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Texas Instruments SN74LS145NE4
- Part No.:
- SN74LS145NE4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS145NE4.pdf
- Description:
- BCD-TO-DECIMAL DECODERS/DRIVERS
- Quantity:
- Payment:
- Shipping:
Inventory:2,376
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Product details
Overview
SN74LS145NE4 from Texas Instruments is a bipolar 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), provides ten active-low decoded outputs (Y0–Y9), operates at 0°C to 70°C, uses PDIP-16 package, and features TTL-compatible input thresholds.
For engineers reviewing the SN74LS145NE4 datasheet, SN74LS145NE4 pinout, SN74LS145NE4 application, or SN74LS145NE4 equivalent, this page delivers verified functional identity, confirmed DC/AC electrical parameters, validated 16-pin DIP pin mapping, real-world use cases in legacy industrial control and indicator systems, and two technically documented alternative parts with explicit compatibility boundaries.
Technical Context
The SN74LS145NE4 implements combinational logic decoding of binary-coded decimal inputs into ten mutually exclusive active-low outputs. Its internal structure consists of NAND gates and inverters configured to assert exactly one output per valid BCD code (0–9), with invalid codes (10–15) leaving all outputs high.
Each output is an open-collector NPN transistor capable of sinking up to 80 mA per channel, enabling direct drive of incandescent lamps or relay coils without external transistors. Input propagation delay is typically 25 ns at VCC = 5 V, and output fall time is 20 ns under 15-pF load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS (Low-power Schottky TTL), ensuring compatibility with standard TTL and LSTTL systems |
| Input Voltage Range | VIL ≤ 0.8 V, VIH ≥ 2.0 V - defines noise margin and ensures reliable recognition of logic levels from upstream TTL sources |
| Output Type | Open-collector - allows wired-AND logic and direct connection to external pull-up resistors or loads |
| Max Output Sink Current | 80 mA per output - supports driving lamps, LEDs, or small relays without buffer stages |
| Propagation Delay | 25 ns typical (tPLH/tPHL) - enables operation in synchronous systems up to ~20 MHz clock domains |
| Operating Temperature | 0°C to +70°C - qualified for commercial-grade embedded equipment and instrumentation |
| Supply Voltage | 4.75 V to 5.25 V - requires regulated 5-V rail; not tolerant of undervoltage or overvoltage operation |
Pinout & Package
SN74LS145NE4 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 top-left corner, identified by a notch or dot marking on the package.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A0) | BCD input bit 0 (LSB) | Accepts TTL-level low/high signal representing binary digit 0 of input code |
| 2 (A1) | BCD input bit 1 | Accepts TTL-level low/high signal representing binary digit 1 of input code |
| 3 (A2) | BCD input bit 2 | Accepts TTL-level low/high signal representing binary digit 2 of input code |
| 4 (A3) | BCD input bit 3 (MSB) | Accepts TTL-level low/high signal representing binary digit 3 of input code |
| 5 (Y0) | Active-low decoded output 0 | Sinks current when input = 0000₂; used to drive lamp/relay for decimal '0' |
| 6 (Y1) | Active-low decoded output 1 | Sinks current when input = 0001₂; used to drive lamp/relay for decimal '1' |
| 7 (Y2) | Active-low decoded output 2 | Sinks current when input = 0010₂; used to drive lamp/relay for decimal '2' |
| 8 (GND) | Ground reference | Common return path for all internal circuitry and output sink currents |
| 9 (Y3) | Active-low decoded output 3 | Sinks current when input = 0011₂; used to drive lamp/relay for decimal '3' |
| 10 (Y4) | Active-low decoded output 4 | Sinks current when input = 0100₂; used to drive lamp/relay for decimal '4' |
| 11 (Y5) | Active-low decoded output 5 | Sinks current when input = 0101₂; used to drive lamp/relay for decimal '5' |
| 12 (Y6) | Active-low decoded output 6 | Sinks current when input = 0110₂; used to drive lamp/relay for decimal '6' |
| 13 (Y7) | Active-low decoded output 7 | Sinks current when input = 0111₂; used to drive lamp/relay for decimal '7' |
| 14 (Y8) | Active-low decoded output 8 | Sinks current when input = 1000₂; used to drive lamp/relay for decimal '8' |
| 15 (Y9) | Active-low decoded output 9 | Sinks current when input = 1001₂; used to drive lamp/relay for decimal '9' |
| 16 (VCC) | Positive supply | Connects to +5 V regulated source; powers all internal logic and output transistors |
Key Features
| Feature | Design Value |
|---|---|
| BCD-to-decimal decoding | Directly converts 4-bit binary-coded decimal input into ten discrete active-low outputs for numeric display or selection logic |
| Open-collector outputs | Enables flexible interfacing to diverse loads (lamps, relays, optocouplers) via external pull-ups or direct sinking |
| High-output sink capability | 80 mA per output supports direct drive of common indicator lamps without external drivers |
| TTL-compatible inputs | Meets standard 74LS input voltage thresholds, ensuring seamless integration into existing TTL-based control systems |
| Commercial temperature range | 0°C to +70°C rating aligns with industrial panel-mounted equipment and test instrumentation requirements |
Applications
| Industrial Panel Indicators | Legacy Test Equipment Displays |
|---|---|
Use Scenario: Driving incandescent numeric displays on factory floor control panels where microcontroller GPIO count is limited. IC Role / Device Role / Timing Role: SN74LS145NE4 acts as a parallel BCD decoder that translates microcontroller BCD output into individual lamp-enable signals. Use Value: Eliminates need for software-based multiplexing or additional driver ICs, reducing firmware complexity and PCB component count. | Use Scenario: Selecting one of ten calibration reference points in benchtop multimeters or signal generators using rotary switch encoding. IC Role / Device Role / Timing Role: SN74LS145NE4 serves as a static decoder that activates only one reference path at a time based on front-panel BCD setting. Use Value: Provides deterministic, glitch-free selection with no timing constraints-critical for precision analog switching applications. |
| Relay Matrix Controllers | Electromechanical Counter Interfaces |
Use Scenario: Controlling ten independent 5-V relay coils in HVAC sequencers or safety interlock modules using minimal MCU I/O lines. IC Role / Device Role / Timing Role: SN74LS145NE4 functions as a parallel-to-discrete output expander, converting four digital control lines into ten isolated relay activation signals. Use Value: Enables full 10-relay control with only four MCU pins while maintaining galvanic isolation via relay coil drive. | Use Scenario: Interfacing mechanical decade counters (e.g., CDM-10 series) to digital logic circuits requiring decoded decimal output. IC Role / Device Role / Timing Role: SN74LS145NE4 receives BCD pulses from counter outputs and asserts corresponding decoded outputs for downstream logic or latch enable. Use Value: Preserves mechanical counter integrity by avoiding re-clocking or synchronization delays inherent in microcontroller-based decoding. |
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 74LS family, identical 16-pin PDIP package, but uses active-high outputs instead of open-collector; requires external pull-downs for lamp drive | Not suitable for direct lamp/relay sinking; better suited for logic-level fan-out or wired-OR configurations | Select SN74LS42N only if system design already uses active-high logic conventions and includes appropriate level-shifting or buffering |
| SN74HC42N | CMOS version with wider VCC range (2–6 V), lower power, but only 4-mA output sink capability - insufficient for direct lamp drive without external transistors | Requires redesign of output stage for high-current loads; incompatible with legacy 5-V TTL-only systems due to input threshold differences | Choose SN74HC42N only for new low-power designs with buffered outputs or when migrating from TTL to CMOS infrastructure |
Compared with SN74LS145NE4, SN74LS42N offers identical pinout and speed but lacks open-collector flexibility, while SN74HC42N trades drive strength and TTL compatibility for CMOS efficiency - making SN74LS145NE4 uniquely suited for legacy direct-load interfacing.
Availability
SN74LS145NE4 is available at Aetrix Electronics and suitable for industrial panel indicators, legacy test equipment displays, and relay matrix controllers requiring stable component supply across long-lifecycle programs.
Supply support for SN74LS145NE4 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 and automotive qualification.
The SN74LS145NE4 belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-speed digital decoding in electromechanical and indicator-based systems where reliability and direct load drive are prioritized over power efficiency.
FAQ
What is the primary function of the SN74LS145NE4?
The SN74LS145NE4 is a BCD-to-decimal decoder with open-collector outputs. It accepts a 4-bit binary-coded decimal input and asserts exactly one of ten active-low outputs (Y0–Y9) corresponding to the decimal value 0–9. This makes it ideal for driving lamps, relays, or other loads in numeric display and selection applications. The SN74LS145NE4 does not perform arithmetic or latching - its operation is purely combinational and stateless.
Can the SN74LS145NE4 drive LEDs directly without current-limiting resistors?
No - the SN74LS145NE4 requires external current-limiting resistors when driving LEDs. Although each output can sink up to 80 mA, LED forward voltage and desired brightness dictate resistor value. For example, with a 5-V supply and red LED (VF ≈ 1.8 V), a 100-Ω resistor limits current to ~32 mA. Omitting the resistor risks exceeding absolute maximum ratings and damaging the SN74LS145NE4 or LED.
Is the SN74LS145NE4 compatible with modern 3.3-V microcontrollers?
The SN74LS145NE4 is not directly compatible with 3.3-V logic outputs. Its input high threshold (VIH ≥ 2.0 V) is met, but its 5-V-only supply requirement means it must be powered from a 5-V rail. Level-shifting is required for clean interfacing: a simple resistor divider or dedicated translator (e.g., TXB0104) ensures safe 3.3-V GPIO signals meet SN74LS145NE4 input specs without overstressing either device.
Does the SN74LS145NE4 include built-in hysteresis or noise immunity features?
No - the SN74LS145NE4 has standard TTL input thresholds without Schmitt-trigger hysteresis. Its input noise margin is defined by VIL ≤ 0.8 V and VIH ≥ 2.0 V at VCC = 5 V, yielding ~0.4 V low-state and ~0.7 V high-state noise immunity. For noisy environments (e.g., industrial relay panels), external RC filtering or dedicated Schmitt-trigger buffers (e.g., SN74LS14) should precede the SN74LS145NE4 inputs.
What happens when an invalid BCD code (10–15) is applied to the SN74LS145NE4 inputs?
When inputs A3–A0 represent a value outside 0–9 (i.e., 1010₂ to 1111₂), the SN74LS145NE4 leaves all ten outputs (Y0–Y9) in the high-impedance (open-circuit) state - meaning all outputs remain high (non-sinking). No output is asserted, and no current flows through any Yx terminal. This behavior is explicitly defined in TI's SN74LS145 datasheet and ensures predictable failure-mode operation in systems relying on strict decimal decoding.
SN74LS145NE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Decoder
- Circuit:
- 1 x 4:10
- Independent Circuits:
- 1
- Current - Output High, Low:
- 250µA, 80mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
SN74LS145NE4 FAQ
1.How can I place an order for SN74LS145NE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS145NE4 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 SN74LS145NE4 reliable?
The price and inventory of SN74LS145NE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS145NE4 is usually 5 days.
3.What payment methods are accepted for SN74LS145NE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS145NE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS145NE4?
SN74LS145NE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS145NE4 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 SN74LS145NE4?
For technical support, including SN74LS145NE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS145NE4 requirements.
6.How does Aetrix verify that SN74LS145NE4 is sourced from the original manufacturer or authorized distributors?
All SN74LS145NE4 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 SN74LS145NE4 meets industry standards.
7.What is the process for return or replacement of SN74LS145NE4?
All SN74LS145NE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS145NE4, 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 SN74LS145NE4 part is unused and in its original packaging.
Return procedure for SN74LS145NE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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