on September 3th 310

Understanding the Key Features and Applications of ULN2003

ULN2003 is a high-voltage, high-current composite transistor array series product. It has high operating voltage, high current gain, wide temperature range and strong load capacity, so it is very suitable for various systems that require high-power drive. This article will introduce relevant information of ULN2003, including its characteristics, pins and functions, working principle, function and application. Let's start.

Catalog

ULN2003 Overview

ULN2003 is a high-voltage and high-current driver that is commonly used in various circuits for electronic lock control, motor drive, stepper motor drive, LED display conversion, smart home equipment, and other occasions where high-voltage and high-current devices need to be controlled. It consists of seven silicon NPN composite transistors, with each pair of Darlington transistors connected in series with a 2.7K base resistor. At an operating voltage of 5V, it can be directly connected to TTL and CMOS circuits, so it can directly process data that originally required standard logic buffers. Therefore, ULN2003 can control multiple devices simultaneously. It has the advantages of high reliability, convenient interface, etc., and is easy to be integrated into various circuits.

Alternatives and Equivalents

• LR2003L

• TBD62003APG

• ULN2001

• ULN2001A

• ULN2003A

What Are the Characteristics of ULN2003?

ULN2003 has the following features:

• Shallow sleep current: When the output is low, the sleep current of the ULN2003 is very low, which helps reduce power consumption and heat generation.

• DIP package: ULN2003 adopts dual in-line package for easy insertion into the circuit board and easy soldering.

• Seven programmable outputs: The ULN2003 has seven output pins, each of which can be controlled independently, making it ideal for driving multiple motors or relays.

• Input and control level compatibility: The input pins of ULN2003 adopt TTL and CMOS level control, which are fully compatible with common logic levels, so it is very convenient to integrate with other digital circuits.

• Built-in free DuPont diode: Each Darlington pair has built-in free DuPont diode to protect the switching components from reverse voltage damage, thereby improving the reliability of the chip.

• High current and high voltage: The output of ULN2003 can withstand high current and voltage. Its maximum withstand current is 500mA and the maximum withstand voltage is 50V, which makes it very suitable for controlling high-power motors and relays.

Pin Diagram and Functions of ULN2003

Pin 1: This pin is the pulse input terminal of the CPU, and the port corresponds to a signal output terminal.

Pin 2 to 7: This pin is the CPU pulse input terminal.

Pin 8: This pin is grounded.

Pin 9: This pin is the common cathode of the seven internal freewheeling diodes. The anode of each diode is connected to the collector of each Darlington tube. When used for inductive loads, this pin should be connected to the positive pole of the load power supply to achieve freewheeling. If this pin is connected to ground, it is actually equivalent to the collector of the Darlington tube being connected directly to ground.

Pins 10 to 16: These pins are the pulse signal output terminals, corresponding to the pin 7, pin 6, pin 5, pin 4, pin 3, pin 2, and pin 1 signal input terminals respectively.

Working Principle and Function of ULN2003

The ULN2003 consists of two main parts, the input side and the output side. The inputs include seven input pins (IN1 to IN7), which are used to receive logic signals from external sources, while the outputs contain seven switching tube output ports (OUT1 to OUT7), which are responsible for controlling the switching state of the load circuits.

The working principle of ULN2003 is as follows: when the input signal is high level, the corresponding switch tube inside the chip will be in a closed state, and the load circuit cannot be driven by current at this time; when the input signal is low level, the switch tube will be turned on, thus allowing current to drive the load circuit. Therefore, by changing the level state of the input terminal, we can achieve switching control of the corresponding pin of the output terminal.

The main function of ULN2003 is to drive high voltage, high current, and high inductance loads. Since ordinary microcontrollers cannot directly control these loads, ULN2003 is required for driving and control. In addition, the chip is equipped with an internal suppression diode to provide reverse protection at the output port, making the entire system more stable and reliable.

ULN2003 Drive Circuit Diagram

ULN2003 is an integrated circuit with 16 pins. It integrates seven pairs of Darlington transistors, each capable of driving loads up to 50V and 500mA. For these seven Darlington pairs, we equip the corresponding seven input and output pins. In addition, it contains ground pins and general purpose pins. Typically, the ground pin is connected directly to ground, while the use of a common pin is optional. Surprisingly, this IC does not have a dedicated Vcc pin. This is because the power required for the transistor to operate will be drawn directly from the input pin. Below is a simple circuit example that can be used to test the operation of the ULN2003 integrated circuit.

In the circuit, we think of the LED as the load and the logic pins are used to connect to digital circuits or microcontrollers like Arduino. Note that the positive pin of the LED should be connected to the positive load voltage and the negative pin should be connected to the output pin of the IC. This is because when the input pin level of the IC goes high, the corresponding output pin goes to ground. Therefore, when the negative terminal of the LED is connected to ground, the circuit is closed, allowing the LED to emit light. The maximum load current connected to each output pin is 500mA and the voltage is 50V. However, if you need to drive a higher current load, you can do so by connecting two or more output pins in parallel. For example, if you connect three pins in parallel, you can drive about 1.5A. The COM pin is used to connect to ground through the switch, this connection is optional. It can be used as a test switch, i.e. when this pin is connected to ground, all output pins will be connected to ground.

Where Is ULN2003 Used?

In practical applications, ULN2003 is often used to drive inductive loads such as stepper motors, relays, and solenoid valves. Since these loads usually require larger currents and higher voltages to drive, ULN2003 has sufficient driving capabilities while having smaller power consumption and higher reliability, making it an ideal choice for driving these loads.

In addition to the basic driving function, ULN2003 can also realize more complex control functions by using external resistors, capacitors, and other components. For example, we can use external resistors to adjust the size of the output current, or through external capacitors to realize the de-jitter and other functions. The realization of these control functions not only further broadens the scope of application of ULN2003, but also enhances the flexibility of its use.

In the design and manufacturing process of electronic equipment, ULN2003 is widely used. It can be used in various control circuits, drive circuits, protection circuits, and other occasions, providing an important guarantee for the normal operation of electronic equipment. At the same time, because ULN2003 has a smaller size and lower power consumption, it has also been widely used in electronic devices that pursue miniaturization and low power consumption.

How to Use ULN2003 to Drive Stepper Motor?

First, we need to connect the power supply of the stepper motor to an appropriate supply voltage and make sure that the supply voltage range of ULN2003 meets the requirements of the stepper motor. Next, we connect the output pins of the ULN2003 to the controls of the stepper motor. Typically, stepper motors have four control lines (A, A', B, B') corresponding to two phases. We connect each of the four outputs (OUT1 through OUT4) of the ULN2003 to these four control lines of the stepper motor. Subsequently, we connect a control signal (e.g. from a microcontroller) to the input of the ULN2003. When the input signal is high, the corresponding ULN2003 output pin will be pulled low, which will cause the stepper motor to rotate. We then need to write the program to control the stepper motor using an appropriate programming language. Depending on the type of stepper motor (single-phase, two-phase, four-phase, etc.), we need to determine the correct step sequence and control signals. Finally, we run the program and test the motion of the stepper motor. As needed, we can adjust the step sequence and speed of the stepper motor to ensure that it operates as expected.

Frequently Asked Questions [FAQ]

1. What replaces ULN2003 Mosfet?

We do have a mosfet equivalent to the ULN2003, called the TPL7407LA.

2. What is ULN2003 used for?

ULN2003 IC is one of the most commonly used Motor driver IC. This IC comes in handy when we need to drive high current loads using digital logic circuits like Op-maps, Timers, Gates, Arduino, PIC, ARM etc.

3. What is ULN2003 chip?

ULN2003 Driver Module is a Stepper Motor Driver, small size and easy to use. It uses the ULN2003 driver chip to amplify the control signal from the Arduino. This Ultra Lightweight and cheap option commonly used to run and control the small applications stepper motors.

4. Why we use ULN2803?

The ULN2803 integrated circuit is used as a power interface for circuits with CMOS and TTL technology. This integrated has 8 NPN transistors in Darlington configuration with protection diodes, to control motors, inductive loads, relays, and more.

5. What is the difference between ULN2002 and ULN2003?

The ULN2002A is specifically designed for use with 14- to 25-V PMOS devices. Each input of this device has a zener diode and resistor in series to control the input current to a safe limit. The ULN2003A has a 2.7-kΩ series base resistor for each Darlington pair for operation directly with TTL or 5-V CMOS devices.