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

Texas Instruments SN74145NS

Name: SN74145NS
Brand: Texas Instruments
SKU: SN74145NS
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74145NS

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

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

Datasheet:: SN74145NS.pdf

Description:: IC BCD-TO-DEC DECODER/DVR 16SO

Quantity:: RFQ Add To RFQ list

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Product details

Overview

SN74145N from Texas Instruments is a bipolar BCD-to-decimal decoder/driver IC in 16-pin PDIP package, operating from 4.75 V to 5.25 V, with TTL-compatible inputs, open-collector outputs capable of sinking up to 80 mA per channel, and specified for 0°C to 70°C industrial temperature range. It drives common-anode LED displays directly in multiplexed or static configurations.

For engineers reviewing the SN74145N datasheet, SN74145N pinout, SN74145N application, or SN74145N equivalent, key selection considerations include its open-collector output architecture, BCD input decoding logic, DC current sink capability, and compatibility with legacy TTL-based display driver systems requiring discrete transistor replacement.

Technical Context

The SN74145N implements a 4-bit binary-coded decimal (BCD) input decoder with active-low decoded decimal outputs (Y₀–Y₉), each configured as an open-collector NPN transistor. It uses standard bipolar TTL process technology and requires external pull-up resistors for output logic level translation.

Its internal logic performs one-hot decoding: only one output is low (active) per valid BCD input (0000–1001); invalid inputs (1010–1111) drive all outputs high. No internal latch or clocking is present - operation is purely combinational and asynchronous.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage	4.75 V to 5.25 V - ensures compatibility with standard TTL logic rails and stable operation under nominal 5-V system power.
Input Logic Levels	V_IH = 2.0 V min, V_IL = 0.8 V max - guarantees reliable recognition of TTL-compatible driving signals without level-shifting.
Output Type	Open-collector NPN - enables wired-AND logic, direct interface to common-anode LEDs, and flexible voltage translation via external pull-ups.
Output Sink Current	80 mA per output (max) - supports direct driving of high-brightness LEDs or small relays without external buffer transistors.
Propagation Delay	45 ns typical (t_PLH/t_PHL) - sufficient for static or low-frequency multiplexed display applications up to ~10 kHz digit scanning.
Operating Temperature	0°C to 70°C - qualified for commercial/industrial equipment where ambient conditions remain within standard room-temperature ranges.

Pinout & Package

SN74145N is housed in a 16-pin plastic dual in-line package (PDIP-N), 0.300-inch wide body, with 0.100-inch lead pitch and through-hole mounting. Pin 1 is located at the left end of the top row, identified by a notch or dot marking.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 6, 7	BCD Input (A, B, C, D)	Active-high TTL inputs accepting 4-bit binary-coded decimal (LSB A on Pin 1, MSB D on Pin 7).
3–5, 9–12	Decimal Output (Y₀–Y₉)	Open-collector NPN outputs; low-active (Y₀ = Pin 3, Y₁ = Pin 4, ..., Y₉ = Pin 12); each sinks current when selected.
13	GND	Ground reference for internal circuitry and output transistor emitters.
14	V_CC	Positive supply terminal (4.75–5.25 V) powering internal logic and output transistor collectors.
15, 16	NC	No-connect pins - internally unconnected; must be left floating or tied to GND/V_CC per board layout requirements.

Key Features

Feature	Design Value
BCD-to-decimal decoding	Direct mapping of 4-bit BCD inputs (0–9) to ten discrete active-low outputs - eliminates need for external logic or microcontroller GPIO expansion.
High-current open-collector outputs	80 mA sink capability per output enables direct LED or incandescent lamp driving without discrete transistor stages.
TTL-compatible inputs	Meets standard TTL voltage thresholds and loading (≤10 unit loads), ensuring seamless integration into legacy 74xx logic systems.
Wide V_CC tolerance	Operates across 4.75 V–5.25 V - accommodates typical 5-V rail variation in unregulated or aging power supplies.

Applications

Industrial Panel Meters	Legacy Test Equipment Displays
Use Scenario: Driving 7-segment or bar-graph LED arrays in analog-to-digital panel meters with discrete digit selection logic. IC Role / Device Role / Timing Role: BCD decoder and segment driver - converts microcontroller or ADC output BCD code into individual digit enable signals for multiplexed display control. Use Value: Reduces component count by replacing four discrete transistors per digit and simplifies PCB routing with single-package decoding + drive capability.	Use Scenario: Replacing failed decoder sections in vintage benchtop multimeters, oscilloscopes, or signal generators using TTL-era display subsystems. IC Role / Device Role / Timing Role: Drop-in functional replacement for obsolete 74145 variants - maintains identical pinout, timing, and drive strength in repair or refurbishment contexts. Use Value: Enables field repair without redesign; preserves original system timing margins and interconnect integrity due to matched propagation delay and loading.
Electromechanical Relay Drivers	Discrete Logic-Based Counters
Use Scenario: Controlling up to ten SPST relays in sequence via BCD counter output in industrial sequencing controllers. IC Role / Device Role / Timing Role: Level-translating decoder and current amplifier - interfaces low-power logic counters to relay coils requiring >20 mA activation current. Use Value: Eliminates need for external Darlington arrays; each output provides sufficient sink current to energize standard 5 V/12 V relay coils directly.	Use Scenario: Building synchronous decade counters using discrete 74LS90/74LS93 cascades with visual decimal state indication. IC Role / Device Role / Timing Role: Combinational decode stage - converts counter Q outputs into mutually exclusive digit-enable lines for indicator lamps or solenoid drivers. Use Value: Ensures glitch-free digit selection during counter transitions due to fully static TTL design with no internal metastability concerns.

Industrial Panel Meters

Legacy Test Equipment Displays

Use Scenario: Driving 7-segment or bar-graph LED arrays in analog-to-digital panel meters with discrete digit selection logic.

IC Role / Device Role / Timing Role: BCD decoder and segment driver - converts microcontroller or ADC output BCD code into individual digit enable signals for multiplexed display control.

Use Value: Reduces component count by replacing four discrete transistors per digit and simplifies PCB routing with single-package decoding + drive capability.

Use Scenario: Replacing failed decoder sections in vintage benchtop multimeters, oscilloscopes, or signal generators using TTL-era display subsystems.

IC Role / Device Role / Timing Role: Drop-in functional replacement for obsolete 74145 variants - maintains identical pinout, timing, and drive strength in repair or refurbishment contexts.

Use Value: Enables field repair without redesign; preserves original system timing margins and interconnect integrity due to matched propagation delay and loading.

Electromechanical Relay Drivers

Discrete Logic-Based Counters

Use Scenario: Controlling up to ten SPST relays in sequence via BCD counter output in industrial sequencing controllers.

IC Role / Device Role / Timing Role: Level-translating decoder and current amplifier - interfaces low-power logic counters to relay coils requiring >20 mA activation current.

Use Value: Eliminates need for external Darlington arrays; each output provides sufficient sink current to energize standard 5 V/12 V relay coils directly.

Use Scenario: Building synchronous decade counters using discrete 74LS90/74LS93 cascades with visual decimal state indication.

IC Role / Device Role / Timing Role: Combinational decode stage - converts counter Q outputs into mutually exclusive digit-enable lines for indicator lamps or solenoid drivers.

Use Value: Ensures glitch-free digit selection during counter transitions due to fully static TTL design with no internal metastability concerns.

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-decimal decoder/driver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS145N	Lower input current (I_IL/I_IH), reduced propagation delay (30 ns typ), same open-collector outputs and pinout.	Optimized for LS-TTL systems with tighter noise margins and lower power; compatible in most SN74145N designs with minor timing margin review.	Select SN74LS145N for new designs targeting lower power consumption and improved noise immunity while retaining mechanical and functional compatibility.
SN74LS145DR	SOIC-16 package (surface-mount), same electrical specs, RoHS-compliant NiPdAu finish, moisture-sensitive level 1.	Required for automated SMT assembly; not interchangeable without PCB redesign due to different footprint and thermal profile.	Choose SN74LS145DR when transitioning to surface-mount manufacturing or when board space constraints prohibit through-hole PDIP placement.

Compared with SN74145N, SN74LS145N offers improved speed and power efficiency in identical through-hole packaging, while SN74LS145DR provides identical functionality in a compact SOIC format suitable for modern high-density layouts - both retain full BCD decode logic and open-collector drive capability.

Availability

SN74145N is available at Aetrix Electronics and suitable for industrial panel meters, legacy test equipment displays, and electromechanical relay control systems requiring stable component supply and long-term obsolescence management.

Supply support for SN74145N 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 global semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and communications applications.

The SN74145N belongs to TI's legacy 74xx TTL logic family, designed specifically for robust, low-speed digital interfacing tasks including display decoding, relay driving, and discrete logic system expansion.

FAQ

What is the maximum output sink current rating for SN74145N?

The SN74145N is rated for 80 mA maximum DC sink current per output terminal (Y₀–Y₉) at V_CC = 5 V and T_A = 25°C. This allows direct driving of high-intensity LEDs or small electromagnetic relays without external buffering. Derating applies above 25°C ambient; consult TI's Absolute Maximum Ratings table for thermal limits.

Does SN74145N include internal pull-up resistors on its outputs?

No, the SN74145N does not include internal pull-up resistors. Its outputs are open-collector NPN transistors requiring external pull-up resistors to V_CC or another logic rail to establish defined high-level voltages. Pull-up values depend on load current and desired rise time - typical values range from 1 kΩ to 10 kΩ.

Can SN74145N decode inputs beyond BCD (e.g., 1010–1111)?

No. The SN74145N decodes only valid BCD inputs (0000–1001). Inputs 1010 through 1111 produce no active-low output - all ten outputs (Y₀–Y₉) remain high (open). This behavior is inherent to its combinational logic design and is documented in TI's functional truth table for SN74145N.

Is SN74145N pin-compatible with SN74LS145N?

Yes, SN74145N and SN74LS145N share identical PDIP-16 pinouts, terminal functions, and mechanical dimensions. They differ only in internal transistor sizing and process - resulting in lower input current and faster propagation delay for the LS variant - but maintain full pin-to-pin and functional compatibility in existing designs.

What is the recommended operating voltage range for SN74145N?

The SN74145N is specified to operate reliably from 4.75 V to 5.25 V DC on V_CC. Operation outside this range may cause incorrect logic states, increased power dissipation, or premature device failure. For stable performance in noisy environments, use bypass capacitors (e.g., 0.1 µF ceramic near V_CC and GND pins) on the SN74145N supply rail.

SN74145NS Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 7400

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

Packaging:: Bulk

Product Status:: Active

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-SO

SN74145NS FAQ

1.How can I place an order for SN74145NS through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74145NS 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 SN74145NS reliable?

The price and inventory of SN74145NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74145NS is usually 5 days.

3.What payment methods are accepted for SN74145NS?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74145NS transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74145NS?

SN74145NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74145NS 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 SN74145NS?

For technical support, including SN74145NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74145NS requirements.

6.How does Aetrix verify that SN74145NS is sourced from the original manufacturer or authorized distributors?

All SN74145NS 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 SN74145NS meets industry standards.

7.What is the process for return or replacement of SN74145NS?

All SN74145NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74145NS, 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 SN74145NS part is unused and in its original packaging.

Return procedure for SN74145NS:

1.Submit a request within 90 days.

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

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