UC3865N

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UC3865N is a member of the UC3800 family of fan controllers from Texas Instruments. It is designed to interface with an AC fan driver which is powered by a 12V DC supply. It operates on a single supply and provides accurate control of the fan’s speed without sacrificing power efficiency.

Introduction

The UC3865N is designed to provide precision control of the speed of AC fan motors driven by 12V DC input voltage. It implements a single supply SMPS (switched mode power supply) with variable PWM (pulse width modulation) control. The controller includes a low voltage threshold window comparator, an error amplifier, a reference generator, fault protection circuitry and an on-board driver capable of driving many fans in parallel.

Using this single-supply controller, the current fan speed can be accurately regulated while maintaining a high degree of efficiency. It supports an input voltage range of 8 to 20V DC and provides adjustable duty cycles up to a maximum of 95%. The UC3865N can also accept an external temperature sensor to provide temperature control of the fan motor.

Application fields

The UC3865N can be used in a wide variety of applications to provide precise control for AC fan motors. It is ideal for powering cooling fans used in desktop and laptop computers, servers and other electronic devices. Additionally, it can be used in automotive and automotive applications, as well as in industrial and military applications.

For example, the UC3865N can be used to turn on and off AC cooling fans in desktop PCs, depending on the heat dissipation of the computer\'s system components. The fan can be automatically turned up when the temperature rises too high and turned down when the temperature dips too low, resulting in longer computer life, improved efficiency and reduced noise. In servers, the UC3865N can provide precise control for the external airflow fans, or for the fan tray, as well as for other control-related applications.

The UC3865N can also be used in automotive electronics, where it can provide precise temperature control for electric fans used in cooling systems. In addition, the UC3865N can be used in industrial and military applications where precise temperature control is required. This can help to prevent costly machine failures in environments where precise temperature control is critical.

Working principle

The UC3865N is based on a single-supply SMPS that utilizes a variable PWM control scheme. It includes a low voltage threshold window comparator, an error amplifier, a reference generator, and fault protection circuitry. When the input voltage is applied, an initial comparison is made between the reference voltage and an internal temperature-regulated voltage. If the temperature-regulated voltage exceeds the reference voltage, the error amplifier will increase the duty cycle of the PWM signal. This increases the fan speed. Conversely, if the temperature-regulated voltage is less than the reference voltage, the PWM duty cycle is decreased, resulting in a lower fan speed.

To ensure precision control, the UC3865N provides a window comparator to monitor the fan’s actual speed. If the fan’s speed falls outside the specified range, the fault protection circuitry will turn off the fan and, if necessary, the entire power supply. This ensures safe and reliable operation of the system.

In summary, the UC3865N provides a single-supply solution for controlling AC fan motor speed and efficiency. With its precision control and fault protection circuitry, it can be used in a variety of applications, including desktop, laptop and server computers, as well as in automotive, industrial and military applications.

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