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Texas Instruments SN74LS148DG4
- Part No.:
- SN74LS148DG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS148DG4.pdf
- Description:
- IC PRIORITY ENCOD 1 X 8:3 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,797
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Product details
Overview
SN74LS148DG4 from Texas Instruments is a TTL 8-line-to-3-line priority encoder IC that converts active-low data inputs (0–7) into active-low 3-bit binary (A0–A2) outputs with enable input (EI), group signal (GS), and enable output (EO). It features 15 ns typical propagation delay, 60 mW typical power dissipation at 5 V, and operates across 0°C to 70°C. It is used in keyboard encoding, interrupt prioritization, and octal code generation in legacy industrial control systems.
For engineers reviewing the SN74LS148DG4 datasheet, SN74LS148DG4 pinout, SN74LS148DG4 application, or SN74LS148DG4 equivalent, this page delivers verified functional specifications, validated SOIC-D package mapping, confirmed priority encoding behavior, and real-world design context for retrofitting and maintenance of 74LS-based logic systems.
Technical Context
The SN74LS148DG4 implements combinational priority encoding logic where only the highest-order active-low input (lowest numeric index) determines the output code. Its internal architecture includes buffered TTL inputs with 9 kΩ nominal input resistance for lines 1–7 and 18 kΩ for all other inputs, ensuring compatibility with standard 74LS fan-out requirements.
It supports cascading via EI (active-low enable input) and EO (active-low enable output), allowing expansion to larger input sets without external gating. GS (group signal) asserts low when any input is active, providing a ready flag for downstream latching or interrupt arbitration circuits.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Encoding Function | 8-line decimal (0–7) to 3-line binary (A0–A2) priority encoder with active-low inputs/outputs |
| Propagation Delay | 15 ns typical (tPHL/tPLH to A0/A1/A2), enabling reliable operation up to ~30 MHz in short-path logic designs |
| Supply Voltage | 4.75 V to 5.25 V - strict 5 V ±2.5% tolerance required for guaranteed TTL logic thresholds |
| Input Resistance | 9 kΩ (inputs 1–7), 18 kΩ (all others) - defines pull-up sizing for open-collector or switch interfaces |
| Output Drive | IOL = 8 mA (VOL ≤ 0.4 V), IOH = −400 µA (VOH ≥ 2.7 V) - compatible with 74LS/74ALS load standards |
| Power Dissipation | 12–20 mA ICC (Condition 1/2), ~60 mW typical - enables dense placement without forced airflow in legacy PCBs |
| Operating Temperature | 0°C to 70°C - commercial-grade rating suitable for non-military industrial enclosures |
Pinout & Package
SN74LS148DG4 is supplied in a 16-pin SOIC (D) package, 7.5 mm wide, with 1.27 mm pitch and 2.00 mm max height per TI NS0016A drawing. Pin 1 is marked by a beveled corner or dot; device orientation follows JEDEC MS-012 standard.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Ground (GND) | Reference return for all internal logic and output drivers; must be low-impedance connection |
| 2 | Data Input 0 (0) | Low-active priority input; lowest priority in encoding hierarchy (asserted = logic 0) |
| 3 | Data Input 1 (1) | Low-active priority input; second-lowest priority (higher than pin 2) |
| 4 | Data Input 2 (2) | Low-active priority input; third-lowest priority |
| 5 | Data Input 3 (3) | Low-active priority input; fourth-lowest priority |
| 6 | Data Input 4 (4) | Low-active priority input; fifth-lowest priority |
| 7 | Data Input 5 (5) | Low-active priority input; sixth-lowest priority |
| 8 | Data Input 6 (6) | Low-active priority input; seventh-lowest priority |
| 9 | Data Input 7 (7) | Low-active priority input; highest priority (asserted overrides all lower-numbered inputs) |
| 10 | Enable Input (EI) | Active-low global enable; disables encoding and forces GS/EO high when high |
| 11 | Binary Output A0 | LSB of 3-bit encoded output; active-low, reflects least-significant bit of selected input |
| 12 | Binary Output A1 | Middle bit of 3-bit encoded output; active-low |
| 13 | Binary Output A2 | MSB of 3-bit encoded output; active-low |
| 14 | Group Signal (GS) | Active-low flag indicating *any* input (0–7) is asserted; used for interrupt request strobing |
| 15 | Enable Output (EO) | Active-low cascading output; low when EI is low *and* no input is active (all high) |
| 16 | VCC | +5 V supply; requires local 0.1 µF ceramic decoupling adjacent to pin |
Key Features
| Feature | Design Value |
|---|---|
| Priority Encoding Logic | Guarantees single-output resolution even with multiple simultaneous low inputs - essential for interrupt arbitration |
| Cascadable Architecture | EI/EO signals allow stacking multiple SN74LS148DG4 units to encode >8 lines without external gates or timing penalties |
| Active-Low Interface | All inputs and outputs are low-active, simplifying direct connection to mechanical switches, open-collector sensors, and legacy bus structures |
| TTL-Compatible Drive | Meets 74LS fan-out specs (1 normalized load), enabling direct interconnection with 74LS, 74ALS, and 74F families |
| Transient Immunity Design | Buffered inputs reduce susceptibility to noise-induced glitches during input transitions - critical in panel-mounted switch applications |
Applications
| Keyboard Encoding | Interrupt Prioritization |
|---|---|
Use Scenario: Mechanical key matrix in industrial HMI panels where 8 keys map to discrete inputs. IC Role / Device Role / Timing Role: Priority encoder translates pressed key into binary address for microcontroller scan cycle. Use Value: Resolves keypress conflicts automatically - if multiple keys are pressed, only the highest-priority key (lowest number) generates valid output, preventing ambiguous scans. | Use Scenario: Multi-peripheral interrupt system in 8-bit embedded controllers (e.g., Z80, 8085) with limited IRQ lines. IC Role / Device Role / Timing Role: Encodes eight peripheral interrupt requests into three-bit vector, fed to CPU's interrupt vector decoder. Use Value: Reduces wiring complexity and eliminates software polling; hardware-level priority ensures fastest response to highest-priority peripheral. |
| Octal Code Generation | Legacy System Retrofit |
Use Scenario: Converting parallel status flags (e.g., fault codes from eight subsystems) into compact octal display format. IC Role / Device Role / Timing Role: Translates eight discrete fault lines into 3-bit BCD-compatible octal code for 7-segment driver or multiplexed display. Use Value: Minimizes I/O pin usage on legacy microcontrollers while preserving human-readable fault identification via octal digits. | Use Scenario: Repairing discontinued equipment (e.g., test instruments, PLC modules) requiring exact form-fit-function replacement. IC Role / Device Role / Timing Role: Drop-in substitute for obsolete SN74148 or SN74LS148 in existing SOIC footprints with identical pinout and electrical behavior. Use Value: Maintains original timing margins (15 ns delay), power profile (60 mW), and logic thresholds - no board rework or firmware changes needed. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar priority encoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS148N | Same logic function, timing, and drive strength; PDIP-16 package instead of SOIC-D | Requires through-hole PCB assembly; not suitable for surface-mount production or space-constrained layouts | Select when hand-soldering, prototyping, or replacing legacy DIP sockets |
| SN74LS148NSR | Identical SOIC-16 footprint and pinout; tape-and-reel packaging (2000 pcs), RoHS-compliant NiPdAu finish | Designed for automated SMT line feeding; same thermal profile (Level-1-260°C) as SN74LS148DG4 | Select for high-volume manufacturing with pick-and-place compatibility and full RoHS compliance |
Compared with SN74LS148N and SN74LS148NSR, the SN74LS148DG4 shares identical electrical performance and logic behavior but differs in packaging: DG4 denotes tube-packaged SOIC-D with legacy marking ("LS148"), making it ideal for small-batch repair and legacy inventory alignment rather than mass production or through-hole use.
Availability
SN74LS148DG4 is available at Aetrix Electronics and suitable for keyboard encoding, interrupt prioritization, and octal code generation requiring stable component supply in legacy industrial electronics maintenance and repair programs.
Supply support for SN74LS148DG4 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, embedded processing, and logic ICs with broad industrial and automotive qualification.
The SN74LS148DG4 belongs to TI's legacy 74LS logic family, designed specifically for robust, low-power TTL-compatible digital interfacing in cost-sensitive, reliability-critical industrial control and instrumentation systems.
FAQ
What is the primary function of the SN74LS148DG4?
The SN74LS148DG4 is an 8-line-to-3-line priority encoder that converts eight active-low data inputs (0–7) into a 3-bit active-low binary output (A0–A2), resolving multiple simultaneous inputs by selecting the highest-priority (lowest-numbered) asserted line. It also provides group signal (GS) and enable output (EO) for cascading.
Does the SN74LS148DG4 require external pull-up resistors on its inputs?
Yes - because all inputs are active-low and internally uncommitted, external pull-up resistors are required to hold unused or open inputs at VCC (logic high). The SN74LS148DG4 specifies 9 kΩ nominal input resistance for inputs 1–7 and 18 kΩ for others, guiding appropriate pull-up selection (e.g., 4.7 kΩ to 10 kΩ).
Can the SN74LS148DG4 be used in place of the SN74148?
Yes - the SN74LS148DG4 is a direct functional and pin-compatible upgrade to the SN74148, offering improved parameters: lower power (60 mW vs. 190 mW), tighter propagation delay control (15 ns typical vs. 10 ns but higher variation), and enhanced noise immunity due to LS-TTL input structure. No PCB changes are required.
What does the 'DG4' suffix indicate in SN74LS148DG4?
The 'DG4' suffix identifies a specific packaging and marking variant: SOIC (D) package, tube packaging (G), and fourth revision of the marking layout (4). It corresponds to orderable part SN74LS148D with top-side marking "LS148", confirming commercial temperature range (0°C to 70°C) and RoHS-exempt status per TI documentation.
How does the cascading capability of the SN74LS148DG4 work in practice?
Cascading uses EI (enable input) and EO (enable output): EO of a higher-priority encoder drives EI of a lower-priority unit. When the upper encoder has no active input, EO goes low, enabling the next stage. GS from each stage feeds an OR gate to generate a global interrupt flag - enabling 16+ input encoding with deterministic priority hierarchy.
SN74LS148DG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Priority Encoder
- Circuit:
- 1 x 8:3
- Independent Circuits:
- 1
- Current - Output High, Low:
- 400µA, 8mA
- 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-SOIC
SN74LS148DG4 FAQ
1.How can I place an order for SN74LS148DG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS148DG4 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 SN74LS148DG4 reliable?
The price and inventory of SN74LS148DG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS148DG4 is usually 5 days.
3.What payment methods are accepted for SN74LS148DG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS148DG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS148DG4?
SN74LS148DG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS148DG4 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 SN74LS148DG4?
For technical support, including SN74LS148DG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS148DG4 requirements.
6.How does Aetrix verify that SN74LS148DG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS148DG4 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 SN74LS148DG4 meets industry standards.
7.What is the process for return or replacement of SN74LS148DG4?
All SN74LS148DG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS148DG4, 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 SN74LS148DG4 part is unused and in its original packaging.
Return procedure for SN74LS148DG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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