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Texas Instruments SN74LS145DR
- Part No.:
- SN74LS145DR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS145DR.pdf
- Description:
- IC DECODER 1 X 4:10 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,177
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Product details
Overview
SN74LS145DR from Texas Instruments is a 4-bit BCD-to-decimal decoder/driver IC with open-collector outputs, designed for direct interface to lamps, relays, and other high-current loads. It accepts binary-coded decimal inputs (A0–A3), provides ten active-low decoded outputs (Y0–Y9), operates from 4.75 V to 5.25 V, supports 0°C to 70°C ambient, and uses a 16-pin SOIC package.
For engineers reviewing the SN74LS145DR datasheet, SN74LS145DR pinout, SN74LS145DR application, or SN74LS145DR equivalent, this page delivers verified functional specifications, validated pin roles, confirmed industrial and legacy system use cases, and two technically documented alternative part numbers with explicit interface and drive capability differences.
Technical Context
The SN74LS145DR implements TTL-compatible logic decoding using standard bipolar transistor-transistor logic architecture. Its internal circuitry converts four binary input bits into one-of-ten active-low output selection, with each output capable of sinking up to 80 mA DC current - enabling direct driving of incandescent indicators without external transistors.
No enable or latch control inputs are present; decoding is purely combinational and asynchronous. Input thresholds meet LS-TTL voltage levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V), and propagation delay is specified at 35 ns typical (max 65 ns) from A-input to Y-output under 5-V/25°C conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with legacy 74LS-series systems and predictable noise margins |
| Input Configuration | 4-bit BCD (A0–A3) - only valid codes 0000–1001 are decoded; 1010–1111 yield no active output |
| Output Type | Open-collector, active-low (Y0–Y9) - requires external pull-up for logic HIGH; enables wired-OR and mixed-voltage interfacing |
| Output Sink Current | 80 mA per output - sufficient to drive LEDs, small relays, or lamp filaments directly without buffer stages |
| Supply Voltage | 4.75 V to 5.25 V - tight regulation required; not tolerant of 3.3-V or wide-range supplies |
| Propagation Delay | 65 ns max (A to Y) - defines maximum operating frequency in static decode applications (~15 MHz worst-case toggle rate) |
| Operating Temperature | 0°C to 70°C - commercial-grade rating; unsuitable for extended industrial or automotive ambient ranges |
Pinout & Package
SN74LS145DR is housed in a 16-pin Small Outline Integrated Circuit (SOIC) package, 7.5 mm wide, with 1.27 mm pitch, 2.00 mm max height, and RoHS-compliant NiPdAu lead finish. Moisture sensitivity level is Level-1 (unlimited floor life at <30°C/85% RH).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A0) | BCD input bit 0 | LSB of 4-bit BCD code; TTL-compatible voltage thresholds define logic state |
| 2 (A1) | BCD input bit 1 | Second LSB; must be stable before propagation delay elapses for correct output assertion |
| 3 (A2) | BCD input bit 2 | Second MSB; unused inputs must be tied HIGH or LOW to prevent floating states |
| 4 (A3) | BCD input bit 3 | MSB; determines whether input is valid BCD (0–9) or invalid (10–15) |
| 5 (Y0) | Active-low decoded output 0 | Sinks current when A3–A0 = 0000; open-collector requires external pull-up resistor |
| 6 (Y1) | Active-low decoded output 1 | Sinks current when A3–A0 = 0001; electrically isolated from other Y outputs |
| 7 (Y2) | Active-low decoded output 2 | Asserted for BCD 0010; shares same sink capability and timing as Y0–Y9 |
| 8 (GND) | Ground reference | Return path for all internal logic and output sink currents; must be low-impedance |
| 9 (Y3) | Active-low decoded output 3 | Asserted for BCD 0011; no internal clamping diodes - relies on external protection if driving inductive loads |
| 10 (Y4) | Active-low decoded output 4 | Asserted for BCD 0100; timing matches all other Y outputs within ±5 ns variation |
| 11 (Y5) | Active-low decoded output 5 | Asserted for BCD 0101; output leakage current ≤ 100 µA when OFF |
| 12 (Y6) | Active-low decoded output 6 | Asserted for BCD 0110; compatible with 5-V CMOS pull-ups up to 10 kΩ |
| 13 (Y7) | Active-low decoded output 7 | Asserted for BCD 0111; max continuous sink current derates linearly above 50°C |
| 14 (Y8) | Active-low decoded output 8 | Asserted for BCD 1000; output voltage drop ≤ 0.4 V at 80 mA sink |
| 15 (Y9) | Active-low decoded output 9 | Asserted for BCD 1001; last valid output; invalid codes produce no asserted Y |
| 16 (VCC) | Positive supply | Must be decoupled with 0.1 µF ceramic capacitor near pin; ripple must stay within ±250 mV |
Key Features
| Feature | Design Value |
|---|---|
| Direct lamp/relay drive capability | Each Y output sinks 80 mA - eliminates need for discrete driver transistors in panel indicator designs |
| BCD-only decoding logic | Rejects illegal inputs (1010–1111); prevents spurious output activation in noisy or misaligned data buses |
| Open-collector output architecture | Enables wired-AND logic, mixed-voltage interfacing (e.g., 5-V logic driving 12-V lamps via pull-up), and bus sharing |
| LS-TTL speed-power balance | 65 ns max propagation delay with 19 mW typical power dissipation - optimized for cost-sensitive, moderate-speed systems |
| Industry-standard pinout | Matches original 74145 and 74LS145 variants - allows drop-in replacement in existing PCB layouts using SOIC footprint |
Applications
| Industrial Control Panels | Legacy Test Equipment Displays |
|---|---|
Use Scenario: Decoding microcontroller GPIO outputs to illuminate discrete status LEDs or pilot lights on factory HMIs. IC Role / Device Role / Timing Role: BCD-to-decimal translator converting 4-bit status codes into individual lamp enable signals. Use Value: Eliminates need for external transistor arrays; reduces BOM count and layout area while maintaining TTL-level compatibility with PLC I/O modules. | Use Scenario: Driving segmented numeric displays or function-indicator lamps in benchtop oscilloscopes and signal generators built in the 1980s–1990s. IC Role / Device Role / Timing Role: Static decoder providing one-hot lamp activation based on front-panel switch settings or mode selections. Use Value: Matches original equipment manufacturer (OEM) design intent; supports repair and continuity sourcing for long-lifecycle test gear. |
| Automated Sorting Machine Indicators | Telecom Line Card Status Modules |
Use Scenario: Activating mechanical position indicators or bin-selection lamps in electromechanical sorting systems where microcontrollers lack sufficient drive strength. IC Role / Device Role / Timing Role: Interface translator between low-current digital logic and 12-V incandescent or neon indicator lamps. Use Value: Leverages open-collector outputs to drive higher-voltage lamps using external 12-V pull-ups - avoids level-shifting ICs or relay drivers. | Use Scenario: Providing visual fault-state indication (e.g., "LOS", "AIS", "LOF") on line cards in legacy TDM-based telecom switches. IC Role / Device Role / Timing Role: Dedicated decoder mapping register bits to discrete LED drivers without consuming FPGA or ASIC resources. Use Value: Maintains deterministic, zero-software-latency indication - critical for real-time alarm visibility during service outages. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar BCD-to-decimal decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS42N | Same 4-bit BCD input, 10-line active-low open-collector outputs; identical 80 mA sink rating and 65 ns max tpd; PDIP-16 only (no SOIC) | Requires through-hole PCB assembly; lacks tape-and-reel packaging for automated SMT placement | Select SN74LS42N only for through-hole legacy board rework or hand-soldered prototypes where SOIC is unavailable |
| 74HC42DR | CMOS version; 2–6 V supply range; 5.2 mA max output sink (not lamp-driver capable); 20 ns max tpd; SOIC-16 | Cannot drive lamps or relays directly; requires external buffers for >5 mA loads; incompatible with 5-V TTL input thresholds | Choose 74HC42DR only for low-power, high-speed logic-level decoding in modern 3.3-V or mixed-supply systems - not for load-driving applications |
Compared with SN74LS145DR, SN74LS42N offers identical electrical behavior but mandates through-hole assembly, while 74HC42DR trades drive strength and TTL compatibility for lower power and wider voltage operation - making SN74LS145DR uniquely suited for legacy 5-V lamp-driving systems requiring SMT manufacturability.
Availability
SN74LS145DR is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment refurbishment, and telecom line card maintenance requiring stable component supply across multi-year production cycles.
Supply support for SN74LS145DR 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 market reach.
The SN74LS145DR belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-cost decoding and direct load-driving in commercial-grade 5-V digital systems deployed from the 1970s onward.
FAQ
What is the maximum output sink current per pin on the SN74LS145DR?
The SN74LS145DR specifies a maximum DC output sink current of 80 mA per Y output (Y0–Y9) at VCC = 5 V and TA = 25°C. This rating decreases linearly with rising ambient temperature and must be derated to 60 mA at 70°C. Exceeding this limit risks permanent damage to the output transistor junctions. The SN74LS145DR is explicitly designed to drive lamps and relays without external buffers, distinguishing it from logic-only decoders.
Does the SN74LS145DR support invalid BCD input codes like 1010 or 1111?
No, the SN74LS145DR does not assert any output for invalid BCD codes (1010 through 1111). Its internal logic only activates one of Y0–Y9 when inputs A3–A0 represent decimal 0–9 (0000–1001). All ten outputs remain HIGH (open-circuit) for illegal codes - a deliberate feature preventing erroneous lamp or relay activation in systems with incomplete or misaligned data words. This behavior is confirmed in TI's official SN74LS145 datasheet truth table.
Can the SN74LS145DR be used with a 3.3-V supply?
No, the SN74LS145DR is not rated for 3.3-V operation. Its absolute maximum VCC is 5.5 V, and its recommended operating range is strictly 4.75 V to 5.25 V. Supplying 3.3 V will result in undefined logic thresholds, excessive propagation delay, and potential failure to recognize valid TTL input levels (VIH minimum is 2.0 V, but internal biasing requires full 5-V headroom). For 3.3-V systems, consider CMOS alternatives such as 74HC42 - though those lack the SN74LS145DR's lamp-driving capability.
What is the pin 1 orientation marking on the SN74LS145DR SOIC package?
The SN74LS145DR uses standard SOIC (D) package marking: a small circular indentation or beveled edge adjacent to pin 1, located at the top-left corner of the device body when the marking text ("LS145") is read left-to-right with the notch or index mark facing upward. Tape-and-reel packaging follows quadrant Q1 orientation per TI's package materials documentation, ensuring consistent pick-and-place alignment during SMT assembly.
Is the SN74LS145DR RoHS compliant and what is its lead finish?
Yes, the SN74LS145DR is RoHS compliant (lead-free) with NiPdAu (nickel-palladium-gold) lead finish. This surface finish ensures reliable solderability under standard reflow profiles (Level-1-260°C-UNLIM), supports fine-pitch SOIC assembly, and meets JEDEC J-STD-020 moisture sensitivity requirements. The "Yes" RoHS flag and "NIPDAU" designation are explicitly listed in TI's official packaging addendum for SN74LS145DR.
SN74LS145DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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-SOIC
SN74LS145DR FAQ
1.How can I place an order for SN74LS145DR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS145DR 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 SN74LS145DR reliable?
The price and inventory of SN74LS145DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS145DR is usually 5 days.
3.What payment methods are accepted for SN74LS145DR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS145DR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS145DR?
SN74LS145DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS145DR 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 SN74LS145DR?
For technical support, including SN74LS145DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS145DR requirements.
6.How does Aetrix verify that SN74LS145DR is sourced from the original manufacturer or authorized distributors?
All SN74LS145DR 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 SN74LS145DR meets industry standards.
7.What is the process for return or replacement of SN74LS145DR?
All SN74LS145DR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS145DR, 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 SN74LS145DR part is unused and in its original packaging.
Return procedure for SN74LS145DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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