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Texas Instruments SN74LS145NS
- Part No.:
- SN74LS145NS
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74LS145NS.pdf
- Description:
- IC DECODER 1 X 4:10 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:473
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Product details
Overview
SN74LS145NS from Texas Instruments is a TTL BCD-to-decimal decoder/driver IC in 16-pin SOP (NS) package, operating from 4.75 V to 5.25 V, with 16 mA sink current per output, 20 ns typical propagation delay, and commercial temperature range (0°C to 70°C). It drives common-anode LED displays and relay loads in industrial control panels.
For engineers reviewing the SN74LS145NS datasheet, SN74LS145NS pinout, SN74LS145NS application, or SN74LS145NS equivalent, this page delivers verified package mapping, confirmed logic function, validated timing specs, real-world drive capability, and direct alternative options for legacy TTL system upgrades.
Technical Context
The SN74LS145NS implements active-low BCD-to-decimal decoding with open-collector outputs, requiring external pull-up resistors. Its four input lines accept binary-coded decimal (0000–1001), enabling ten discrete low-active outputs (Y₀–Y₉); inputs 1010–1111 yield no active output.
Designed for direct interface with common-anode LEDs and electromechanical relays, it features TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) and guaranteed 16 mA sink capability at VCC = 5 V and TA = 25°C - sufficient to drive standard 7-segment displays without buffer stages.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS TTL - ensures compatibility with legacy LS-series logic and predictable noise margins in mixed-logic systems. |
| Supply Voltage | 4.75 V to 5.25 V - mandates stable +5 V rail; not tolerant of wider ranges or 3.3 V operation. |
| Output Type | Open-collector - requires external pull-ups; enables wired-OR logic and voltage-level translation up to 15 V. |
| Max Sink Current | 16 mA per output - directly drives standard LEDs (2–20 mA) and small relays (≤100 mW coil) without added transistors. |
| Propagation Delay | 20 ns typical (tPLH/tPHL) - supports synchronous decoding in systems with clock rates up to 25 MHz. |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade equipment; excludes extended industrial or military environments. |
| Package | SOP (NS), 16-pin - surface-mount footprint compatible with automated assembly; 1.27 mm pitch, 10.4 mm × 5.3 mm body. |
Pinout & Package
SOP (NS) package: 16-pin plastic small-outline package, 1.27 mm lead pitch, 10.4 mm × 5.3 mm body size, maximum height 2.00 mm, pin 1 marked by beveled corner or notch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Y₀ (Output 0) | Active-low decoded output for decimal 0; open-collector, sinks up to 16 mA. |
| 2 | Y₁ (Output 1) | Active-low decoded output for decimal 1; identical electrical characteristics to Y₀. |
| 3 | Y₂ (Output 2) | Active-low decoded output for decimal 2; shares same timing and drive specs as all Y outputs. |
| 4 | Y₃ (Output 3) | Active-low decoded output for decimal 3; no internal pull-up; requires external resistor. |
| 5 | Y₄ (Output 4) | Active-low decoded output for decimal 4; valid only for BCD inputs 0000–1001. |
| 6 | Y₅ (Output 5) | Active-low decoded output for decimal 5; undefined behavior for illegal BCD codes (1010–1111). |
| 7 | Y₆ (Output 6) | Active-low decoded output for decimal 6; no internal clamping diodes - external protection needed for inductive loads. |
| 8 | GND | Ground reference for all logic and output circuits; must be low-impedance connection. |
| 9 | B (BCD Input) | Second least-significant BCD input bit (2¹); TTL-compatible threshold (VIL ≤ 0.8 V, VIH ≥ 2.0 V). |
| 10 | C (BCD Input) | Second most-significant BCD input bit (2²); accepts standard TTL logic levels. |
| 11 | D (BCD Input) | Most-significant BCD input bit (2³); completes 4-bit BCD word with A, B, C. |
| 12 | Y₇ (Output 7) | Active-low decoded output for decimal 7; electrically identical to Y₀–Y₆. |
| 13 | Y₈ (Output 8) | Active-low decoded output for decimal 8; no internal current limiting - external series resistor required for LEDs. |
| 14 | Y₉ (Output 9) | Active-low decoded output for decimal 9; final valid output in BCD sequence. |
| 15 | VCC | +5 V supply pin; bypass capacitor (0.1 µF ceramic) recommended adjacent to pin. |
| 16 | A (BCD Input) | Least-significant BCD input bit (2⁰); ties to system ground or logic high to set digit value. |
Key Features
| Feature | Design Value |
|---|---|
| BCD-to-decimal decoding | Direct mapping of 4-bit BCD (0–9) to ten independent active-low outputs - eliminates need for software lookup or combinational logic. |
| Open-collector outputs | Enables shared bus configurations, voltage-level shifting (up to 15 V), and wired-OR summing of multiple decoder outputs. |
| 16 mA output sink capability | Drives standard LEDs and small-signal relays directly - removes requirement for external driver transistors in low-power interfaces. |
| 20 ns propagation delay | Supports real-time digit selection in multiplexed display systems running at ≥200 Hz refresh without ghosting or timing skew. |
| TTL input compatibility | Accepts standard 74LS/74HC logic levels - integrates seamlessly into mixed-technology boards without level-shifting circuitry. |
Applications
| Industrial Panel Meters | Legacy Test Equipment Displays |
|---|---|
|
Use Scenario: Driving 7-segment LED digits in programmable logic controller (PLC) status panels with fixed decimal readouts. IC Role / Device Role / Timing Role: BCD-to-decimal decoder providing parallel active-low digit enable signals to common-anode display drivers. Use Value: Eliminates microcontroller GPIO overhead and reduces firmware complexity by offloading digit decoding to hardware. |
Use Scenario: Controlling discrete indicator lamps on aging benchtop oscilloscopes and signal generators using front-panel BCD switches. IC Role / Device Role / Timing Role: Direct interface between manual BCD thumbwheel switches and lamp driver transistors. Use Value: Provides deterministic, glitch-free lamp activation with no software latency or debounce logic required. |
| Electromechanical Relay Boards | Automated Manufacturing Jigs |
|
Use Scenario: Selecting one of ten pneumatic solenoid valves in a factory fixture based on 4-bit DIP switch configuration. IC Role / Device Role / Timing Role: Decoder translating static BCD address into individual relay coil enable lines. Use Value: Enables fast, reliable hardware-based valve selection without processor involvement or timing-critical code. |
Use Scenario: Sequencing test point access in production-line PCB functional testers via rotary BCD encoder inputs. IC Role / Device Role / Timing Role: Generating strobe signals for multiplexed test probe selection logic. Use Value: Guarantees synchronized, non-overlapping probe activation - preventing short-circuits during board testing. |
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 74LS family, 16-pin PDIP, but features active-low outputs *and* active-high enable (G̅); lacks open-collector outputs - requires pull-ups only if wired-OR needed. | Best suited for PCBs already using through-hole PDIP footprints and where enable control is required. | Select SN74LS42N when board layout uses PDIP sockets and system-level enable gating is needed. |
| SN74HC42DR | CMOS version with 2 V–6 V supply range, lower power (µA vs mA), higher noise immunity, but only 4 mA sink current - requires external buffers for LED/relay loads. | Appropriate for modern low-power designs with mixed-voltage rails and no legacy TTL interfacing requirements. | Choose SN74HC42DR only when redesigning for CMOS compatibility and adding buffer stages is acceptable. |
Compared with SN74LS145NS, SN74LS42N offers enable control in PDIP form but no open-collector flexibility, while SN74HC42DR trades drive strength for voltage flexibility and power savings - making SN74LS145NS uniquely suited for drop-in replacement in existing 5 V TTL systems driving LEDs or relays directly.
Availability
SN74LS145NS 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 mitigation.
Supply support for SN74LS145NS 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 leader founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.
The SN74LS145NS belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-cost BCD decoding in commercial-grade instrumentation and control systems where TTL compatibility and direct load drive are essential.
FAQ
What is the function of SN74LS145NS?
The SN74LS145NS is a BCD-to-decimal decoder with ten active-low open-collector outputs. It accepts a 4-bit binary-coded decimal input (A–D) and asserts exactly one of Y₀–Y₉ low for valid inputs 0–9. Inputs 10–15 produce no active output. This function is fixed in silicon and requires no programming or configuration.
Can SN74LS145NS drive LEDs directly?
Yes, SN74LS145NS can drive common-anode LEDs directly: each output sinks up to 16 mA at VCC = 5 V and 25°C, sufficient for standard indicator LEDs. An external current-limiting resistor (e.g., 220 Ω for ~16 mA at 5 V) must be placed between the LED anode and +5 V, with the cathode connected to the SN74LS145NS output pin.
What is the supply voltage range for SN74LS145NS?
The SN74LS145NS operates strictly within 4.75 V to 5.25 V. Operation outside this range violates TI's absolute maximum ratings and may cause incorrect logic states, excessive current draw, or permanent damage. It is not rated for 3.3 V or 12 V operation - no internal regulation or level-shifting is provided.
Does SN74LS145NS have an enable input?
No, SN74LS145NS has no dedicated enable (G or E) input. All outputs respond immediately to changes on inputs A–D. To gate decoding, external logic (e.g., AND gate on each input line) or system-level control of the BCD source is required. Contrast with SN74LS42N, which includes an active-low enable pin.
Is SN74LS145NS RoHS compliant?
Yes, SN74LS145NS is RoHS compliant, with lead finish NIPDAU (nickel/palladium/gold) and full compliance documented under TI's RoHS Statement. The "Yes" RoHS flag applies specifically to the NS package variant (SN74LS145NSR.A), confirming exemption-free conformance for commercial use.
SN74LS145NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.209", 5.30mm 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 (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
SN74LS145NS FAQ
1.How can I place an order for SN74LS145NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS145NS 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 SN74LS145NS reliable?
The price and inventory of SN74LS145NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS145NS is usually 5 days.
3.What payment methods are accepted for SN74LS145NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS145NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS145NS?
SN74LS145NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS145NS 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 SN74LS145NS?
For technical support, including SN74LS145NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS145NS requirements.
6.How does Aetrix verify that SN74LS145NS is sourced from the original manufacturer or authorized distributors?
All SN74LS145NS 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 SN74LS145NS meets industry standards.
7.What is the process for return or replacement of SN74LS145NS?
All SN74LS145NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS145NS, 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 SN74LS145NS part is unused and in its original packaging.
Return procedure for SN74LS145NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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