The KA3845BN is a fixed frequency current-mode PWM controller from Fairchild Semiconductor, now part of ON Semiconductor. This controller is specifically designed for off-line and DC-to-DC converter applications. It offers a complete set of features that allow for the construction of cost-effective and reliable power supplies. The current-mode control provides inherent line feedforward, improved noise rejection, and cycle-by-cycle current limiting.

Applications:

• Switch-Mode Power Supplies (SMPS)
• DC-DC Converters
• Offline Power Supplies
• Battery Chargers
• Uninterruptible Power Supplies (UPS)

Features:

• Fixed Frequency Operation
• Current-Mode Control
• Automatic Feed Forward Compensation
• Latching PWM for Cycle-by-Cycle Current Limiting
• Internally Trimmed Reference
• Under Voltage Lockout (UVLO) with Hysteresis
• Low Start-Up Current
• Totem Pole Output

Benefits:

• Simplified Design due to integrated features.
• Improved Transient Response due to current-mode control.
• Enhanced System Reliability with built-in protection features.
• Reduced Component Count leading to lower BOM cost.
• Precise Output Regulation.

Additional Details:

The KA3845BN operates at a fixed frequency, typically 500 kHz, which simplifies the design of the power supply. It features an internally trimmed reference voltage, ensuring accurate output regulation. The Under Voltage Lockout (UVLO) prevents the controller from operating until the input voltage reaches a certain threshold, protecting the power supply from damage. The totem pole output is capable of driving a power MOSFET directly. It comes in a DIP-8 package. It is a popular choice for a wide range of power supply applications due to its versatility and reliability.