UC3843BNG
Adjustable voltage stabilizers and PWM controllers for power management
Manufacturer： ['rochester', 'onsemi', 'lrc']
series introduction
# Introduction to the UC3843BNG Product Series
## 1. Overview
The UC3843BNG is a highly popular and widely used integrated circuit (IC) belonging to the family of current - mode PWM (Pulse Width Modulation) controllers. It is specifically designed for use in switching power supply applications, offering a comprehensive set of features that make it an ideal choice for engineers and designers looking to develop efficient and reliable power conversion systems.
## 2. Key Features
### 2.1 Current - Mode Control
One of the standout features of the UC3843BNG is its current - mode control architecture. This control method provides several advantages over traditional voltage - mode control. In current - mode control, the inductor current is used as a control variable in addition to the output voltage. This allows for better line and load regulation, improved transient response, and inherent cycle - by - cycle current limiting. As a result, the power supply can quickly adapt to changes in input voltage or load current, ensuring stable output voltage under various operating conditions.
### 2.2 Adjustable Oscillator Frequency
The UC3843BNG features an adjustable oscillator frequency, which can be set by an external resistor and capacitor. The oscillator frequency can typically range from a few kilohertz to several hundred kilohertz. This flexibility allows designers to optimize the power supply design for different applications. For example, in applications where size is a critical factor, a higher oscillator frequency can be used to reduce the size of the magnetic components such as inductors and transformers. On the other hand, in applications where efficiency is the primary concern, a lower oscillator frequency may be more suitable.
### 2.3 Built - in Error Amplifier
The IC is equipped with a built - in error amplifier. This amplifier compares the output voltage of the power supply with a reference voltage and generates an error signal. The error signal is then used to control the duty cycle of the PWM output. The high gain of the error amplifier ensures accurate regulation of the output voltage, minimizing voltage variations due to changes in input voltage or load current.
### 2.4 Under - Voltage Lockout (UVLO)
The UC3843BNG has an under - voltage lockout feature. This feature ensures that the IC does not start operating until the supply voltage reaches a certain threshold. Once the supply voltage drops below the UVLO threshold during operation, the IC shuts down to prevent improper operation and potential damage to the power supply components. The UVLO feature helps to improve the reliability of the power supply system.
### 2.5 Soft - Start Function
To reduce the inrush current during startup, the UC3843BNG incorporates a soft - start function. During the startup phase, the duty cycle of the PWM output gradually increases from a low value to its normal operating value. This slow increase in the duty cycle limits the inrush current, protecting the power supply components from excessive stress and extending their lifespan.
## 3. Pin Configuration and Functionality
### 3.1 Pin 1 (COMP)
This is the output pin of the error amplifier. It is used to connect an external compensation network, which is designed to stabilize the control loop of the power supply. The compensation network helps to optimize the transient response and stability of the power supply.
### 3.2 Pin 2 (VFB)
The feedback voltage input pin. The output voltage of the power supply is fed back to this pin through a voltage divider network. The error amplifier compares the voltage at this pin with the internal reference voltage to generate the error signal.
### 3.3 Pin 3 (ISENSE)
The current sense input pin. It is used to sense the inductor current in the power supply. The current sense signal is used for current - mode control and
Images for reference
8-DIP
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