ULN2804A

Overview

The ULN2804A is an eight-channel NPN Darlington transistor array manufactured by STMicroelectronics, designed for driving high-voltage and high-current loads. It features a common emitter configuration with integral suppression diodes to protect against inductive load transients. The device operates within a collector-emitter voltage range of up to 50 V and supports a continuous collector current of 500 mA per channel, with a peak rating of 600 mA. Each input includes a 10.5 kΩ resistor, facilitating direct interfacing with 6 V to 15 V CMOS logic families. Packaged in an 18-lead plastic DIP (PDIP-18), the component offers an input-opposite-output pinout to simplify printed circuit board layout. It functions reliably across a temperature range of -20°C to +85°C.

Feature Summary

• Integrated suppression diodes provide protection for inductive loads such as relays and solenoids.
• Built-in 10.5 kΩ input resistors enable direct compatibility with 6 V to 15 V CMOS logic levels.
• Input pins are positioned opposite corresponding output pins to streamline PCB routing and design.
• Outputs can be paralleled to increase total current handling capability beyond single-channel limits.

Applications

• Driving stepper motors and coil actuators
• Controlling relay banks and solenoid valves
• Powering LED display matrices
• Interface circuits between microcontrollers and high-power loads

Procurement Notes

Verify the specific manufacturer marking and date code on the component body to confirm authenticity, as counterfeits exist. Ensure the package matches the standard 18-pin DIP form factor. Check for RoHS compliance documentation if environmental regulations apply to the final assembly. Confirm that the supply chain source provides original manufacturer packaging or authorized distributor certificates to guarantee electrical parameter consistency.

Selection Notes

Select the ULN2804A when interfacing with 6 V to 15 V CMOS logic families requiring built-in input resistance. Choose this variant over the ULN2803A if the system does not require TTL compatibility or lower input impedance. Consider the ULQ2804A for applications demanding an extended industrial temperature range of -40°C to 105°C. Evaluate thermal dissipation requirements carefully, as the 2.25 W power dissipation limit may necessitate heat sinking in high-density configurations.

Part Context

The ULN2804A belongs to the ULN28xx series of Darlington arrays from STMicroelectronics, which also includes the ULN2801A, ULN2802A, and ULN2803A. These components share identical internal transistor structures and pinouts but differ primarily in their input resistor values to match specific logic families. The ULN2804A specifically targets mid-range voltage CMOS applications, distinguishing it from the ULN2803A's TTL focus and the ULN2802A's PMOS optimization.

Replacement Considerations

The ULN2803A serves as a functional substitute if the application utilizes 5 V logic, though its 2.7 kΩ input resistor differs from the ULN2804A's 10.5 kΩ value. For extended temperature requirements, the ULQ2804A offers the same electrical characteristics but operates from -40°C to 105°C. Cross-referencing with other manufacturers' octal Darlington arrays requires verifying pinout compatibility and input threshold voltages.