Professional IC Distribution & Technical Solutions

The UC3845N is a high-performance current-mode PWM controller manufactured by Unitrode (now part of Texas Instruments). Below are its specifications, descriptions, and features based on the Manufactor Datasheet:

Specifications:

• Output Configuration: Single-ended
• Topology: Flyback, Forward, Boost, Buck
• Switching Frequency: Up to 500 kHz
• Duty Cycle Range: 0% to 50% (internally clamped)
• Supply Voltage (Vcc): 8.4V to 30V (operating), 36V (absolute max)
• Output Current (Source/Sink): 1A (peak)
• Reference Voltage: 5V ±1%
• Error Amp Bandwidth: 1 MHz
• Current Sense Input Threshold: 1V
• Operating Temperature Range: 0°C to +70°C

Description:

The UC3845N is a fixed-frequency pulse-width modulation (PWM) controller optimized for high-performance DC-DC converters. It features current-mode control for improved loop response and simplified compensation. The device includes an internal oscillator, a temperature-compensated reference, a high-gain error amplifier, and a current-sensing comparator.

Features:

• Current-Mode Control: Provides cycle-by-cycle current limiting.
• Under-Voltage Lockout (UVLO): Ensures proper startup with hysteresis.
• Internally Trimmed Reference: 5V with ±1% tolerance.
• High-Current Totem Pole Output: Directly drives power MOSFETs.
• Low Startup Current: Typically 0.5 mA.
• Pulse-by-Pulse Current Limiting: Enhances protection.
• Adjustable Oscillator Frequency: Via external RC components.
• Soft-Start Capability: For controlled power-up.

The UC3845N is commonly used in offline and DC-DC power supplies, battery chargers, and SMPS applications.