ULN2003– A high current drive IC

In many cases we require to drive high current output but at a cost effective manner. Either we use a high current transistor or a discrete Darlington pair to drive high current load. But the common way is to use a Darlington pair IC which has inbuilt number of Darlington pair transistors to drive many loads.

The ULN2001, ULN2002, ULN2003 and ULN 2004 are high-voltage, high-current Darlington arrays each containing seven open collector Darlington pairs with common emitters. Each channel is rated at 500 mA and can withstand peak currents of 600 mA. Suppression diodes are included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout.

These versatile devices are useful for driving a wide range of loads including solenoids, relay DC motors, LED display filament lamps, thermal print heads and high-power buffers. Taking look at its features we get below points.

· Contains 7 high-voltage and high current Darlington pairs

· Each pair is rated for 50V and 500mA

· Input pins can be triggered by +5V

· All seven Output pins can be connected to gather to drive loads up to (7×500mA) ~3.5A.

· Can be directly controlled by logic devices like Digital Gates, Arduino, PIC etc

· Available in 16-pin DIP, TSSOP, SOIC packages

This is available in a simple 16 pin DIP package. Taking look at its pin configurations and layout, we get what is shown in below figure.

ULN2003 Pin out Configuration is shown below

Pin Number	Pin Name	Description
1 to 7	Input 1 to Input 7	Seven Input pins of Darlington pair, each pin is connected to the base of the transistor and can be triggered by using +5V
8	Ground	Ground Reference Voltage 0V
9	COM	Used as test pin or Voltage suppresser pin (optional to use)
10 to 16	Output 1 to Output 7	Respective outputs of seven input pins. Each output pin will be connected to ground only when its respective input pin is high(+5V)

As already said that this contains an array of Darlington pair for driving high current loads. The internal circuit of each block is shown below.

The application is quite simple. Just connect the output of your controller pin to the input of this device and get the high current drive output at the device output.

A more closer look can be found in the video