SN74LS145 - BCD-to-Decimal Decoder/Driver | Texas Instruments
MPN: SN74LS145 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.72 | $7.20 |
| 100 | $0.58 | $58.00 |
| 500 | $0.49 | $245.00 |
| 1,000 | $0.42 | $420.00 |
Drop-in alternatives for SN74LS145 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
SN74145
β Drop-Inπ Reference alternative (not in catalog)
SN54LS145
β Drop-Inπ Reference alternative (not in catalog)
SN54145
β Drop-Inπ Reference alternative (not in catalog)
CD4028B
β‘ Same Packageπ Reference alternative (not in catalog)
74HC145
β‘ Same Packageπ Reference alternative (not in catalog)
SN74LS145 Maximum Ratings & Electrical Characteristics
| Function | BCD-to-Decimal Decoder/Driver |
| Output Type | Open Collector |
| Output Current (Sink) | 80 mA |
| Output Voltage (Max) | 15 V |
| Number of Inputs | 4 (BCD) |
| Number of Outputs | 10 |
| Supply Voltage | 4.75 V to 5.25 V |
| Propagation Delay Time | [DATA_NEEDED: Propagation Delay Time] |
| Operating Temperature Range | 0Β°C to 70Β°C |
| Package Type | PDIP-16 |
| Mounting Type | Through Hole |
| Logic Family | 74LS |
| RoHS Status | Compliant |
| Lead Free | Yes |
| Number of Pins | 16 |
SN74LS145 Pin Configuration
| Pin 1 | B β BCD input B |
| Pin 2 | C β BCD input C |
| Pin 3 | D β BCD input D (MSB) |
| Pin 4 | A β BCD input A (LSB) |
| Pin 5 | OUT 0 β Output for decimal 0 (open collector) |
| Pin 6 | OUT 1 β Output for decimal 1 (open collector) |
| Pin 7 | OUT 2 β Output for decimal 2 (open collector) |
| Pin 8 | GND β Ground |
| Pin 9 | OUT 3 β Output for decimal 3 (open collector) |
| Pin 10 | OUT 4 β Output for decimal 4 (open collector) |
| Pin 11 | OUT 5 β Output for decimal 5 (open collector) |
| Pin 12 | OUT 6 β Output for decimal 6 (open collector) |
| Pin 13 | OUT 7 β Output for decimal 7 (open collector) |
| Pin 14 | OUT 8 β Output for decimal 8 (open collector) |
| Pin 15 | OUT 9 β Output for decimal 9 (open collector) |
| Pin 16 | VCC β Positive supply voltage (5 V) |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this digital IC. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
SN74LS145 is suitable for 6 applications: Incandescent Display Driver, Relay Driver, BCD-to-Decimal Decoding, Lamp and LED Matrix Driving, Industrial Control Logic, Test and Measurement Equipment.
Incandescent Display Driver
The SN74LS145 is designed to drive 10-digit incandescent displays directly. Its open-collector outputs can sink up to 80 mA at 15 V, which is sufficient for typical incandescent lamp segments. The BCD input simplifies interfacing with digital counters or microcontrollers. When driving displays, ensure the lamp current does not exceed the 80 mA rating and use appropriate current limiting if needed. The device's high-voltage capability allows the display supply to be separate from the logic supply, improving noise immunity.
Recommended
Relay Driver
The SN74LS145 can drive relays directly due to its 80 mA sink capability and 15 V output rating. This eliminates the need for external transistor drivers in many low-power relay applications. When driving inductive loads like relays, always place a flyback diode across the relay coil to protect the output transistor from voltage spikes. The open-collector output allows the relay supply voltage to be up to 15 V, independent of the 5 V logic supply. This simplifies power distribution in industrial control panels.
Recommended
BCD-to-Decimal Decoding
The SN74LS145 converts a 4-bit BCD input into one of ten active-low outputs. This is useful in applications such as digit selection in multiplexed displays, channel selection in test equipment, or address decoding in industrial controls. The open-collector outputs can be wired-ORed to create custom logic functions. The device's full decoding ensures that invalid BCD inputs (1010-1111) produce no active outputs, preventing erroneous activation. This makes it a reliable choice for safety-critical decoding applications.
Recommended
Lamp and LED Matrix Driving
The SN74LS145 can drive lamps and LEDs in matrix configurations. Its high sink current (80 mA) allows direct driving of lamps, while LEDs can be driven with series resistors. The open-collector outputs enable multiplexing by connecting multiple outputs together. When driving LEDs, calculate the series resistor value based on the LED forward voltage and desired current. The device's 15 V rating allows series strings of LEDs to be driven from a higher voltage supply, improving efficiency.
Recommended
Industrial Control Logic
The SN74LS145 is used in industrial control systems for decoding BCD inputs from thumbwheel switches or PLCs to drive output devices like relays, solenoids, and indicator lamps. Its robust open-collector outputs can handle industrial voltage levels up to 15 V, and its TTL compatibility ensures easy interfacing with other logic families. The device's ability to sink 80 mA per output reduces the need for additional driver stages, simplifying PCB design and reducing component count. Its wide operating temperature range (0Β°C to 70Β°C) suits most industrial environments.
Recommended
Test and Measurement Equipment
The SN74LS145 is used in test and measurement equipment for channel selection, range switching, and display driving. Its open-collector outputs can drive relays that switch signal paths, and its BCD input simplifies interfacing with digital control logic. The device's high output voltage rating (15 V) allows it to control relays with higher coil voltages, while the logic operates at 5 V. This separation of logic and load supplies improves noise immunity and simplifies power supply design. The device's low power dissipation (LS technology) is beneficial in densely populated equipment.
Recommended
Engineering reference data for SN74LS145 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SN74145 | SN54LS145 | CD4028B |
|---|---|---|---|---|
| Package | PDIP-16 | PDIP-16 | PDIP-16 | PDIP-16 |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Output Type | Open Collector | Open Collector | Open Collector | Push-Pull |
| Output Sink Current | 80 mA | 80 mA | 80 mA | 1 mA (at 5V) |
| Max Output Voltage | 15 V | 15 V | 15 V | VDD (up to 18V) |
| Logic Family | 74LS | 74 | 54LS | CMOS |
| Operating Temperature | 0Β°C to 70Β°C | 0Β°C to 70Β°C | -55Β°C to 125Β°C | -55Β°C to 125Β°C |
| Supply Voltage | 5 V | 5 V | 5 V | 3V to 18V |
Key Differentiators
- High output sink current of 80 mA (vs CD4028B)
- Open-collector outputs with 15V rating (vs 74HC145)
- TTL-compatible inputs (vs CD4028B)
Design Notes
When driving inductive loads such as relays or solenoids, always connect a flyback diode (e.g., 1N4148) across the load to protect the open-collector output transistor from voltage spikes. The diode should be oriented to block normal current flow and conduct when the load is de-energized. Failure to do so can damage the SN74LS145 output transistor.
For high-current outputs (up to 80 mA), ensure the PCB traces are wide enough to handle the current without excessive voltage drop. Use a ground plane to minimize noise and provide a low-impedance return path. Decouple the VCC pin with a 0.1 Β΅F ceramic capacitor placed close to the IC to suppress high-frequency noise.
The SN74LS145 dissipates power when sinking current. At maximum output current (80 mA) and 15 V output voltage, each output can dissipate up to 1.2 W. In applications with multiple outputs active simultaneously, ensure the total power dissipation does not exceed the package's thermal limits. The PDIP package has a thermal resistance of approximately 80Β°C/W, so keep the ambient temperature within the specified range.
Compliance Information
RoHS compliant per TI product page. Not AEC-Q100 qualified.
