ULN2003AD Equivalents, Symbol, Working Principle and Layout Guidelines
03 November 2023
Ⅱ. Symbol, footprint and pin configuration of ULN2003AD
Ⅳ. Technical parameters of ULN2003AD
Ⅴ. Working principle of ULN2003AD
Ⅵ. Layout guidelines for ULN2003AD
Ⅶ. What are the applications of ULN2003AD?
ULN2003AD is a high voltage, high current Darlington transistor array. Each device consists of seven NPN Darlington pairs with high voltage outputs with common cathode clamping diodes for switching inductive loads. A single Darlington has a collector current rating of 500mA, and pairs of Darlingtons can be used in parallel when higher current capabilities are required. Additionally, each Darlington pair of the ULN2003AD has a 2.7Kohm series base resistor for direct connection to TTL or 5V CMOS devices. Typical applications for the ULN2003AD include lamp drivers, relay drivers, display drivers (LED and gas discharge), hammer drivers, logic buffers and line drivers.
Replacements and equivalents:
The figure below shows the symbol, footprint and pin configuration of ULN2003AD.
The ULN2003AD features a total of 16 pins, typically organized into two rows, with 8 pins in each row. Among these pins, there are seven output pins labeled as OUT 1 to OUT 7, one input pin designated as IN, a ground pin denoted as COM, and seven power supply pins labeled as VCC1 to VCC7.
• It is specially designed for use with 14V to 25V PMOS devices.
• The input of ULN2003AD is compatible with TTL (logic level 0 and 1) and CMOS (logic level low and high) levels, so it can be easily connected to a variety of digital circuits.
• It has the ability to withstand higher current loads. Typically, it can handle current ranges from 500mA to 600mA.
• ULN2003AD has built-in intelligent over-current protection and over-temperature protection functions so that it will not be damaged when dealing with high current or high temperature environments.
• It is equipped with a Zener diode and resistor in series at each input. The function of these components is to control the input current to ensure that it is within a safe range. In this way, the ULN2003AD is able to protect circuits and systems from too much or too little current while maintaining efficient current transfer capabilities.
• It integrates a reverse voltage protection diode internally to protect the output port from reverse voltage impact of inductive loads.
The ULN2003AD operates based on the following principle: when the input signal is at a high level, the internal Darlington pair enters a cut-off state, resulting in a low-level output at the terminal. Conversely, when the input signal is at a low level, the Darlington pair becomes saturated, causing the output terminal to provide a high-voltage output. To regulate the input current and ensure safety protection, each Darlington pair's base is linked to the input signal through a series of Zener diodes and resistors.
Thin traces are suitable for input connections, thanks to the low-current logic commonly employed to operate the ULN2003AD device. It's crucial to keep the input channels well-separated to minimize crosstalk. For output connections, Tl recommends using thicker traces to accommodate high current requirements. The wire thickness should be determined based on the trace material's current density and the desired drive current.
Because all of the channels currents return to a common emitter, it is best to size that trace width to be verywide. Some applications require up to 2.5 A.
Usually, the ULN2003AD device is employed to control high-voltage, high-current, or both, peripherals connected to an MCU or logic device that is sensitive to such conditions. This represents a prevalent use case for the ULN2003AD device, particularly in driving inductive loads like motors, solenoids, and relays. The figure above illustrates the model for each type of load.
First, we need to connect the power supply to the Vcc pin (positive power supply) and COM pin (negative power supply) of the ULN2003AD chip. When connecting to the power supply, we must ensure that the voltage range is within the specifications of the ULN2003AD chip to avoid unnecessary damage.
Afterward, we establish a connection between the input signal, typically sourced from a microcontroller, Arduino, or another digital electronic device, and the input pins (IN1 to IN7) of the ULN2003AD. Each input pin corresponds to an output pin.
Next, we establish a connection between the load we wish to manipulate, which could be a relay, light bulb, stepper motor, or similar devices, and the output pins (OUT1 to OUT7) of the ULN2003AD. Each output pin is associated with a transistor switch. Simultaneously, it's essential to ensure that the ground (negative pole) of all connected loads is linked to the COM pin of the ULN2003AD.
ULN2003AD is an integrated driver, and we can activate or deactivate its output pin by controlling the state of the input signal. When the input signal is in a high-level state, for example, when the Vcc power supply is turned on, the corresponding output pin will be energized, thereby driving the connected load to start working.
It should be noted that the ULN2003AD has internal current limit protection to help prevent overcurrent from damaging the load. We need to ensure the current requirements of the load and select a suitable current limiter. Additionally, the ULN2003AD does not provide isolation between power and ground, so caution should be considered when using it for specific applications.
Frequently Asked Questions
1. What is the use of ULN2003?
Typical usage of the ULN2003A is in driver circuits for relays, solenoids, lamp and LED displays, stepper motors, logic buffers and line drivers. A ULN2003 installed in a breakout board to be used as a unipolar stepper motor driver with a 28BYJ stepper motor on the left.
2. What is ULN2003 driver?
The ULN2003 Driver Board. The ULN2003 is one of the most common motor driver ICs, consisting of an array of 7 Darlington transistor pairs, each pair is capable of driving loads of up to 500mA and 50V. Four out of seven pairs are used on this board.
3. What is the replacement and equivalent of ULN2003AD?
You can replace the ULN2003AD with the ULN2003ADR, ULN2003ADR2G, ULN2004ADR or ULN2004AD.
4. What is the purpose of the ULN2003AD?
The ULN2003AD is designed to interface between low-level digital or microcontroller outputs and high-power loads such as relays, motors, solenoids, and lamps. It provides amplification of current to control these loads.
5. What are some typical applications of the ULN2003AD?
Typical applications include driving relays, controlling stepper motors, switching high-power LEDs, driving solenoids, and other tasks that involve interfacing between low-power logic signals and high-power loads.
