I₇ = LOW).
EO	Enable Output	Active-low; enables downstream encoders in cascade chain when no higher-priority inputs are active.

Key Features

Feature	Design Value
Priority Encoding Logic	Fixed hardware priority (I₇ > I₆ > … > I₀) eliminates software arbitration overhead in real-time interrupt handling.
3-State Outputs	Allows direct connection to shared data buses without external bus transceivers or pull-up resistors.
Cascade Capability	GS/EO signaling enables scalable encoding architectures-e.g., 64-line to 6-line encoding with eight devices.
TTL-Compatible Interface	Direct interoperability with SN74LSxx, SN74Sxx, and legacy 7400-series logic without level-shifting.

Applications

Keyboard Scan Encoder	Interrupt Priority Arbiter
Use Scenario: Matrix keyboard with 8 rows scanned via microcontroller port lines. IC Role / Device Role / Timing Role: Hardware priority encoder converts pressed row to 3-bit code; reduces CPU polling load and latency. Use Value: Eliminates need for firmware-based priority resolution; ensures deterministic response to simultaneous keypresses.	Use Scenario: Multi-peripheral system (UART, timer, ADC) asserting interrupt requests on shared INT line. IC Role / Device Role / Timing Role: Encodes highest-priority pending IRQ into vector index for CPU branch table lookup. Use Value: Reduces interrupt latency by 2–5 µs versus software polling; supports hard real-time deadlines.
Address Line Compressor	Legacy Bus Interface Adapter
Use Scenario: 8-bit peripheral select lines mapped to 3-bit address decode in memory-mapped I/O space. IC Role / Device Role / Timing Role: Static encoding of chip-select signals to reduce address bus width and simplify decoding logic. Use Value: Cuts required gate count by ~60% vs discrete NAND/NOR implementation; improves board routing density.	Use Scenario: Retrofitting modern microcontrollers into vintage test equipment with TTL-encoded control buses. IC Role / Device Role / Timing Role: Translates native GPIO states into legacy 3-state encoded command bus format. Use Value: Preserves original system timing margins; avoids redesign of backplane wiring or daughterboard interfaces.

Keyboard Scan Encoder

Interrupt Priority Arbiter

Use Scenario: Matrix keyboard with 8 rows scanned via microcontroller port lines.

IC Role / Device Role / Timing Role: Hardware priority encoder converts pressed row to 3-bit code; reduces CPU polling load and latency.

Use Value: Eliminates need for firmware-based priority resolution; ensures deterministic response to simultaneous keypresses.

Use Scenario: Multi-peripheral system (UART, timer, ADC) asserting interrupt requests on shared INT line.

IC Role / Device Role / Timing Role: Encodes highest-priority pending IRQ into vector index for CPU branch table lookup.

Use Value: Reduces interrupt latency by 2–5 µs versus software polling; supports hard real-time deadlines.

Address Line Compressor

Legacy Bus Interface Adapter

Use Scenario: 8-bit peripheral select lines mapped to 3-bit address decode in memory-mapped I/O space.

IC Role / Device Role / Timing Role: Static encoding of chip-select signals to reduce address bus width and simplify decoding logic.

Use Value: Cuts required gate count by ~60% vs discrete NAND/NOR implementation; improves board routing density.

Use Scenario: Retrofitting modern microcontrollers into vintage test equipment with TTL-encoded control buses.

IC Role / Device Role / Timing Role: Translates native GPIO states into legacy 3-state encoded command bus format.

Use Value: Preserves original system timing margins; avoids redesign of backplane wiring or daughterboard interfaces.

Equivalent & Alternatives

The following parts are listed as comparable options for similar priority encoding applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS148N	Same 8-to-3 priority encoding function but with active-high outputs and different enable polarity (EI active-HIGH).	Requires inverted output logic and modified enable control in existing schematics.	Choose when redesign allows output inversion and simplified enable drive (e.g., direct MCU GPIO control).
74HC148N	CMOS version with wider V_CC range (2–6 V), lower I_CC, but incompatible input thresholds and slower t_pd (≥ 25 ns at 4.5 V).	Not drop-in replaceable due to voltage-level mismatch and lack of guaranteed TTL input compatibility.	Prefer only in new designs targeting low-power operation and mixed-voltage interfacing with level-shifting.

Compared with SN74LS348NSR, SN74LS148N offers identical encoding logic but inverted output polarity and enable behavior-requiring schematic updates-while 74HC148N trades TTL compatibility for CMOS power efficiency and voltage flexibility, necessitating interface redesign.

Availability

SN74LS348NSR is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment refurbishment, and embedded keyboard interfaces requiring stable component supply and long-term obsolescence management.

Supply support for SN74LS348NSR 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 ICs, embedded processors, and logic devices with broad industrial and automotive qualification.

The SN74LS348NSR belongs to TI's legacy 74LS TTL logic family, designed specifically for robust, noise-tolerant digital encoding in commercial-grade control and instrumentation systems.

FAQ

What is the function of the GS and EO pins on the SN74LS348NSR?

The GS (Group Select) pin is an active-low output indicating that at least one input (I₀–I₇) is asserted LOW. The EO (Enable Output) pin is also active-low and goes LOW only when no higher-priority inputs are active-enabling cascaded SN74LS348NSR devices downstream. Together, they implement hierarchical priority encoding across multiple chips without external logic.

Does the SN74LS348NSR support 3-state output control during power-up or power-down?

No-SN74LS348NSR does not include power-on reset or bus-hold circuitry. Its 3-state outputs remain undefined during V_CC ramp-up or ramp-down unless EI is held HIGH externally. For safe hot-plug or partial-power-down scenarios, external pull-up/pull-down networks on EI and outputs are recommended to prevent bus contention.

Can the SN74LS348NSR be used with modern microcontrollers operating at 3.3 V?

Direct interfacing is not recommended: SN74LS348NSR inputs require V_IH ≥ 2.0 V but are designed for 5 V TTL levels, and its outputs swing near 0 V / 3.5 V-not 0 V / 3.3 V. A level-shifter or buffer (e.g., SN74LVC245) is required to ensure reliable communication with 3.3 V microcontrollers.

What is the maximum fan-out capability of the SN74LS348NSR outputs?

The SN74LS348NSR can drive up to 10 LS-TTL loads (I_OL = 8 mA, I_OH = –0.4 mA). This corresponds to standard fan-out for legacy TTL systems. Exceeding this limit risks output voltage degradation and increased propagation delay; additional buffering is required for larger loads or longer traces.

Is the SN74LS348NSR RoHS compliant?

Yes-the SN74LS348NSR (PDIP package) is RoHS compliant per TI's packaging documentation, with lead finish specified as NIPDAU (nickel/palladium/gold) and no lead content exceeding EU RoHS Directive limits. Full compliance documentation is available in TI's official packaging addendum dated November 2025.

SN74LS348NSR Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 16-SOIC (0.209", 5.30mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Type:: Priority Encoder

Circuit:: 1 x 8:3

Independent Circuits:: 1

Current - Output High, Low:: 400µA, 24mA

Voltage Supply Source:: Single Supply

Voltage - Supply:: 4.75V ~ 5.25V

Operating Temperature:: 0°C ~ 70°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 16-SO

SN74LS348NSR FAQ

1.How can I place an order for SN74LS348NSR through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS348NSR 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 SN74LS348NSR reliable?

The price and inventory of SN74LS348NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS348NSR is usually 5 days.

3.What payment methods are accepted for SN74LS348NSR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS348NSR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS348NSR?

SN74LS348NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS348NSR 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 SN74LS348NSR?

For technical support, including SN74LS348NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS348NSR requirements.

6.How does Aetrix verify that SN74LS348NSR is sourced from the original manufacturer or authorized distributors?

All SN74LS348NSR 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 SN74LS348NSR meets industry standards.

7.What is the process for return or replacement of SN74LS348NSR?

All SN74LS348NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS348NSR, 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 SN74LS348NSR part is unused and in its original packaging.

Return procedure for SN74LS348NSR:

1.Submit a request within 90 days.

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

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