My Inquiry
My Account
Texas Instruments SN74LS348D
- Part No.:
- SN74LS348D
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS348D.pdf
- Description:
- IC PRIORITY ENCOD 1 X 8:3 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,547
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74LS348D from Texas Instruments is an 8-line to 3-line priority encoder with active-low inputs, 3-state outputs, and TTL-compatible logic levels. It encodes up to eight active-low input lines (I0–I7) into three binary-weighted active-low outputs (A0–A2), includes enable (EI) and group-select (GS) control, and operates over 0°C to 70°C. It is used in keyboard scanning, interrupt request encoding, and digital system address reduction.
For engineers reviewing the SN74LS348D datasheet, SN74LS348D pinout, SN74LS348D application, or SN74LS348D equivalent, key selection factors include its priority encoding behavior, 3-state output drive capability, TTL-level compatibility, propagation delay (typ. 25 ns), and SOIC-16 package thermal and layout constraints.
Technical Context
This TTL-family priority encoder resolves multiple simultaneous low-active inputs by selecting the highest-priority line (I7 highest, I0 lowest) and asserting corresponding binary-coded outputs. Its 3-state outputs are controlled by the EI (Enable Input) and GS (Group Select) signals, allowing bus sharing in multi-device systems.
The device features open-collector-compatible outputs when enabled, supports wired-OR expansion via GS cascading, and maintains valid encoding only when EI is low. Propagation delays are specified at VCC = 5 V, TA = 25°C, with typical tPLH/tPHL of 25 ns and maximum of 45 ns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with legacy 74LS-series systems and predictable DC noise margins. |
| Input Configuration | 8 active-low priority inputs (I0–I7) - highest-numbered asserted input dominates encoding result. |
| Output Format | 3 active-low binary outputs (A0–A2) + GS - GS goes low when any input is active, enabling cascade chaining. |
| Output Type | 3-state (tri-state) - outputs enter high-impedance state when EI is high, supporting shared bus architectures. |
| Propagation Delay | Max 45 ns (VCC = 5 V, TA = 25°C) - defines worst-case timing budget for synchronous encoding paths. |
| Supply Voltage | 4.75 V to 5.25 V - requires regulated 5 V rail; operation outside this range risks invalid logic states. |
| Operating Temp | 0°C to 70°C - rated for commercial-grade environments; not qualified for extended industrial or automotive ranges. |
Pinout & Package
SN74LS348D is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package, 7.5 mm wide, with standard 1.27 mm pitch and gull-wing leads. The package supports surface-mount assembly and meets JEDEC MS-012 standards.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| I0–I7 | Active-low priority inputs | Input lines ranked I7 (highest) to I0 (lowest); only one needs assertion for valid encoding. |
| A0–A2 | Active-low encoded outputs | Binary representation of highest-priority active input (e.g., I5 → A2=H, A1=L, A0=L). |
| EI | Enable Input | Active-low global enable; when high, all outputs (A0–A2, GS) go to high-impedance state. |
| GS | Group Select Output | Active-low flag indicating at least one input is active; used to enable downstream encoders in cascaded systems. |
| GND | Ground reference | Signal and power return path; must be low-inductance connection for stable TTL switching. |
| VCC | Positive supply | +5 V DC supply; bypassing with 0.1 µF ceramic capacitor near pin is required for noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Priority encoding resolution | Selects highest-priority active input among eight lines without arbitration logic overhead. |
| 3-state output control | Enables direct connection to shared data/address buses without external gating or buffers. |
| Cascadable group select (GS) | Allows hierarchical encoding of >8 inputs using multiple SN74LS348D devices in master-slave configuration. |
| TTL-compatible voltage thresholds | Guarantees interoperability with 74LS, 74S, and 74F logic families without level-shifting circuitry. |
| Commercial temperature range | Validated performance across 0°C to 70°C ambient, suitable for office, lab, and non-harsh industrial control panels. |
Applications
| Keyboard Interface Encoding | Interrupt Request Prioritization |
|---|---|
Use Scenario: Matrix keyboard with 8 rows scanned sequentially, where only one key press must generate a unique 3-bit code. IC Role / Device Role / Timing Role: Priority encoder converts row activation into binary address; resolves multiple key presses by selecting topmost row. Use Value: Eliminates microcontroller polling overhead and provides deterministic encoding latency under 45 ns. | Use Scenario: Microprocessor system with eight peripheral interrupt sources competing for CPU attention. IC Role / Device Role / Timing Role: Encodes pending IRQ lines into 3-bit vector; GS signal triggers CPU interrupt while A0–A2 identify source priority. Use Value: Reduces interrupt latency versus software polling and avoids need for dedicated priority arbiter ICs. |
| Address Line Reduction | Legacy System Bus Expansion |
Use Scenario: 8-bit microcontroller with limited I/O pins needing to monitor eight status flags from external hardware. IC Role / Device Role / Timing Role: Compresses eight status inputs into three encoded outputs read via port pins; GS indicates "any flag active". Use Value: Saves five GPIO pins while preserving priority-based status identification without firmware decoding. | Use Scenario: Retrofitting modern peripherals into vintage TTL-based computer backplanes requiring 3-state bus compatibility. IC Role / Device Role / Timing Role: Provides TTL-level 3-state encoded outputs that electrically match original bus timing and drive strength. Use Value: Enables drop-in replacement of obsolete encoders without modifying bus termination or timing margins. |
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 uses active-high enable (EI) and active-high outputs; no GS output. | Lacks group-select flag, limiting cascading capability; requires external logic for multi-stage encoding. | Choose when bus-sharing via 3-state is unnecessary and system uses active-high signaling conventions. |
| 74HC148PW | CMOS version with wider VCC range (2–6 V), lower power, but higher propagation delay (max 160 ns) and no 3-state outputs. | Not pin-compatible; requires level-shifting for TTL systems; unsuitable for direct bus sharing. | Prefer for battery-powered or mixed-voltage designs where power efficiency outweighs speed and bus integration needs. |
Compared with SN74LS148N and 74HC148PW, the SN74LS348D uniquely combines 3-state outputs, active-low encoding, and GS signaling-enabling compact, cascaded, bus-shared implementations in legacy TTL systems without added logic.
Availability
SN74LS348D is available at Aetrix Electronics and suitable for keyboard interfaces, interrupt controllers, address compression circuits, and legacy TTL system upgrades requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS348D 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 solutions with broad industrial and automotive reach.
The SN74LS348D belongs to TI's legacy 74LS logic family, designed specifically for reliable, low-power, medium-speed digital control and interface functions in commercial-grade systems.
FAQ
What is the function of the GS (Group Select) output on the SN74LS348D?
The GS output on the SN74LS348D is an active-low signal that goes low whenever any of the eight inputs (I0–I7) is asserted. It serves as a ready flag for downstream logic and enables cascading multiple SN74LS348D devices-e.g., a master SN74LS348D's GS can enable a slave's EI to encode additional input groups. This feature is absent in alternatives like SN74LS148N.
Is the SN74LS348D pin-compatible with the SN74LS148?
No, the SN74LS348D is not pin-compatible with the SN74LS148. While both perform 8-to-3 priority encoding, they differ in pin assignment: SN74LS348D uses pins 1–8 for I0–I7 and includes dedicated GS (pin 14) and EI (pin 15), whereas SN74LS148 assigns I0–I7 to pins 1,2,4,5,9,10,12,13 and lacks GS. PCB layout changes are required for substitution.
Does the SN74LS348D support wired-OR bus connections?
Yes, the SN74LS348D supports wired-OR configurations through its 3-state outputs. When EI is high, A0–A2 and GS enter high-impedance mode, allowing multiple SN74LS348D devices to share a common bus without contention. This eliminates the need for external tri-state buffers in multi-encoder systems.
What is the maximum clock or data rate supported by the SN74LS348D?
The SN74LS348D does not operate on a clock; it is asynchronous. Its usable input transition rate is governed by propagation delay: max 45 ns (tPLH/tPHL), supporting reliable operation up to approximately 10 MHz for clean, monotonic input edges. System-level timing must account for worst-case skew and setup/hold relative to downstream sampling clocks.
Can the SN74LS348D be used in place of the SN74LS148 in existing designs?
Direct substitution of SN74LS348D for SN74LS148 is not feasible without circuit modification. Differences include active-low vs. active-high enable polarity, presence of GS output, pinout mismatch, and distinct truth table behavior under multiple-input conditions. Functional equivalence requires redesign of enable logic and bus interface.
SN74LS348D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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-SOIC
SN74LS348D FAQ
1.How can I place an order for SN74LS348D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS348D 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 SN74LS348D reliable?
The price and inventory of SN74LS348D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS348D is usually 5 days.
3.What payment methods are accepted for SN74LS348D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS348D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS348D?
SN74LS348D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS348D 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 SN74LS348D?
For technical support, including SN74LS348D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS348D requirements.
6.How does Aetrix verify that SN74LS348D is sourced from the original manufacturer or authorized distributors?
All SN74LS348D 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 SN74LS348D meets industry standards.
7.What is the process for return or replacement of SN74LS348D?
All SN74LS348D units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS348D, 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 SN74LS348D part is unused and in its original packaging.
Return procedure for SN74LS348D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74LS348D Tags
-
SN74HC138DR
Texas Instruments
-
TC7SB3157CFU,LF(CT
Toshiba Semiconductor and Storage
-
74CBTLV3257PW,118
Nexperia USA Inc.
-
SN74CBTLV3257PWR
Texas Instruments
-
74CBTLV3257GUX
Nexperia USA Inc.
-
74HC154BQ,118
Nexperia USA Inc.
-
P3S0200GMX
NXP USA Inc.
-
SN74CB3Q3245PWR
Texas Instruments
-
SN74CB3Q3257RGYR
Texas Instruments
-
TCA9543APWR
Texas Instruments
-
TCA9546APWR
Texas Instruments
-
SN74HC138N
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
