ULN2804A Transistor Array Equivalents, Symbol, Working Principle and More
22 November 2023
Ⅱ. Symbol, footprint and pin configuration of ULN2804A
Ⅴ. Technical parameters of ULN2804A
Ⅵ. Working principle of ULN2804A
Ⅷ. Absolute maximum ratings of ULN2804A
The ULN2804A is an integrated circuit that belongs to the ULN family and is commonly used as a driver for light bulbs, stepper motors, relays and other electronic components that drive high current loads. It contains eight independent transistors with a common emitter and integrated suppression diodes for inductive loads. Each transistor has a peak load current rating of 600 mA and can withstand at least 50 volts in the off state. The outputs of this IC can be paralleled for higher current capabilities.
The ULN2804A has a 6 to 15V CMOS input resistor. It comes in an 18-lead plastic DIP package with copper leads and has convenient input and reverse output pins, which helps simplify board layout.
Replacements and equivalents:
• ULN2802A
• ULN2803A
• ULQ2803A
The following figure shows the symbol, footprint and pin configuration of ULN2804A respectively.
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• It has built-in suppression diodes that help prevent back EMF from inductive loads.
• It has a high input impedance allowing interfacing with various logic drivers and microcontrollers.
• Each output channel integrates a TVS diode to prevent load reverse voltage from impacting the power supply.
• It has overheating protection function, which can effectively prevent the chip from overheating, thereby protecting the safety of the chip and the entire circuit system.
• The ULN2804A features eight separate output channels, with each channel capable of managing a load.
• The internal input resistor in the device enables seamless interaction with a microcontroller or other digital circuit, eliminating the necessity for external resistor dividers.
Its input terminal receives low-level digital signals and converts them into high-level analog signals to drive high-current loads. ULN2804A contains 8 transistors internally. Each transistor has an input and an output. The input terminal receives a low-level digital signal, and the output terminal outputs a high-level analog signal to drive a large current load.
• Lighting control: Due to its high current characteristics, the ULN2804A can also be used to control lighting loads. Whether it is stage lighting or home lighting systems, it can achieve precise control and add unlimited colors to each scene.
• Displays and digital tubes: This chip can also be used to control LED displays, digital tubes, etc. By supplying enough current, it ensures that these display elements light up properly.
• Switching power supply control: The ULN2804A has the capability to function as a control switch for switching power supply control. Through the incorporation of external components, it can be configured to regulate a switching power supply, allowing for the control of the connected load.
• Stepper motor driver: A stepper motor usually requires a large current to operate properly, so it requires a driver that can provide sufficient driving force. ULN2804A is an integrated circuit suitable for stepper motor driving. It can provide sufficient current to meet the operating needs of the stepper motor. This chip has multiple Darlington pairs that can effectively amplify the input signal to provide powerful driving capabilities.
• Relay driver: ULN2804A is widely used to drive relays. It has eight independent switch pins, each capable of delivering sufficient current and voltage to activate the relay.
First, we need to determine the power supply voltage range used. The voltage range that ULN2804A can withstand is 4.5V to 8.5V, and ULN2804A can work normally within this range. Next, we connect the input signal to the input pin of the ULN2804A. These pins have high input impedance, so they have very little effect on the signal source. Then, we connect the load that needs to be controlled to the output pin of the ULN2804A. In order to meet actual needs, we need to appropriately select the output type and quantity of ULN2804A.
When using ULN2804A, we need to pay attention to the stability of the power supply voltage to avoid damage to it due to excessive voltage fluctuations. At the same time, we should also pay attention to the layout and routing of the circuit board to ensure stable signal transmission. If debugging or modification is required, we should disconnect the power supply first to ensure safety.
Frequently Asked Questions
1. What is the replacement and equivalent of ULN2803?
You can replace the ULN2803 with the ULN2802A, ULN2803A or ULQ2803A.
2. What is a Darlington transistor array?
The Darlington transistor is a compound structure consisting of two bipolar transistors connected in such a way that the current amplified by the first transistor is amplified further by the second one.
3. What is the difference between ULN2803 and ULN2804?
The ULN2803 is designed to be compatible with standard TTL families while the ULN2804 is optimized for 6 to 15 volt high level CMOS or PMOS. package, unless otherwise noted.) RθJA = 55 °C/W Do not exceed maximum current limit per driver.
4. What is the ULN2803 used for?
The ULN2803 is used to interface low-level logic signals (such as those from a microcontroller or a digital circuit) with high-power devices like relays and motors.
5. How is the ULN2803 commonly connected to a microcontroller or digital circuit?
The ULN2803 is often connected to the output pins of a microcontroller or digital circuit, and the input pins of the ULN2803 are used to control the corresponding Darlington pairs.
