SMPS Controller 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 Ic-phoenix technical data files:
### **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.
