ULN2004A

Overview

The ULN2004A is a high-voltage, high-current Darlington transistor array manufactured by STMicroelectronics. It comprises seven NPN Darlington pairs with common emitters and integrated suppression diodes for switching inductive loads. Each channel supports a collector current of 500 mA and withstands peak currents up to 600 mA, with an output voltage rating of 50 V. The device features a 10.5 kΩ series base resistor per pair, enabling direct interface with CMOS logic operating between 6 V and 15 V. Supplied in a 16-pin DIP package with a copper leadframe to minimize thermal resistance, it serves as a versatile driver for various digital-to-analog load applications.

Feature Summary

• Seven independent NPN Darlington pairs with integrated common cathode clamping diodes for inductive load protection
• High voltage output capability rated at 50 V with 500 mA continuous collector current per channel
• Internal 10.5 kΩ base resistors allow direct interfacing with 6 V to 15 V CMOS logic families
• Input pins positioned opposite output pins on the 16-pin DIP package to simplify printed circuit board layout

Applications

• Relay drivers
• Stepper motor and DC brushed motor drivers
• LED and gas discharge display drivers
• Line drivers and high-power logic buffers

Procurement Notes

Verify component authenticity through authorized distributors or official manufacturer channels. Confirm the specific package variant, such as the standard DIP-16 or SO-16, matches design requirements. Check for active status or last-time-buy notices, as availability may vary across regions. Ensure proper handling procedures are followed due to the sensitivity of semiconductor components during storage and assembly.

Selection Notes

Select the ULN2004A when driving loads requiring 50 V and 500 mA from a 6 V to 15 V CMOS control source. Choose this over ULN2003 if the input voltage exceeds 5 V, as the higher base resistance prevents excessive input current. Consider the ULN2002 only if interfacing with 14 V to 25 V PMOS devices. Paralleling outputs can increase current capacity beyond single-channel limits for heavier loads.

Part Context

The ULN2004A belongs to the ULx200xA family of high-voltage Darlington arrays. Unlike the ULN2003, which targets 5 V TTL/CMOS, the ULN2004A includes larger base resistors optimized for 6 V to 15 V operation. This distinction allows it to interface directly with higher voltage logic levels without external current-limiting components, differentiating it within the broader ULN series lineup.

Replacement Considerations

Direct substitutes include the ULN2004D1 (SO-16 package) and generic equivalents like the SN75489 or TC78008F. Verify pin compatibility and electrical ratings before substitution. Note that some alternatives may lack the specific 10.5 kΩ base resistor configuration required for 15 V CMOS inputs.