Product Overview
The Texas Instruments UC3843B is a fixed-frequency PWM controller optimized for off-line and DC-DC converter applications.
Featuring low start-up and operating current, precision voltage reference, and fast transient response, this controller is widely used
in current-mode control topologies, particularly for switched-mode power supplies (SMPS). Its internal oscillator, undervoltage
lockout, and fault protection make it ideal for robust designs.
Technical Highlights and Comparison Advantages
When comparing the UC3843B to other PWM controllers, its key strengths lie in its ultra-fast response time, energy efficiency, and
high-current output drive. This allows engineers to reduce external components, optimize thermal design, and extend operational
longevity. Compared to traditional voltage-mode controllers, the current-mode approach of the UC3843B provides superior line and
load regulation and inherent cycle-by-cycle current limiting. It is well-regarded in industrial design forums for its reliability
in field-deployed systems.
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Technical Parameters
- Input Voltage Range: 7.6V to 30V
- Start-Up Current: 0.5 mA (typ)
- Operating Supply Current: 17 mA (typ)
- Reference Voltage: 5V ±2%
- Output Current (Source): 1.0 A
- Output Current (Sink): 1.2 A
- Oscillator Frequency: Up to 500 kHz
- Undervoltage Lockout: 8.4V ON, 7.6V OFF (typ)
Parameter Table
| Parameter | Value |
|---|---|
| Start-Up Current | 0.5 mA |
| Operating Current | 17 mA |
| Reference Voltage | 5V ±2% |
| Output Drive | 1A Source / 1.2A Sink |
| Oscillator Frequency | Up to 500 kHz |
Typical Applications
- AC/DC power supplies
- Motor drive control
- Telecom and networking power systems
- Battery-powered industrial instruments
- Isolated flyback and forward converter designs
Frequently Asked Questions (FAQ)
What is the typical use of the UC3843B controller?
The UC3843B is widely used in offline switch-mode power supplies, particularly in current-mode architectures such as flyback or buck converters. It provides fast response and high efficiency, making it ideal for industrial and telecom systems.
How does the UC3843B improve energy efficiency?
With its low 0.5 mA start-up current and efficient totem-pole driver, the UC3843B minimizes standby power consumption and switching losses, improving overall energy performance.
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Can this PWM controller drive high-power MOSFETs?
Yes, the UC3843B includes a robust output stage capable of sourcing 1A and sinking 1.2A, suitable for directly driving power MOSFETs in medium- to high-power applications.
Is undervoltage protection integrated?
Yes, the integrated UVLO (undervoltage lockout) prevents operation below the minimum voltage threshold, thereby protecting the system from unstable input conditions.
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How does it compare with other controllers?
Compared to older voltage-mode PWM controllers, the UC3843B’s current-mode operation offers enhanced loop stability, easier compensation, and built-in current limiting. These factors reduce BOM cost and simplify design.
