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Texas Instruments SN74LS145DG4
- Part No.:
- SN74LS145DG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS145DG4.pdf
- Description:
- IC DECODER 1 X 4:10 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,469
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Product details
Overview
SN74LS145DG4 from Texas Instruments is a bipolar TTL BCD-to-decimal decoder/driver IC with open-collector outputs, designed for direct interface to lamps, relays, and other high-current loads. It features 16-pin SOIC packaging, operates from 4.75 V to 5.25 V, supports 0°C to 70°C ambient temperature, and delivers 40 mA sink current per output.
For engineers reviewing the SN74LS145DG4 datasheet, SN74LS145DG4 pinout, SN74LS145DG4 application, or SN74LS145DG4 equivalent, this page provides verified package mapping, confirmed BCD decoding behavior, real-world drive capability, and validated drop-in alternatives for legacy TTL system upgrades and industrial control logic design.
Technical Context
The SN74LS145DG4 implements active-low decoded decimal outputs (Y₀–Y₉) driven by a 4-bit BCD input (A₀–A₃), with no internal pull-ups. Its open-collector architecture requires external pull-up resistors for logic-level translation or load driving.
It uses standard LS-TTL process technology, ensuring compatibility with 74LS-series timing and voltage thresholds. Input clamp diodes provide ESD protection, and output transistors are rated for continuous 40 mA sink current with guaranteed saturation at IC = 40 mA and VCE(sat) ≤ 0.5 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS TTL - ensures compatible noise margins and propagation delay with legacy LS systems |
| Supply Voltage | 4.75 V to 5.25 V - matches standard 5 V TTL rail; operation outside this range invalidates specs |
| Output Type | Open-collector - enables wired-AND logic, level shifting, and direct drive of 5 V lamps/relays |
| Sink Current per Output | 40 mA - sufficient to drive LED arrays or small solenoids without external buffers |
| Propagation Delay | 40 ns max (tPLH/tPHL) - supports synchronous decoding in sub-25 MHz clock domains |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded control and instrumentation applications |
| Input Compatibility | Standard TTL - accepts 0.8 V (VIL) and 2.0 V (VIH) thresholds; no CMOS-level tolerance |
Pinout & Package
SN74LS145DG4 is housed in a 16-pin SOIC (D) package with 1.27 mm pitch, 7.5 mm body width, and 2.00 mm maximum height. Pin 1 is located at the top-left corner with notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 6, 7 | BCD Inputs (A₀–A₃) | Active-high binary-coded decimal address inputs; A₀ = LSB, A₃ = MSB |
| 3–5, 9–11 | Active-Low Decimal Outputs (Y₀–Y₉) | Open-collector outputs; each sinks current when corresponding BCD value is present |
| 12, 13 | NC | No internal connection; must be left unconnected or tied to GND per TI layout guidelines |
| 14 | VCC | Positive supply terminal - requires local 0.1 µF ceramic decoupling capacitor |
| 16 | GND | Ground reference - connects to system ground plane with low-inductance path |
Key Features
| Feature | Design Value |
|---|---|
| BCD-to-decimal decoding | Direct 4-bit binary input → 10-line active-low decoded output mapping, eliminating need for discrete gate logic |
| Open-collector outputs | Enables shared-bus wiring, mixed-voltage interfacing (e.g., 5 V logic to 12 V lamp), and current-sinking up to 40 mA |
| TTL-compatible inputs | Guaranteed recognition of standard TTL logic levels (VIL ≤ 0.8 V, VIH ≥ 2.0 V), ensuring interoperability in legacy 74LS systems |
| Commercial temperature grade | Validated operation from 0°C to 70°C - suitable for office equipment, test instruments, and non-military industrial panels |
Applications
| LED Display Driver | Industrial Relay Interface |
|---|---|
Use Scenario: Driving 7-segment or bar-graph LED displays in test equipment front panels. IC Role / Device Role / Timing Role: BCD-to-decimal decoder providing individual segment enable signals via open-collector outputs. Use Value: Eliminates need for discrete transistor arrays; each output directly sinks LED current up to 40 mA with <0.5 V saturation. | Use Scenario: Controlling 10-channel relay bank in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Decoding microcontroller BCD commands into discrete relay activation lines. Use Value: Open-collector outputs interface directly to 5 V relay coils or optocoupler inputs without level-shifting circuitry. |
| Legacy System Replacement | Address Decoder in Microprocessor Systems |
Use Scenario: Replacing obsolete SN74145 or SN54LS145 in fielded military/commercial hardware. IC Role / Device Role / Timing Role: Pin- and function-compatible drop-in replacement preserving existing PCB layout and firmware. Use Value: Same 16-pin SOIC footprint, identical timing, and identical electrical behavior as original 74LS145 variants. | Use Scenario: Selecting peripheral devices (e.g., UARTs, timers) in 8-bit microprocessor buses. IC Role / Device Role / Timing Role: Translating upper address bits into chip-select signals for memory-mapped peripherals. Use Value: Provides ten independent, mutually exclusive enable signals synchronized to bus timing with <40 ns delay. |
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 |
|---|---|---|---|
| SN74LS145N | Same logic function and electrical specs, but in 16-pin PDIP package with through-hole mounting | Preferred for prototyping, breadboarding, or legacy through-hole PCBs where SOIC rework is impractical | Select SN74LS145N when manual assembly, socketing, or thermal mass requirements favor DIP over SOIC |
| SN74LS42N | Also a BCD-to-decimal decoder, but with active-high outputs and no NC pins; different pinout and output polarity | Requires redesign of pull-up/pull-down network and firmware logic inversion due to active-high Y₀–Y₉ | Choose SN74LS42N only if system already uses active-high decoding and board layout allows pinout change |
Compared with SN74LS145N and SN74LS42N, the SN74LS145DG4 offers surface-mount compatibility and identical open-collector drive behavior, making it optimal for automated assembly and direct lamp/relay interfacing without logic inversion.
Availability
SN74LS145DG4 is available at Aetrix Electronics and suitable for industrial control panels, test instrumentation, legacy system repairs, and LED display subsystems requiring stable component supply across extended production lifecycles.
Supply support for SN74LS145DG4 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 SN74LS145DG4 belongs to TI's legacy 74LS logic family, engineered for reliable BCD decoding and high-current load driving in commercial-grade digital systems.
FAQ
What is the maximum sink current per output on the SN74LS145DG4?
The SN74LS145DG4 guarantees 40 mA sink current per output with VCE(sat) ≤ 0.5 V at IC = 40 mA. This rating applies under specified conditions: VCC = 5 V, TA = 25°C. Exceeding 40 mA risks thermal overstress and parametric shift. Derating is required above 25°C ambient.
Does the SN74LS145DG4 require external pull-up resistors?
Yes - the SN74LS145DG4 has open-collector outputs and cannot source current. Each output (Y₀–Y₉) must be pulled up to VCC or another logic rail using external resistors. Typical values range from 1 kΩ (for fast rise time with capacitive loads) to 10 kΩ (for low power); exact value depends on load capacitance and speed requirements.
Is SN74LS145DG4 pin-compatible with SN74LS145N?
Yes - SN74LS145DG4 and SN74LS145N share identical pin functions and signal assignments. Both use 16-pin layouts with matching BCD inputs (pins 1,2,6,7), decimal outputs (pins 3–5,9–11), VCC (pin 14), GND (pin 16), and NC pins (12,13). Only package type (SOIC vs. PDIP) differs.
Can SN74LS145DG4 decode non-BCD inputs like hexadecimal or excess-3 code?
No - the SN74LS145DG4 is strictly a BCD-to-decimal decoder. Inputs outside the 0000–1001 (0–9) range produce undefined or multiple active outputs. For example, input 1010 (decimal 10) activates both Y₀ and Y₁. It does not support hexadecimal (0–F) or excess-3 decoding; dedicated logic or FPGA preprocessing is required.
What is the recommended decoupling for SN74LS145DG4?
A 0.1 µF ceramic capacitor placed between VCC (pin 14) and GND (pin 16), as close as possible to the device, is mandatory for stable operation. TI further recommends adding a bulk 4.7 µF–10 µF electrolytic/tantalum capacitor near the power entry point of the board to suppress low-frequency ripple affecting multiple LS devices.
SN74LS145DG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- 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
SN74LS145DG4 FAQ
1.How can I place an order for SN74LS145DG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS145DG4 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 SN74LS145DG4 reliable?
The price and inventory of SN74LS145DG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS145DG4 is usually 5 days.
3.What payment methods are accepted for SN74LS145DG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS145DG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS145DG4?
SN74LS145DG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS145DG4 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 SN74LS145DG4?
For technical support, including SN74LS145DG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS145DG4 requirements.
6.How does Aetrix verify that SN74LS145DG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS145DG4 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 SN74LS145DG4 meets industry standards.
7.What is the process for return or replacement of SN74LS145DG4?
All SN74LS145DG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS145DG4, 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 SN74LS145DG4 part is unused and in its original packaging.
Return procedure for SN74LS145DG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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