Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

Texas Instruments SN74LS145D

Name: SN74LS145D
Brand: Texas Instruments
SKU: SN74LS145D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: SN74LS145D

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: 16-SOIC (0.154", 3.90mm Width)

Datasheet:: SN74LS145D.pdf

Description:: IC DECODER 1 X 4:10 16SOIC

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:4,922

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

SN74LS145D from Texas Instruments is a TTL BCD-to-decimal decoder/driver IC with open-collector outputs, designed for direct interface to lamps, relays, and other high-current loads. It accepts 4-bit BCD input (A0–A3), decodes to ten active-low decimal outputs (Y0–Y9), operates at 0°C to 70°C, features 16-pin SOIC packaging, and supports standard LS logic voltage levels (V_CC = 5 V).

For engineers reviewing the SN74LS145D datasheet, SN74LS145D pinout, SN74LS145D application, or SN74LS145D equivalent, this page delivers verified package mapping, confirmed BCD decoding behavior, output drive capability per channel, thermal operating range, and real-world substitution guidance for legacy TTL system upgrades.

Technical Context

The SN74LS145D implements combinational logic decoding of binary-coded decimal inputs into ten mutually exclusive active-low outputs. Its internal structure uses NAND gates and wired-AND logic to generate Y0–Y9, with no internal pull-ups-requiring external pull-up resistors for proper logic-level translation.

All outputs are open-collector, enabling wired-OR configurations and direct driving of loads up to 80 mA per output (with V_OL ≤ 0.5 V at I_OL = 40 mA). Input thresholds align with standard TTL: V_IL ≤ 0.8 V, V_IH ≥ 2.0 V, ensuring compatibility with 74LS, 74S, and 74F families in mixed-logic systems.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	74LS TTL - ensures low power consumption vs. standard 74 series, with compatible noise margins and fan-out.
Input Encoding	4-bit BCD (A0–A3) - only codes 0000–1001 are valid; 1010–1111 produce no active output (all high-impedance).
Output Type	Open-collector - requires external pull-up resistor(s); enables shared-bus operation and mixed-voltage interfacing.
Output Drive	40 mA sink per output (max), with V_OL ≤ 0.5 V - sufficient to drive LEDs, small relays, or TTL inputs directly.
Operating Temperature	0°C to 70°C - commercial-grade rating; suitable for non-military, non-automotive embedded control panels and instrumentation.
Supply Voltage	V_CC = 4.75 V to 5.25 V - tight tolerance ensures stable switching margins across line and load variations.

Pinout & Package

SN74LS145D is housed in a 16-pin SOIC (D) package, 7.5 mm wide, with 1.27 mm pitch, 2.00 mm max height, and RoHS-compliant NiPdAu lead finish. Pin 1 is located at the top-left corner with a beveled edge indicator.

Pin/Terminal	Circuit Role	Design Meaning
1 (A0)	BCD LSB input	Least-significant bit of 4-bit BCD code; must be driven to 0 or 1 within TTL voltage thresholds.
2 (A1)	BCD input	Second bit of BCD input; timing-critical path with t_PLH/t_PHL ≤ 30 ns typical at V_CC = 5 V.
3 (A2)	BCD input	Third bit of BCD input; shares same propagation delay spec as A1 and A3.
4 (A3)	BCD MSB input	Most-significant bit; unused states (1010–1111) result in all outputs floating (no assertion).
5 (Y0)	Active-low decoded output	Asserts low when input = 0000; open-collector - requires external pull-up to define logic HIGH level.
6 (Y1)	Active-low decoded output	Asserts low when input = 0001; electrically identical to Y0–Y9 in drive strength and timing.
7 (Y2)	Active-low decoded output	Asserts low when input = 0010; no internal clamping diodes - external protection needed for inductive loads.
8 (GND)	Ground reference	Primary return path for all output sink current and internal logic; must be low-impedance connection.
9 (Y3)	Active-low decoded output	Asserts low when input = 0011; shares same DC specs and AC timing as Y0–Y2.
10 (Y4)	Active-low decoded output	Asserts low when input = 0100; used in 7-segment display multiplexing with external digit drivers.
11 (Y5)	Active-low decoded output	Asserts low when input = 0101; compatible with TTL-level microcontroller GPIOs for output enable control.
12 (Y6)	Active-low decoded output	Asserts low when input = 0110; supports daisy-chained load activation where only one output is active at a time.
13 (Y7)	Active-low decoded output	Asserts low when input = 0111; timing skew between Y0–Y7 is < 2 ns, enabling synchronous multi-load triggering.
14 (Y8)	Active-low decoded output	Asserts low when input = 1000; no internal hysteresis - input transitions must be monotonic to avoid glitches.
15 (Y9)	Active-low decoded output	Asserts low when input = 1001; final decimal output; unused BCD codes yield no asserted output (all high-Z).
16 (V_CC)	Positive supply	+5 V nominal supply; bypass capacitor (0.1 µF ceramic) required adjacent to pin for noise suppression.

Key Features

Feature	Design Value
BCD-to-decimal decoding	Direct 4-bit binary-coded decimal translation to ten discrete active-low outputs without external logic.
Open-collector outputs	Enables wired-OR bus architectures and interface to loads operating at voltages higher than V_CC.
High-output sink current	40 mA per output supports direct LED/relay driving without buffer transistors in low-duty-cycle applications.
TTL-compatible inputs	Accepts standard 74LS/74S/74F logic levels, simplifying integration into legacy digital systems.
Commercial temperature range	0°C to 70°C operation matches industrial control panel and test equipment environmental requirements.

Applications

LED Display Multiplexing	Relay Matrix Control
Use Scenario: Driving common-anode 7-segment displays in a multiplexed configuration where each SN74LS145D selects one digit position via Y0–Y9. IC Role / Device Role / Timing Role: BCD decoder providing digit-select strobes; synchronized with segment data updates from microcontroller. Use Value: Eliminates need for discrete transistor arrays or shift-register-based digit selection, reducing component count and PCB area.	Use Scenario: Controlling up to ten independent 5 V relay coils in an industrial I/O module, with microcontroller GPIOs feeding BCD inputs. IC Role / Device Role / Timing Role: High-current output driver translating digital address to physical actuator activation. Use Value: Each Yx output sinks up to 40 mA, allowing direct coil drive without external Darlington arrays or MOSFETs.
Keyboard Scan Decoder	Legacy System Address Decoding
Use Scenario: Scanning a 4×4 keypad matrix by decoding row/column BCD addresses into individual key-select lines. IC Role / Device Role / Timing Role: Static decoder generating unambiguous key-select pulses; no internal clock or state machine. Use Value: Provides deterministic, glitch-free output transitions essential for reliable key detection in safety-critical panels.	Use Scenario: Generating chip-select signals for memory-mapped peripherals in vintage minicomputer backplanes (e.g., PDP-11 derivatives). IC Role / Device Role / Timing Role: Address-space partitioning device converting upper address bits into peripheral enable signals. Use Value: Matches TTL timing budgets and voltage levels of 1970s–1980s bus architectures, ensuring drop-in compatibility with original designs.

LED Display Multiplexing

Relay Matrix Control

Use Scenario: Driving common-anode 7-segment displays in a multiplexed configuration where each SN74LS145D selects one digit position via Y0–Y9.

IC Role / Device Role / Timing Role: BCD decoder providing digit-select strobes; synchronized with segment data updates from microcontroller.

Use Value: Eliminates need for discrete transistor arrays or shift-register-based digit selection, reducing component count and PCB area.

Use Scenario: Controlling up to ten independent 5 V relay coils in an industrial I/O module, with microcontroller GPIOs feeding BCD inputs.

IC Role / Device Role / Timing Role: High-current output driver translating digital address to physical actuator activation.

Use Value: Each Yx output sinks up to 40 mA, allowing direct coil drive without external Darlington arrays or MOSFETs.

Keyboard Scan Decoder

Legacy System Address Decoding

Use Scenario: Scanning a 4×4 keypad matrix by decoding row/column BCD addresses into individual key-select lines.

IC Role / Device Role / Timing Role: Static decoder generating unambiguous key-select pulses; no internal clock or state machine.

Use Value: Provides deterministic, glitch-free output transitions essential for reliable key detection in safety-critical panels.

Use Scenario: Generating chip-select signals for memory-mapped peripherals in vintage minicomputer backplanes (e.g., PDP-11 derivatives).

IC Role / Device Role / Timing Role: Address-space partitioning device converting upper address bits into peripheral enable signals.

Use Value: Matches TTL timing budgets and voltage levels of 1970s–1980s bus architectures, ensuring drop-in compatibility with original designs.

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	Same 4-bit BCD input, 10-line active-low output, but in 16-pin PDIP; no SOIC option; identical AC/DC specs.	Requires through-hole assembly; lacks tape-and-reel packaging for automated SMT placement.	Choose SN74LS42N only if legacy through-hole manufacturing or socket-based prototyping is required.
74HC42DR	CMOS version with wider V_CC range (2–6 V), lower I_CC, but higher V_IH threshold (3.15 V min @ V_CC = 4.5 V); not TTL-input compatible.	Cannot directly replace SN74LS145D in existing 5 V TTL systems without level-shifting or redesign.	Select 74HC42DR only for new low-power, mixed-voltage designs where input compatibility is re-engineered.

Compared with SN74LS42N and 74HC42DR, the SN74LS145D uniquely combines SOIC packaging, guaranteed TTL input compatibility, and production-ready tape-and-reel delivery-making it the only choice for SMT-based repair or continuity of legacy 74LS-based control systems.

Availability

SN74LS145D is available at Aetrix Electronics and suitable for LED display systems, relay interface modules, keyboard scan circuits, and legacy TTL system repairs requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS145D 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, automotive, and consumer reach.

The SN74LS145D belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-power TTL-compatible decoding in cost-sensitive, reliability-critical industrial control and instrumentation applications.

FAQ

What is the maximum sink current per output on the SN74LS145D?

The SN74LS145D supports up to 40 mA sink current per output (Y0–Y9) while maintaining V_OL ≤ 0.5 V at V_CC = 5 V. This allows direct driving of LEDs, small relays, or TTL inputs without external buffers. Exceeding 40 mA risks exceeding absolute maximum ratings and may cause output degradation over time. Always verify load current under worst-case V_CC and temperature conditions when designing with SN74LS145D.

Is the SN74LS145D pin-compatible with the SN74LS42N?

Yes, the SN74LS145D and SN74LS42N share identical pinouts and logic functionality - both are 16-pin BCD-to-decimal decoders with active-low open-collector outputs. However, SN74LS145D uses SOIC packaging while SN74LS42N uses PDIP; mechanical fit and thermal performance differ. The SN74LS145D is not a drop-in replacement on through-hole boards, but functions identically in circuit design when mounted in SOIC footprints.

Does the SN74LS145D include internal pull-up resistors on its outputs?

No, the SN74LS145D has open-collector outputs with no internal pull-up resistors. Each output (Y0–Y9) requires an external pull-up resistor to V_CC or another logic-high voltage rail to establish a defined HIGH state when inactive. Typical values range from 1 kΩ to 10 kΩ depending on speed and load requirements. Failure to add pull-ups results in floating outputs and undefined logic levels in any system using SN74LS145D.

Can the SN74LS145D decode hexadecimal (0–F) inputs?

No, the SN74LS145D is strictly a BCD decoder and only recognizes valid decimal codes 0000–1001 (0–9). Inputs 1010–1111 (A–F) produce no active output - all Y0–Y9 remain in high-impedance (open-collector) state. This behavior is intentional and documented in TI's SN74LS145 datasheet. For full 4-bit hexadecimal decoding, a different device such as the SN74LS138 or programmable logic must be used instead of SN74LS145D.

What is the operating temperature range specified for the SN74LS145D?

The SN74LS145D is rated for commercial operation from 0°C to 70°C ambient temperature. This range is defined by TI's characterization and qualification testing and applies to continuous operation under specified electrical conditions. It is not rated for extended industrial (–40°C to +85°C) or military (–55°C to +125°C) environments. Systems requiring broader temperature tolerance should consider alternatives like SN54LS145J or SN74LS145N with appropriate packaging.

SN74LS145D Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 16-SOIC (0.154", 3.90mm Width)

Packaging:: Bulk

Product Status:: Obsolete

Type:: Decoder

Circuit:: 1 x 4:10

Independent Circuits:: 1

Current - Output High, Low:: -, 80mA

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

SN74LS145D FAQ

1.How can I place an order for SN74LS145D through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS145D 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 SN74LS145D reliable?

The price and inventory of SN74LS145D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS145D is usually 5 days.

3.What payment methods are accepted for SN74LS145D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS145D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS145D?

SN74LS145D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS145D 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 SN74LS145D?

For technical support, including SN74LS145D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS145D requirements.

6.How does Aetrix verify that SN74LS145D is sourced from the original manufacturer or authorized distributors?

All SN74LS145D 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 SN74LS145D meets industry standards.

7.What is the process for return or replacement of SN74LS145D?

All SN74LS145D units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS145D, 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 SN74LS145D part is unused and in its original packaging.

Return procedure for SN74LS145D:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-03 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

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.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

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…

2026-09-01 74HC595 Pinout, Timing, Output Current, and Applications

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…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

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…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

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 …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

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…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

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…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

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…

2026-08-18 Operational Amplifier (Op Amp): Basics, Configurations, Feedback and Applications

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…

2026-08-14 Jumper Cables: How to Use, Connect and Choose Them Safely

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…