The UC1823A/B, UC2823A/B, UC3823A/B, and UC1825A/B, UC2825A/B, UC3825A/B series are high-speed Pulse Width Modulation (PWM) controllers from Texas Instruments designed with significant improvements over their predecessors, targeting a wide range of power conversion applications. These devices support operational frequencies up to 1 MHz, making them suitable for high-frequency power supply designs.
Key Enhancements and Features
The improved PWM controllers provide a range of enhancements such as:
- Error amplifier: Offers a gain bandwidth product of 12 MHz and an input offset voltage of only 5mV, which improves overall system accuracy.
- Current limit threshold: Comes with a tight tolerance of 5%, ensuring reliable performance under varying conditions.
- Oscillator discharge current: Specified at 10 mA for accurate dead time control and a frequency accuracy improved to 6%.
- Startup supply current: Features a low startup current typically at 100 µA, ideal for off-line applications.
- High-current output drivers: Redesigned to actively sink current during under-voltage lockout (UVLO) without sacrificing startup current specifications, capable of delivering peak currents of 2 A.
Functional Improvements
The datasheet details significant functional upgrades such as:
- A faster overcurrent comparator with a 1.2 V threshold in the UC3825 version.
- An overcurrent comparator that sets a latch ensuring full discharge of the soft-start capacitor before restart, which prevents fault frequency from exceeding the designed soft-start period.
- The CLOCK pin, now labeled CLKILEB on the UC3825, combines clock output functions with leading edge blanking adjustment and includes buffering for easier interfacing.
- The ‘A’ version parts maintain the original UC3823 and UC3825 UVLO thresholds, while ‘B’ versions offer tailored thresholds of 16 V and 10 V for ease of use in off-line applications.
Applications and Support
These PWM controllers are compatible with voltage-mode or current-mode control methods and offer practical features, such as pulse-by-pulse current limiting and latched overcurrent comparator with full cycle restart, well-suited for complex power supply systems.
The datasheet encourages consultation of the application note ‘The UC3823A,B and UC3825A,B Enhanced Generation of PWM Controllers (SLUA125)’ for detailed technical and application information, reflecting Texas Instruments’ commitment to providing comprehensive design support.
The datasheet features a block diagram, revision history, ordering information, pin configuration and functions, specifications, and detailed application and implementation guidelines. It also advises users on where to find device and documentation support, including support resources and notifications of updates.
References:
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